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2 stroke lost power

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I bought my 85 kdx200 with only one hour on the top end rebuild. It ran perfect for a week or so and now It's lost lots of power.

It's difficult to get it to lift at all, and before i could tap up and it would lift high.

It's hard to explain but it hits powerband quicker and it feels + sounds like it maxes out before it gets high enough rpms to really get power.

When I start the bike, it runs fine while cold for a couple seconds then instantly goes back to barely pulling.

So far, I've:

  • Cleaned the Carb
  • Checked Reeds
  • Replaced Spark

Not sure what else it could be, I'm no mechanic

Let me know any suggestions you have!

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65:1, after it stopped working right I tried out 40:1 also and i saw no difference in power.

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Pull the exhaust off and have a good peak at the piston through the exhaust port would be my next step.

 

I would also be wary of the truth behind this rebuild most people will say the bike they are selling is fresh when it really isnt.

Edited by moose_338

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Already pulled off the exhaust, piston looks perfect.

I'm aware most people lie about that, but i chose carefully and bought it from a gearhead.

Any other ideas?

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Is it hard to start when cold?

Along with everything else I am going to assume the air filter is clean.

My next step would be to test the compression, and have a look to see if the stator plate hasn't come lose and is messing with your timing.

 

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65:1 seems real light on oil for an air cooled 200. You said the piston looks good but it's only part of the equation for good compression, worth testing, should probably be in the 115+ range.

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