After years of problem free red head riding, we seemed to be running into some issues that we can't resolve.
We picked up this really clean low mileage sled and it had been sitting for a season or two after getting fully serviced at the dealer. It was running on two cylinders (clutch side cylinder dead). The the plug was dry. Off came the carbs and we soon had it running great. Everything appeared fine and we even added a bit of seafoam to the fuel system to aid in further cleaning, etc. It is the nicest and smoothest running red head that we ever had.
Then a month later the sled went back to two cylinders and a deeper investigation found the clutch side piston skirt had broken off on the intake side and then punched a hole in the bottom of the cases. Piston was melted a bit at the exhaust port. However we still had great compression lol.
Anyhow, we just installed a good used engine and it appears to have the same/simmilar symptoms right out of the box.
Compression is good, new plugs, we've got spark, fuel pump is pumping fuel when we crank the engine over, carbs have been off many times and weren't even bad to start with. I'm still thinking it's a lean cylinder hence the wear/failure.
I don't consider myself a sled engine expert, but have a lifetime of experience in auto repair, small engines, vtwin mower racing, etc, etc. I've built and repaired a lot of engines. With the season coming to a close, and a lot of frustration, I'm just reaching out to see if we can figure this one out before I second guess myself to death.
Am I missing something obvious.....?
We picked up this really clean low mileage sled and it had been sitting for a season or two after getting fully serviced at the dealer. It was running on two cylinders (clutch side cylinder dead). The the plug was dry. Off came the carbs and we soon had it running great. Everything appeared fine and we even added a bit of seafoam to the fuel system to aid in further cleaning, etc. It is the nicest and smoothest running red head that we ever had.
Then a month later the sled went back to two cylinders and a deeper investigation found the clutch side piston skirt had broken off on the intake side and then punched a hole in the bottom of the cases. Piston was melted a bit at the exhaust port. However we still had great compression lol.
Anyhow, we just installed a good used engine and it appears to have the same/simmilar symptoms right out of the box.
Compression is good, new plugs, we've got spark, fuel pump is pumping fuel when we crank the engine over, carbs have been off many times and weren't even bad to start with. I'm still thinking it's a lean cylinder hence the wear/failure.
I don't consider myself a sled engine expert, but have a lifetime of experience in auto repair, small engines, vtwin mower racing, etc, etc. I've built and repaired a lot of engines. With the season coming to a close, and a lot of frustration, I'm just reaching out to see if we can figure this one out before I second guess myself to death.
Am I missing something obvious.....?
Are you sure it the plug is good and the fuel is getting into that cylinder?
Actually, it was too much fuel fouling the plug. Resolved.
What was the cause of too much fuel?
I would like to know too? Float stuck? Bad inlet needle?
The carb was reassembled incorrectly. The main jet was screwed back in without first pushing the nozzle all the way back down. This happened because he had the carb in a vice upside down.
After going back through the ignition system and finding no fault. I jacked the sled off the skid and ran it hard until it cleaned up on the bad cylinder and then I could see fuel vapour coming out between the cylinder and exhaust gasket every now and then. It was enough to wet my glove. That's when I knew it was time to look at the carbs and found the error my son had made when reassembling them. Sadly, this would be the root cause of the initial motor failure.
Well that sucks.. live and learn. Carbs can be simple if they are checked .. and its easy to just go back if its dont fire up clean.