my 98's indy 500's idle at right around 1200rpm's & the clutch starts to grab at
4000 to 4200rpm's with the P85 clutch. your 1990 may be a little diff. but the
fuji 488cc motor was used for alot of years with not that many changes.

 

I think in one of the earlier responses somebody mentioned the choke. I'd pull both of the choke plungers out and clean them, very common for one or both to stick and not close properly.

 

im pretty sure that in the mid 90's they went to the p91 clutch. at least on my 93 xlt it was. on my 90 500 i think it was the 85. the enrichner circuit(choke) is designed to let more gas in at start up to warm up.if indeed its out of ajustment or sticking it would be flooding it out. easy to tell by checking the plugs being too wet.

 

Clean the carbs, take a good look at the pilot jets. Also with it idleing spray some carb cleaner between the primary clutch and the block and see if the rpms change. If they do, bad crank seal output side. Good luck Doc

 

All the 500's came with the P85 as did all the xlt's .The only thing they put P90's on was the 250,340,440 fan cooled sleds.Weights and springs work in either.Come on over to www.hardcoresledder.com if you need more help.LOts of good tips to check here.I set idle a little higher on the 500's about 1400,I find they will load up if let idle too long at 1250.Does it idle good??no rpm hunting up'n'down.

 

Ok I finally got around to taking the carbs off and cleaning them out real good with carb cleaner. Got the idle set. Starts and idles really nice. Clutch engages at about 3000. Still though from idle I really have to play with the throttle to get it going. Just bogs down when I give it gas. Once I get it to about 2000 though it's fine. Just the low rpm is where it's really doggin.

 

does the bog go away if u half choke it? did u run it around long enough to make
sure the motor was totally warmed up (like 15 mins or so)? did u make sure that
all the jets & jet needle are the correct ones, is the jet needle in the right postion?
start with it in the middle on the e clip then move it to see if it gets better or worst.
your problem is most likely the wrong pilot jet or with your needle jet & jet needle
combination. but there are other things also.

 

I haven't really tried any of that. But I will be sure to. By the way how do I know what the correct pilot is?

 

have a polaris dealer look it up in the service manual or the machine supplement
spec sheet that tells them what the machine came with. the # is wrote on the side
of the pilot jet.