Rough acceleration

[SuperRat2110]

Hey guys, so things went pretty smooth rebuilding the squirt but I have some issues with 1st and 2nd gear acceleration. There is a subtle stutter most of the time when opening the throttle up that I dont get in 3rd, 4th or fifth. The bike starts great and idles fine. Wondering if I have a jetting issue? I've got the carb float set and seems to be where it needs to be. I've cleaned the carb multiple times too. Where should I start? Here is a video.. you can kind of hear it a couple times. Ignore the tall goofy guy on the bike. https://youtu.be/HmccUKc5U0o

[Bullfrog]

See the photo and do the same thing on your throttle grip. Here's why. Jetting adjustments in the Mikuni carburetor result in changes at specific throttle positions - without regard for which gear you are in, or even engine RPM. So it is VERY important to know what throttle setting matches up with the "problem" in the way the engine runs.

I'm pretty sure about what you are going to find . . . but you should do the testing so we will know for sure. Do the same sort of test runs as you did in the video, but note the throttle position when the problem is evident . . . and the throttle position when the problem goes away. I'll wait to hear the results of your testing.

Ed

[SuperRat2110]

Thanks Ed, I'll do that tomorrow. Is that 1/8 inch increments?

[Bullfrog]

Nope, 1/8th turns of throttle increments.
Ed

[SuperRat2110]

Is that a trick answer? How do you mark your tape? Every 8th of an inch?

[Bullfrog]

Just after I clicked on "Submit" . . . I thought to myself, "I should probably have provided just a bit more information." Sorry 'bout that.

So . . . put the large piece of tape on the throttle housing and cut a fancy-dancy little pointer out of tape and stick it on the grip so it points to a place near the front of the big piece of tape on the housing.

Then wiggle the throttle around a bit to find the spot where the throttle cable freeplay has just been taken up. Hold the grip in that position and put your ZERO throttle mark on the big piece of tape.

Then twist in full throttle and mark the big piece of tape for FULL throttle.

Then find the spot which is 1/2 of the distance between ZERO and FULL throttle - mark it "1/2".

By splitting the difference you can pretty darned accurately mark "1/4" and "3/4" throttle. I like to mark "1/8" throttle too - and I recommend that you do too. A bit of precision on knowing throttle position can be especially useful for jetting situations involving the pilot circuit and slide (throttle valve cut-away in technical parlance).

Does that help?
Ed

[SuperRat2110]

Ed, that makes perfect sense. If I would of been thinking more forth dimensionally I would of figured it out but I have a real problem with that. Thanks for explaining.

[Joe Ormonde]

Check the Needle and make sure it`s a 4F6. I found that the VM 20 carb is super sensitive when it comes to the clip position on the needle. In third, fourth and fifth, the engine is under a load and runs clean I can bet moving the clip to #2 or #1 position will clean things up. It cleaned up my model 96 Dirt Squirt and it was acting the same way you described. Couldn`t see the video. I assume your Hodaka is a Model 96.Joe

[matt glascock]

It's an 01, Joe. Totally different induction, carb, reeds, oil injection and such. I think those had a VM26.

[SuperRat2110]

Ed, after replicating your test, I've found that my choppy acceleration seems to occur between 1/4 and half throttle. Usually evening out right before or around half but it definitely begins at 1/4.

[Joe Ormonde]

Move the Needle clip one step leaner and see what happens. Also, check if the needle is the correct one. Sounds like you`re real close now! Joe

[Bullfrog]

See the attached diagram which was created in discussions with Hodaka (and Mikuni) tuning guru Harry Taylor a few years ago.

With this diagram, you can see that Joe's recommendation for raising the clip (dropping the needle) may well have an effect on jetting at 1/4 throttle - but it also has significant effects up to 3/4 throttle. And since "dropping the needle" is going leaner on fuel/air mixture, do so cautiously.

You may also notice that is the "SL" (short hand for "slide") which has dominance in the 1/4 throttle range. Checking a change is somewhat more difficult there since most folks don't have an inventory of slides on the shelf. However, I'll check my stock to see if I can come up with a loaner (may take a while . . . Hodaka Days is coming up soon )

Ed

[Joe Ormonde]

It`s so easy to get lost when dialing something in. The first thing I do is to make sure that the parts in the carb are correct . The Schematics show how things came from the factory: start there. Quite often the carb is blamed when it`s something else. An air bleed passage quite often is partially blocked and can make dialing things in tough. Then, that passage clears out and you have to start all over! As Bullfrog posted BE CAREFUL! That`s why I advised ONE STEP and see what happens. Remember: A Task Slowly Done Is Surely Done! Joe.

[SuperRat2110]

Hey guys, thanks for the great advice. After a long weekend of watching my son's baseball team struggle it was good to have something go right...lol. Ran the bike tonight with needle clip on the 3rd slot...was in the 4th the bike had zero stutter. Pretty proud of it. But thanks again!

[SuperRat2110]

Here is photo of spark plug....I know color doesn't mean everything but this is what it looks like. Normal?

[viclioce]

Looks honey gold to me. Maybe a tiny bit lean? But then, it’s a photo and not an eyeball look! Victor