Cam chain xr 250 honda

chains are not repairable only replace with new ! remove camshaft etc then cylinder head , then barrel and with the side cover etc removed then replace the chain ! tdc the piston when barrel back on feeding the chain up , fit head then fit cam with all valves closed and should line up to a mark on cam cog , fit chain then bolt the cam down , rotate the engine several times back to tdc and check valve clearences and refit all parts and change the oil !

The valve timing is a static setting. As a rule it will either work or not. The only adjustment is usually the ignition timing.

Ensure the engine is on TDC. Then join the dots on the gears.

Both the 1985 honda xr250r and xr350 look loke they have self adjusting cam chain tensioners. You may have a broken tensioner or tensioner guide. With the age of the bike you may need a new cam chain. There is nothing to adjust so you need to just figure out if the chain is stretched , if a guide is broken, or if the tensioning mechanism is malfunctioning.

the ignition timing is electronic, you dont adjust it.
if you mean valve timing.. if it is out of time then you probably need a cam chain and tensioner,

you can't adj. it the cam chain adj. is spring loaded. if your chain is lose there would be three things i would replace, the cam chain. the followers and the adj.
Given the age it wouldn't hurt please it will give a chance to look over the vavle trian.
Mark
C.C. Motorsports

Remove the spark plug then put the piston at Top Dead Center compression. Look at the position of the timing marks on one side of the cam, parallel with the gasket surface. Remove the cam as you described.

Any chance the valve spring has collapsed? Cam shaft thrust washers missing? Cam shaft bearing gone bad?
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sounds like it could be 2 things. the valve tappets, meaning valves need adjusting and or loose cam chain which may need adjusting.