chain issues

[Dick Yates]

Racing a KT100 11-78 gear and notice that when I turn the rear axle, when the chain reaches a certain spot, it tightens up and the axle doesnt turn as easy. I have eyeballed the alignment of the clutch hub and sprocket and all seems well. If you take the chain off, the axle spins free so its not a bearing. Help!!!

[Kyle. Daughtery]

Try replacing the sproket carrier. If this does not work then my guess is a bent axle or worse a bent crank. Cheepest solution first is sproket carrier.
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Kyle Daughtery
RaptorRacing.us

[Pete Muller]

There's a good chance that the sprocket is not running dead true on the hub.

Loosen up the bolts a bit that hold the sprocket on, then turn the rear axle. When you get to the tight spot, give the chain a bit of a "squeeze" (one side of the chain to the other) which will tend to pull the sprocket forward. Do that a few times (spin the axle, check for the tight spot, then try to move the sprocket "away" from that tight spot).

If that doesn't do it, then as has been mentioned... you may have a bad sprocket hub, a bent axle, etc.).

[Dick Yates]

Thanks. I wanted to add one more thing see if you think this indicated anything. It spins freely when the motor is not fully tightened to the frame but after I torque it down it starts to drag again. Anything there?

[Rick Begeman]

It could be just the way your axle gear mounted on the hub. Loosen the gear bolts and find the tight spot and squeeze the upper and lower chain runs together to pull the sprocket closer to the motor, then tighten while holding tension.

If that does not work mark sprocket and hub for gear orientation and tight spot, remove sprocket from hub and check to be certain gear (if 2 piece) is assembled correctly and that gear and hub are clean. Reinstall gear on hub 180 degrees off where it was previously. If problem still exists note if tight spot is same or moved. If tight spot is same hub or axle is bent. If tight spot has moved the problem lies with the gear. Try a different (new) gear to prove.

Note some gears have a burr on the inside radius from the punch press die, orient the burr to the outside of the hub or remove burr, I never install the gear with the sharp side to the hub as it can get stuck and or wont seat properly.

[Scott Heavin]

I've had that happen on my TaG and every time it's been a stretched chain. Have you thrown the chain and wrapped it around the axle, causing a stretch just in a certain area?
I fought this forever trying to figure it out until I realized that chain stretch doesn't mean just the length of the chain (necessitating moving the motor forward), but the chain links them selves will be affected - especially if you throw it.
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Spec TaG Masters @ NCMP / #23

[Dick Yates]

The cart is used so Im not sure if its been thrown or not. We have to race this weekend and I dont think I can get a chain or a sprocket hub. Is it ok to race it like this?

[jim wirtz]

loosen your chain a bit more
we like about 3/4" to 1" of play in the chain.

What is happening is the frame rails are not perfectly paralel, but your mount is. when you tighten your mount, you are actually twisting the frame a little.

to check if this senario is correct, place your motor on the frame and see if you can rock it at all on the rails. there should be NO rocking at all.

good luck

Jim Wirtz
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Jim Wirtz


http://www.wirtzswoodworks.com/

[Dick Yates]

3/4 to 1" total up and down? I wondered about that because I can get it to turn free with some more slack but i was worried i was allowing too much slack.

[Rick Begeman]

When you adjust the chain slack set it at the tight spot. Your chain should never be taunt. If chain is too loose at the loose spot tighten chain but never so far that the chain is taunt at the tight spot.

And I second that the chain can be the problem, do not use low quality chain it will just wreck your sprockets. Lube chain before every run, use a chain lube that goes on thin so it can get into the chain, Motul, Torco, etc

Also if you are running a 10 tooth or smaller driver they wear very fast and will take out any chain if let go too far. It's probably best to start with all new parts so you are certain of the condition of all the parts. Unless the hub is a super light weight piece it is probably not bent unless there is some wobble present. I don't like the real light weight hubs as they can be ruined if you dip a wheel off the track. It's easier to change or replace a sprocket than a hub and probably cheaper too cause if you bend a hub you have more than likely bent the sprocket too.

Lastly I would not take any chances with a chain because when they come off they eat up anything in their path, right arms in particular, engine fins, clutch drums, throttle cables, ignition wires, fuel line, etc.

[al nunley]

I found that the sproket hub shoulder, where the sprocket sits, is not always the exact same I.D. as the sprocket.

Turn the axle until the chain gets tight. Grab a piece of wood, (very thick) and put it up agaiinst the chain at the rear. Give it a light blow with a hammer. Ceck the chain. Good slack? Yes? Have fun. Still tight? Hit harder. Continue a while until the chain gets loose. If it doesn't get slack, it must be something else. The sprockt hub could be bad. If you have a lath you could check that. Maybe a friend, or the kart shop you go to. Easy thing to check.

Another thing, make sure the chain always gets tight in the same exact spot. Put a mark on the tire.
_________________
If the data does not support the theory, get a new theory. (Al Nunley)
All else being equal; Compression is the Holy Grail.
45 years, in and around karting

[Marshal Vortriede]

simply buy a new chain. they stretch over time... i cant believe everyone is blaming the sprocket and carrier.

[John Matthews]

[Steve O'Hara]

Marshal, John,

Sorry guys, you flunked this test Go back an read Pete's answer again... it is correct. I might add to Pete's explanation that sometimes grime gets in between the ID of the sproket and the OD shoulder on the hub and prevents the sprocket from centering up on the hub. I would encourage anyone with the problem described by Dick to remove the sprocket from the hub and be sure the surfaces are clean and free of any junk and then assemble and adjust per Pete's description.
The basic problem stems from the OD of the step on the hub being just a little undersize and it allows the sprocket to mount out of concentric with the hub. We've been dealing with the problem since the 60s and even with the much improved quality of the modern parts it still happens in some cases.
Regards,
Steve O'Hara

[John Matthews]

Hi Steve,

Test? I didn't know there was a test

I've seen the problem described many times and various things have fixed it including removing and replacing the sprocket. However, Dick indicated that this is a used kart so I'm guessing he has no idea how long the chain has been in service. He also kept posting after Pete's answer so maybe he still needs help....

IMHO, chains and sprockets are expendable parts and the new guys who come on here to ask questions about them should always be instructed to carry spares. If you don't have them you can't eliminate them as possible sources of your problem (one of the basic procedures in any troubleshooting tree). It might also be that Jim is correct and he just had the chain too tight.


The best thing about this forum is that someone can tap into literally hundreds of years of experience just by typing a question. I do sometimes get the answer wrong, kinda hard to have 100% sucess when you're not looking at the problem with you own eyes but hopefully everyone here agrees that carrying an extra chain is a good idea for kart racing

Cheers,
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John Matthews
Heartbeat Power, LLC.