Any way we can dampen the engine?

retromike3

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I road my motorbicycle about thirty miles today and half way to my destination my carburetor top rattled off and I lost power right away. Well I got it going again but it seems like every part on that bike will rattle off unless it has ether lock tight or two blots or welded in place. There has to be a way you can mount the engine so that it won't transfer all of that "buzzing" to the frame and rider.:geek:

Any Ideas?

mike Frye the bike guy
 
retromike3, be thankful your engine is rattling, just loctite every nut and bolt in place - when vibration becomes almost bearable, you're soon to be left with one option - pedal power.

Also, be thankful your engine is spewing out copious quantities of 2-stroke oil that coalesces into black filth and grime - when your engine starts running clean, pedal power is close at hand.

Fabian
 
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I had LOTS of vibration on my folder bike - my bottom would actually start to tingle quite bad after a km or so at higher speeds, even with having a cloud9 sprung/gel seat.

I upgraded to a 40 tooth rear sprocket from the 44 a few weeks ago to get a bit more speed (the bike has 20" wheels so with the 44 it was quite slow). Not wanting to deal with the rag joint BS again (and wanting to take the stress off the spokes) I had a buddy WELD the new sprocket directly to the rear hub (too cheap to get a clamshell adapter...). We managed to get it dead center which was impossible with the rag joint (spokes never lined up properly because of the hole/spoke count) and BAM, all the bad vibes are gone! Seems that the vibration was due to the chain getting tight/loose (even just slightly) as the rear sprocket turned. The bike also rolls a lot easier/quieter now with the clutch in/engine off. After this I am starting to think that the rear sprocket being off center may be one of the main causes of vibrations (while riding) on HT setups. I am definitely welding the rear sprocket on again on my next build.

I get very little vibration from the engine itself and it is mounted to the frame SOLID (front mount welded to frame). I recall that I did get a bit more vibration when the engine (zoombicycles pk 80) was new, but that got a lot better after break in (maybe 200km).

Some people put rubber between the mounts and the tubes, however I suspect this just protects the bikes paint more then anything - I wouldn't expect a thin, highly compressed piece of rubber to dampen much of anything, you need rubber blocks to do that effectively. I personally don't like that idea - I think that rubber between the frame/engine would just make it easier for the engine to "turn" outwards when under load. I like when stuff is solid.

I have seen some nice aluminum/rubber block mounts for the HT that look like they would do a good job absorbing engine vibes, possibly on the motorized ridley twin bike that was discussed in a recent thread here on the forum (not 100% sure on that). I think somebody actually found the "source" of the mounts (in an older thread about the same bike), but they were expensive, over $100 if I recall.

I also remember reading about somebody filling the frame tubes with expanding foam to reduce vibrations, maybe look that up.

Hope this helps, Dilly Bar Rob
 
Hey Dilly Bar Rob,
Like Fibian said loctite every nut and bolt in place. Do a inspection often. I don't have much vibration on my bike I barley feel it. The vibration comes with speed changes on mine. The motor mounts should installted with rubber on the frame.

My front mount is made of Oak the back mount is wrapped in
rubber, too much vibration than I can feel.

Good Luck On Yours,

... Jim
 

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IMO: Thats too much! My oak motor mount cost $2.00 from Home Depot. That mount for $199.00 is a beautiful thing if your building
a custom bike.
 
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I used rubber handlebar grips under my engine mounts and have 0 vibration even at 30mph.
And i have 1,000miles on my engine.
 
I used rubber handlebar grips under my engine mounts and have 0 vibration even at 30mph.
And i have 1,000miles on my engine.

that is an excellent idea... i love the ingenuity on this site. Its endless... hundreds of solutions for any given problem.
 
I used rubber handlebar grips under my engine mounts and have 0 vibration even at 30mph.
And i have 1,000miles on my engine.

And I was going to use them as grips for a dog stick. (something to whack chasers who got to close) I figured with the soft grip it would only stun them.
 
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