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Discussion Starter · #1 ·
See if anybody here has an idea. First off, this is a 2004 Arctic Cat 500 manual shift, not a Vinson, but the engines are virtually identical as far as I know.
Machine had sat a long time in my garage. I started having issues with my '02 KQ 300, and decided to get this thing back out. I did a thorough fuel system cleanup/rebuild - steam cleaned tank, new petcock, fuel lines, full carb disassemble and went back together with a rebuild kit.... Gave the engine some seafoam, warmed it up, then changed fluids. Cut the engine oil filter open and inspected pleats, nothing abnormal found. It was running excellent and ready to ride.
Put 20 or so miles on, was purring along at 50 mph and it fell on its face, thought it was going to die, but before I came to a stop, it took off again, ran like nothing happened. I got back to camp and looked everything over, all ok.
Couple hrs later, fired it up, no problem. Got out in a logging area, torquing over trees and terrain just over clutch engage RPM, wondering why I had let this thing sit so long..... slight pop/backfire and died. Started right back up. Repeat, 3-4 more times, each time a little sooner than last - then nothing, cranked fine, sounded normal as in no mechanical noises, pulled by hand and compression seemed OK....
Pulled it back to the trailer, went home and bought a 19 KQ 750 ;) !

Now it's time to get this thing out of my garage. Thought about just calling a scrapper,, but with current prices I just might get something out of the ol girl.
Did everything mentioned in previous threads, new plug, new cap, new coil, tried another CDI. Reason I've been concentrated on spark, (which is visibly there, but not necessarily as strong as I would like) is even with the carb and exhaust removed, cranking with the starter and give it a shot of carb cleaner it doesn't even pop.
I verified the flywheel is still keyed to TDC and checked that the valves open and close at roughly the correct time and valve lash does open, meaning valves are closing.

2 things I haven't gotten a grasp on. First, I did a compression test and only got 80 PSI, the AC manual listed spec at 85 psi for a 500, that number makes no sense to me, I would think it should be much higher. But either way, I should at least get a huff out the exhaust port cranking with starter and fueling the intake port.
Second, in an attempt to check spark timing, I set up a timing light. Cranking over, the timing light won't pick up the spark. I do recall being told timing lights struggle to pick up CDI voltage though.
So, what am I missing?
 

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Discussion Starter · #2 ·
Update, I finally figured this one out. The A'Cat uses an adapter harness that sends voltage to the auto choke feature on the carb and connects to the voltage regulator. This harness has a nice high temp sleeve covering the not so high temp rated wires. The wires overheated inside that sleeve and fused together causing a short.
I probably could have just replaced the adapter harness, but I could see signs of heat on the regulator and the stator wires, I elected to replace the stator and regulator - both from RM Stator, highly recommend. All together and starts/runs better than it did for a long time.
Word has it this is also a weak spot on the Vinson. I used this machine for commercial snow removal for a few seasons, so a lot of winch use. It's advisable that if you run a winch and handwarmers regularly that you keep an eye on the regulator and stator wiring. It probably isn't a bad idea to replace the regulator with a HD unit preventatively.
 

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Glad you got it all sorted out. Thanks for sharing your fix.
 

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Thank you for posting your solution...hopefully it will help someone and it great to see solutions posted as often we dont get an update.

Your solution does highlight the idea that we should always thoroughly check wiring if we suspect an electrical problem.
 
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