I own a 1998 Arctic Cat Jag 440 with 1,300 miles on it. It is a decent sled, being on a budget, but it starts hard when warm. It will run decent for a while, but if I stop to take a short break from riding it is difficult to restart.
Many people have told me that with a (cheaper) fan-cooled sled you basically have to accept this, but Iâ€™m not sure I agree with them. Any suggestions?
You could check the spark intensity when it is warm, which should tell us if this has anything to do with it, but I believe it is far more likely for this to be excessive fuel related than it is ignition or mechanical wear related. With a 440 fan-cooled the carbs are going to be set on the rich side. I would be curious to learn how cold-blooded the sled is when you first start it; if our theory is right, it runs good when cold with little use of the choke for very long. When you shut it down, it is over-fueled and takes a few extra pulls and often a cracked throttle to clear out all of the excess fuel.
Take a look at your spark plugs when this happens, Iâ€™d also bet theyâ€™re really wet. Theyâ€™re also going to be dark, or black, indicating a rich fuel mixture. If all of these indicators tell you the engine is getting too much fuel, letâ€™s act upon it. Start by checking the setting of the air screws. They should be at least 1.5 turns out from lightly seated, chances are theyâ€™re at 1 turn out right now, so (lightly) index them and go out an extra 1/2 turn. This will help to clean up the low end. Iâ€™d also drop the needles (raise the clips) in each carb for cleaner midrange operation and install smaller main jets as well; two sizes should be fine if everything indicates a rich mixture.
If this doesnâ€™t clean it up and make the little fan run clean, it is also possible (yet less likely) there is fuel getting past the inlet needle and seat in the carb float bowls, so you may want to consider replacing them if excess fuel continues to plague the warm starting.
Donâ€™t accept that crap about it being a fan-cooled sled. A Jag 440 can be a really fun machine, but like anything else it has to be set-up properly for the conditions.