The Hodaka Club Forum

Recently rebuilt 99 Toad engine, crankcase air tight, exhaust cleaned, original reed petals. Can obtain a steady, repeatable idle when only opening throttle to about 1/4. When opening throttle larger amount, slightly higher idle, then a lower than original idle.
Could these original reed petals be the problem?

Mike Perrett ( a guy that loves piston port or rotary valve engines)

I know that you know what you meant to say. But I am lost Michael. can you try it again. -------Clarence

Do the reeds lay flat on the "A" frame webs? Or, said another way, are the reed petals warped? What color are the reeds? What thickness?

You didn't mention anything about going through the carb (though I'm pretty confident you did). All jets clear? All passages in the carb clear too?

I too am a bit stumped about the description of what is going on. However, if you are saying that it simply can't be kept running unless you hold at least 1/4 throttle . . . then the pilot jet or pilot circuit passages in the carb are plugged.

Ed

Hi Mike, I guess I'm a bit confused too. Do you have to maintain the throttle cracked to the 1/4 open position to maintain idle and if you close the throttle, will the motor die?

Ok, I have a nice idle, then when I run the engine up to 1/4 engine speed and letting it idle (no throttle action) down, I have a nice constant idle. When running the engine up above 1/2 engine speed and letting it idle (no throttle action), the idle now is faster and eventually goes down a bit lower than the nice idle I had before. My crankcase pressure test did include the reed assembly (had a plug to replace the carb).
Yes I had the carb apart, not much corrosion at all. Jet were clean. Did not have the reed assembly apart. I wonder if these 32 year old reeds do not perform as well as new?
I will remove the reed assembly today and do the measurements, inspection etc .

It sounds like idle would be no throttle just setting there by it's self that every thing is fine. Then if you hold it at 1/4 throttle the rpm is steady but at a half throttle held steady the RPM drops off a little. I think everything just stabilized a little. I think that could be a bit common. Clarence

Is the throttle slide sticking?

Thanks Mike. Could you report the MJ, JN, NJ, PJ, and slide cutaway specs? I'm interested in your situation having recently dealt with M99 carburetor issues - that is until the "guys at the shop" pointed out that I was running a non-OEM carburetor (off a Suzuki RM100). I've had a few bikes that demonstrated the delayed returning to idle you describe. In all three instances, a lean condition was at fault. The causes were air leak at clutch-side seal, a partially obstructed pilot jet, and a similar partial occlusion of the needle jet.

MTrat wrote:Is the throttle slide sticking?

Or the throttle cable? Also, not enough slack in the cable could be the culprit. This seems to be a little too obvious but it's happened to me recently.

Max

Here we go: Ed, the reeds are a green color, they are flat against the cage. No chips. Jetting is MJ 170, NJ O2, needle 5EJ13 middle notch, slide 2.5, pilot 50.
A note here, while attending to the idle situation, a test run of the bike revealed a 1/4 throttle rich condition. I replaced the 1.5 slide with a 2.5, which cleaned up the 1/4 throttle condition.
Matt, I am aware of a lean idle condition that will imitate a air leak or a improper pilot jet/air screw adjustment.
Again, is there anyone that was plagued with old reeds causing carburetor problems?
The Toad runs quite nicely other than the idle situation.
I hate a bike that will not idle properly.

A 50 pilot jet seems pretty big. You might be trying to compensate for a rich pilot through the air screw and slide cutaway, and possibly needle position; that would allow it to run right below 1/4 throttle, but might be contributing to a lean condition at slightly above 1/4 throttle. How many turns out is the air screw? If it's 2 turns or more it could mean that the pilot is too big. Just a thought. I know what you mean about hating a bike that won't idle properly.

Reeds are flat and not chipped/frayed . . . so no, I don't think the reeds are a part of the problem.

Air leak has been eliminated as a contributing cause of slow return to stable idle.

That pretty much leaves carb condition, jetting and cable or sticky slide possibilities.

Drop that pilot to a 30 and readjust. Sounds sort of like what my Wombat was doing with a 40 pilot last year. Went back to a 30 pilot and if ran better!

The 40 pilot in mine started without opening the choke, but as it warmed up it would flood and stall the bike. Yours sounds like it runs cold on the 50 and then gets too lean attempting to compensate for the extra fuel at idle. I bet your air jet is way open. Shouldn't be more than a turn & 1/2 from fully closed. D Victor

On my first inspection of the jets last week, I forgot to record the pilot jet. Now looking at the #50 jet and seeing that specs call for a 40 or 30, I will try a 40 first then a 30. I will probably be reinstalling the 1.5 slide before this is all over.
Forgot to mention, I did lube the throttle cable over the winter.

To answer the question you asked - could the idle phenomenon be attributed to the reeds - no. I don't see how the reeds, regardless of age alone, could affect the tendency to idle differently depending on what throttle position you were at when you let go of the throttle, and I assume from what you write that this is what you mean. That if you release the throttle from a quarter throttle steady state position your idle is normal, but when you release the throttle from a half throttle steady state position, it hangs at high idle for a bit, then drops to a somewhat lower than normal idle speed. If I have paraphrased you correctly, you are describing a jetting issue, not a reed valve issue. My guess is that you are too lean at mid throttle, and would think that the 2.5 slide isn't right, or the needle is not right, or both.

Start by resetting all carb specs to stock and go from there. Once you start mixing jets and needles and slides, you are on your own as to the result. Not that you can't do these things successfully. You can. But the results ultimately depend on your tuning skills, not on the bike. There is a reason Hodaka engineers long ago settled on the jetting they did, and a stock Road Toad is really quite an impressive 100cc engine. The situation you describe more usually occurs when dropping from a prolonged full throttle run to dead idle position but the engine continues to idle very high, only dropping off gradually if at all. This is a lean carb, and i believe there is a 70's era tech note, probably from Harry Taylor, on Paul's website about this under tuning notes. It has happened to me in motocross when I ran full bore rather than shift up from third to fourth to outrun someone to the finish line. From 10,000 plus for ten seconds to dead idle, the engine would not idle down even though it otherwise had a normal idle. I used the kill button to bring down the revs, and it idled fine once I got the revs down. This is simply a tuning issue. I do not believe the reeds have anything to do with it.

I found out the problem. I will have to write up an article for the Resonator concerning this. Here is a preview of one of the steps in the solution. Remove all the jets, the needle, slide, floats and needle and seat from the Toad carb. Use as much of your strength as possible and throw that carb down through the woods as far as possible. If you do it correctly, it will land near the early 03 Wombat carb you placed there.
Mike Perrett

Uh-oh. Did I get a whiff of "manufacturing defect" just before I heard something crash into the woods?

Ed
PS: I have a Mikuni carb from back in the day which is missing the small (teensy) angled hole which is part of the final fuel delivery system for the pilot circuit. I have been puzzling (off and on) for ten plus years over the best/most fun way to address the fault. 1) Attempt to drill a teensy (reeeealllly teensy), angled hole, deep within the carb throat, with precise placement and with precise depth control . . . or 2) follow Mike's recommendation above.

My experience with older Bing carbs on BMW motorcycles (slide valve, idle air adjustment, like our Mikunis) is that the "high idle" situation is from poor idle adj procedures. Warm the bike up with a ten mile ride, balance the airflow through the twin carbs, adjust the idle air screw, back and forth. FWIW.

They do make nifty pencil holders. Reuse/repurpose, you tree huggers out there. Then again, returning it to the earth from whence it came has a certain satisfaction index as well.

Correction on my post, I meant early model 94 carb, the one that should be already down in the woods.

Mike Perrett

Oh. Well then . . . yes, it has long been recommended to use that particular carb as a paper weight or pencil holder.
Ed

I was channeling your Resonator article, Captain.

Ommm.
Or rather, Ommm-dap-dap.
Ommm-dap-dap-dap...