my sled 99 XC500 RUNS TO RICH AT LOW END. WHEN WORM ITS HARDER TO START.WHAT GOULD THIS BE THANKS DAN

 

When the engine is warm what does it take to start it .(Do you have to have throttle wide open when pulling the rope)

 

yes, when slowing down it bogs .

 

I own a 99 700 RMK and have the same problem some time I would pull on the rope for 5 min with lots of cussing.You probably donot have the altidude compensator I'm assuming.Ill give you a round about process you can check and some jetting tips from experience.Stock Polaris Snowmobiles after broken in drop 2 sizes in main jet without question.Sounds like you are rich on bottom?maybe .Drop main needles in carbs ,Put E-clip on top slot of needle.See if that helps.If not drop 1 size on pilot jet.See what that does.Pull off and clean carbs thouroughly taking them apart and using compressed air and carb cleaner.Check to make sure there are no kinks in any of the vent lines (Gas Tank Etc.)Let me know how you make out or find.

 

Let me enter this post...I have the same problem...in more!
I have a 440MXZx. When cold, it starts, almost well (have to keep the throttle wide open though), but once it's hot, no way it will start if I don't take off the plugs, empty the crankcase, put the plugs bakc on. Then it will start (with throttle wide open).
I have recently seized in, and changed pistons rings gaskets (not rechromed the cylinders, just cleaned off the aluminium deposits from the melted piston). Could this cause such a bad jetting (since you seem to say it the cause on his 500XC). Could my plug/plug wires have overheated and now not give all the electricity?
Other than this, it runs great...it did lost some power though, but idles fine...just impossible to start when hot.

Thanks for any help!!

 

>>>MY sled 99 XC500 RUNS TO RICH AT LOW END. WHEN WARM ITS HARDER TO START.WHAT COULD THIS BE? THANKS, DAN

Since you do not have EFI it has to be the carburetors.

#1. Because it is hard to start when warm consider this. Float inlet needle valve, gasoline is leaking into the induction system and flooding the crankcase when parked. Because you have to open the throttle wide open, means that there is too much gas in there to start with.

#2. Check your choke cable adjustment. It may be adjusted too tight and causing the engine to run rich, because the circuit is always partially engaged.

#3. It should be okay with the stock pilot jet if indeed this is the stock jet and the dropping the needle could cause you to be lean in the mid-range giving you an unexpected melt-down.

#4. Check out the first two items, take two aspirins and call me in the morning.

 

Zorro, did you replace the pistons or just re-ring it?

 

#1:I have cleaned both carbs twice, cleaned fuel filter...just about everything from the fuel tank to the exit of the carb...nothing changed...
#2:I have no choke but a primer (it injects fuel right after the carb slide).
#3:The jetting is stock...or at least worked great the whole past winter.
#4:the aspirin box is empty.

ting, ting, idea!! could it be the primer that keeps priming when I don't want him to?

 

I changed pistons (the old ones were half melted), rings, base gasket, and both head gaskets. The rods seemed to be perfect, as did all bearigns (I didn't notice anything gripping).
I know that in order to repaur things perfectly, I should have rebored and rechromed (Nikasil, I think) the cylinders, but it takes 1 full week, and 400$can per cylinder!!!!!!!!!! I don't want to spend 1000$ for that!!! At least not now, or one at a time.
If you want to see pics of the destroyed engine, see the signature, I have posted pics of the engine (the album called "poor 440")

 

The choke adjustment was directed toward Sportsman HO.

I wonder if the fuel could be draining down through the primer? You could watch the position of the air bubbles in the line I guess.

How about your float inlet valves? Did they look good and sharp when the carbs were apart?

Some how, some way, gas is getting past the carbs into the engine while it is sitting.

Can you just turn the gas off when you leave the machine? Or is it electrically controlled like it is on the Grand Touring models?