Drive Gear Out of round upon manufacturing

Apr 11, 2020
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I replaced my drive gear in my engine today. Granted the driven sprocket on the rear wheel is worn to saw blade sharp and slightly out of round on the lands of the teeth and makes the chain losen and tighten on every rotation. The new gear in the front was causing the chin to bounce up up up up up down down down down, up up up up etc and so on. I had 2 different bounce rates as the chain went around. Upon inspection of the small gear in the engine, the troughs of the gear had a Damm wobble! I've been successful in riding further than even experienced performance builders. Been at this almost a year. Have been to northeast to northwest Houston. Been to Kingwood and Humble numerous times. Only had to change CDI box last week, clutch cable last year. Replaced that cable with Mazda Miata gas pedal cable. No more of that problem anymore . Yes the cylinder will work in any bicycle brake or clutch handle. May need to file to length depending on your handle. I have also had to change that drive sprocket twice with this being gear 3. But I have the original engine, clutch and bicycle. Ladies and gentlemen, this is a serious science experiment as well as my primary way of transportation. I still wonder if it's a common malady about the gears being pressed offset from center thereby causing a double note wobble. I even tried pressing the top of the chain with a socket with engine running and back tire raised up. It definitely had two bounce rates. And this is guiding the chain left and right of center. This is very very dangerous and I will advise EVERYONE:; PLEASE DON'T TRY THAT AS YOU CAN LOSE A FINGER OR WORSE. The biggest fear I have of these bikes is the drive train locking up the wheel at 31mph. In closing, my engine still running awesome and knock on wood, have been blessed to not have that happen.
 
Apr 11, 2020
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And yes, I had purchased 3 of the gears at once. I replaced wobbly after the tooth wobbled my finger right between it and the chain! I shouted a few choice, and not so choice words as I sent the bent bastard flying into the woods! The new one doesn't generate secondary bounce on my chain. I need to get a chain and replace the back gear.
 

PeteMcP

Well-Known Member
Jun 27, 2017
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Welcome.
Glad you're enjoying plenty opportunity to ride your motorized bike.
Sounds to me like the source of your gear problem can be traced to one single cause - not enough attention being paid to correctly centring your rear sprocket when installing it via the rag joint. With the rear sprocket installed correctly, any chain 'bounce' can be minimised with a properly installed chain tensioner.
I'm extremely sceptical about any new motor drive gear being incorrectly machined. I'll lay good money on that not being the source of your problem.
 
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Reactions: Tom from Rubicon
Apr 11, 2020
3
0
1
55
Welcome.
Glad you're enjoying plenty opportunity to ride your motorized bike.
Sounds to me like the source of your gear problem can be traced to one single cause - not enough attention being paid to correctly centring your rear sprocket when installing it via the rag joint. With the rear sprocket installed correctly, any chain 'bounce' can be minimised with a properly installed chain tensioner.
I'm extremely sceptical about any new motor drive gear being incorrectly machined. I'll lay good money on that not being the source of your problem.
I took the small gear out, lost the key pin. I still put the gear on the engine shaft with no key to check free spin radius and the damn thing was eccentric ever so slightly. That wobble is what pulled my finger into the chain. After replacing it, that every engine shaft rotation bounce is gone! Only have every wheel rotation bounce again. That gear needs replacing. That's just more work involved. I need a chain, have plenty of 40 tooth gears around here. It's just a bit of work to change it. Trying to draw myself to get out there and deal with it.