Gearbox Ratio

  • Thread starter Deleted Member 4613
  • Start date
Here's a pic of the shaft. I learned BGF has 15mm ID clutches and a an 87mm belt
drive to fit these 4-stroke motors.
motoredbikes.com

49cc 4 stroke - What kind of shaft is this?

It measures 15MM on the end, and 17mm where it goes into the engine block. Is this considered tapered or a straight shaft? Most of it is straight...but it is definitely not a 5.8" straight shaft. Too small for that. I'm just hoping I can put on any tapered shaft transmission. Thanks!
motoredbikes.com motoredbikes.com
 
No, I have no interest in repairing a motor kit. It has to come engineered
correctly and ready for reliable use. But thanks for the suggeston. I would
just buy a replacement clutch or trans that fits properly, and it looks like
BFG is the only seller offering these parts, but thanks anyway.
 
Deleted Member 4613 said:
No, I have no interest in repairing a motor kit. It has to come engineered
correctly and ready for reliable use. But thanks for the suggeston. I would
just buy a replacement clutch or trans that fits properly, and it looks like
BFG is the only seller offering these parts, but thanks anyway.
Click to expand...
Mike, did you end up getting the kit? As outlined in other posts, I did get one. It's definitely a 20/100T, or 5>1 drive, with a 44T rear sprocket, which is too low of a ratio (24 mph @ 6800 rpm), unless you want to climb trees with the thing. I pre-emptively purchased a 32T rear sprocket and it pulls decently with that. I have not pulled the clutch apart, but it sounds like the 15mm straight shaft might be the new "normal" for the next wave of budget 4-stroke kits. I'm fine with that, as long a they catch on, and parts can be found. Right now, I want to source a few of those bronze bushings, since they seem to be a wear point. The belts are easy and relatively cheap, and you already found the clutch.....

As far as verifying the 53cc claim- unless I pull the head off, I have no clue. I have not tried to rev the snot out of it yet until I'm absolutely sure it's broken in and gone over, first. Definitely worth the $170 I paid for it, though.
 
I'm leaning towards the chinese T-belt drive kit like you bought, now
that I know more about this oillite bushing issue. Now I know how to
treat it perodically with oil. If I can keep the bushing working, I can
boost the power of the motor, and use a smaller rear sprocket like
you did for more top end speed. Right now, I only know BGF as
a source for the 15mm id bushing. Keep us informed of your bike's
performance. Thanks.
 
Deleted Member 4613 said:
I'm leaning towards the chinese T-belt drive kit like you bought, now
that I know more about this oillite bushing issue. Now I know how to
treat it perodically with oil. If I can keep the bushing working, I can
boost the power of the motor, and use a smaller rear sprocket like
you did for more top end speed. Right now, I only know BGF as
a source for the 15mm id bushing. Keep us informed of your bike's
performance. Thanks.
Click to expand...
No problem. I honestly don't see anything horribly wrong with the kit itself except for the short gearing and the damage from shipping. Will keep you guys posted. I hope to get a few bushings to spare, especially since I lubed THIS one wrong!
 

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