base for a new build

[Moto]

I've been collecting parts for this build for a while, and I'm pretty excited to get it going. first got to make it a functional bike though. It's gonna be rear rim brake, front disk. I would ideally use a jack shaft but I am not sure I will go that route because I'm trying to build this on the cheap. will probably use a spring loaded chain tensioner to take the slack out of the drive chain caused by rear suspension. should be very fun to ride! power plant is going to be a 50cc Chinese engine.

 

[TheNecromancer13]

If you want a cheap jackshaft, get 2 heavy duty 5/8" bearings, a foot of 5/8" keyed shaft, a 5/8" mini hub, and then whatever size sprocket to bolt onto the mini hub, as well as a sprocket that bolts directly onto a 5/8" shaft. Use a bit of steel shapes from the hardware store to mount the bearings. Including the sprockets it should easily cost less than a hundred bucks. If you can't figure out how to assemble it all I will take a picture of one of my bikes and post it for you.

 

[crassius]

pic doesn't show area that swingarm pivots on, but distance between that pivot and rear axle should remain constant - you might be able to hang a double sprocket on a sealed bearing there with chain dropped from motor to that sprocket, then 2nd chain from that sprocket to rear sprocket

should work and shouldn't be expensive to make

 

[Moto]

the issue is that I would want to keep the pedals functional. I cant see how I would do that without buying a sbp crankset and freewheeling chainring.

edit: Crassius: I see what you mean. Installing a jackshaft that still outputted on the left hand side but lower and closer to the pivot would significantly drop the amount of slack created when the bike's suspension moves.

 

[scratchbuilder]

I've got a frame like that id like use...but seat position is way to high for me, I like to stop sitting down with feet on the ground. I haven't found a way to have a shifter w/o spending at least 100$. And that's with your own Js. But its worth it!!

 

[crassius]

the issue is that I would want to keep the pedals functional. I cant see how I would do that without buying a sbp crankset and freewheeling chainring.

edit: Crassius: I see what you mean. Installing a jackshaft that still outputted on the left hand side but lower and closer to the pivot would significantly drop the amount of slack created when the bike's suspension moves.

I was thinking NOT closer to pivot, but replacing pivot with a bit longer shaft for the sprocket, that way chain should stay constant length.

 

[Moto]

I was thinking NOT closer to pivot, but replacing pivot with a bit longer shaft for the sprocket, that way chain should stay constant length.

ooh. that makes sense. the pivot doesn't go all the way through though :-(. would be dope asf. I'll see if it is possible.