Have been trouble shooting my 02 Yamaha 50 4 stroke for the past few months. Starts fine , idles fine, but when in gear between 1000rpm and 2200rpm engine runs rough. Once past this range it runs fine.
Initially, I assumed it was a fuel issue and did all of the usual trouble shooting, new gas , new bulb, new fuel lines, carb cleaner, new plugs. Still ran rough. Carbs were beyond me so I asked a local mechanic to clean the carbs and change the oil while he was out there. Still ran rough. He could not figure it out.
Found another mechanic ASE certified, he said for sure it's carbs and said sometime they need two or three cleanings. I went along and was never ther when he finished up to do a water test. He came out three times and after each time it still ran rough, same rev range. I noticed some steam/smoke coming from exhaust port and decided to check the oil level. It was above the 'full' line on the dipstick, so I drained it to the proper level and checked the plugs for signs of oil. The only oil I found was on the threads but I replaced all four plugs anyway. It ran perfect for the first time in 2-3 months.... After about ten minutes of low rpms in gear the splutter/roughness came back. I thought I'll run it at WOT try to burn off any remaining oil. Ran great, once I came back down to 1500rpms it ran rough again. Still showing steam/smoke at the port and I though I noticed a pingy knocking sound. Any guess, this above my pay grade at this point! Do I have a leaking valve? Blown gasket? All or none of the above? I was hoping I could find an anwers here. Appreciate your help.
Compression test was done and checked out o.k.
Initially, I assumed it was a fuel issue and did all of the usual trouble shooting, new gas , new bulb, new fuel lines, carb cleaner, new plugs. Still ran rough. Carbs were beyond me so I asked a local mechanic to clean the carbs and change the oil while he was out there. Still ran rough. He could not figure it out.
Found another mechanic ASE certified, he said for sure it's carbs and said sometime they need two or three cleanings. I went along and was never ther when he finished up to do a water test. He came out three times and after each time it still ran rough, same rev range. I noticed some steam/smoke coming from exhaust port and decided to check the oil level. It was above the 'full' line on the dipstick, so I drained it to the proper level and checked the plugs for signs of oil. The only oil I found was on the threads but I replaced all four plugs anyway. It ran perfect for the first time in 2-3 months.... After about ten minutes of low rpms in gear the splutter/roughness came back. I thought I'll run it at WOT try to burn off any remaining oil. Ran great, once I came back down to 1500rpms it ran rough again. Still showing steam/smoke at the port and I though I noticed a pingy knocking sound. Any guess, this above my pay grade at this point! Do I have a leaking valve? Blown gasket? All or none of the above? I was hoping I could find an anwers here. Appreciate your help.
Compression test was done and checked out o.k.
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