Snowmobile Repair: engine cuts out.., time 1989, delivery problem

Question
Thank you in advance for your time.

1989 Polaris 650 Indy sks snowmobile.  Going along at about 70 mph and engine cuts out ( dies ) check all things after being towed back to cabin. nothing, one person thinks it is one of the cylinders...

start it up, goes great, get all my gear on ...dead again, and on top of that it won't start.

decide not to risk any more adventure with it..

Can you help with suggestions.

tom  

Answer
Hello Tom,

  Here is where to start, check that it has spark to both cylinders. If there is spark, then crank the engine over with the plug wires removed, about 10 times. After cranking, remove the plugs, and check to see if they are wet with fuel, they should be. If these check fine, then keep the plugs off, and put your thumb over the plug hole, one at a time, and have a friend crank the engine over as fast as possible. There should be enough compression so that you cannot keep the hold sealed, in otherwords, your thumb should be pushed off while it is cranked, from the compression. The more accuarate way to do this would be with a compression guage, and the PSI should be at least 120 PSI. If the sled is getting a good spark, what I would suspect is a fuel delivery problem, or a intermittent electrical problem. Try cleaning both the carbs and fuel pump, and even better, install a rebuild kit in them from somewhere like www.denniskirk.com or www.mfgsupply.com  .  Also, make sure the key switch plug is tight, as well as the tether if equipped, and any plugs in the electrical circuit. Also be sure to use NGK BR8EYA spark plugs, this would be a cheap way to rule out one of the most common problem with snowmbiles, which is the plugs sparking when tested, but not firing under compression. Let me know how it goes, or if you need any help at all. If you're riding it on snow, send some this way! Good luck with the sled! --Arcticatman