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Recently replaced the crankshaft seals in my 1996 SL780 and after getting it back together found that it won't start and after cranking for a while it backfires in a big way ! ( I think it is the PTO cylinder generating the backfire). During the rebuild I did the following work - replaced the crankshaft seals and had the motor pressure tested - it passed. I also rebuilt the carbs with rebuild kits and rebuilt the fuel pump with a kit.
I didn't make any adjustments to the low or high speed mixture screws from the settings that worked fine prior to the rebuild. The stator timing mark was aligned with the crankcase join and all 3 cylinders are getting spark and there is fuel going to the carbs. I used all new gaskets and as far as I can tell all the hoses , manifolds and exhaust are sealed tight. As a test I tried starting it on the front 2 cylinders but there was no sign of life (at least it didn't backfire !). Any insight into the problem or general info on what causes a 2-stroke to backfire would be great.
I didn't make any adjustments to the low or high speed mixture screws from the settings that worked fine prior to the rebuild. The stator timing mark was aligned with the crankcase join and all 3 cylinders are getting spark and there is fuel going to the carbs. I used all new gaskets and as far as I can tell all the hoses , manifolds and exhaust are sealed tight. As a test I tried starting it on the front 2 cylinders but there was no sign of life (at least it didn't backfire !). Any insight into the problem or general info on what causes a 2-stroke to backfire would be great.
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