Jerky clutch

[vincent713]

Hello all,

Every time I cruise at a low speed, my engine or clutch seems to be very jerky, my whole bike jerks. Does anyone know how I can solve this problem? Any suggestions would be much appreciated.

 

[2door]

How slow is your "low speed" ? If you go very slow, maybe eight to ten mph or less with the clutch engaged, jerking might occure. You can't downshift to a lower gear so at very low speeds you might have to disengage the clutch and pedal.
Can you be a little more specific at what speed you're having this problem?
Tom

 

[PerryP180]

Jerking is normal at speeds less than @ 8 mph. You can fix it by getting a larger rear sprocket. Of course you lose all of your top end. It's all a trade-off. Unless you want to install a jack shaft kit. That's a totally different animal though.

 

[vincent713]

When I'm cruising around 8mph the bike jerks and I can hear the gears causing the jerks. My friend's bike does not do this, he's cruising same speed as me and runs very smooth no jerking. Could it be the adjustment of my clutch cable?

 

[GearNut]

Cable adjustment will not cause transmission slop or "jerking".

Gearing, and quality internal parts on the transmission can though.
If you are running a Chinese in frame 2 stroke, I wish you the best of fortune on the quality part of the equation.

Have you tried lubricating the transmission gears with a high quality grease? That might help out a little......

 

[vincent713]

I am running a Chinese 2 stroke in frame. The motor I have is the Flying Horse from Zoom "suppose" to be a good engine. It starts up on first attempt and runs very strong, stronger than my friend. This is the only issue I have with the engine, anything pass 8mph it's smooth and strong. I will try lubing the gears and see if that will help. Thanks guys for your input.

 

[rohmell]

You could try installing one of those centrifugal clutch kits. I have them on all of my builds and have no shuddering or jerkiness at any speed.

 

[vincent713]

Do you also need a pull starter to use this centrifugal clutch?

 

[rohmell]

No pull-start needed because it has a built-in sprag (one-way bearing).
You can still start the engine as usual by pedaling and dropping the clutch, after that, you can forget about using the clutch lever when slowing down and braking.

 

[decoherence]

wish my vespa's centrifugal clutch had a one way bearing so i could push start it.

 

[vincent713]

No pull-start needed because it has a built-in sprag (one-way bearing).
You can still start the engine as usual by pedaling and dropping the clutch, after that, you can forget about using the clutch lever when slowing down and braking.

That is awesome! Where can I get one and how much do they normally cost?

 

[rohmell]

Several vendors sell them, but they all seem out of stock right now except for BGF:
Motorized BIKE GAS ENGINE parts - centrifugal clutch | eBay

 

[vincent713]

Several vendors sell them, but they all seem out of stock right now except for BGF:
Motorized BIKE GAS ENGINE parts - centrifugal clutch | eBay

I checked out BGF, the clutch seems a bit pricey. Have you had an issues with these clutch? My pocket bike has a centrifugal clutch, the springs break and clutch pads wear out pretty quickly.

 

[rohmell]

I checked out BGF, the clutch seems a bit pricey. Have you had an issues with these clutch? My pocket bike has a centrifugal clutch, the springs break and clutch pads wear out pretty quickly.

No issues at all, I am 100% satisfied with the performance of the centrifugal clutch.
All my future builds will have one installed, I just picked up another three pieces for more builds.

 

[vincent713]

No issues at all, I am 100% satisfied with the performance of the centrifugal clutch.
All my future builds will have one installed, I just picked up another three pieces for more builds.

Did you buy it from BGF? If not where and how much did you pay for it? Did you have to make any modification to the clutch? I'm kinda leaning towards buying one. Thanks for your input.

 

[rohmell]

Did you buy it from BGF? If not where and how much did you pay for it? Did you have to make any modification to the clutch? I'm kinda leaning towards buying one. Thanks for your input.

The first few I bought from ZoomCycles, but then they were constantly out of stock, so now I buy them from BGF.
On the first few installs, I would machine a keyway into the clutch so that it would mate with the Woodruff key on the crankshaft, but lately I have not had to do that, they go on and stay on using the taper-fit of the crankshaft, so right now, no modifications are being made to them.

Try one out and see how you like it. If it is no good for you, you can always sell it on eBay.

 

[vincent713]

The first few I bought from ZoomCycles, but then they were constantly out of stock, so now I buy them from BGF.
On the first few installs, I would machine a keyway into the clutch so that it would mate with the Woodruff key on the crankshaft, but lately I have not had to do that, they go on and stay on using the taper-fit of the crankshaft, so right now, no modifications are being made to them.

Try one out and see how you like it. If it is no good for you, you can always sell it on eBay.

So the ones from BGF now are all taper-fit? If so then I will order one, I would hate to have to do some modification. It sounds like you build alot of these bikes. Do you sell them?

 

[rohmell]

So the ones from BGF now are all taper-fit? If so then I will order one, I would hate to have to do some modification. It sounds like you build alot of these bikes. Do you sell them?

The centrifugal clutches have always been taper fit.
Some others members on this forum reported that their centrifugal clutch slipped and machined away the taper, so for the first few, I added the keyway to prevent this from happening.

I wanted to see if I could recreate the problems that some were having with slipping clutches and started to install then as is, but so far none of them have slipped.

There are some locals around here that have MBs, and they come to me for repairs and upgrades. I have convinced just about all of them to go with the centrifugal clutch, and those that have are very satisfied with them, and probably would not go back to manual clutching.

They are cheaper here:
Motorized BIKE GAS ENGINE parts - centrifugal clutches

 

[vincent713]

The centrifugal clutches have always been taper fit.
Some others members on this forum reported that their centrifugal clutch slipped and machined away the taper, so for the first few, I added the keyway to prevent this from happening.

I wanted to see if I could recreate the problems that some were having with slipping clutches and started to install then as is, but so far none of them have slipped.

There are some locals around here that have MBs, and they come to me for repairs and upgrades. I have convinced just about all of them to go with the centrifugal clutch, and those that have are very satisfied with them, and probably would not go back to manual clutching.

They are cheaper here:
Motorized BIKE GAS ENGINE parts - centrifugal clutches

I just ordered one from the site you gave me, I hope it's an easy install and will not slip on me. Thank you so much for your help!

 

[rohmell]

Good Luck with your centrifugal clutch.
Yes, it's a real easy install.
Let me know how it goes and how you like it after you have used it on your MB for a coupla miles.