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Everything Dirt Bike
Make / Model Specific
Yamaha
2001 YZ250 Idle
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<blockquote data-quote="Chandlerh93" data-source="post: 195891" data-attributes="member: 2683"><p>Another project, running into issues.</p><p></p><p>This one had been sitting for years. So once again I cleaned it all up... Drained everything, new fluids, new air filter, carb is beyond clean, ill stress that (so I don't think its a carb issue). Now at this point I will say I hadn't gone into the motor yet. I started it up and it sounded just weird, it was unable to idle correctly. I even took it to the desert with no major problems but the idle sounded like the RPM's were just going up and down and up and down over and over and over (and I mean fairly quick, they would do a full loop from low to high back to low within a second or so repetitively... and then it would get lower and try to die so I always had to be revving the engine even when I was holding in the clutch.</p><p></p><p>So, I pulled the top end. The cylinder looked very good and the piston didn't look terrible so I had a shop professionally clean up the piston. I put back together what I would consider to be a "new" top end... BTW I BOUGHT NEW RINGS AND CIR CLIPS FOR THAT PISTON...INCLUDING THE CYLINDER GASKET AND O RINGS FOR THE CAP AT THE TOP</p><p></p><p>Now its all back together and sounding the exact same. Although I technically didn't put in a new top end, it might as well have been. I mean I consider myself knowledgeable enough to know when it actually needs a new motor and id say it all looked in pretty good shape. Could it be the power valve??? If its not the carb and not the top end what could it be? Like I said, the carb is super clean. All the jets are cleared. The air/fuel is at 1 1/2 turned out (even when I try to adjust that + the idle screw it doesn't help)</p><p></p><p>Ill try to post a vid of the sound. Its almost like after I rev it once it sits there and revs itself over and over and over. I cant just rev it and have it come right back down to a normal idle RPM.</p></blockquote><p></p>
[QUOTE="Chandlerh93, post: 195891, member: 2683"] Another project, running into issues. This one had been sitting for years. So once again I cleaned it all up... Drained everything, new fluids, new air filter, carb is beyond clean, ill stress that (so I don't think its a carb issue). Now at this point I will say I hadn't gone into the motor yet. I started it up and it sounded just weird, it was unable to idle correctly. I even took it to the desert with no major problems but the idle sounded like the RPM's were just going up and down and up and down over and over and over (and I mean fairly quick, they would do a full loop from low to high back to low within a second or so repetitively... and then it would get lower and try to die so I always had to be revving the engine even when I was holding in the clutch. So, I pulled the top end. The cylinder looked very good and the piston didn't look terrible so I had a shop professionally clean up the piston. I put back together what I would consider to be a "new" top end... BTW I BOUGHT NEW RINGS AND CIR CLIPS FOR THAT PISTON...INCLUDING THE CYLINDER GASKET AND O RINGS FOR THE CAP AT THE TOP Now its all back together and sounding the exact same. Although I technically didn't put in a new top end, it might as well have been. I mean I consider myself knowledgeable enough to know when it actually needs a new motor and id say it all looked in pretty good shape. Could it be the power valve??? If its not the carb and not the top end what could it be? Like I said, the carb is super clean. All the jets are cleared. The air/fuel is at 1 1/2 turned out (even when I try to adjust that + the idle screw it doesn't help) Ill try to post a vid of the sound. Its almost like after I rev it once it sits there and revs itself over and over and over. I cant just rev it and have it come right back down to a normal idle RPM. [/QUOTE]
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Everything Dirt Bike
Make / Model Specific
Yamaha
2001 YZ250 Idle
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