XR250 won't start when hot

[buju]

Well I've had this '84 XR250 sitting around for about 3 months now and I haven't been able to ride it at all. It's a real hard start, but it will fire up after a few cranks with a lot of choke. Fouls a lot of plugs too (although, I haven't ridden it a lot... just sits in the driveway pretty much for now). But if I kill the engine, it simply will not start back up when it's hot.
I'm sure this is a carburetor problem, but specifically I don't have a clue and would like some opinions as to what you think the problem is.
I can't find anyone who knows an independent mechanic or anyone who could do this cheaply, so I'm looking at spending a few hundred (not sure how much yet) on getting it fixed... I have to get the fork seals replaced to while it's in the shop....
I haven't had the time or money to deal with it yet, but I spent 7 hours today just riding street bikes in a MSF course up at the community college... and I really, really need to get my own bike working!
Thanks for your help,
Ben

 

[biglou]

Sounds like it needs some tuning. Sounds too rich for when it's warm. Try holding the throttle wide open and starting when hot. That will allow more air in, leaning out the mixture. Just be sure to back off a bit when it fires! If that doesn't work, sounds like time to clean and adjust the carb, maybe time for some jetting changes.

 

[Ol'89r]

buju.

A couple things to check if it won't start when hot.

First check your valve clearance. Make sure the valves are not too tight.

Check the pick-up coil. This is the small square coil inside the right side engine cover. Over time they get hot and crack. When this happenes the bike will hard to start when hot.

Sometimes the coil wire gets corroded where it connects to the plug cap. Unscrew the sparkplug cap from the ignition coil wire. Nip about 3/8" from the end of the wire with some wire cutters. Look inside of the plug cap where the plug goes. You will see a screwdriver slot. Take a screwdriver and unscrew the brass peice. Remove the brass peice and the spring and resister underneath.

Replace the resister with a peice of steel or brass rod and put it back together. When you screw the plug cap back on, be sure to center the pointed screw part directly into the center of the coil wire.

One other thing to check would be your intake manifold. When these XR's get old, the rubber on the manifold gets hard and will seperate from the mounting flange. Try to move your carb back and forth and look to see if the aluminum mounting flange bolted to the engine has unattached or seperated itself from the rubber boot.

Good luck. :thumb: