engine vibration

Hello, I just joined. I couldn't find anyone mentioning severe vibration in the forum. I've got a chinese "80" cc engine on an old Giant mtn bike. My brother has the identical motor on an old Schwinn mtn bike. They both produce hand (and crotch) numbing vibration between 15- 22 mph. This vib. goes away at higher speeds. At lower speeds it's still there but not as intense. Any ideas? Thanks, Joe.

nevermind, I just found a couple of relevant threads.

Welcome to the forum. Lots of motorized bicycle information on this forum. Glad you found what you were looking for and and glad you joined us. Be sure to post some pictures of your bikes...................................

__________________
There are only 10 kinds of people in this world. Those that understand binary and those that don't............

Become a Forever Family, it'll change your life.
http://www.galtx.org/

http://bdconner.com

Thanks for the welcome. I intend to post some pictures of my bikes, including the infamous, belt-drive "lawnboycycle". But I don't see where to add the attachments. Thanks, Joe.

Welcome Joe to the forum, Glad you joined us

If you scroll down when posting a reply, you will see " Additional Options" Thier you will find Attach files, click on "Manage Attachments" A new window will open where you can browse and upload photo's. Hope that will help

A lot of these engines have a vibration area around the lower to middle rpm. It gets better with miles (like 3-400) Some are worse than others.

__________________
If it ain't broke, and you mess with it long enough, it will be.

Welcome to the group Joe. Enjoy the ride...Kelly

__________________
I'm racin' Spitfire, turnin', poppin' wheelies, burnin' evil chasin' pop,pop, pop,pop,pop.... (The Pixies-Tony's theme)