OK, here is my story. A few months ago a purchased a 1998 SRX 700 with a blown engine. Basically the motor looked like a gernade went off in it. The piston on the stator side was seize up and had broke off the connecting rod. The middle cylinder was also trashed, i think it may have sucked up fragments of carnage from the first cylinder. The case was also cracked in three spots. I figured the problem was that the crank had moved out of timing because that year was notorious for that. Upon further examination I saw that the crank had been welded and rebalanced per the warranty. So I basically have know idea why the engine smoked. I picked up a used complete lower crankcase,crank,and rods off ebay that was off a running sled with 3200 miles on it. This crank has had the warrenty welding and balancing done as well. I also picked up two jugs and pistons from that same running engine on ebay. I was able to salvage the jug and piston on the PTO side of the blown engine. I also reused the oil pump from the blown engine. I bought all new rings for all three pistons and a gasket kit. I assembled the whole engine and put it into sled. I made sure to take my time and clean everything to surgical standards. I used all the torque specs in book to reassemble engine. I also replaced all oil and fuel lines on the sled. I took the float bowls off the carbs and cleaned all the needles, seats, jets, and passages i could find. I also put in brand new boeysen reed valves and took apart all three power valves cleaned and replaced seals. I topped off the oil resevoir and put in 3 gallons of fresh gas. I did however premix the 3 gallons to 32:1 so I could make sure the oil pump was working. The engine started up on the 4th or 5th pull. I ran it for about 15 minutes to warm it up and kept an eye on coolant level. I then took it out for about a ten mile ride and it ran great. The next week I took it for a 30 mile ride and it also ran great. The oil level in the resevoir was going down so I figured the pump was working. By this time I needed to put in gas. I filled it with premium gas and hit the trails with friends. About an hour into riding the sled started to backfire. I pulled over and checked the plugs. They all looked ok so i started pulling wires one at a time while the sled was running to find out which cylinder it was. I found which cylinder it was and realized there was no compression. Towed sled home to find a melted piston and a scratched up cylinder. The piston was melted on the exhaust side of piston. This was the piston and cylinder the I was able to salvage from blown engine. I got new parts but I need to find out why. If anyone can help me out I would appeciate it. Are Carbs running lean? Did putting in boeysen reeds make it lean with stock jets? Is it lack of oil?
Thanks for help
Thanks for help
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