Chopper Vibrations

[kdaddy1980]

I just got my schwinn stingray chopper project done. it took a while to get used to it. very different than a cruiser or mountain bike. ive got a 66cc, with fancy tailpipe that shoots out the back im using a two wheel tensioner system for the chain, its a larger chain i think 410, not the real big 415..i built a 26 inch wheel for the front, to make the bike look bigger and add a little pedal clearance. its got craploads of torque, but suffers at topspeed. it will manhandle a steep hill faster than a cruiser .. i havent clocked it with a speedo yet but i plan to. it feels like it tops out around 20mph or so, but at wide open throttle i get these huge vibrations that shakes the whole bike and my poor arms lol it really kicked up my carpal tunnel syndrome from reving it up like that today. i know that it still has to be properly broken in and everything, but i wonder what i can do to calm these vibrations down, more rubber? maybe if i get the vibrations down i can add a couple more mph's to the top speed. anyone have a chopper that vibrated you half to death at w.o.t.? what did you do about it?

 

[2door]

If you have rubber in your engine mounts now, that's what is causing some of your problems. You should mount the engine as solidly to the frame as possible. No resilient material should go beteen the frame and engine.

Can you post a photo of your bike showing how you have the engine mounted? That would help us offer some advice on how to eliminate at least some of your vibe problems.

Tom

 

[maniac57]

Switch to a smaller rear sprocket to reduce revs and vibrations.
When I switched from a 44 to a 36 on The Pig II, it made a HUGE difference in comfort.

 

[kdaddy1980]

 

[kdaddy1980]

 

[kdaddy1980]

theres just a small less than a 1/8 inch thick piece of rubber under the bracket and the front bolt has a clear plastic tube around it to keep from scratching the frame. could this be causing all that vibration? i would like to get a smaller sprocket but would it be harder to start?

 

[fatdaddy]

get rid of ALL the rubber. It does NOT help with vibration. In fact, it will increse vibration by letting th engine move. most engine vibration is caused by a loose or WRONG installation. rubber is wrong. SOLID is the best way to go. I tried rubber mounting when I was a newbie. almost ten years of experience has shown that I was Wrong about rubber mounting. IT just makes it worse. I've also built about 10 of the OCC choppers and even one Jesse James chopper, They all ran 30-35mph with very little vibration.
fatdaddy.
IT'S YOUR BIKE, BUILD IT YOUR WAY.

 

[2door]

Look at it this way: an 1/8th inch of rubber is an 1/8th inch of potential movement (room for vibration) in the mounts. It is not possible to eliminate the inherent vibrations produced by a single cylinder 2 stroke engine. Due to crankshaft balancing differences some will vibrate less, or more than others but they all vibrate.

Trying to isolate those vibrations by rubber mounting only transfers the vibrations to the engine mounts and fasteners. Failure of one or both is inevitable and you'll feel more vibrations through the frame.

If you're only interested in protecting the paint you might try wrapping a layer of vinyl electrical tape around the frame tube where the mount attaches but eventually, if there is any looseness in the mount, it will wear and the paint will suffer anyway. If the mount remains tight there is no movement and the tape will last. No movement means no chafing/rubbing/wear.

Tom

 

[kdaddy1980]

@ fatdaddy im gonna take your advice, on your choppers, what kind of a sprocket did you have on the rear ,of the ones that did 30? this thing is really awkward to pedal until you get the motor going, does a smaller, say 36 tooth make it even more difficult to start?@ 2Door im not really worried about the paint if it doesnt move you wont see any scratches. im going to pull that rubber piece out of the bottom and the clear tube from the front u bolt..i can get the same color paint and touch it up which i need to do in some spots anyways.thanks guys for all your help. ill let you know how it does without the rubber.

 

[maniac57]

The smaller sprocket made starting slightly easier due to the motor spinning faster at normal pedal speed.
Try it, you won't regret going smaller. (unless you live in a very hilly town)

 

[kdaddy1980]

The smaller sprocket made starting slightly easier due to the motor spinning faster at normal pedal speed.
Try it, you won't regret going smaller. (unless you live in a very hilly town)

actually I DO live in a very hilly town, the way the chopper is set up though it climbs these hills like a beast..will the smaller sprocket have a big impact on hill climbing? i could imagine it would cut the torque down a little but i would still think should still climb better than a cruiser with a 26 in back wheel

 

[kdaddy1980]

wow, the difference is like night and day, i took the rubber off the mounts and now it runs smooth and i'm sure i'm getting at least another 5 mphs out of it. it still has a very small spot on the rpm range where it vibrates a little bit,but it smooths out when i speed up over that i think that just has to do with the fact that this engine still isn't fully broken in.all that vibrating had caused my intake bolts to loosen up and almost fell off on my way home today. i managed to hold the one nut on and ride it up the hill to get home, then i put some new nuts and lock-washers on it and i'm back in biz. thanks a bunch guys that totally solved my vibration problems now i'm riding in style.

 

[maniac57]

Good job! The 36 will cut hill climbing ability compared to the 44, but I can't say if you will like it in your area. Here in flat Memphis, I love the smoother ride and better cruising speed. (I run a 26" MTB)