Back to reed valve jetting on a Super Rat

[viclioce]

Is there anyone here who is running a reeded Super Rat and can tell me what main jet they are using?

I know the theory about starting big & working down. I’m just not sure how big. Even Hodaka Dave told me “Try a 300 and then drop about 50 on the main jet. And this motor is tight from a new bore. So it doesn’t spin a lot yet.

I’m at 270 now, with a 30 pilot, have spark, but I’m not getting the bike to fire up. I notice the 98 Super Rat uses a 60 pilot jet. Am I using too small a pilot jet? Still using my 24mm Super Rat carb as well.

So, I’m open to a suggestion or two.... Where are you jetted with your reeded Super Rat? Maybe you can get me closer??? Victor

[olddogs]

I have test started engines without a carb by just squirting some carb cleaner into the intake manifold. Incorrect jetting should not keep it from at least firing. A new bore should not drag on the rotation of the engine during kick starting. Does it spin normal without a plug? A clutch side seal seal not seated deep enough can cause a drag on the crank. A mag side seal set to deep can also cause drag, Just some ideas to think about.

[viclioce]

OK. Yes it spins more freely with the plug out. I get maybe 3 rotations with the plug in place.

I had a lot of issues trying to start my reeded CW motor with a 30mm carb on it. The minute I changed to a 26mm carb for an 03 Wombat I had a lot less issues & it started easily. I’m just wondering if even 270 is way too big a main. This is why I was asking where other folks are with their main jet. It also speaks to my question about the pilot jet. Victor

[matt glascock]

320 to 360 MJ depending on conditions.

[viclioce]

Matt. Which pilot jet? Thx! Victor

[Bullfrog]

The main jet is utterly unimportant in getting the engine to start.

Let's go with the basics. (Starting with the assumptions that you KNOW you have properly timed spark, good compression and fresh fuel)

1. Fuel ON.
2. Starting circuit activated ("Choke" ON)
3. Remove right hand from throttle grip. Why? Activating the throttle at the same time as the kick de-activates the starter circuit exactly when you need it the most.
4. Kick start. (if it fires, go ahead and get that hand back on the throttle grip )

A properly operating starter circuit ("choke") provides rich mixture for cold starts. Main jet size matters not. Pilot jet size only enters into the picture AFTER the cold start (or during hot starts without "choke"). You'll be able to start "dialing in" on the proper pilot jet as soon as you get 'er fired up. Recommended reading - pilot jet and pilot air screw tuning procedures as described in the Official Hodaka Workshop Manual (and elsewhere). NOTE: "Tune" pilot jet/pilot air screw FIRST . . . then shift focus to other throttle positions and carb components (slide, needle, main jet).

Ed

[viclioce]

All known information, Ed. What’s not known is the questions I asked. I also mentioned that I looked up the 98 Super Rat, which is reeded, and that it has twice the pilot jet. A 60 vs. a 30 pilot jet.

So my original question again, because there isn’t “published information” on jetting for a reeded Model 93 Super Rat, is, do I use the stock 30 pilot jet or do I use closer to a 60 pilot jet like on the 98 Rat, with the 24mm carb?

As I recall, the manual does specify setting the pilot jet first, along with the air screw. My problem again is, there is nothing published, as a starting point, for a reeded 93 Super Rat, at least none I can find in the usual resources.

I’m trying to “bank on the experience of others,” to avoid multiple carb disassembles to avoid determining blindly which jets to use. Surely there are 1 or more folks here who have successfully reeded a 93 Rat, with the 24mm stock carb, and can advise me where they ended up?

That’s what I’m after. Hopefully, someone who’s reeded a 93 Super Rat with a stock 24mm carb, can share their jetting info with me. Victor

[ossa95d]

Vic, I am convinced as others have suggested, that your starting issues are totally separate from jetting concerns. If there are no air leaks, and the needle valve and float are working correctly, and there are no obstructions to fuel flow, it should start on the enrichening circuit (choke) regardless of the jetting. If it doesn't start there may some other issue. After it starts it will become readily apparent if the jetting is close or not. Since nobody has chimed in with a good starting spot with jetting, you may have to work through that. However with the smaller 24mm carb jetting will not be as finicky as would be with a larger carb.

[taber hodaka]

Victor did you read page 102 of the ace 90 carburetor tuning page? There are many factors that affect carb tuning air cleaner and many other factors. No perfect answers here. The slide cutaway is a factor. Learn and study and you can help others tune their carburetors. some other PABATCO employees wrote some great articles on tuning, Harry was just a master at it. _____________ Clarence

[Bullfrog]

The specific answer you are searching for would be nice, but is not needed to proceed. Various "experts" have offered guidance.

NOTE: Pilot jet spec from a 28mm carb on another model of 100cc Hodie is NOT a reliable indicator of what might be needed for a 24mm carb on your bike. There are MANY details in addition to carb size which are not a match between the two models which have an effect on final jet selections.

Ed

[olddogs]

2 statements in your first post still puzzle me and need priority. Not enough rotation with kick starter and no pop, bang or fire. Tried and true method of a squirt of gas in the plug hole and push starting in second gear may get you going. Once running jetting needs can be worked out.

[Stever]

Hi Victor,
I have lots of experience with reeded model 93 Rats and the later 98 Rat, but back in the day. I even built a reeded 93 ported it myself per the Pabatco instructions, with a 30mm Amal that took a while to get jetted just right, but eventually ran beautifully. Interestingly, my model 98 required no jetting change after switching from the stock down pipe to a snail pipe for Hare Scrambles. I'll echo that the two models were very different, not just in carburetion but in exhaust, air box, and very significantly different ignition.

And a couple of thoughts that I have often ignored to my own frustration, it might help as you work toward the perfect pilot settings.

-make and evaluate only one jetting change at a time (do as I say, not as I do!)

-Cleanliness is next to Godliness in the starting/pilot circuits, it takes almost nothing to block such tiny passages.

-Stever

[viclioce]

Old dogs, I’ll give that a go. The carb has been meticulously cleaned & rebuilt. The only thing different than the OEM configuration is the 270 main jet. I was suggested I start at a 300 main & work my way down.

The no spark issue was worked out. It was brand new heavily coated points. Cleaning the points got me spark. She now has spark, fuel & air, and the choke circuit is clean & functional best I can tell.

To those who think I’m not listening to recommendations which are less than specific, own it up to owning other brands of motorcycles and being able to go to a forum for other bikes, and asking a question and getting specific, defined instructions for something like jetting. I’m not at all used to this try something, see if it works, then try something else type of guidance.

I thought a forum’s greatest benefit was being able to learn from others trial & error mistakes & training. Is that something which doesn’t apply to 2 strokes? I know I have done a bit of trial and error things with these 10 or so Hodakas I have restored.

It just seems to me that there should be folks who can say something more definitive, like, “When setting up a Super Rat with reeding for the first time, stick with “X” pilot jet, try “Y” main jet and “Z” turns on the air screw, as a starting point.”

Yes, there may be differences maybe a mild change or two in the main jet, but there sure seems like there should be some kind of standardization.” At least that’s what I’m used to.

Are there no service bulletins from the past on converting a Super Rat from standard config to a reeded config? If there are, I haven’t been able to find them. But there is no evidence of that kind of information coming forward here.

Surely, some of you who were dealers did this kind of configuring for customers of the time? I would hope that it isn’t a completely forgotten thing.

Why is it anyone can go to Terry’s library and look up the std specs for, say, jetting on a VM24 carb for a Super Rat, but you can’t find a bulletin on a standardization for when you decide to convert the same unit to reed valve? It’s not like it was something which wasn’t and still isn’t done. This is what I find frustrating. Not “pointing at anyone” or inferring anything other than why can’t I find information to rule out that the configuration of the carb is close or too far out and something else is causing the start issues..... Bictor

Victor

[Stever]

Pabatco published a beautiful service bulletin for installing a reed, with exact details for porting the cylinder and placing holes in the piston skirt. My local dealer gave me a copy, and I followed it to the letter. But, I don't recall if it included jetting recommendations. Anyway, back then it was very common, almost to the point of being of standard operating procedure, to bolt on a bigger carb. One of the Pabatco bulletins I had, but I don't recall on which subject, even had instructions for using an Amal monobloc carb.

For all of the aggravation and idiot mistakes I made, I would not change how it was back then, I learned so much, though often painfully. I'm even glad there was no internet in the 1970s. I feel that it can become kind of a fine line between trying to help and sounding preachy, so sorry for that. I know everyone here is trying to help each other.

-Stever

[MTrat]

I reeded & ported numerous 93 SRs following the REED CAREFULLY pamphlet from PABATCO and never found it necessary to change the pilot jet of the stock carb, only the main jet.

[olddogs]

A lot of the guys trying to help are former dealers or Hodaka mechanics who are working from memory. Many of us are in our late 60s or 70s. I worked at a Hodaka dealership from 1971 to 1973. Those days are far from clear. We sold tons of reed kits, but this was seat of the pants racing with no internet, texting or online sharing. Sometimes we would recommend jetting changes and were then blamed if something seized. Guys would expect replacement pistons and cylinders for free. None of us expected 50 years later anybody would care about this stuff. Part of the problem is the dozens of engine combinations you can come up with. Not so with the other big 4 bikes of this era.

[viclioce]

Well, like I said, there was no offense intended. It just strikes me as funny that there’s no documentation for jetting with reeds, yet there’s a full set of porting instructions for the cylinder conversion.

Kind of says “Be this precise & careful when porting, but jetting...heh! You’re on your own buddy!” LMAO!!! Victor

[Stever]

OK my friend, maybe I have found what you are looking for. Bear in mind that I posted earlier, regarding the Pabatco reed installation instructions, "I don't recall if it included jetting recommendations". I kind of figured it did, but my copy was long gone years ago. I looked a bit online and found that someone just sold a copy on ebay. I lifted one of the photos, and it does indeed have starting point jetting recommendation for the stock 24mm carb. If the attachment worked, see photo, carb ref circled in red. Only the main jet is changed, all else is standard.

Bottom line, the bike should crank with standard jetting. Forgive me if I offend, but since it doesn't, and given the recent work in the ignition, if it were me and my bike I would double check that the timing is still correct. Good luck.

-Stever

[taber hodaka]

I try to not treat people like they don't know anything. But if someone wanted a specific answer it would be like this. When starting up a super rat with a reed valve installed. For the first start up I would begin with a 30 pilot jet, 1&1/4 turns on the air screw and a 300 main jet but this is only the starting point, A motocross bike requires specific tuning, For a person just out fun riding things can be a little different like size of sprocket. terrain, weight of the rider and the speed one would generally be going, would be the critical rpm where the jetting should be spot on. There was a old saying keep it on the pipe. (in the power band) otherwise you would be lugging the motor and probably overheating it. Building a motor is a mechanical process, fine tuning is a science tu------ Clarence

[matt glascock]

Standard jetting otherwise, Victor. The only exception is occasionally raising the needle one notch. This is race bike tuning for high revs all the time. It would be totally wrong for light trailing.

[taber hodaka]

Good point Matt. Also there are many variables to porting you can port for high end or low end. endless factors, it is not 2+3=5. We did some wild porting on ace 90's the bom speck porting was so wild there was tittle performance untill you hit the high RPM, then you were in wheelie mode and had to back off. Every change we made required jetting changes. Recommendations are the same, we are trying to not just talk the talk but also help others walk the walk, so hope you understand. ---------------- Clarence

[taber hodaka]

Victor I found a really good article (SPECIFICS ON MIKUNI CARBURETORS) by Leon Wilbanks
The article is in the RESONATOR dated July 1970 Volume 4 number6 it is a good read covers everything we have all tried to tell you. It is about a full page and a half. Excellent read could we put it in the next resonator?? I will print the first paragraph here "Many variables can effect carburetion--- temperature, humidity, altitude, rider weight, terrain, etc.because of this it is impossible to set a carburetor (and especially a racing engine carburetor) at the factory. It is therefor a must for any mechanic to be very familiar with the specifics involved in carburetor adjustment."-------------- Clarence

[taber hodaka]

Victor A wet fouled plug will not fire. If the plug isn't wet and you primed it a little it should run, if you have compression and spark at the correct time. I would put a timing light on it. Is the ignition primary coil located in the right spot my super rat manual 1971 on page 26B shows it on the right side and page 27B shows it on the left side. The old timing lights did not use a battery. Hope you have ir running already. ---------------- Clarence

[viclioce]

Alas Clarence, I do not have a timing light. Would like to have one. How do you make one for a 2 stroke & how do you use it. I’ve been very good, up until now, at gapping points with my small feeler gauge at .013.

I was finally getting spark after cleaning the points, but don’t seem to be getting any fire.
in the motor. Plug hasn’t found yet I’m going to check it now to see if it’s wet from kicking it over.

The carb was missing the needle jet O-ring, but I was able to obtain a couple of replacements this morning, and install one. Still no luck. Victor

[Tether]

Victor,
A regular timing light works just fine on a two stroke. Mine requires 12v so I just connect to a jump battery. Buzz box or ohm meter is even easier. I have tested with a light after setting with the buzz box and it has always been spot on.