BAD Vibrationat 30+?

kornbread

kornbread

New Member
I have a raw 60cc engine and it runs good but as I'm rideing when I get about 30mph i start feeling a bad vibration through my feet that really starts to feel real intense is that normal?.crt.drn2
 
You might be bumping the speed of time barrier thing. Sort of like the sound barrier.
Does things around you start to move slowly as you reach that speed?
I'm pullin your chain.
No really is your chain tight or loose? or out of line with the sprockets, rear sprocket running true, got a loose mounting bolt?
Once a mounting bolt breaks the bike will shake like a dog passing a razor blade.
Then again some of these finely made engines will vibrate worse in the upper rpms you might have one of them.
I got one that tries to walk away just idling, its a sneaky B**t**d tries to run and hide.
 
laff...That was good Norman.

kornbread:

Some of these engines do vibrate a lot worse than others. I 've had several that had crankshafts that were so poorly manufactured, that the effect was similar to a bent a crank! Vibration BIG TIME.

Just stay out of the "zone" and get all the mileage you can get out of it before it starts chucking parts.

Jim
 
did it just start or has it always done it?

my first bike started doing it suddenly, and then i noticed the frame was cracked.

if it just started happening, something's about to fail.
 
Norman, you must listen to Alkaline Trio, ha!

My bike always starts to shake and shimmy over 30+, so I just gun it and get to 40 where it starts to smooth out. Or at least I'm so busy hauling you know what, I don't notice the vibration. First thing you can do for any MB, is either get your tires overhauled, or buy nice wheels 26x2+, nothing smaller than 12g spokes. Or maybe some mag wheels without spokes. The funniest thing to me is after 30mph, my butt starts swinging on my seat and the springs underneath seem to start singing with the road. Hmph, TMI....
 
something is broke or too tight! inspect bicycle and motor real good then check frame! it has to be one of those! I have built and repaired about a dozen of these and never had a bad motor to blame for vibrations. then again maybe I've just been lucky! most of my motors have come from BGF. the most common motor stud to break is on the left rear of motor, thats where most of the tension is at especially if you have the chain tight or the rear sprocket is not true center. or a front motor mount if you have drilled through your frame! I only speak of experience to know what I say are true!
 
kornbread, consider yourself lucky. I was one of the few who recieves not only a dud, but a really bad dud. anything over 15mph is unbarable. my crank must be out of kilter. i have no tools to fix it or the time or the knowledge. If anyone wants to balance my engine send me a PM with pricing. thanks
 
Vistaman73 said:
kornbread, consider yourself lucky. I was one of the few who recieves not only a dud, but a really bad dud. anything over 15mph is unbarable. my crank must be out of kilter. i have no tools to fix it or the time or the knowledge. If anyone wants to balance my engine send me a PM with pricing. thanks
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Vistaman,

Feb 09 I bought kits from nearly every supplier. 2 were exactly as you describe. The vibration was so bad that the bike was not rideable.

I took them apart and found that the holes for the con-rod, (big-end), pin had been drilled out of square to the face of the crank. This essentially mimics a bent crank condition. There is no fixing it, or balancing it. You'll need a new crank, or a new engine.

Jim
 
Damn, I was afraid of that. I will buy the crank first cause its cheaper. Once I get it in, I will start a thread on the difference. Can anyone direct me to a thread about replacing it? (I have not found one yet.)
 
kornbread,

The other guys suggestions are definitely the place to start. I just assumed that this was a new install. If it's not, and this problem started suddenly...something is wrong, other than the engine.

I would also check to make sure that the muffler isn't fouled...these engines will vibrate more if they are restricted too much.

Jim
 
Vistaman73 said:
Damn, I was afraid of that. I will buy the crank first cause its cheaper. Once I get it in, I will start a thread on the difference. Can anyone direct me to a thread about replacing it? (I have not found one yet.)
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Look through Normans threads...I'm fairly certain he has a total tear down procedure with photos on his forum.

Jim
 
well i checked everything on my bike and motor and found nothing.mine is a new build and everything is in order.I have a 6 month warranty,should i contact zone8 and let them know about the problem and see about replacing the engine?drn2
 
kornbread said:
well i checked everything on my bike and motor and found nothing.mine is a new build and everything is in order.I have a 6 month warranty,should i contact zone8 and let them know about the problem and see about replacing the engine?drn2
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First things first...Let's back up a minute and look at the total picture.

What bike are you using? 20", 24", 26" Do you have pics?

What size rear sprocket are you using?

What fuel to oil ratio are you currently running?

Have you looked at the plug after a run?

Vibration can be caused by a number of things...trust me, it will be better to exhaust all possibilities before going the warranty route. You've already got it built...if it's a minor problem, you don't want to go through all that hassle for nothing.

Jim
 
Hey Jim, I have one question, is it safe to ride with the crank like that? Will it destroy the engine? Tell me what you reccomend.
 
Vistaman73 said:
Hey Jim, I have one question, is it safe to ride with the crank like that? Will it destroy the engine? Tell me what you reccomend.
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The likelyhood that you'll get hurt is slim...The engine will let you know when it's done! If the crank is bent, the rest of the engine will not last long.

I forgot to ask...what is the top speed you have been able to reach?

Have you stopped accelerating at 15mph because of the vibration, or have you tried running through it by going faster?

The reason I ask, is that I did have a few that vibrated pretty good at around 15mph, (Not like the bad crank ones though), and would then smooth out again at around 25-28.

Just in-case you haven't tried pushing it beyond that initial vibration: try it, you might be surprised.

That's really how you can tell if it's the crank or not...If it vibrates bad at 15, and keeps getting worse the faster you go...it's the crank!

Jim
 
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