Re: first build!
The 2 most important things rookies fail at is is the motor mount and rear sprocket so get them right before anything else.
Once your motor is installed grab your top frame with one and your motor head with the other than yank back and forth as hard as you can, if it moves it will fail.
The rear sprocket can cup in or cup out, you can't tell which lines up best best without the motor in or until you temp fit it on and run the chain across but usually cupped in depending on the back wheel hub diameter.
The rear sprocket also has 3 dimensions of adjustment.
1. Centered. Flip you bike over, put the wheel on, spin it and look from the side.
If the sprocket seems to go up and down (vertical alignment) your chain will get tight in one spot and loose in another, you will never get it tight and throw chain.
I always have to smile at all the ways some guys make clever spring loaded tensioners to try and compensate for this opposed to just putting the rear sprocket on right.
2. Spin the wheel and look from behind, if it wobbles back and forth (horizontal alignment) that will also throw chain, a little is OK so long as vertical alignment is good as it has good tension to help and a little wobble 1/8" is OK.
3. The line between the motor sprocket and rear wheel sprocket (lateral alignment) and if the the sprockets do not line up you will throw chain even if the top two are correct once the chain wears in a bit.
You change this by cupping in or out but again a little is OK if the top are OK.
Another thing I smile at is the guys that think they can compensate for misaligned sprockets with tensioners. Sure you can bend 7-speed chain a little with their spring loaded tensioners but you won't pull that off with 410 or 415 chain and trying to bend a tight chain around a fat tire just won't work.
Get those 2 things as perfect as possible and the rest is a breeze ;-}
Last edited by KCvale; 10-17-2012 at 02:08 PM.