Chain tension & axle creep?

[noseoil]

I keep having a problem with chain tension & wonder what I can do to help keep it from happening. Basically, I adjust the chain to get it where I want, but after riding, it seems like I get axle creep & the tension increases until it's too tight. I have the axle in place & tighten the nuts to lock it in place. After yesterday's hood ride, it was too tight again.

It's an old Baja Warrior with a modded motor, jackshaft, drum brakes & good tires. I'm thinking it might be due to heavy braking at high speeds (pulling on the axle too hard), but I can't seem to figure out a way to keep it in one place & have it stay there. Maybe clean the inside & outside frame members better, degrease the washers & then put it all back together again? Different washers that grab better? Anybody else have this happen on their bike & come up with a fix that works?

 

[mrpat]

Do you have the axle adjusters on that bike?

 

[Raskin]

Looks like the adjusters on the ct200u they really are weak even w my stock engine it snapped the adjuster on the sprocket side and was always a problem and if i crank down on the axle it crushes the bearings so i put a bolt and nut to freeze its position and adjust moving engine..if i welded i w just put a big washer there..

 

[noseoil]

It has the adjusters, but they work the wrong way to keep the axle from moving back on the frame. Thinking I should try using 2 nuts next, so I can lock it onto the adjuster to keep it from moving the wrong way. Hopefully that will work ok, or I'll have to get the bigger adjusters & see if that's better using 2 nuts per side.

 

[Charles S]

Are you checking/adjusting the chain with it at its tight spot every time? You should. Nearly every drive chain has a tight spot and a loose spot with the rest in between. There is usually a significant difference in chain tension between the tight and loose spot. Adjusting at the loose spot will cause the chain to be overly tight at the tight spot causing stretching, or worse. Prop your rear wheel off the ground and check the slack; rotate the wheel slightly and recheck; repeat many times and you should find the tight spot. If, by chance, you were to adjust at/near the loose spot, go riding, then recheck at/near the tight spot, you might think the chain had become tighter.

To verify whether the axle is actually moving rearward, dab a few small spots of paint where the washer contacts the frame and where the bolt/nut contacts the washer. Use a paint color that will contrast the frame color and the hardware. Allow the paint to dry before riding the bike. Next time you think the axle has moved, check the paint spots for cracking. Since you think the axle is moving rearward, it would be best to dab the paint at the forward edges.

 

[Charles S]

...if i crank down on the axle it crushes the bearings...

That shouldn't happen. A crush tube (inner spacer) that's the proper length should prevent side-loading the bearing; all pressure should be on the inner race (crush tube contacting the inner race inside the wheel; a spacer or washer contacting the inner race on the outside), and no pressure on the outer race. It would take a hydraulic press to crush the inner race; you aren't going to faze it with a wrench. Check the crush tube; it may be missing or it may be too short.

 

[Raskin]

That shouldn't happen. A crush tube (inner spacer) that's the proper length should prevent side-loading the bearing; all pressure should be on the inner race (crush tube contacting the inner race inside the wheel; a spacer or washer contacting the inner race on the outside), and no pressure on the outer race. It would take a hydraulic press to crush the inner race; you aren't going to phase it with a wrench. Check the crush tube; it may be missing or it may be too short.

Thanks,yeah i get what you're saying.This fixed location has worked for me,but next time i service it i will see if inner spacer is flimsy and mushroomed out or too big..i still don't like those adjusters.The trailmaster has much better ones..

 

[noseoil]

Added an extra nut to the inside of the tensioner & adjusted it again. This locks the adjuster from both directions, front & back. Added a washer to the inside of the adjuster, to get just enough clearance for the inner nut to turn next to the frame. I may need to change it slightly, since the axle has a little bit of slop in the adjuster at the axle itself. There's a few 100ths of movement where the adjuster hole is too loose, so I will have to find a sweet spot where the tension is correct & the adjuster can't move the wrong way. A better adjuster with less slop & tighter tolerances at the axle would be a big help here, but it's probably not worth the cost.

I know when the axle creeps & the chain tightens now. The modded motor shakes so much from 4k-5k rpms it can come up through the bars & it feels different. With the chain being slack, a lot of the vibration is cancelled out & doesn't make it up into the grips. Live & learn.

 

[mrpat]

Added an extra nut to the inside of the tensioner & adjusted it again. This locks the adjuster from both directions, front & back. Added a washer to the inside of the adjuster, to get just enough clearance for the inner nut to turn next to the frame. I may need to change it slightly, since the axle has a little bit of slop in the adjuster at the axle itself. There's a few 100ths of movement where the adjuster hole is too loose, so I will have to find a sweet spot where the tension is correct & the adjuster can't move the wrong way. A better adjuster with less slop & tighter tolerances at the axle would be a big help here, but it's probably not worth the cost.

I know when the axle creeps & the chain tightens now. The modded motor shakes so much from 4k-5k rpms it can come up through the bars & it feels different. With the chain being slack, a lot of the vibration is cancelled out & doesn't make it up into the grips. Live & learn.

Sounds like you figured it out to me. Maybe you can look into making or buying a setup like the one [MENTION=54903]Raskin[/MENTION] has in the post above yours. I like the way that one wraps around and catches the axle 2 places.