Chain skipping

[LouTX]

Greetings,
I have inherited a strange and unfinished uild. A UTV powered by a GY6 150cc go-kart engine and with a 12:1 rear diff.
While trying to finish what someone started, I am having a problem with the chain skipping and eventually coming off.
The chain is tensioned well, no slop. But it still comes off. In reverse faster than in fwd gear.
This is an overdrive setup with a 48T sprocket on the transmission and 16T sprocket on the rear shaft. 1/2" pitch. All connected with a 420 chain. Did I mention it's a bastardized setup?
Looking at the alignment of the sprockets, they don't look that badly misaligned. Am I incorrect?
I would appreciate any input on how to improve this situation. This needs to run and run reliably.
Any good advice or questions are welcome.

Thank you
Lou in TX

 

[Karttekk]

Greetings,
I have inherited a strange and unfinished uild. A UTV powered by a GY6 150cc go-kart engine and with a 12:1 rear diff.
While trying to finish what someone started, I am having a problem with the chain skipping and eventually coming off.
The chain is tensioned well, no slop. But it still comes off. In reverse faster than in fwd gear.
This is an overdrive setup with a 48T sprocket on the transmission and 16T sprocket on the rear shaft. 1/2" pitch. All connected with a 420 chain. Did I mention it's a bastardized setup?
Looking at the alignment of the sprockets, they don't look that badly misaligned. Am I incorrect?
I would appreciate any input on how to improve this situation. This needs to run and run reliably.
Any good advice or questions are welcome.

Thank you
Lou in TX

View attachment 141633

View attachment 141634

I would replace the chain with a #50 chain. Your chain more than likely isn't sitting down in the sprocket teeth enough. Every kart with a GY6 engine I've worked on shipped with a #50 chain.

 

[Karttekk]

Your sprocket appears to be a #50 sprocket also.

 

[Karttekk]

Refer to this chart to learn the chain differences.

Go Kart Chain | Masterlinks | Half Links | Tools

Go Kart Chain and Mini Bike Chain. High Quality Go Kart Chain, Mini Bike Chain, Masterlinks, Halflinks, Go Kart Chain Breaker Tools and Chain Tensioners. Standard Roller Chain for most brands. 35 Chain, 40 Chain, 41 Chain, 420 Chain and 50 Chain.

www.gokartsupply.com

 

[LouTX]

I would replace the chain with a #50 chain. Your chain more than likely isn't sitting down in the sprocket teeth enough. Every kart with a GY6 engine I've worked on shipped with a #50 chain.

Isn't #50 chain 5/8" pitch? These sprockets and chain are 1/2" pitch.

 

[BrownStainRacing]

Isn't #50 chain 5/8" pitch? These sprockets and chain are 1/2" pitch.

Looks to me, that the chain is too big for the bigger sprocket. It's not sitting down far enough to get a good hold.

Measure how far down the top of the teeth are to the top of the link.

Looks like the chain is setting down deeper on the small sprocket. The teeth are sticking up farther, getting a better hold.

 

[LouTX]

Looks to me, that the chain is too big for the bigger sprocket. It's not sitting down far enough to get a good hold.

Measure how far down the top of the teeth are to the top of the link.

Looks like the chain is setting down deeper on the small sprocket. The teeth are sticking up farther, getting a better hold.

The chain fits snugly around the whole sprocket. The links seat in the grooves between teeth. I measured the depth and it checks, plus minus a few thou for measurement error.
In all my (young) years of dealing with chains, the sprockets were always farther apart. These are much closer than what I am used to. How much does distance affect reliable chain engagement?

 

[Karttekk]

Double check the pitch on your sprocket. I have one from an American Sportworks Carbide that measures 5/8" pitch. Try a #40 chain maybe.

 

[Karttekk]

Rather than guess, I would pick up matching chain and sprockets. You have an obvious mismatch unless something is worn which it doesn't look like it. The Go Kart Supply site explains chains and sprockets in detail. I would get all new matching parts.

 

[LouTX]

Both sprockets and chain are 1/2" pitch, confirmed.
I even measured the chain. 20 links (inner + outer) measure 20". Chain fits great around both sprockets.
The primary (48T) sprocket has a very slight amount of lateral runout (maybe 1/8") and I wonder if that is throwing it off and making the chain kick up in a tooth and come off.
With the drive engaged, I hear and feel "bumps" which I verified visually are the chain attempting to come off. Not sure how to stop it.

 

[Karttekk]

Both sprockets and chain are 1/2" pitch, confirmed.
I even measured the chain. 20 links (inner + outer) measure 20". Chain fits great around both sprockets.
The primary (48T) sprocket has a very slight amount of lateral runout (maybe 1/8") and I wonder if that is throwing it off and making the chain kick up in a tooth and come off.
With the drive engaged, I hear and feel "bumps" which I verified visually are the chain attempting to come off. Not sure how to stop it.

Once you figure it out let us know.

 

[Hellion]

........The primary (48T) sprocket has a very slight amount of lateral runout (maybe 1/8") and I wonder if that is throwing it off and making the chain kick up in a tooth and come off. With the drive engaged, I hear and feel "bumps" which I verified visually are the chain attempting to come off. Not sure how to stop it.

That could very well be it. Any misalignment or angular deflection could derail it.

Look for burrs too, somewhere on the sprocket or a bad/bent tooth. You can always force the chain to stay on the sprocket with those sprocket chain guides.

 

[Master Hack]

ditch the 420 use #40 and check all the above.

What Is Roller Chain Wear & Elongation - Causes & Solutions

www.nitrochain.com

 

[Karttekk]

I don't see any slack in the chain. There MUST be some slack in the chain for it to work properly. If you don't allow for some minor flexing and movement the chain will skip and pop.

 

[Karttekk]

 

[JimD]

The 1/2 inch chain looks good in most of the sprockets. The only thing I would double check on and that is to make sure you don't have a #428 sprocket in your mix. ONLY 428 chain will fit that sprocket. Yes #41 , #40, #420 and #428 chain are all 1/2" pitch but the #428 chain has a much bigger roller than the first 3 chain sizes. I have written this before and it is worth repeating, the roller in #41 and #420 is the same size .306 and the roller in #40 is .312 but the roller in #428 chain is .333 and it needs the correct sprocket and chain or it will climb and not seat itself in the valley of the sprocket.

I like to use #40 chain with a #41 sprocket because you have some extra side play so your alignment doesn't have to be dead nuts correct. Also #41 and #420 are the same chain but the #420 has been pre-stretched and was the choice of all the kart manufacturers when they made fun karts in the US up to 2005 -the day the music stopped for the kart manufacturers.

 

[JimD]

Your very first picture the roller seems to lifted up in the front sprocket but in the smaller sprocket it looks to be well seated. I would concentrate on the front sprocket that one looks to be wrong but it could be your picture also but heck you are looking for suggestions and that is what we are doing.

 

[Karttekk]

Your very first picture the roller seems to lifted up in the front sprocket but in the smaller sprocket it looks to be well seated. I would concentrate on the front sprocket that one looks to be wrong but it could be your picture also but heck you are looking for suggestions and that is what we are doing.

He's looking for suggestions and he's gotten a bunch of them but he keeps throwing the specifications of what he has out there instead of trying different solutions. My suggestion was to replace everything with matching components so he could enjoy his machine instead of figuring out why his current setup isn't working. Makes you wonder why people use this forum for help then question any responses they get.