82 xr250r

[eskort]

I got this bike and it had some serious timing issues and seriously bad oil leaks. Took the thing apart, finally got the timing on, sealed the engine and put it back together. Once i got the carb on and turned the gas on, it was overfueling and gas pouring everywhere. I ordered a float valve for it and pu tthaqt in so now that issue is no longer. I can set the airscrew at 2 turns out and it starts but has a bogging point in it. I can drive it for a few minutes then it gets worse. I tried to play with the settings on the carb and it made it worse. So again i set it back to normal. No it is just backfiring and when it does start i have to hold the throttle about half way and it surges on its own. I got this bike for free and its only cost me 7 dollars so far for the float valve, but i just want it to run and go for a rip. By the way, when it fires up cold it runs like a top, it idles and everything. If someone could please give me a suggestion or 2 on where to start looking for issues i would greatly appreciate it. Thanks. One last thing. Yes i cleaned the carb about a million times.

 

[dirt bike dave]

Have you checked the the valves?

If they are too tight, all the clearances will disappear when the motor warms up, and the valves won't close all the way. Then the motor runs very bad and won't hot start.

 

[2strokerfun]

$7 for a float valve!!! Last one I bought from Honda set me back $30.
Recheck the timing.

 

[eskort]

i kid you not, 6.99 from JJ's recreation here in town. But you are right my price at honda was 37.27 canadian. Thats rediculous. But anyway have a feeling i have a burnt valve seat, so im on my way out the door to the garage to pull the engine apart. Wish me luck.

 

[eskort]

how does this sound. I messed around with this thing forever and it runs then dies then it wont run then it will. So i was convinced it wasnt a carb issue anymore. I rechecked my valves and rechecked my timing and the only thing was my timing marks on the cam were off just about half a tooth. If i tured them back or forward to line up the marks it was still out half a tooth. Now i knew there was something wrong. So its too cold to ride most days here now so i decided to tear the engine down. Found a few small scores on the cylinder wall, the piston in fine, but there is one valve that has a couple of nicks on it around the edge and where the cam sits in the head is worn out. I measered the height of the cam in the old head and compared it to the cam sitting in a spare one i have and i was right it is sitting way to low causing slack in the timing chain. My spare head has a smashed out valve seat though so i hope i can find a cylinder head. Does this make sense to anyone? I think it does. But maybe some pointers from here on would help me out. Thanks.

 

[Ol'89r]

and where the cam sits in the head is worn out. I measered the height of the cam in the old head and compared it to the cam sitting in a spare one i have and i was right it is sitting way to low causing slack in the timing chain. My spare head has a smashed out valve seat though so i hope i can find a cylinder head. Does this make sense to anyone?

eskort.

Yes, that makes a lot of sense.

This is pretty common with the older XR,s. The cam rides directly on the aluminum journals in the head. If the bike runs out of oil or gets low on oil or has dirty oil, the journals can wear out and allow the camshaft to move around in the journals. This constantly changes the valve clearances and on the models with points, it causes the points to bounce around and not maintain a constant point gap. There are two ways to fix it. Either replace the head or contact a company named Megacycle Cams. They used to offer a service where you can send your head in and they will bore the journals and install a cam with ball bearings. End of problem.

It may be less expensive to have a new seat installed in your spare head if the journals are in good condition. Any good motorcycle machine shop should be able to install a new seat.