sprockets and chain

Yes, the difference is mainly quality. The 420 is much more severe duty and rated for higher speed. Steve

I just found an old #40 sprocket I had from another project and it will not fit into the 420 chain, it is too wide.

. You might have better luck finding a smaller front sprocket, as the chinese clone bike/quad engines are usually very close copies of various japanese designs.
Dave

I just found an old #40 sprocket I had from another project and it will not fit into the 420 chain, it is too wide.
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Many years ago we used to do this on the small Yamahas, 180cc and smaller. We had good luck running the #40 chain on the Yamaha sprockets, and often drilled the rear sprockets for #40 as well. We never broke a chain, and wore many of them out running them in dirt and sand. The narrow countershaft sprocket never seemed to be a problem, and was cheap enough we always used the factory replacement on it, while running #40 chain and rear sprockets.

. --=AD------------- .- Hide quoted text - So you can use a #40 chain on 420 sprockets but not the other way around, anyway I found the proper one through JT 46 tooth sprocket for 20 bucks and it has the proper bolt holes as well.

So you can use a #40 chain on 420 sprockets but not the other way around, anyway I found the proper one through JT 46 tooth sprocket for 20 bucks and it has the proper bolt holes as well.
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I don't recall for certain the factory Yamaha chain back then was 420, but it was the same pitch as #40, but just a little narrower. We assumed it was a metric thing, and the pitch was same by accident.
Back in those days, about 1965 to 70, the local dealer was getting $12 for a front sprocket, $40 for a rear sprocket, and about $30 for a chain. Something like $48, $160 and $120 respectively today. Because of bolt pattern and hub diameter, most folks just saved the bucks on the chain, but a few others had access to machine shops, and did the rear sprockets as well.
Later we found a dealer in a neighboring town, about 70 miles away, selling these items for about 1/3 the cost. He also showed us those prices in the Yamaha parts data as suggested retail. Our local deal, and the only one know to us in those days, was ripping people off selling parts at about a 300% markup.