The 1989 Safari 377 have a constant problem of fouling plug on #1 Cyl ( clutch side). Friend told me that it is probably the the crank seal causing this prob. I got the carb rebuild and rejetted etc. Runs smotther without cracking sound finally. The last issue is: spark plug. Wow, The fan side spark plug is a lovely brownish coulour as for the clutch side, black and cold. My solution while finding a solution is changing spark plug #1 to #2 cyl vice versa.
I tried running mix fuel ratio 60:1 no changes ( removed the oil jet pump and plugged both oild supply line).
Any suggestion from experience snowmobile maintainer. Perhaps a link on how to replaced crankshaft seal..etc.