83 XC 250 - Bad topend power

As the title says I have an 83 XC250 with stock jetting, good compression, and great low end power. When I get into the top end it seems to load up a ton and loses power.

I tried a smaller main and needle clip position and that did not help. . Any ideas would be helpful.

Thanks!

what are you getting for your compression test? kicking until the needle quits climbing, wot

Also check that your spark arrestor screen is clean. Was the this 83 250XC running great and all of a sudden loose top end power or has it been getting gradually worst?

Marty

I will recheck the compression.

The screen is clean, I just cleaned it during a light restoration of the bike.

It has always seemed down on power but now it is really bad.

Sounds like you've checked obvious stuff so consider the motoplat ignition. I've read that when an ignition begins to fail top end power loss can occur due to the loss of adequate spark thats required to burn all the fuel within the short period of time that exists at high RPM. The result from an inadequate burn is loading up and loss of power. I don't have any experience testing a motoplat but attached is testing information I found and saved to my tech files some time ago. Hope this helps!

maybe good to do. let us what you are able to get...make sure to kick until it quits climbing, and hold wide open throttle.
my 84wr was wanting less main but running ok everywhere else years ago..compression had slipped to 140 psi