Chain skipping...

TTCarr

Member
Hey guys, I tried to figure this one out before I bothered anyone else, but I’m stumped. I have had several issues that seem to come and go with the chain keeping consistent slack. Spinning the axle it seems one side of revolution is real tight and the other has way too much slack in it. I’ve spent a solid 5 hours using lasers and making very small adjustments to ensure the chain is riding the sprocket as perfect as possible, but it is still happening.
Using several different chains (new gold on gold RLV #35) trying out several link lengths, it looks to be skipping on the clutch driver sprocket, and when I roll the axle in reverse, it’ll ride up the sprocket and then release.
For the tracks I run, using an animal modified, I really need to use 12 & 13 clutch drivers and anywhere from a 63 to a 70 rear gear.
I would greatly appreciate any info as this has worn me out (in the shop until 4am last night) and want to move on and get back to more important things. Any other info I didn’t add, please ask and I’ll answer ASAP.
 

flattop1

Dawg 89
Not knowing what condition the equipment is in .
Sprockets worn , chain stretched or twisted . 219 intermixed with 35 .
Rear hub out of round . Wrong snap ring , more typical with 11 tooth .
Rear sprockets miss matched or out of round .
Driver teeth hooked / worn .
Chain wore out , not well lubed .
2 different chain types linked together .
Chain pin too tight .
Is it all gear sets or just one or two ?
I had a couple off brand that just weren't right had to toss em .
 

CarlsonMotorsports

Site Supporter
Use a magnetic based dial indicator and check where the run-out is.
Likely axle, sprocket hub, sprocket. At least check it so that you know.
One tight link (roller) in the chain will do the same thing. Remove the chain and lay it flat on a table and check for any links that don't move freely.




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TTCarr

Member
Not knowing what condition the equipment is in .
Sprockets worn , chain stretched or twisted . 219 intermixed with 35 .
Rear hub out of round . Wrong snap ring , more typical with 11 tooth .
Rear sprockets miss matched or out of round .
Driver teeth hooked / worn .
Chain wore out , not well lubed .
2 different chain types linked together .
Chain pin too tight .
Is it all gear sets or just one or two ?
I had a couple off brand that just weren't right had to toss em .

Front and rear sprockets are either brand new, or are in really good condition. No odd wearing or hooking. Chain is also brand new with no links binding at all and the other chain has been used but shouldn’t be stretched and also no binding links. All sprockets are matched up correctly and everything I have is #35 so that’s not the issue.
There is a slight wobble side to side in the sprocket hub, but it is soo small I can’t imagine it causing this issue to the extent that it’s happening. It seriously seems like the chain is not long enough using that 12 clutch driver. On the verge of replacing damn near everything but the axle spins true, chains and sprockets all new or just not damaged in any way.. only thing it MAY be is the sprocket hub but don’t see that SLIGHT wobble causing this.
 

KART//74

Member
Most likely cause is axle runout. Even a small amount when added to the diameter of the rear sprocket will increase the run out.
 

flattop1

Dawg 89
Light weight hubs can get an oval shape , due too off track excursions .
Pull sprocket off the hub , mount up a good stiff pointer or indicator and check the rotation of the hub .
Alternatively I've heard where some take a block of wood lay it on the sprocket with chain and give it a good whack . On the tight spot , not rocket science I know but they said it works .
 

flattop1

Dawg 89
Magnetic dial indicator is easiest .
Clamp a 1 by 2 across the rear frame rails then clamp a 1/4 inch rod sharpened to a point to that . Adjust as close as needed to the object your checking .
 

TTCarr

Member
This is all good stuff guys I greatly appreciate it all. Wasted a lot of time ensuring the sprockets were aligned and messing with chain length... Will check all that has been said ASAP.
I just want to confirm that chain length is not a factor when running a smaller clutch sprocket?
 

Kj26

Member
How many link chain you using ? I start with a 120, put a 13/65 on the kart and have the motor mount a 1/2" in front of the right side rear nerf bar mount and take links out to achieve that distance. That way I can go from a 12 to a 18 tooth driver without changing chains.
 

TTCarr

Member
Pretty sure I tried a 107, 108 and 110. 107 was an older chain so I don’t know how accurate that test was, but the 108 and 110 are both new or in great condition. I’ve heard that smaller clutch drivers need longer chains, and it would seem that COULD be the issue, but didn’t want to keep wasting time on a breaking the chain and adding links just to take them back off. Will spend a lot more time checking everything else including any runout.
 

flattop1

Dawg 89
I don't think chain length is an issue . We ran 11/85-78 for a long time .
It would eat up the driver though .
 

Kj26

Member
One other thought, used to have this problem with some sprockets. How tight are you tightening the rear sprocket and what style guards are you using (plastic, metal or carbon fiber ?
Try putting the rear together finger tight plus a 1/4 turn and see what happens.
 

Outrider

Member
Just to emphasize much of what was said above in a couple of different ways, your problem is NOT with the chain. Something in the rear axle, hub or rear sprocket is where it's at, and what you're looking for is radial run out. When I have had a similar problem, it was usually the concentricity of the rear sprocket in relation to the axle and mounting hub or stacking of tolerances among 2 or all three of them, but usually just the rear sprocket. Just because the sprocket is new does not mean it will be concentric when mounted and the axle and spun. Use a dial indicator on the axle by the hub; that will tell you of it is bent. I've had to pitch more than one rear sprocket over the years because the mounting holes were not concentric with the true center of the sprocket in relation to the rear axle and hub, but more usually it was not that extreme and one could simply find an adjustment point where the chain was short of too tight at one extreme and still not too loose at the other. A dial indicator is your friend, but if the hub and/or sprocket are not running on center as they should be, you can spot it by eyeballing it as you rotate them by hand with no chain installed, especially when the problem is as bad as you describe. The hardest to identify (you can't dial indicate that area) is the bolt circle on the hub where the sprocket bolts on not being concentric with the rest of the hub. Swapping in a new hub will usually identify that problem.

I have also used a variant of what kj26 describes above; tighten the rear sprocket assembly hand tight or very slightly tighter and then spin the rear axle rapidly by hand with the left rear tire (no wheel or tire on the right when we're this desperate) to see it the assembly finds a "natural center" within the clearances available, then tighten everything down

Just some thoughts to consider; it is an annoying problem. Good luck.
 
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