Terrible vibration

crassius

Well-Known Member
Joined
Jul 23, 2012
Messages
4,568
All the pre-2012 engines (still being sold by some folks on ebay) are called the bone-shaker motors for a reason.
 


Bern

New Member
Joined
Aug 1, 2017
Messages
11
I to have a lot of vibration at high speeds. It's a new 80 cc motor I bought on Ebay. With shipping it was about $110.00 . The bike is a old cruiser I picked up at thrift store for $37. Don't know the model, it might be a Target or K mart special. I strip it down and repainted it and added new tire. I also had the rear tire trued up but there is still a little misalignment. I don't think the vibration comes for the bike but from the motor itself and the misalignment of the sprockets and chain.
One thing I did when I installed the sprocket. I measured the distance from the axle to the end of the teeth at four apposing positions, making them equal. I also measured the distance from the bike sprocket to the large motor sprocket at different positions and tighten it so that they were somewhat parallel. I don't see any other way to align the sprocket. I'm also thinking of a way to make the small sprocket on the motor inline and parallel to the large sprocket. I'm not positive that all these things will reduce the vibration but if you think about it, wouldn't you want all these things in a true position to each other and balanced. It may be difficult to do sense the tolerances on these part must be wide open but you got to try.
I'm also going to install motor mounts but I'm still researching the engineering. I read that it's better to install one motor mount and making the other side ridge so the engine will stay inline. Or would it be better to instill two mounts. One on each side. I guess it may depend on how hard the rubber is.
I welcome any input.
 

Bern

New Member
Joined
Aug 1, 2017
Messages
11
I to have a lot of vibration at high speeds. It's a new 80 cc motor I bought on Ebay. With shipping it was about $110.00 . The bike is a old cruiser I picked up at thrift store for $37. Don't know the model, it might be a Target or K mart special. I strip it down and repainted it and added new tire. I also had the rear tire trued up but there is still a little misalignment. I don't think the vibration comes for the bike but from the motor itself and the misalignment of the sprockets and chain.
One thing I did when I installed the sprocket. I measured the distance from the axle to the end of the teeth at four apposing positions, making them equal. I also measured the distance from the bike sprocket to the large motor sprocket at different positions and tighten it so that they were somewhat parallel. I don't see any other way to align the sprocket. I'm also thinking of a way to make the small sprocket on the motor inline and parallel to the large sprocket. I'm not positive that all these things will reduce the vibration but if you think about it, wouldn't you want all these things in a true position to each other and balanced. It may be difficult to do sense the tolerances on these part must be wide open but you got to try.
I'm also going to install motor mounts but I'm still researching the engineering. I read that it's better to install one motor mount and making the other side ridge so the engine will stay inline. Or would it be better to instill two mounts. One on each side. I guess it may depend on how hard the rubber is.
I welcome any input.

I wasn’t speaking about the engine. It’s oblivious that engine vibrates. These engines are designed using the maximum tolerances allowed to reduce cost.
I was talking about the overall performance of the bike. If the sprocket is not symmetrical to the axle/wheel there will be an imbalance. It’s like a wheel on a car that is out off balance or misaligned. The wheel will wiggle and/or vibrate. And most likely you will only feel it at high speeds. As an example, what would happen to the ride of the sprocket was pushed to one side maybe an inch, it would be similar to a car tire that is out of balance. Which in turn applies stress through the sprockets and chain to the shaft of the engine, causing more vibration? All I'm saying is simply, if you try to make everything as straight and balanced as possible the better the ride.
 

jaguar

Well-Known Member
Vendor
Joined
Nov 25, 2010
Messages
3,482
so why did you use the word "vibrate" when now it is obvious you should of used "wobble"?
 
B

Bernrocks

Guest
I made some engine mounts using rubber pipe coupling with a ¼ wall thickness. It helped reduced the vibration some but not entirely. So far this set up seems tight enough so the engine hasn’t misaligned.
 
B

Bernrocks

Guest
Another issue I have is that when I let off the gas the bike seems to lunge back and forth a bit. Is this normal? Is it just that the engine is out of balance? Could it be the chain is not tight enough? My chain has about ½ of play in it, as recommended. In another thread, someone said to make the chain tight. I don't think it's a good idea but I might try it. Any input will be appreciated.
 
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Bermrocks

Guest
Well guys I have tried everything I can to fix the stalling at full throttle except replacing the carburetor. While the engine was idling I use a detergent bottle spraying for leaks around the head, were the carb meets the intake manifold, where the intake manifold meets engine and around the exhaust manifold. There are no leaks. I changed spark plugs with recommended electrode tang spacing. I tried various carb linkage adjustments.
In a video if found online a guy shows how to inspect the float in the carb and how to adjust the brass fork that controls the shut off. So I did all that and it still stalls the same way. Now I’m thinking about replacing the carb. What else is there other than going in to the engine and trying to make some adjustments that I have seen in another video, which I really didn’t want to do? Anyone have any other ideas. No I’m not going to buy a new engine. LOL
 
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