Just finished 99cc build! But... some issues

Hello,
I just finished my 99cc predator build using the agk jackshaft and maxtorque clutch along with manic mechanics sprocket adapter. The power is amazing! Such an improvement over the 2 stroke engines. With that said, I have a couple concerns/questions:

-Is it normal for the bike to vibrate a lot until the clutch fully seats? For example, when i sit on the bike and give it throttle, the clutch starts to engage and up until about 10 mph it is vibrating quite heavily (everything on the bike is shaking madly). There seams to be a magic zone where after I go over 10 mph, all vibrations go away and it is a very smooth ride.

-Also, the manic mechanic adapter seems to be slipping on the hub. After I cranked it down and took the bike for a spin, I noticed that the little arms that hold the sprocket onto the adapter are right up against the spokes. When I setup the adapter, the arms were right in the middle of either side of the spokes, not touching either.

If anyone has insight/advice for these issues please let me know!

Thanks

wayne z said:

Make sure that your engine mounts are real tight, and the valve cover isn't too close to the seat tube. This caused mine to vibrate badly. Might consider adding a top, front engine mount to the downtube as I did.

I would try some strips of abrasive sanding screen in the sprocket adaptor. This works great in the chain idler clamp to keep it from moving too.

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Engine mounts are tight and there is clearance between the valve cover and seat tube. What causes the bike to vibrate so badly at low speeds? Is the clutch engaging and disengaging very rapidly, creating a hammer effect on the rear tire?

Also, what is sanding screen? Is this the same thing as sandpaper or emory cloth? I have emory and sandpaper at home, but not sanding screen...

wayne z said:

Does it vibrate in that range if you hold the rear tire off the ground? Try it also without the primary chain, to see if it is, or isn't, coming from the engine. Some clutches do chatter some, they seem to do better taking off hard with a lot of throttle than trying to take off easy. Also grease or oil in the clutch could cause chatter.

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Ok, I ran some tests, and I found that it does not vibrate (well, it vibrates but it is the normal vibration expected of an engine) when either the main chain is disconnected, or when the back tire is off the ground.

My rear sprocket is a 48 tooth. I dont rememmber what the ratio was, but I think it was something like 10.9:1.

wayne z said:

That's a good ratio, little on the low side for that motor, good for easy takeoffs.
Watch the drive chain to see if it is whipping hard when it's vibrating.
If the chain is too tight could also cause those vibes.
Is your sprocket very secure to the adaptor?
Do you have a rear fender or chainguard that's sorta loose?
Are the wheel bearings adjusted right?
Is the gas tank securely mounted with rubber tape or something in between the frame and tank?
Rubber in the engine mount has caused vibes for some.

Sometimes strange harmonic vibes come from strange places or things. Wouldn't hurt to try a top front engine mount to see what effect that has.

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Well, I just ran through your list of things to do, and did all of them except the front mount. I am happy to say, that something really helped the issue, and the vibration is a lot better now. Not too annoying when going slow, but definitely still smoother when up to speed.

Maybe as the clutch wears in, the vibes will go away even more...