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Strange day at the track. Any ideas?

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So I took my 03 rm250 to the mx track. It was screaming all day and then I decided to shift up a gear and try riding a gear taller. Now I bogged it a little bit open it up again to burn off the fuel build up. Nothing changed, bike was runnimy flawless. The first time I noticed a change was when the exhaust tone changed and it sound like the bike had pure straight pipe. Like there was no silencer. The bike was loud! Power was very similar. Pulled in the clutch gave it a good blip of the throttle and the exhaust sound returned to normal. Kept riding and all was good.

 

Two hours later, I went riding and I rode between a taller gear and a lower gear and was not really bogging except one area. The loud straight pipe exhaust tone came back and the power delivery did feel slightly different. I tried to correct it by blipping on the track and not a quick change. I pulled off the track gave it a few good twists of the throttle it change back to normal. I rode easy back to the truck. Let it idle, which was normal then turned it off. I packed up and headed home. Got home pulled the plug and it is a dark on one side and perfect tan on the other side of the spark plug.

 

Didn't have time to pull the air filter to see if it was dirty as it was my wife birthday. Lucky I got to ride today. Any ideas on what it could be?

 

I checked coolant level and that's good. Did not change premix ratios. Stuck power valve maybe? This makes me think it could change the tone the most.

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Broken exhaust spring?? Could allow the pipe to push out from the exhaust port causing blow by

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No that is still intact. The sound was from behind. Thanks for the info

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I would think you have an air leak or a partially clogged jet from the description. If my bike started doing that I would check everything from the reeds back in the intake system. Air boot connections, clamp tightness, take the carb apart and clean it out.

If the problem is not coming from the intake then it may be a carboned up power valve, but it reads more like an intake problem.

I have the same bike and once I started using a #7 slide, a necj needle, and went through everything it has been solid. Hope you get it pin pointed.

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These are the jetting specs
168
42
N8rh 2nd
.7 slide
48 power jet
32:1
I haven't changed anything to the bike from the last time I rode and it has been flawless. I didn't think of a clogged jet. I will have to pull it apart and see.

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So I changed my plug just to see what would happened. I checked the air filter and its what you would expect after to visits to a mx track, not a dusty track by the way, hardly any dust. I washed the bike and took it for a quick spin. Bike ripped like always. No change however when I stopped and gave it a good full throttle twist and let it idle down, that loud tone came back. Almost like it has a crackle to the normal 2 stroke tone. Gave it a couple more blips and it returned to normal. Makes me think its again either jetting or power valve. Once the bike dries off I'll pull the carburetor. I would hate to pull the jug off to inspect the powervalves if someone else knows what this is.

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