My buddy's sled (91 Indy 650) has the bigger of the three jets in the center carb. I've never seen anyone put the larger jet anywhere but on the clutch side. Should he change it around or is this some wierd thing no one really knows about?
I think that's because the cylinder on the clutch side is the one getting the hot coolant. Wherever the coolant enters the cylinder head is going to be the coolest one of the three. By running a larger jet on the warmest cylinder, you might lessen the chance of a burn down. Maybe the 650 just has a bad design. I've always used the same jets in all three on my 600, but i always run a bit rich to be safe. Just my thoughts.
I realize this is a little late but I was checking back on the old stuff and want to add my two cents in. 650's are notorious for holeing the center piston, this why almost everyone jetted the center carb fatter.
As an unwritten rule, most sleds are hotter on the mag side. The theory is the electronics in there holds the heat more, while the pto side runs cooler because of the spinning clutch. Hot rod is right the old triples were famous for burning down the center hole for no apparent reason. A quick plug colour and piston wash check will tell you for sure whats going on in there. Plugs should be a nice light brown colour and the wash should be about the size of your little finger nail. Good luck.
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