1999 Polaris 500 Magnum - running rich - lots of black smoke. I’ve tried different idle jet settings, have even turned it all the way in to get it to run lean. Doesn’t seem to affect it. I’ve checked the choke, it could be stuck open, but I think I’ve ruled that out.

Couple of observations- idle jet screw needs to be turned out less than 2 turns or it won’t start hot. When starting up, I have to hit the override to reverse (first time only), or else there is no power and coolant blows from the overflow.

Otherwise the machine instantly fires up cold, and runs like a bat out of hell. Of course it’s using way more fuel than it should.

Is it possible I’ve damaged the carburetor or idle jet? What should I look at next?

 

Check valve clearance(.006 intake and exhaust) plus look for excessive cam exhaust lobe wear. Common problem on these older machines. If the lobe looks the same as the intake lobes,no excessive wear,sounds like you need to go into the carb. A worn needle and seat can cause excess fuel and smoking. Some kits out there aren't the best,but this one is. Magnum 500 uses the same kit as the Sportsman 500.New Shindy Carb Repair Kit For Polaris 500 Sportsman 1999-2000 03-416

 

I should have mentioned I rebuilt the carb already. Took 3 tries. Hence my question on the idle jet - I know there is a warning not to tighten. Wondering if there is damage there. I checked the valve clearances with you in the past - they are ok. Had to reset them after finding out cam chain wasn’t on right from previous owner.

 

"Couple of observations- idle jet screw needs to be turned out less than 2 turns or it won’t start hot. When starting up, I have to hit the override to reverse (first time only), or else there is no power and coolant blows from the overflow." Think you have more problems than just the carb.If I'm understanding this correctly you have to push the over ride to crank it or is it just in reverse? You won't have full power in reverse unless you push the over ride button,but if it's causing problems,this model has the limiter build into the speedo assy that may be causing problems. There are ways to bypass the over ride,but since you've gone though the carb 3 times that someone else has already messed with,sound like a used carb OR as a last case scenario an aftermarket Chinese one that some have done alright with.Shouldn't be using a lot of fuel if the needle and seat are new and float set right. If you happened to break the tip off the pilot screw,this would block fuel to the low speed circuit which doesn't sound like what's happening.You might want to do a compression test (55-90 psi) on average because of the compression release on the cam,plus a leak down test also.You may also have mechanical problems to deal with.

 

May just buy a replacement carb. The compression is ok - was 60 on first test. Added a little bit of oil and then compression was 90. So rings may be a bit worn. The override is needed to start motion into reverse, first time only. Otherwise there is no movement and coolant blows out overflow. Once it backs up, I can go forward and then backup without override. I already replaced speedo sensor. The wiring had been hacked to keep the fan on and disable the override, I backed all that out and cleaned up the wiring.

Tried to do a leak down test before, but at that time there was no compression due to timing chain not set right. Will have to take back to garage or find someone with the tool. After I reset the chain, it hasn’t slipped.

 

Hope you get this figured out as this is what turns a lot of people off one brand or another atv. Not that the Magnum wasn't a good machine,IT was.. It's just that prior owners can screw up so many things that a new owner has to deal with.If you buy a project machine always expect the unexpected. Good luck on this one.

 

Thanks again. Was able to order a new carb fairly cheaply. To be fair, this machine is 18 years old. If carb doesn’t work then I’ll start to dig into the motor. It’s entirely possible I messed up the old carb.

 

If it's one of those Chinese aftermarket carbs,make sure you remove the float bowl,check that jetting is the same as the oem carb and no trash or debris. I'd blow out every opening.

 

Dropped in the new carb from wincycles off eBay. Was spotless inside. Didn’t have to change or adjust anything. Way better option than trying to rebuild the carb. Seems like all my issues have disappeared, must have been carb related. Can’t wait to get this thing out for a longer test on the trails.

Thanks again for your help.

 

Glad you got it running,but don't chunk that 500 buck Mikuni carb. Have some one check into it.