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Need Help
Dec 11, 2014 19:15:57 GMT -5
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Post by justin on Dec 11, 2014 19:15:57 GMT -5
Hello,
Im new to the forum and reaching out in hopes of figuring out my bike problem. I have a 2004 rm 125. First symptom is it has an extremely erratic idle. It will idle fine then the revs will drop and almost die then I blip the throttle and revs to the moon ill blip the throttle again and the rpms drop and bike dies. Next symptom is the bike cuts out at the top of the revs in every gear. It just sputters and doesnt pull. Stock jetting is 390 main 42.5 pilot. Ive ran a 380, 370, 360 and a 40, 37.5 with absolutely no change. I did a whole carb rebuild replacing the fuel inlet needle etc and saw no change. Ive adjusted the air screw from 0 to 2.5 turns with no change. The reeds check out and ive also sprayed carb cleaner all over the carb while the bike is running looking for leaks and found none. Air filter is fresh and Im running 32:1. Top end has 24 hours on it. I just recently bought the bike and its been a nightmare so far trying to figure out this issue and im tired of staring at it and dying to ride. The bike has race #992 if maybe someone is familiar with this bike. Any help or guidance would be very much appreciated.
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Post by lawnman on Dec 12, 2014 17:10:19 GMT -5
If you are certain it is not the function of the carb, all good gaskets, o-rings, needle seats, diaphragm in float bowl, top plate gasket and throttle cable not kinked, not the fuel and not an obstruction of the fuel delivery (line, petcock filter, etc.) and your rings are seated properly, then it is time to perform a leak down test. Not a compression test, a leak down test. Two stoke engines require a certain amount of crankcase pressure to help seal the lower end from the top end in order to help move the fuel/air mixture through the transfer ports. On a bike this age, if the lower seals have not been changed, or changed recently...well a leak down test will tell you this.
Oh yeah, check for cracks in the rubber reed valve boot, btwn the reeds and the carb, it doesn't take much for air to be pulled through.
Try using WD-40, it will bubble more readily, and spray it around the intake manifold area and the cylinder base gasket and if you access the left-side crank seal (remove ignition cover) spray around that seal. You can also remove the clutch cover and try that side.
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Need Help
Dec 12, 2014 21:38:55 GMT -5
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Post by justin on Dec 12, 2014 21:38:55 GMT -5
That is exactly what I needed. I appreciate your time and the in depth response!
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