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Discussion Starter · #1 ·
I have a 92 mach 1 w/ a 617 type 643. My problem is that I foul the left plug out every twenty miles. I have cleaned both carbs which were very clean. I took the machine to our local dealer and they resunk the carbs after I did it w/ my vacuum guages (they were near perfect). I have 135 lbs in both cylinders. I had to install a new coil since the previous one was not within spec. If anyone can help I would greatly appreciate it.
 

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I am Spartacus
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I've got the same sled, and it had the same problem. I thought it was the carbs also, I must have cleaned them 15 times. It turned out to be ANTI FREEZE fouling. Are you using any coolant? Next time you can, try this (this is how I found out). Run it with the left plug out of the motor (won't hurt it a bit). Get the track off the ground, and give it a little throttle, and see if a mist comes out of the plug hole. You won't see fuel doing this, it doesn't put out enough to see. If you see mist, put your hand over the hole about 6 inches and get some on your hand. It will smell just like coolant. Hope that's not it, but it's what happened to mine.

Replaced the base and head gaskets, no problems since. Let us know what you find.
 

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Discussion Starter · #4 ·
fouled plugs

I ran the sled w/ the plugs out. I didn't smell coolant nor was the level low either. I am open to any other suggestions.

Thanks
 

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what brand plug are you using and what is the heat range?
i have never had luck with NGK or BOSCH plugs in my older doos
try a set of CHAMPION POWER SPORT plugs and see if that helps
also try backing off the oilpump cable A VERY LITTLE or have the dealer check it for you. hope this helps good luck!
 
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