Trashed JS Sprocket

[Eric1204]

So, we chewed through the JS sprocket today on the Manco Silver Fox and I had a couple questions....but first the particulars.

Robin EX17 6.5hp
Comet 30 Series
9t JS sprocket (or at least it was)
60t axel sprocket
18" tires

All of the above are stock.

First question - is that a "normal" wear item or indicative of a different problem?

2nd - I asked previously about moving,to a bigger JS sprocket and based on all of the advice - that is not the way to go.

Now, given that most of the driving is not at full due to yard constraints, I'm thinking about going smaller for better quickness. Would going to a 8t sprocket make much of a difference?

As always - thanks for the input.


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[KartFab]

Yeah it makes a noticeable difference.

Here's the one you want. http://gokartsusa.com/GTC-TC2-Torque-Converter-and-TAV2-Replacement-Sprocket-2.aspx

I think it's a type C so it should work fine.

As far as premature wear goes, you need to make sure you change your chain along with the sprocket. A damaged/worn sprocket will also damage your chain.

Make sure you line up the axle sprocket to the jackshaft sprocket with a straight edge.

Chain tension plays a big part too. Too tight or too loose and you could get that type of wear.

Also if you have a bent or slightly out of round axle, it could make excess tension at one spot in rotation vs another. When checking chain tension, do it at multiple spots in axle rotation.

 

[chancer]

Itsid AKA "thanks" Mentioned on here twice that very low tooth sprockets will wear excessively. I do not know what your answer will end up being but going now to 1 less tooth may cause the same issue. Unless of course you can confirm the problem was improper chain tension or something. Just my 2 pennies.

 

[MadManAndrew]

Adding on to what Chancer said since he is correct, the best thing to do would probably be to replace the axle sprocket with say, a 72 tooth and stay with the same size drive sprocket, or maybe even a couple teeth larger one, to decrease wear.

 

[Eric1204]

Thanks Chancer. I'm not sure if it's excessive wear in so much as I've only had the kart for a little more than a month and it may well be the original sprocket. The chain was a bit rusty and while I did lubrciate it I hadn't gotten around to changing it. It is a bit loose now, though I did tighten it a couple weeks ago. I don't think the kart got a lot of attention by the previous owners.

After reading Karfab's post I ordered a new chain and 8t sprocket and if we burn through this one then I will go with bigger sprockets.

EDIT: How does one set the correct chain tension?

 

[landuse]

EDIT: How does one set the correct chain tension?

You either cut the chain to length, or you use the engine mounting slots to move the engine forwards or backwards to loosen or tighten the chain. There are things called half links that can also be used

 

[Eric1204]

You either cut the chain to length, or you use the engine mounting slots to move the engine forwards or backwards to loosen or tighten the chain. There are things called half links that can also be used

Got that part - but I was wondering how much flex there should be if the chain is properly adjusted.

Found the answer in the maintenance instructions (who knew?) - 1/4" to 3/8". Based on how much flex there is now, the chain had become too loose.





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[landuse]

Got that part - but I was wondering how much flex there should be if the chain is properly adjusted.

Found the answer in the maintenance instructions (who knew?) - 1/4" to 3/8". Based on how much flex there is now, the chain had become too loose.





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Sorry about the miscommunication. Yes 1/4" to 3/8" is the standard amount of flex

 

[Eric1204]

No apology - it's a safe assumption that I'm working from a limited knowledge base.

Cheers!


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[Eric1204]

So, finally got the new 8t JS sprocket and chain installed and my son definitely noticed that it's a bit quicker. Haven't checked top speed with the speedometer app yet, but illy doesn't feel like we lost much top speed.

Thanks again for the suggestions and help.

 

[landuse]

So, finally got the new 8t JS sprocket and chain installed and my son definitely noticed that it's a bit quicker. Haven't checked top speed with the speedometer app yet, but illy doesn't feel like we lost much top speed.

Thanks again for the suggestions and help.

Awesome!