Case Reed 125 Hodaka Project

[thirdstone]

Thanks
The first run was good , the engine has a nice strong midrange and pulls all the way to max RPM but does hit a wall where it drops off .I would like a bit more over rev , this could be the pipe though. I did start the day with the very top end extended full throttle front straightaway almost cutting out unless I rolled off the throttle a bit to get back on the needle jet whereby it would pick up again. I changed from a 400 main jet to a 410 and it got a lot better but not completely gone. I didnt have any larger jets but that is the direction I should go. However I think the 30mm carby experiment was a failure on this high speed track . I’ll go back to 34mm , I just feel there is more top end advantage in that and in my experience the bottom end isn’t too bad with a 34.
The bike handling was a nice surprise, better than my race bike . Foot peg handle bar positioning is much better than a stock Wombat and the front end really stable and predictable. I would like to take out the seat mid dip to raise it a bit as well as a few other minor things.
One bad thing happened was that in the middle of the second day it nipped up , I’m pretty sure this was a case of not running it in enough. The worlds of my engineering shop ringing in my head “ run it in a while , it’s a tight bore” . I’ve pulled the cylinder off and no bandage except a bit of aluminium piston smeared on the skirt that came off quickly with some hydrochloric acid. All in all I’m happy with the first run , the porting design works at least. Now the tweaking starts .

[matt glascock]

Third, I ran into the same issue with my pumped up M94 Wombat in terms of searching for overrev. The port mods on mine are moderate compared you yours, but my guess is if you are getting noticeable overrev, you are probably getting pretty close to maximal output. Its not a thumper. I'm happy the port mapping is working well. I have leveled and raised the seats on all my Hodaka race bikes so that they are essentially flush with the back edge of the tank and board flat. It really facilitates fore/aft movement on the seat. The stock saddle design seems to want to keep you in the "sweet spot" down in the dip - not the place to be when you are trying to stuff the bike into a corner. It also reduces the need for a "fruit and veggies" search patrol after the singular - make that dual - thrill of running the boys into the back edge of the tank. Ouch. When you get time, it would be sweet if you could fire up the GoPro on a few hot laps. I'd like to hear that bike on the pipe. Its hard going through the heat cycling process in lieu of dropping the hammer, isn't it? Been there.

[thirdstone]

The go Pro thing - my stupid racing association has banned helmet mounted Recording things , in fact anything mounted on your helmet. It’s okay for the AMAand FIM but oh no not in Australia. I have a Go Pro and used to use it helmet mounted but not anymore.
The bike is all stripped down now until next year However I might put the engine in the race bike later in the year. Actually it would then be using a different pipe and 34 mm carby. My race bike is of course heavily modded , even down to different gear ratios but it’s standard configuration reed valve induction.

[matt glascock]

That blows! I've seen some folks mount a GoPro on their roost guard. Might give it a shot before they get around to banning that too.

[Bullfrog]

Here are three alternatives for GoPro mounts.
1) There is a GoPro chest harness. I've shot some video with one. Camera bounces more than helmet mount, but the point of view is pretty interesting.
2) Just today in a scuba dive shop, I saw a "bite mount". It uses what is essentially a mouth-piece from a snorkel with the GoPro mounted to it. This would only work with an open face helmet. I'm probably gonna try this idea out on trails. Will also use a "safety lanyard" - so I can spit the mount and camera away and the lanyard will tether it all to me.
3) There are GoPro mounts for mounting to handle bars or frame tubes - there might be some possibilities in that way. I've thought before about a frame mount just out to one side or the other from the frame down tubes a bit below the steering head.
Ennnneywayeeee - a couple of thoughts.
Ed

[MTrat]

I have tried and would avoid the handlebar mount. Too much vibration caused the mount to break. When I found the GoPro it had some (un)interesting footage of trailside vegetation.

[thirdstone]

Back to more development. The first outing was promising but hampered by a surprisingly very lean main jet ,400 . Might be other things going on with the angle of the carby so I decided to bury the main jet deeper in fuel using the deep nut and main jet extender that Mikuni sell. At least next time I won’t be wondering.
I ended the day with a 4 point piston seize so not good. Another thing was the ART piston ring locator pin tried to come out . Admittedly it was repositioned . Back to the YZ or MX piston as it’s pin is in a good position. It’s not always going to go to plan .

[thirdstone]

An added benefit to this design that I’ve just noticed is the the big end bearing gets lots of love.

[thirdstone]

I can report that the clutch gear mod worked , as in the clutch works . Weather it’s going to stop gear breakage only time will tell. To note the first gear strengthening didn’t get a run as I worked out there was no room for the clutch to travel when the lever was pulled in. I worked that out prior to fitting. This is just a steel washer press fit over a turned down gear, also using bearing retainer locktite. There are 4 weld spots to take up the space between the gears so that the washer can’t come off the press fit.

[thirdstone]

Here is a picture showing the welded cases allowing larger transfer tunnels with out breaking through. Never a good thing .

[thirdstone]

I’ve had a rethink in the reed valve. I’ve gone for a Yamaha RD 250 reed block . Essentially a 125 cylinder as the RD 250 is a twin.
Let’s see how this goes !

[Joe Ormonde]

Check out the Design of the FMF Ram Valve. Time to play with Reeds! Impressive project! Joe.

[thirdstone]

Thanks Joe, I had a look at the FMF reed valve. From What I can make out its not much different to the Boyesen reeds.. I made a big effort to keep the internal volume down with stuffing but apart from that its pretty standard gear. I thought of adding a vane to separate the bottom and top reeds but in the end I didn't go down that path.

[thirdstone]

A bit of an update after quite some time off .
It’s all together now ready to fin in the frame .
I just want to get it to the point of running , you know how it is !

[matt glascock]

Great to see the project back on the rack Kev. I will live vicariously through yours. My 94 motor detonated - not in the overheated cylinder sense but more in the "what happens if you explode a hand grenade inside the motor" sense. Clutch gear shattered, main shaft bent, 3rd and 4th gears reduced to shrapnel. Too bad, but I was writing checks the motor could no longer cash.

[viclioce]

Bummer Matt. Tuesday I’m going up to Paul Schwarting’s place to pick up all the remaining Hodaka parts he has left. Maybe I’ll bring something back that can rescue your 94? Don’t know what the entire list is yet, but maybe. I’ll let you know! Victor

[matt glascock]

Thank you, Victor. Unfortunately, the motor is totally destroyed. A lot of dirty work took place inside the motor when everything flew apart. I did get the measurements of the port mapping if I decide to build one again someday... So many projects, so little time!

[thirdstone]

Oh Matt that’s a bummer, certainly sounds like game over! That’s the risk we take though isn’t it. Might happen here as well and a couple of grand goes up in smoke and countless hours as well. However when you make your own little works project the journey is half the fun. There are plenty of examples of factory failures out there all the way to F1 , it’s just the budget that is different.

[matt glascock]

Indeed, Kevin. Its an accepted part of the tradition of squeezing the last few ponies out of a motor. I suppose, in a sense, its a testament to the quality of the stock Hodaka motor in that it spent most of its life operating 30-40% above its design envelope. That's pretty good. Looking forward to following your project. I've been eyeballing the spare 125cc cases out in the shed with interest. The frame is now a play bike with a stock M94 motor back in the saddle, but as you know, that will likely change.

[thirdstone]

Big step achieved today . Up and running !
I still have the fuel tank to re spray but apart from that it’s fit the forks and wheels .

[swcaudill]

Mr. Thirdstone,
When you do the sleeve replacement, how much interference between the cylinder and sleeve? I am doing a 03 Wombat sleeve that requires turning ID and OD. I'm thinking .002 .003". Appreciate your input,
Sterling

[thirdstone]

Hi mate
Sorry I don’t know. My machine shop did it for me. I just gave all the parts to them and said I want this to fit in there.

[michael_perrett]

Yes, that would be interesting to know the interference fit between the liner and cylinder.

Mike

[Bullfrog]

I am sooooo waiting in anticipation for reports on how the clutch spur gear modification works. I had done some brainstorming on ways to aid reliability of that part in those stratospheric horsepower engines you guys are building . . . and the light bulb didn't come on for me with your concept. Looks like a worthy modification to test! I am sooooo . . . waiting . . .
Ed

[thirdstone]

Hi Ed that is easy to report on , it works . I have it in my other race engine. When I say it works I mean the clutch still works , I can’t say it stops cracking rotor gear until it cracks and then I can say I doesn’t, if that makes sense.
The only thing to watch out for is making it too wide as the clutch moves towards it when you pull the lever .