pred 212 vibration

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magna_503

Member
Apr 13, 2009
251
0
16
Portland, OR
Ok, so i've been having this 212 vibratiion issued. at idle, the whole bike is vibrating badly. I put on isolator and add a few supports bar and gusset but it is still vibrating quite a bit. The only time that i didn't feel any vibration was with the isolator loosely bolted. I'm not sure if it's a bad motor to begin with or it's an idling issued at this point. I had it idling on the ground and it jumps up/down about 1/4" to 1/2" off the ground.

The motor had 18lb spring, billet flywheel, and a gx390 carb.
 
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culvercityclassic

Well-Known Member
Sep 27, 2009
3,115
177
63
Culver City, Ca
I built a bike for a friend and he built the motor, after assembly the test ride was so bad I could not hold on to the bike from the vibration of the motor. The crank turned out to be way out of balance, we sent the crank out to have it repaired and the bike ran smooth. I say it's a hit and miss with these motors but the majority have no issues. I say try a new motor. FYI- I have built a bunch and have no vibration issues with any on my bikes.

This is the bike build: http://silodrome.com/motorized-bicycle-wolf-creative-customs/
 
scotto-

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,505
24
38
Ridin' inSane Diego, CA.
My old original 212 vibrates no more than a china girl 66cc, in fact less. They are hit or miss as CCC is sayin, most don't over vibrate in my experience either.

Most likely crank balance related when they do.
 
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magna_503

Member
Apr 13, 2009
251
0
16
Portland, OR
I remember it was vibrating pretty bad too when I firt got it, but didn't think it would vibrate the whole frame when mounted. I'm temped to just pick up another 212 and see how it vibrates on the bike.
 
professor

professor

New Member
Oct 14, 2009
500
1
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Buffalo ny area
Mine was atrocious.
I actually bought a 196cc gokart clone to compare it to, and it also vibrated.
So the 212 went back on.

I sent for isolators from McMaster Carr- 4 under the engine and made snubbers held to the motor for the top of the engine to work against the frame, to restrain it side to side.
This worked.
It will shake the handlebar at a fast idle.
Otherwise the engine is great.


The 79cc HF on my other bike is fine.
 
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magna_503

Member
Apr 13, 2009
251
0
16
Portland, OR
I swapped out the motor earlier today, vibration reduced just a bit less, but I can still feel it through the seat / handle bar. Howerver, this motor looks like it was returned. I'm gonna tried a different one that hasn't been returned tomorrow or so. I'm about to call this build a Ball Buster.

Anyhow, here's the setup the motor mount is welded to the frame, with 2 support bars, one connecting to the bottom bracket, the other about 2.5" infront of it. Another support bar about 4" behind the headtube. 3 small gussets right at the seat, and one at the head tube.

I guess i'll grab some pic real quick.
 
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magna_503

Member
Apr 13, 2009
251
0
16
Portland, OR
Don't mind my welding, it's just chicken droppings for now.
I didn't have the rubber isolator on this one motor as I wanted a baseline first.



Professor, do you have the part # for your isolator? I saw your pics and looked through mcmaster, but the bolts length was only 5/8" - 9/16" long.






I had the support bar by the head tube getting ready to weld up another mounting location for the motor. I really hate this vib crappp....
 
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magna_503

Member
Apr 13, 2009
251
0
16
Portland, OR
Yeh, i'll take this one back either tomorow or this weekend and start welding up a top mount. Mainly because it had blue permanent markers on the side covers and various bolts. I don't know if it's a refurb though. I rather have one that do not have any markings. I do think that i need a new motor though, because the old one i have had extreme vibration from possibly an imbalance crank.
This motor reduced the vibration to tolerable level (non ball buster level) on the seat.
 
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magna_503

Member
Apr 13, 2009
251
0
16
Portland, OR
CCC, i think you are definitely right on the securing the motors on top and sides. I took a wrench and started tapping the sides of the motor mount with out the motor installed. I felt the vibration on the sides a lot more then when tapping the around the center of the mount. What I also found were gussets area had the least vib, and the support bar by the head tube didn't seem to do chit. But i'll use it for the top mounts though. I'll tap it with the wrench tomorrow and start feeling for vibration location on the frame. I'll add bigger gusset next to where it vibrates most. I'm betting it's gonna be the top tube and the rear triangle.

And of course I just remember I beat the crapped out of the crank shaft to remove the stock flywheel too, so that probably did some damage to the shaft which cause excessive vibs. Gear puller this time around to keep the shaft intact.
 
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magna_503

Member
Apr 13, 2009
251
0
16
Portland, OR
culvercityclassic said:
These motors are no joke with the torque. Another bike with a race motor. All kinds of support and no vibration.
Click to expand...
That's a really nice build!!

Please let me know if this is adequate mounting/bracing to prevent vibration.
Top


Rear gas tank mount




I'll don't have any bracing on the left side of the motor yet though.
 
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magna_503

Member
Apr 13, 2009
251
0
16
Portland, OR
Added another mount to the heatshield mounting location on the left side, started her up and it idle w/o vibration... But with 1/4 throttle turn and it vibratate a little now. Does this sound normal to you guys?



added bracing for the exhaust




I think it needs an oil change since the break in, some carb tuning to smooth it out, and it should be good soon.

thanks guys for all the help....
 
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