DA Chopper Drive Belt Alignment

[bobp]

Hello All,

Can anyone give me some advice on Final Drive Belt Alignment?

I am building a 2008 DA Chopper; but cannot prevent drive belt from walking in against frame on trans pulley when spinning the rear wheel by hand.

I believe the axle spacers should be 1-1/4" on left side, 15/16" inside of brake caliper bracket and .600" on right side. When I place my level against either side of rear rim; alignment looks great at frame with approx 1/8" gap outside of frame on either side.

Level across face of trans pulley or rear drive pulley also apprears to be parrallel.

But no matter what I do.... drive belt will track inward and hit frame near trans pulley when I rotate rear wheel or trans pulley by hand (in either direction).

I have tried jacking rear wheel both directions; but seemed to have no effect.

I have also tried to loosen motor and trans frame bolts and shift trans toward left; but trans does not appear to move sideways at all given existing front to back slots.

Motor will shift left - right slightly but does not appear to improve belt tracking.

Any ideas if my spacers are correct or what else to check to ensure proper alignment?

Any help or input would be greatly appreciated. I also have pics that I could e-mail.

Thanks again for your help.

[RB Donovan]

Run a straight edge across the face of the rear pulley to the face of the front pulley.
Should contact both front and rear of each pulley squarely. If not, then rear pulley spacer thickness needs to be adjusted accordingly.
By this I mean that if the straightedge sits square and flat on the rear pulley, but does not touch the front pulley at all, then the rear spacer needs to be adjusted to a thinner one.
If the straight edge sits flat on the front pulley, but leaves a gap on the rear pulley, then a thicker spacer is needed.

[MechWerks]

First step is to center and square the rear wheel (use temporary spacers and washer shims as needed), wheel has to be aligned straight with the front wheel (parallel). Check the final drive pulley with a straight edge to the transmission output pulley. This is the point where you determine if offset is correct, how offset will be accomplished, or corrected. A compromise in rear wheel center may be necessary, other parts or shims may be required. This has to happen before the belt is even tried (it can be installed but is just ignored for the time being). It is essential that the pulleys faces are parallel. If the driveline is off twisted slightly belt tracking will never be accomplished. After offset is worked out, final wheel spacers can be installed and the belt should drive true.

If a belt crowds to one direction, there is no doubt the transmission mainshaft and rear axle are not parallel. The belt will always climb to the high spot on a pulley or in this case where the mainshaft and rear axle are widest apart. There is one of two instances where a belt (and even chain) move sideways: either the drive sprockets are not in line (off centerline). Axle centers are not parallel (keep in mind that there is more than one plane of parallel, an axle high or low on one end is not parallel).

[woodbutcher]

and it is always possible that the frame itself is tweaked just a little bit. sometimes just a little too much heat from a weld can cause a problem.

[MAKO6]

Remove both axle spacers and re-install the rear wheel. with the rear wheel "floating" on the axle, attempt to true it up (while rotating the wheel) with the drive pulley on the trans. You will need to ensure the axle tensioners are correct and that the belt runs true (relative to the trans). You may need to loosen the tensioners a few times to find the "sweet spot" where the rear pulley runs true, so take your time and get it exact. Once this is obtained, measure the distance on each side of the wheel, meaning from the face of the wheel bearing to the inside of the frame rail on each side. Compare these dimensions with your removed spacers, I think you will be surprised at what you find. Even a 1/16" will make ALOT of difference. Cut replacement spacers accordingly, re-install, button things up and you should be on your way.

Good Luck

Mako

[kenart]

Also, do all your rotating of the tire as if the bike were moving "forward" not backwards. The belt will track differently rotating the tire and wheel backwards.