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Discussion Starter · #1 ·
Here's the story of this problem. We have had this sled for about 3 years now and the plugs have always looked good (good tan) even on cold days after lake runs. Now I am experiencing a lean condition. But both plugs are not the same all the time. Was out this weekend and only made it 30k and I found out it was running lean after it was backfiring. One plug was fouled and one was white. You could still see the dark tan under the white, so it must have just began. Put a new set of plugs in it and they were both white. It was about -10'C that weekend. Now its + 2 and its still lean (to light of a tan) Sometimes the mag side looks hotter. I have checked the carbs twice, checked fuel pickup, 2 dealer mechanics reasured me that its not the fuel pump. Tested the dpm and have seen no difference with it pluged in or not to the mpem box. Compression is 120-pto and 122-mag. It doesn't seem to idle lean after checking plugs a few times. Only when driving at speed it is lean. Checked the carb boots and reds- there fine. Can the ingition do this or is the mpem module doing it? Everything else points to the motor itself maybe crank seals or gaskets? I tried spraying wd-40 on pto side seal with no rpm increase.

Please help me out, I would like to get this figured out before the season ends.
Thanks in advance for any help.
 

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Discussion Starter · #3 ·
I did a leak-down test today. Presurized each side seperatly to 6psi. They both held it for over 5min and Then I let it out and was convinced its not the seals. What elese could it be? I need some help because I have talked to 2 difference dealer mechaics and they don't know either. Would like to finish the season to.
Dealer says compression is ok and I have had the carbs apart twice this week. All is good. Could it be the mpem module? or something has come loose under the mag?

Help please
 

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Discussion Starter · #5 ·
It is using oil, not sure if thats it? How can you check this? The lines are lining up on the lever right on the pump. But the plugs look great after idleing for awhile.
 

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Discussion Starter · #6 ·
Ok. I have put in larger main's for the time being in the carb. Still ran a bit off, but it was a darker plug colour. I put on a new set of NGK caps and wires and started it up, then took it for a test drive. It idled great and had way more power. Checked the plugs and they were wet black- so I thought the problem was solved. I was going to put the stock jets back in later. So we went out this weekend. After the first 20 min of riding I stoped and checked the plugs they were still wet black. Then I started it up and kept driving and it almost seemed like it went back to what it was like before where it idled rough and had alot less power. Checked the plugs at the end of the day and they were a very light tan to a light grey. Back to lean again. Whats up? Then in the morning when we were getting ready to leave I took it for a ride. It ran great again, then after a shutdown and being warmed up it seemed to go bad and run lean again. Seems to run like its suppose to when cold and after a warm-up and a shutdown it seems to go lean and run bad. My dad says its not the external coils. He thinks its the mpem module. Is this possible?
 
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