1999 Ski Doo MXZ 600 roughly 3,500 miles (I have another matching sled to this one so I can swap parts)
I need help friends! I've tried about everything I can think of and I'm going crazy. I'm fairly mechanically inclined but I'm really new to snowmobiles. Please help. SOS
First trip of the year, the carbs were cleaned out and some general maintenance was done. We rode both sleds 70 miles with ZERO issues.
Came home and put the sled in the garage to replace the carb boots (cheap amazon boots) and I added aftermarket Hot Grips to the sled since the the stock ones no longer worked. Checked the reeds when the boots were replaced and they looked great, no chips and they laid flat.
Took the sleds to northern Michigan to go for a ride, started them up on the 3rd pull and warmed them up for a few minutes then took off across the lake to the trail head, everything seemed fine. When we got to the trail head I noticed my fiance's sled was sounding weird and instantly thought it was running on 1 cylinder. I changed the plugs because they look exactly as the picture shows, 1 really good spark plug with good color and burn (PTO side) and the other looks like a brand new plug. It didn't show it running lean and it didn't show it running rich. It literally looks like its not sparking and just covered in fuel (MAG side). So I took off on the sled and ran it hard and fast thinking I could clean it out and it would run better. I drove it for 40 miles and the whole time I swear its on 1 cylinder. It doesn't drive too bad like its still got a little power but its boggy and you can hear it almost "knocking" or sounding hollow and feel it. If you get it past the bog and hit WOT it will lift the ski's up and go like its on both cylinders (but I have no idea if its firing on both I was able to hit 50MPH without much problem) and it sounds good but, its clear from idle to 3/4 throttle its on 1 cylinder. After the 40 miles trip I pulled the plugs and they looked the same as before, the picture attached is after 40 miles.
Came home, put the sled in my heated garage and started the investigation.
Compression check was done with 5 pulls each time, both plugs pulled, I did not hold it WOT, cold engine. 5 tests per cylinder
- MAG Side: 115-121
- PTO Side: 123-129
Both carbs were taken off and sprayed out with carb cleaner. I attempted to replace the needle and seat but I could not drive the pin out. I replaced both jets on both carbs. They looked fine and were not clogged but I replaced them anyways.
- Put everything back in the original place with 2 fresh plugs.
- I then swapped the carbs keeping the fuel lines the same.
- I then swapped fuel lines.
- I pulled both fuel lines off and started the sled and both lines produced the same amount of gas with a steady flow.
- I then swapped 1 carb off of my sled that's in good working condition
- I then swapped fuel lines. Every time I take the fuel lines off gas comes out so I know its getting fuel to the carbs
None of this worked, every time I tried something new I started the sled and lifted the back up and let it idle then did a couple hits then an idle and a shut down to look at both plugs. When I pull the plug out of the MAG side white smoke will come out for a minute or two and you can visually see the top of the piston is wet.
NOTE: At the beginning of the year the MAG side of the sled did have an issue where after it was shut off the carb would continue to puke gas out of the overflows. I took the cap off a couple of time and it never happened again. (no idea what caused this but maybe its important)
After more thinking the plug wasn't showing fuel problems its showing more of a spark issue. Both plugs were pulled and tested on the head and show good spark. Both firing at the same time and both good blue spark. Just to make sure I purchased a used coil and swapped it out with no change. I took the coil off of my sled and still no change (I swear it sounded better and acted a little better but I don't think it was). I even changed the plugs out again to make sure it wasn't a bad plug. I took the coil off of the tank and swapped wires and still no change. I can pull the plug wire off of the MAG side and the engine does not change tune and continues to idle, if I pull the plug off of the PTO side the engine dies instantly. This happens with all 3 coils.
After all of this testing I can touch the Y pipe on the MAG side about an inch away from the head and its warm like I can leave my hand it and not get burnt but if I try that on the PTO side it will burn me.
Something else I've noticed that might be related is when I started the year both headlights worked, when I started day 1 of testing the low beam stopped working, when I started day 2 of testing the high beam no longer works. The dash lights and tail light work still, when the RPM's are low they are dim but as soon as I hit the gas they turn up. All of this testing was done with the hand warmers and thumb warmers turned off.
I'm so lost with what to do next. I can swap MPEM boxes from my sled does that require anything else? I'm assuming I would have to swap the tether as well? Just at a loss with where to go next.