99 cr250 carb issues and powervalve questions.

[Big80Wr450f]

Hey guys just picked up a 1999 cr250 kinda beat up. I rebuilt her top end and freshened her up now she looks good but I'm having certain issues. One is with the carburetor and the other is with the powervalve.

 

I have 2 screws on the side of the carb. I want to know what the top screw with the spring does. And I want to know what the screw on the bottom does.

 

Second I think I put the powervalve back together correctly. But when I rev the bike I see that the powervalve opens up but does not return to the closed position.

 

Any ideas guys? Any replies would be greatly appreciated.

[bergilong]

The screw with the spring is the idle screw. Turn it out for lower idle, in for higher idle. The lower brass screw is the pilot air/fuel screw. You can turn it in for richer and out for leaner. Keep track of how much you turn it so you can always set it back to where it was.

 

 

 

 

[timbanditos]

Make small adjustments with the air screw that is brass, if you are jetting right it should be close to 1.5 turns out from full close. I would try turning in all the way to the right, then back it out 1.5 turns and go from there. The black idle adjuster raises the idle speed as you screw it in and lowers it as you unscrew it out. There is a great "how to" called Spanky's Jetting that you can locate on google, I would recommend it. Also, do you know what you have for pilot jet, needle size and main jet and slide size? Are you sure you reassembled the power valve correctly when you put the top end back together? It can be easy to miss a small detail that prevents it from functioning properly. 

[Big80Wr450f]

Make small adjustments with the air screw that is brass, if you are jetting right it should be close to 1.5 turns out from full close. I would try turning in all the way to the right, then back it out 1.5 turns and go from there. The black idle adjuster raises the idle speed as you screw it in and lowers it as you unscrew it out. There is a great "how to" called Spanky's Jetting that you can locate on google, I would recommend it. Also, do you know what you have for pilot jet, needle size and main jet and slide size? Are you sure you reassembled the power valve correctly when you put the top end back together? It can be easy to miss a small detail that prevents it from functioning properly. 

I'm pretty sure I put it back together right, The only thing I was worried about was the side of the cylinder where the spring and the two Allen heads are. I reassembled it right now and I had it recoilling back and forth to the H and back to the L on it's own. But now that I put the bike back together and rev it it stays on the H and doesn't come back to the L.

The screw with the spring is the idle screw. Turn it in for lower idle, out for higher idle. The lower brass screw is the pilot air/fuel screw. You can turn it in for richer and out for leaner. Keep track of how much you turn it so you can always set it back to where it was.
 
 

Thanks for the feedback!

[bergilong]

Sorry, I don't know anything about CR250 powervalves, but I do know a little about carbs. I mistyped, you should turn the screw in for higher idle and out for lower idle. Also, did you clean the carb and did you buy the bike from somewhere with a different climate? I'd make sure the carb is nice and clean and check the reeds as well. Bad reeds will cause a lot of symptoms such as hard starting, fouling plugs, and a hanging idle.