Balancing the motor?

[fin-addict]

I have an 80cc motor, just went though the break in period. Motor vibrates more then I like when I get up past 20 mph. I've been reading about how to dampin the vibs. This balancing of the motor has my attention. I would rather fix the problem instead of damping it. I'm mechanically inclined, but have never done this. Is this something I can do myself or should I leave it up to the pros?

 

[BarelyAWake]

When you say "just went though the break in period" - how long have you run it? Is it still "4 stroking"? I'd suspect that might be part of the vibe problem, even if it's broken in these things are notorious for runnin' rich and firing every other stroke... Another thing is to double check your rear sprocket mount, if it's offset even a lil it'll shake like a SOB at speed. Spin the rear wheel slowly and watch to see of your chain tightens and loosens - a sure sign of an offset sprocket. Check the motor mounts of course

Vibrations are part of these lil thumpers, realistically - there's not really much to be done other than external "fixes" like soft hand grips and a sprung seat. Your right about "dampening" the vibes though - be wary of the rubber motor mount "fix" in particular as it often leads to other problems like sheared mount bolts and frothed fuel.

Welcome to the forum BTW - good to have ya here!

 

[bairdco]

are the other parts of your bike tight? fenders, chainguards, headset, cones, loose pedals, bottom bracket... you get the picture.

every loose or rattling part on your bike will help transmit vibration. make sure they're tight.

what kinda tires do you have. knobbies or street tread? aggressive tread tires will make your bike "buzzz" down the street.

and finally, don't ride barefoot.

 

[fin-addict]

I ran the motor at about 15 mph to and from work for about two weeks. My job is about 3 1/2 miles from my house one way. Altogether I've been running this motor since Sept. I read on another web site that if you can deal with it for 300 miles the vibs will go away. I don't know exactly how many miles I've put on this motor, but I'm pretty sure I've put 300 miles on it and the vibs haven't gone away. I'm not sure what you mean by 4 stroking. It doesn't seem like its misfiring. My sproket is straight and the chain runs true. I can rev the motor setting still with the clutch pulled in and it vibrates all the way up through my handlebars. I have the wide cruiser type bars. I have the wide GT cruiser street tires. Every nut & bolt is tight. You're right about the rubber motor mount, tried that and it made the vibration worse. Haven't tried the lead shot or sand in the bars. How well does that work?.

 

[Cabinfever1977]

I am using pieces of rubber handle bar grips under my mounts and have o vibrations until around 30mph. no loose or broken nothing cause everything is doublenutted and i have over 800 miles on mine. i also have pieces of rubber hose inbetween the fins on my engine head top and sides(gets rid of rigging noises) and rubber between fender and frame and removed chain guards(they would vibrate too much). my engine is also mounted 6 inches above the usually mounting spot because i have a pullstart and cent clutch. i also am using a custom front mount i got off a exercise bike(but its just a metal bracket). i also have a muffler strap to hold muffler to frame,my engine will not fall off.

 

[fin-addict]

Tried my hand at balancing the crank and I think I've got it. Put it all back together today, road it around the block a couple of times and theres alot less vibration. Still has some at top speed, but thats fine. I'm not going to run her at top speed. Don't want to abuse my little motor.