Help! I'm stumped, We have a 1995 Polaris Magnum 425 4x4 in our shop. The customer's complaint was when it warmed up it bogged badly, he said he would stop shift the bike into nuetral and rev it up a bunch of black smoke would come out and then it would run fine for a short while then he would have to repeat the same proceedure again. Now don't get too excited I'm fairly sharp with mechanics. First I started the bike and ran it around the yard for a good ten to fifteen minutes the bike seemed somewhat sluggish and non-responsive running extremely poor and backfiring a bit. Next I removed the air filter, no improvement, I left it out and removed the exh. springs and seperated the exh at the cylinder head, loud but no inprovement so a hooked it back up, next I removed the carb for the second time and throughly cleaned it, it's perfectly clean the needle and seat are the best I've seen the jet needle in the slide is locked propperly by the spring and the diaphram's perfect. I hooked up the carb to a gravity fed tank to bypass the fuel pump and still bike idles perfectly but when you throttle up it starts to stutter, I'm aware of the rev limiter and it does act any differently when the button is depressd I opened the throttle bay and the limiter switch is 100% operational. HERE'S THE KICKER with airbox completely removed from the carb the bike throttles up perfectly, BUT as soon as you hook it back up it won't rev. this is with the airfilter out completely vacant box ABSOLUTELY NO RESTRICTION GAURENTEED, AND NO IT'S NOT COLAPSING UPON ACCELERATION. You can literally rev the bike with the air box sitting 1/2" off the intake throat on the carb and while your revving it slide the airbox intake tube on the carb and it falls flat on it's face, and I mentioned THERE ARE NO OBSTRUCTIONS IN THIS TUBE. P.S. I pulled the valve cove and set the tappets to .006" according to service manual, they were almost perfect, i would say I may have increased the tappet clearance if anything by a thou or two.
PLEASE HELP I LOOSING SLEEP!!!
