Stutterring XR 250L

Joined
May 19, 2003
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#1
Hi people,

my 93' XR250L is able to start and idle. When the engine cold, the bike seems normal enough, but after warming up, the bike stutters very badly when ridden with partial throttle.

When not in gear and reving the bike, it stutters badly when I twist the throttle too quickly, but seems alright if I twist it slowly.

This symptom appeared after I attempted a top end rebuild. I have checked and double checked that everything was assembled correctly.

Does this sound like an air leak anywhere? or a jetting problem, or.... Anyone has any ideas?

Cheers!
 
Joined
Jan 27, 2000
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#2
What you describe sounds a lot like tight valves. Runs worse after warming up.

If your cam timing and valve clearance is correct, you may want to check your carb. Make sure the slide is in correctly and the needle is not bent. Remove the slide from the carb and spin the needle with your fingers.

If the needle is bent, replace it. If not, make sure the needle is in the recommended position.

If your intake manifold is rubber, check closely where the rubber meets the aluminum flange. If there are any air leaks, that's where they will be.

Sometimes the pick-up coil can come loose inside the engine. Have seen this happen on a couple XR's. It is the small square coil inside the right side cover next to the crankshaft. Make sure the mounting bolts are tight.

Hope this helps. :thumb:
 
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#3
Hi, just need to check:

when installing the cam and cam sprocket, I aligned the two marks on the sprocket face parallel to the cylinder head surface while ensuring the "T" mark is in line with the mark on the left side cover. At this point, the piston should be at TDC.

Question is, is there such a thing as "compression stroke" or "exhaust stroke" at this point of time? Does it matter if I rotated the crank another 360 degrees then install the cam?

Thanks for your help!

Cheers!
 
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#4
Originally posted by new_dirt


Question is, is there such a thing as "compression stroke" or "exhaust stroke" at this point of time? Does it matter if I rotated the crank another 360 degrees then install the cam?
new_dirt.

Your crank doesn't know which stroke it is on until you install the cam.
What determines the compression or exhaust stroke IS the position of the cam. When installing the camshaft, be sure the crank is on the "T" mark and both lobes of the cam are pointing down towards the crank. If your cam was 180degrees off, it would be hard to assemble the top end since you would be pushing against the valve springs while trying to torque down the head/top cover.

Be sure to recheck your valve clearance and maybe do a compression test to make sure everything is sealing properly.