Slowly but surely . . .



FNTPuck

Well-Known Member
Joined
Jul 2, 2018
Messages
657
Glad you posted to remind me to come back here...

If you do go the jackshaft route and try a kit, do NOT use the bearings they come with. They are absolute trash and when I ran the numbers and compared online they are freaking wheel barrow bearings not even meant for motorized use.

I tried them out and they have a dramatic amount of excessive bearing play under load - as soon as I started giving it gas from a ~15mph roll the bike got a nasty clunking vibration and snapped the short crank chain since the jackshaft actually moves forward ~1/8" due to bearing play which brings the sprockets out of alignment. Added a half link thinking it was just too tight and tested with final drive chain disconnected so I can free rev it and it did the same thing - you can see the movement that causes the sprocket teeth to hit the side plate of the chain, which snapped a link. Even though I was only going like 10mph when it happened it was still very unsettling.

I am replacing them with proper sealed flanged bearings and supporting them with ~1" of a bearing race tube on each side, with a ~1/2" hold drilled in each tube so I can still use inner lock collars instead of just outer. Only ~$20 extra for priceless amount of piece of mind.
 

Randall

Active Member
Joined
May 23, 2016
Messages
534
Glad you posted to remind me to come back here...

If you do go the jackshaft route and try a kit, do NOT use the bearings they come with. They are absolute trash and when I ran the numbers and compared online they are freaking wheel barrow bearings not even meant for motorized use.

I tried them out and they have a dramatic amount of excessive bearing play under load - as soon as I started giving it gas from a ~15mph roll the bike got a nasty clunking vibration and snapped the short crank chain since the jackshaft actually moves forward ~1/8" due to bearing play which brings the sprockets out of alignment. Added a half link thinking it was just too tight and tested with final drive chain disconnected so I can free rev it and it did the same thing - you can see the movement that causes the sprocket teeth to hit the side plate of the chain, which snapped a link. Even though I was only going like 10mph when it happened it was still very unsettling.

I am replacing them with proper sealed flanged bearings and supporting them with ~1" of a bearing race tube on each side, with a ~1/2" hold drilled in each tube so I can still use inner lock collars instead of just outer. Only ~$20 extra for priceless amount of piece of mind.

Thanks FNT.

Yeah I think I am going to go the route of pillow block bearings and 5/8ths shaft (size of the sprockets). I dont think I trust
my fabricating techniques just yet. Critical area not to have any misalignment or bad welds. I'm going to fabricate the mount
though (easy peasy).
 
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