Hello out in Hodaka land.... I am in need of your help in building a 100cc bike for the Bub's Motorcycle Speed Trials in Bonnieville. Yup that is right I want to run a Hodaka at Bonnieville.. There are several classes in the 100cc's but I plan on running the class M-AG which is modified frame, modified engine, on their gas... Sounds like fun doesn't it? The national record for that class is 93.173 T. Connway riding a Kawasaki set it in 1973. I think we can beat that. Anyway, I sure could use your input on frame modifications, rake, length of swingarm, and best rim size, also could use help on engine and gearing.
Look forward to hearing from you guys... Thanks in advance
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Bullfrog - 05/31/08 at 8:11pm
Do you get to add some streamlining structure in that class? ie fairing?
Gearing will depend greatly upon wheel and tire size . . . and I have no road race or Bonneville experience to draw on for guidance on wheel and tire sizes. Best recommendation I have is to go look at the Road Race tuning information sheet @ Strictly Hodaka. Since those tips were good enough for Harry Taylor to break 100 mph @ Daytona back in the '60's, they ought to be pretty much on target for your use. Click on HOME at the top left of this page and then go searching.
Interesting project!
Ed
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100mx - 05/31/08 at 9:38pm
Thanks for the information Ed, the MAG class is what we call a naked bike class no aerodynamic improvements at all. They do have classes that are partial streamlined and streamlined. Those records are at about 104 -113 miles per hour top class. Surprised to hear that Harry Taylor went 100 miles per hour at Daytona, he should have taken his bike to Bonneville.
Thanks again
Reggie
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sachs175 - 05/31/08 at 11:46pm
Reggie,
Can you liquid cool the cylinder in this class?
Could you find some pictures of bikes that run in this class and post them? A head light turned around , would that classify as streamlining? What a neat project.
John D.
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100mx - 06/01/08 at 1:45am
Hey John,
As far as I know you can water cool the engine, in the M-modified engine class... I will see if I can find some pictures and I will post them. You can only run a head light if it came stock on the bike in this class. I doubt they would let you turn it around, but as you know every little bit helps in this class.
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sachs175 - 06/01/08 at 2:04am
You could start out with a 100 B+ or the later alloy barrel model 100 then . They came with a head light. Use the curved lens sealed beam.
That would be a lot better on incoming air than the forks bear i would think.
There is a close ratio 5 speed tranny that comes up on ebay and in other places for sale from time to time. It was a stock Hodaka accessory they sold. I think it was for road racing . I had one in my old MX 100 . It was not the right gear set for that but i tried it anyway.
The iron barrel model 92 would be no disadvantage if you could water cool the cylinder so that opens up a lot more engines to use.
Hope you can get this built. It is a neat once in a life time type project that you will remember forever.
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100mx - 06/01/08 at 2:36am
Thanks for responding, that's a great idea using the B+ since it did come with a headlight. I have been going over all the gears and different models to see whats compatible as far as main shaft and different primary gears. I believe my case has to be from a 100cc bike but I know there's a lot of really smart guys out there that can help me with some gear ratios and hopefully some tire sizes.
.... ( Here is the best I can do for a picture).. Let me know what you think
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frenfroe - 06/02/08 at 11:07am
All I can say is Wow! 100+mph! Go for it.
The Bonneville Problem is elevation, 4200 ft above sea level. Tuned and producing 100 in Daytona is going to get you 90mph, at best, on the salt flats.
And you have to run flat-out for a running mile in 2 directions.
I have a series of articles from Trials Competition over several years I believe from the late 80's-early 90's about a fellow's record attempts with a YZ80 and other bikes. He blew up a LOT of engines.
I'd start with a late rat alloy barrel, a Super Combat carb and modded reed cage, and a little port work. Are Paul's SuperHeads available yet and for a 100?
Definitely a PVL ignition.
Definitely a ceramic coated head, piston crown, and exhaust port to control heat.
High altitude=need more compression.
Reduce drag and friction. Lower bike, lengthen so you can stretch out. Perfectly balanced/trued smaller wheels. Maybe from a Honda MB5? Lightest chain possible.
Reduce weight. Lightest wheels, minimal seat & tank. Find a 90lb teenage girl to pilot it!
Frank
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100mx - 06/03/08 at 2:00am
Hey Ed and Frank, thanks for all the great info.
I am worried about aerodynamics, in this class I wonder how much advantage a ferring will provide, cause there is a mps - ag class with the record I have of 81.96 mph, but I am wondering about how up to date the information is that I have, anyway I am sure it has to be around 100 mph.
I was wondering about rake angles: stock 98 rat, 29.20. I was wondering what the optimum rake angle would be for going fast. and how far can I stretch the swing arm, stock is around 53.26. Does anyone have any information on having gears coded for less friction? or super precision barrings?
Thanks again for all the help you guys have provided.. I look forward to getting all the information and advice...
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BATMAN - 06/03/08 at 11:05am
About the frame. Think about contacting Charlie Robinson at Sooner Hodaka. Charlie has a vast amount of knowledge and is one of the best fabricators around. Your project is right up his alley. Fabricating a frame for your project is well with in his ability and he is a super nice guy, and he is one of us Hodaka nuts..........Good luck and be sure to keep us posted as the bike comes together.......Leo
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frenfroe - 06/03/08 at 12:11pm
The stock rake is around 30 degrees, sport bikes run steeper, like 25 degrees. But....they turn a lot and you want to run straight. I wouldn't fool with it unless I stretched it out a little more. Fork angle should not affect speed.
I'd put smaller diameter wheels on it, narrower the better if they can stand the speed, push the forks up as fat as they'll go w/o hitting anything, then measure and fit shocks in the rear to level it out. The lower you can make it the less frontal area you'll have.
You might extend the top seat rails to fit a club man seat and you shouldn't have any problem extending the swingarm 4" or so if you add gussets. Fit light weight rearsets to where you are comfortable. You could just flip and extend the shifter.
By friction elimination I mean insure you have NO brake drag, that the chain runs absolutely true, the wheels have fresh bearings and run perfectly true, etc. You can get super ceramic bearings.....at about $150 each and I'd be surprised if they made any difference. Run a very light gear oil in the transmission.
Why use a front brake at all? Run a light spool. Adapt a light disk for the rear.
I'm fooling around now with a product called GearKote for my piston and head. It's an old product that is used on gears/shafts too. It's a moly-polymer that's baked on. Many people claim it will double or triple small bore piston life. They have a higher tech product that has teflon and moly too. Their tech recommended the GearKote for the pistons though and said it will lower head temps. For the most temp control, they have a ceramic product too but it takes very high heat to cure.
An old article from the 70's about building a Honda SL125 racer had all the internals GearKoted and the exterior coated with GunKote. They had very substantial reduction in oil temps using the coatings.
SwainCoat will do pistons, heads, etc. Pistons run $25 per. They use a moly coating on the sides and ceramic on the crown. It's good stuff I hear.
Frank
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sachs175 - 06/03/08 at 2:51pm
Reggie,
Salt is a lot different than asphalt . You need to find someone who has run at the flats for a while. Get them to help with what will work for frame design and wheel sizes. You find soft spots and rough areas some times groves. High speed wobbles are no fun and depending on the bikes set up you have to do different things to recover from them . I have had 2 street bike that would go into wobbles . One at 110 + the other at 100. It will get your attention chuckle chuckle
If you go with a reed induction intake, find out what is being used for reed material now at the flats. Figure the rpm you will need with the wheel/ tire size and drive ratio 's . Primary , transmission and sprockets. You would need to know what RPM you have to run to have the speed to make the record with the above ratios.
The reeds would have to survive at least 10 miles at that rpm to do runs. Unless you are willing to change them out at the turnaround. A piston port setup might work for a top end run. Bet Harry would know if that would work or not.
Keep us updated on how your doing pleases.
John D.
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hodakgem - 06/04/08 at 7:30pm
Some off the wall ideas. First the rider goes on a strict diet and drops 35 lb. or get a horse jockey who can ride a bike.
2nd. There is no reason why you cannot experiment with Steens or Gemini frames that carried hodaka engines. I have a Gemini with a wombat 125 engine and previously had a steens.
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100mx - 06/05/08 at 12:06am
Hey thanks again for all your help, i loved the idea about the steens. i happen to have one in the garage, all though i have two frames ones a steen and ones another mini. but considering how low the frame is with enough extension on the swing arm it just might work. yea john D, i was very interested in what you said about high speed wobbles i wonder what you do at high speed when you have no more acceleration. you cant shut down so you would have to shift your weight, or just hang on and pray. yea frank, about the coding on the gears i will have to research this a lot more, this has to be the way to go. anyway thanks for all your help again guys.
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hodakgem - 06/06/08 at 6:56pm
Without measuring, I think a steens is lower in rider height than a Hodaka Frame and I know the gemini frame is certainly inches lower. My suspicion is both of them weigh less to begin with. just guessing, but both were "stock bikes" that happened to have Hodaka motors.
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hodakaronwa - 06/07/08 at 12:03am
Was discussing the Bonneville thing today with a close friend.
We have our eye on a rolling chassie from a Yamaha 80 f? something mini road racer.
I have personally exceeded 100MPH with an ACE 100 engine and cast iron cylinder years ago. I was not the rider he was 89 pounds soaking wet.
Our runs were on pavement "Black Top" We ran an air cooled reeded motor with a 34 mikuni. A close ratio box with synthetic ATF. It also ran a custom total loss ignition. I experimented with CDI but have yet to get one of those ignitions to perform well at ultra high RPM's.
We used the early hodaka hubs and small AKRON rims. I believe we also used the stock street rear drive sprocket and the early lighter chain.
The frames were VAN TEK.
The heads were WEBCO and we later used WEBCO cylinders but I didn't feel we gained anything with the WEBCO cylinders.
We also experimented with water Kooling by wrapping the cast iron cylinders with soft copper and use a heater core for our radiator. We had no water pump and relied on thermocline to circullate the water.
We really didn't do much if any better than the 34 mikuni and a reed and a special cut through the piston.
We learned that with the bigger carburetor and the reed at WOT so much air was going through the engine that it alone kept the engine cool from the inside out. I felt we were very successful and had very few engine failures. Hey we were not starting from a dead start so the clutch held up pretty well as did the crankshaft. But! now we have a better solution to eliminate the crankshaft and clutch weakness. The later larger crank half of the 98 and it's clutch.
I would use the small side on the flywheel and the large size on the clutch side.
With modern available ignition components and lighter batteries I think a total loss is still the best bet AND WILL OUT PERFORM ALL THE AVAILABLE CDI UNITS. Plus you do not need the advance which is built into the black box as the engine will always work up stairs beyond any advance curve.
A pipe with a very small stinger about 8 to 10 inches long. Possibly as small as 1/2" I.D. I have one of those pipes I have experimented with on my 98 but it was just too far up stair to be useful for motocross.
I am sure you will bring other old timers out of the closet for this one. It could become a Hodaka Club Project for sure.
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100mx - 06/08/08 at 4:04pm
thanks for responding, i really appreciate all of your experience. i was wondering what alterations, if any, you made to the van tek frame? and what forks you ran? and did you extend the spring arm? i have heard of total loss ignition before, but could you explain how it works and the benefits from it?
p.s. are you eyeing that yamaha 80 to make a run yourself?
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hodakaronwa - 06/11/08 at 1:51pm
The Van Tek frames at the time were basically stock length, with baby cerioni forks and shocks. These were actually 1/2 milers. Total .loss ignition is battery operated and requires a battery to be carried on the bike. Hodaka at one time either sold or made plans available to fabricate a battery box. Before the Hodaka CDI came out total loss ignition was what the serious racers used. I removed the rivets which retained the flywheel so as to use only the point cam. The cam was then machined to only a peak so after opening the rest of rotation was dwell or saturation. The points used a double spring to eliminate float at high RPM.
Also the kick start portion of the transmission was eliminated and these bikes were push start only.
This reduced both weight and mechanical drag.
When we timed the ignition it was always done with a dial indicator.
They also had no front brake just a spool hub as they were 1/2 milers.
At the time we exceeded 100MPH 104 these bikes did not have a ferring.
The Yamaha I have my eye on? When I saw it the thought of putting a hodaka motor just instantly came to mind. I had no major purpose in mind. The Bonneville thing came along later. I would have to check the rule book to see if this would even fit into a class which it might be competitive with.
I have seen some suzukis which are extremely fast.
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Threw-a-Rod - 06/11/08 at 6:17pm
Hi Reggie This is just the shot in the arm Hodaka needs. I'm the guy on the other post asking about Mikuni carb questions.
Interesting project you have and the desire for speed has everybody’s mind for decades. Primarily I was a certified Ford technician and uncertified Harley builder too. However ever since I was a kid Hodaka 2 stroke was buried in my mind. Some of my suggestions are unrelated but apply in the tinker’s world from the beginning as serve as a guide line that some folks forget about.
I was taught by an old feller who was old school the fine art of carburetion and engine tuning and how to get around stumbles and flat spots and proper acceleration on the road, drag racing, oval track. Some of this information is clear off but the theory still applies for it's for big motors but scale it down and it works for just any motor out there.
I used to build monster Shelby’s, Pant eras, Boss mustangs, and jumped the fence and helped out guys with Chevys and Dodge products all perfect contenders and different in each way it's built -a tuners nightmare so to speak. Then I got into bikes with all sorts of different headaches to deal with let alone build the motor.
Basically no matter how the motor is beefed or how it's timed your carburetor is going to have to win or lose for you period.... You have to control the vacuum in the center of the main jet area period.... now when your motor is idling you’re pulling on the low speed jet and when the throttle is cracked the center of vacuum moves its center to the main jet simple. Now there are other complications that affect the center of vacuum when you jack the throttle center of vacuum just flat out goes wild and moves clear off the map so to speak. To control this flat spot the accelerator pump suffices enough fuel by a short squirt of fuel till the vacuum returns to the main jet. Also a major break through was the addition of the power valve used when the motor was say half way wide open and you jack the throttle and the demand for more fuel is more than the main jet can provide so the vacuum goes through a passage and draw on a rubber diaphragm valve that just plain has big holes in it to dump fuel so that helps as a temporary patch till vacuum returns to center over the main jets again.
This motor you’re going to run is flat out and searching for top speed and that's different. Beings how these motors are primarily half drag racing and half slowing down for a turn so they are tuned for that.
You can stick any carburetor on any motor providing you tune it for the fuel you use and proper air fuel atomization. It's happened before and will continue to do so to get that better edge on the competition.
I always felt not enough air and you got problems or vise versa. Motors act strange at different sea levels and of course the weather has a lot to do with it. Ever notice in you automobile or bike on a foggy or damp day it runs like a jackrabbit. Well that water contains H2O that’s Hydrogen and Oxygen - hydrogen burns and Oxygen speeds up the burning process, Old prop piston airplanes in the old wars used water to inject into the carb throat and got the edge to power up real quick and snuff out the enemy hmm.... just a passing thought.
Down to what you’re doing different ways to get the max out of your carb if you don't have a dyno then some how take a vacuum gauge to take a reading. so you know what works for the area your racing in it will be different from one location to the next and take notes on what you used on every thing that means from the spark plugs to the jets to the timing and etc. At least you can review and set it up the way it was the last time you was there. In Racing what beat the competition one weekend is junk the next weekend because someone tuned a better carb or motor than you did. I saw that every weekend at the drags and oval - truly a tuners nightmare.
Anyway pay attention to this changing the distance from the carb to the head helps controlling vacuum centers maybe a longer - shorter intake or fine tune with thicker or mounting gaskets. Your header pipe will play a big role in how your motor burns fuel efficiently and can affect your center of draw on vacuum too.
We used to on cars and bikes take the header pipe and mark them with a piece of chalk the whole length of the pipe and make a blast down the strip and take a look where the chalk stopped burning off and make our cut off there this is where your greatest heat dissipation starts to disappear.
From that point you start tweaking your pipes for max performance adding length or shorting the pipe or the bigger or smaller pipe dial. remember that motor's got to breathe right. I mean you might have a straight pipe but might have to scale down the end of it to a smaller diameter.
Here is a classic example my car had terrific take off with single exhaust but no top end. I put on dual and lost take off but had terrific top end catch the drift... Using back pressure in the motor has advantages depending solely on what type of racing your doing. As drag racing is different than road is different to oval as oval is different to flat out racing. They all breathe different from one another....
I don't know if they will let you run exotic hot fuels or not but if it is. Watch the piston to cylinder tolerances. and I would open up the gap a little on the top piston ring because of the excess heat that fuel puts out and it will make that ring expand and if it butts solid in the cylinder wall your in trouble and same for piston - cylinder clearance.
I watched a buddy of mine on his Harley dragster with out me knowing it and not being there to warn him he changed the motor set up to a different class running hot fuel and it sheered the solid steel cylinder right in two - the rings end gap showed shiny from rubbing together and well you know the rest hard and expensive lesson to learn.
I hope you can get to tune you motor somewhere near the salts altitude that helps a lot and remember it will be hot there so tune that carb to compensate for it.
And last but not least is the air intake your carb is pointing towards the rear kind of in a dead air space vacuum maybe just maybe pointing your air horn towards the incoming wind may or may not help. Seems ram air systems on aspirated gasoline engines seemed to help.... And plus moving the air cleaner back and forth will help centralize your center of vacuum in the throat to as well restricting or unrestricting the air flow too...
I hope you find the right gear ratio to flat out with and hang on....
These are just subtle hints from my drawing board and some from other boards as well. Just never be afraid to be different because that's how you get in the winners circle.
I'll guess I’ll get back to thrown chains suggestion of putting a Tecumseh carb on my ace chuckles..... maybe put a nice huffer or a turbo to ram charge it up real good. hmm That just might do the trick with out blowing the motor up....
I hope it's a fast one for you....
Chris
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sachs175 - 06/11/08 at 7:12pm
Chris,
Have you ever tried a Lectron carb on a bike?
We have 2 one on a 175 Penton KTM and one on my hybrid
Sachs KTM 175
Its a flat slide and just used a dual taper needle to jet with.
The needle is ground in a compound curve from top to bottom on one side only.
Wonder if they would work on a 2 stroke that was set up for top end.
I know they do mellow out the hit on piston port engines and still let you turn in fast lap times on MX and CC type events,
I used it on my engine to keep the torque load down on the shift key. It was a 125 engine to start with.
The smallest they make is 30 mm though . That may be a bit large unless he goes with a reed intake.
You can get some information on them from their web site.
( http://www.lectronfuelsystems.com/technical_info.htm )
Fast By Gast uses them in drag racing .
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Threw-a-Rod - 06/11/08 at 8:35pm
Hi John sadly I have not got the golden opportunity to use this carburetor flat side carburetion is kind of new to me and yet to see what I can make of it. I've been off in the world of the Karaki air intake and it has tremendous advantages beyond belief.
I hate to wander off into the Harleys again but we just about seen it all. When the first S.S came out it was a straight bore straight air horn sticking straight out whew what a pain worked great after messing with it trying to get it to get it to fly down the 1/4 mile seems the air horn was pulling more air away from the carb because it was sideways to the air flow going by it. Then it was off to dual webers with a angled intake to point the air horn into the wind better. If you got a engine demanding huge amounts of fuel then you got to feed it huge amounts of air or the combustion is going to way off as far as correct atomization of fuel air mixture. So the angled intake was a small step in the right direction.
Take a look at top fuel funnys remember the old style huffers had a flat oval shape opening for the air to come in it was a direct in the wind all you can get air flow. I believe it was John Force who dared to be different and put the curved 3 port air induction in their huffer made them big bucks in the winners circle.
Now get this I had a 92 wide glide nothing special but the cv carb and a $300.00 Karaki air intake on it which pointed straight into the wind and was the two butterfly flaps were vacuum operated by the carb simple buy a $30.00 jet kit and drill out and don't change a thing.
I got my first stop light drag with another Harley with a stroker and cams and dual webers. We lit the tires and I saw him in my rear view mirror when I banged 2nd gear and he was fruitless after that. Well the next stop light he said I wasn't in my power curve I said ok I'll let you get in your curve and we'll get it. Same thing left him in the weeds. Everyone was awed including me.
So check this out not only is it functional with draging It's awesome on a 55mph rollout. My buddy is a mech for Harley day in day out. His had dial in computer assist for ign. we're cruising 55 and he gives the high sign to race and I down shift and cobbed it and blew him away so hard he shook his head. Hmm
This is what you guys should be after. You can bumb your motor anyway you want but if you need speed you need air. The only difference was I used 1/2 of a tank of hot fuel like Blue flash 150 octain racing fuel and top grade Shell prem 92 octain but I didn't tell them that.
Me I'd get that carb in to the wind because you got a monster between your legs and he wants air just as much as he needs fuel.
It sucks now days Indy and nascar took away the run what you got and put restricter plates on them. and now you can put a monkey in there if you can get him to hang on to the steering wheel and be a better driver than the rest and hang on because all the motors are the same cu made by same co. To me that's not racing It simply ruined the tinkers world flat out.
They tried that at the Drag strip too because Goodyear said you guys are going faster than our tires can stand and wanted to restrict the power of the motor but after they threw a tiz because they need that edge of tuning experiments to step into the winners circle.
Anyway think about the Karaki setup it's bad if you can get that carb pointed into the wind somehow......
As usual hate to talk about off the wall stuff like cars and all but they got terrific ideas to run with. Me I'm still lucky to be alive after all the speed demon trips I've been on....
Nice to hear from you John and I guess I better get off the board before Paul kicks me off for rambling on...
Chris
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sachs175 - 06/11/08 at 11:06pm
Reggie,
In this quarters Resonator George Cone has a 125 set up for road racing.
You might get some ideas from his work. Does someone in the group have some pictures of that bike that we could post to give Reggie a look see?
John D.
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100mx - 06/13/08 at 1:43am
Thanks for all the information on the flat slide carburetor. i am getting so much information i will have to start a journal. I knew if i asked the question about the bonneville bike i would have alot of great engineers responding. A couple years ago i saw George Cones road race bike, the bike was a outstanding piece of engineering. I would like to see it run on a track. Does anyone know if george is going to attend hodaka days this year? Im sure he has some great ideas on this project. Well im packing up for hodaka days i hope to see some of you guys there, Thanks again.
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Threw-a-Rod - 06/19/08 at 7:24pm
Hi guys I still haven't heard much out of you guys trying to help this guy out with some more ideas on tweaking his motor. In fact haven't heard from him either... Anyway I'm going to have to at least correct my spelling in my last post. about this carb add on it won't fit but the results are staggering. (so make it fit)
The ram air butterfly system- carburetor vacuum actuated unit is spelled "KURYAKYN" um never was good with foreign spelling anyway it's now cheaper than when I bought one - see this site for ideas. copy and paste to your browser.
http://www.kuryakyn.com/achd.asp?bn=har ... r+Cleaners
I got my ace motor today and I'm scratching my head now...
This Kuryakyn set up has me thinking and I've long fogged over since then and well somebody stole the bike anyway. From what I can remember the two butterflies were closed and when you fired up the motor the vacuum pulled the flies open. When you took off you could see the flies move back and forth. When you got a hand full the flies closed shut off air to reestablish the vacuum center over the main jets again. And soon as the vacuum inches were back to normal the flies opened up again. Anyway you look at it either running at 55 mph or dragging take off or flat out it's keeping up with what your doing instantly.- I like it.... period.
Just a little insight on how this improves your motor
The unit has a little vacuum hose that runs to your drilled into your carb throat or intake. and you'll see also they say " More air = More Power" like I always said. also longer intakes give more time to mix fuel and air for the proper atomization of your fuel. That gives you maximum fire power period.... Fuel injection or short intakes don't allow that to happen ( just a thought for you guys to think about) That's the key (Proper fuel atomization) if you dump fuel in your motor even if it's hot fuel it's nothing with out AAAIIIRRR
This chart will show what I mean about this air induction set up will do. Sorry I forgot to add this to last post........
http://www.kuryakyn.com/chart.asp?sku=8350
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sachs175 - 06/19/08 at 10:27pm
Chris,
I think most everyone one the list is tied up with Hodaka Days right now.
I don't know how the air induction set would work on a 2 stroke
They are a bit different than 4 strokes in a lot of ways.
All the air fuel mix goes into the crankcase and is then pumped up through transfer ports to the combustion chamber.
From what you are describing and what i glanced at on the web page it looks like it works a lot like CV carbs used on 4 strokes for years. A difference in atmospheric pressure between the CV chamber and in the venturi of the carb regulates where the slide was located no mater what you did with the throttle butterfly.
A side draft setup like the Harley has a lot of problems with delivering the right amount of air to the carb.
Looks like this setup would help a lot with that on the Harley.
The old XR 750s used a different intake setup. they ran heads with the intake kicked back to the rear and 2 carbs. If i had some old pictures i could show you a lot better than i can describe it.
On a 2 stroke like your 100 you can flip the cylinder around 180 degs and have the ram effect of what ever speed you are doing minus the disturbance the front wheel introduces. Almost acts like a minimal supercharger.
I have a picture or 2 of a 125 Sachs that the cylinder was flipped around like this on.
The man that did it also liquid cooled it and added a rotary valve in place of the piston porting
The Rotary valve was a side draft and gave him fits at speed due to air flow across the bell of the carb even with a full fairing.
He did final get it working right. It was a 30 year old 125 cc air cooled single cylinder dirt bike engine design modified to liquid cooling and making about 32 hp. He finally retired it because the clutches would last just one race.
I can put you in contact with him if you like. He is still involved in 50 to 100 cc road racing , designs and builds his own frames , sells them and different hard parts to make unbelievable power out of 50 to 100 cc engines
Let me know what you would like to look at and i will try and get you pictures or in contact with people that do this kind of thing a lot.
John D.
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100mx - 06/27/08 at 1:01am
Hi guys just got back from hodaka days, met a lot of interesting people who had a lot of good ideas about our project. the highlight from my trip was getting some advise from harry taylor. we decided to run a 98 super rat engine and were going to start with a 98 frame, but we have to figure out the modifications and the swing arm length. you guys blow me away with some of these ideas i especially like the idea about turning the cylinder around and working the ram air effect. in the class i'm running i have to use their fuel so were working with lower octain. anyways i have a lot of smart guys working on it with me and i appreciate all your help. thanks a lot and keep it coming.
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hodakaronwa - 06/27/08 at 12:03pm
Well I read a lot of old hot rod and drag theories which is good but not so applicable to two strokes. No need for accelerator pumps or power valves.
Back in the days of the 100cc 1/2 milers. (read previous) We experimented with many different carburetors. We got Hodaka ACE 100 motors "reeded" to run perfectly with as large as 40mm nikunis. It was found that the 34 worked best all around. At sea level the main jet was somewhere around 470 with a 40 pilot. 3.5 slide with needle all the way up. Perfect idle, instant throttle response. They would almost bury the rear shocks when the throttle was cracked.
Like a single cylinder AA fueler.
I am not much of a frame and fork guy but if I were you I would contact some one that has the bonneville experience. Get your frame and such together and just keep your ears open for more motor feed back and info.
Possible some of the genius will come up with different motor combinations for you to try.
Possibly someone could build you a water cooled cylinder head? If you have ever played with R/C Nitro Boats you know about the water cooled heads. They are two piece the fire deck plate and then a cavity cover which actually is the water jacket. If you can run the head cooler then you can run a richer main jet, which in turn will increase performance.
I still believe that a close ratio gear set is what you will need. But you can play with the primary gear ratios.
No mater what! You will be pushing the machine to get it rolling up on first gear and in the power band before it will assume the load. I have and do machine my gear cases on all my bikes to except all ball bearings and needle bearings. "NO BUSHINGS" at all in the engines.
The rear sprocket will be in the 30's somewhere?
I think a lot of math and research has to be accomplished yet "Reggie"
Get the rolling chassie figured out and use a rear hub which many sprocket sizes are available.
REGGIE" Another thought about carburetion is the tillotson "Pumper" Carb. We experimented with kits made by Kendrick Engineering which came with a reed block and a pumper carb made especially for The hodaka engine. They worked perfectly well and made jetting a cinch since they had needle valves on both the low speed and the high speed. They also produced exceptionally good torque and acceleration as they are a demand carb. Which means the engine only receives fuel as it is needed for what ever situation the the motor's power band requires.
I think that Harry's suggestion to use a 98 rat motor is the way to go myself. The transfer ports are already much larger and the possibility of increasing those ports or modifying those ports are endless. Plus many different gear combinations are available. And don't throw away any Road Toad cylinders as they are a good base cylinder to start with. I used to throw them away or give them away, now I keep every one of them and all my 98 motors started with Toad cylinders.
Also remember the porting starts with the case first and what you take away you should find a way to put back? On a two stroke it compresses on both the up stroke and the down stroke? The easiest way to increase or replace what you take away from the case pressure is to plug the 4 holes in the crankshaft with Teflon plugs machined and pressed into those holes.
Another tip is to spread the crank halves apart a bit so as to increase the side play of the rod. Free float the wrist pin, this all helps the engine to overcome minor alignments at high speed it will reach equilibrium and find it's own center where it wants to make the most power. It also helps cool and lubricate the rod big end bearing.
We did experiment with Baking on graphite to the gear sets to try and reduce friction and even ran with no oil in the gear case at all. But an old friend who worked with OSSA road racing in the old days came up with another solution.
We assembled the gear set in the case with sealed bearings. Then turned it with an electric motor using ATF and casting sand to polish and match the gears. Then they were removed and washed prior to installing back into the race engine.
Here is another old trick we used for break in which some of you old timers may not have herd of.
This one was from my father and his associates.
After the engine is assembled and running, the motor was run an a load bench which at the time was an automatic transmission converter of a home made rig.?
Mix jewelers rough in a small squirt bottle of say 1-2 ounces with the fuel oil mix you are going to run in your engine. While the engine is running with a light load this mix was conservatively sprayed into the intake. With each spray the engine RPM's would come up. This was polishing the bearings and the cylinder walls which increased HSP dramatically and also extended overall engine life under severe usage. They were careful to not go too far as the engine could be literally worn out prematurely. They were so fanatical that if the engine was disassembled and new rings or bearings were installed they would go through the process again.
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sachs175 - 06/27/08 at 2:24pm
Ron,
Thats a good idea , the lapping in of the tranny gears. Dick Obrian had all the factory KR's done that way for RR.
They used an old set of cases and an electric motor.
Stopping before you go too far would be the the only thing to watch for.
For a flat head design those things would fly.
John D.
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Threw-a-Rod - 06/28/08 at 7:50pm
Hi John thanks for the insight on your post. That man is not stable getting that kind of horsepower out of a little motor like that. My kind of man. You were right about Mr Jennings I'm still reading.... However this guy that wants' to run the Bonneville flats is really going to have to push his motor I mean like well his piston is going to meet extreme heat. piston tolerances are going to fluctuate and heat expansion due to wrist pin bosses and structures for piston durability are going to in a sense grow elliptical in shape and that means it's going to get tight in certain areas in the cylinder more than other areas on the piston.
Correct durable alloys in the piston design will help a lot such as silicone or ceramic. I'd look at thinner rings too. Standard rings are for durability however he's flat out and racing so I wouldn't go too thin or they will warp or kick to much in the piston landings. cast rings are no no and modular rings are better but titanium or other better alloy rings are what to look for. d**e rings or better for the shopping list.
His next thing is proper oiling since no oil pump and just relying on a fog of fuel and oil. Just like any motor chamfering the oil hole surfaces will force and spread oil quicker at high speeds. He needs a good oil so it won't flash and burn a film on surfaces and slow or plug up the passages.
Naturally he will need a tremendous oil seal system that won't rupture and cause eternal air coming in nor gases going out if that that fails all fails and that applies to any motor. A good teflon coated seal or better should help. I guess you guys have a warning about not pounding the seal in to far and causing oiling problems?
Of course bullet proof upper and lower rod bearings. custom made out of Toughest material available Titanium or etc. A trip to the shop to shot peen and magnafllux and x-ray to find imperfections on any critical parts. Since this is one cylinder not much to balance really cept side to side proper shimming is critical for movement on the rod and correct line bore in ref. to being true 90 degrees to crank surface. The water cooling is a plus or rather mandatory.
Like I said 2 cycle is new to me but not that new I'm still uneducated in trial and error. My dilemma is this is a system waiting on the piston for a charge of fuel and when that happens it shuts off flow from the carb and backs up the air flow for just 2 cycles. Completely different from 2 cyl 4 cyl 8cyl than I'm used to messing around with. and as you mentioned the reed system is the hands down as far as fuel back pressure from the pumping of the piston. This guy you mentioned of getting that much power out of a dinky little piston is phenomenal. Give me time and I'll catch up on my own or help from tried and true or already done failures. Even if I got to put a Tecumseh Carburetor on it lol....
Me and John had a nice talk through email and I thought I'd share this letter with you that I sent to him.
"Don't want you guys feel left out...."
It's just basics that you all most know about anyway. But I'm seeing now on this board about different types of carburation set ups - the one's that work for them and other types of pumper carbs working for those who tried it. and even Ram Air.
So some getting good results and even the ram air and even the information help with building motors is also helpful to avoid that tried and true already done mistakes.
Someday when I fire my motor I'll drill out the intake to install a vacuum small nipple vacuum port that I can put a rubber cap on it to seal it up again. So I can take my vacuum readings on different hot and cold days and maybe even altitude changes while it's still stock and take my readings before when I start hoping the engine up or rejetting the carb the readings will also reveal any hop ups done to the cylinder such as porting.
I was a firm believer in the vacuum gauge it showed flaws in the other motors such as 2cyl 4cyl and 8cyl valve train problems or even timing on the dist or points or even a bad spark plug or piston ring problems and just by watching the needle and the way it bounces when you jack the throttle it gives a lot of hints on what's going on. I've even timed big motors with vacuum gauges and put the timing light on them and well it was so close I really didn't need to check it with a timing light anyway.
Actually you can mount the gauge on the bike to check it out while your running it. Kind of nice when your jetting and trying to find your power band.... If you got a tachometer then you can make your studies at that rpm.and it will end up showing the best air flow for you application. Tune in later somebody will come up with some wild idea.....
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