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Just another newbie with a hard to start 2007 CRF 250r . Bought last summer to get into mx and some singletrack, ran great in summer but started to get hard to start when hot , then as we came into a Canadian winter wouldn’t start at all. Checked valve clearances last night intake was in spec if not a tad loose, exhaust valves were at 0.009 maybe 0.010 inch but very tight fit ( spec is 0.011 inch ) am I right in thinking as the exhaust valves are steel they won’t wear as fast so can be shimmed a few times rather than a whole top end and head recut like the intakes ?
I also noticed what seems like excessive play in the auto decompression pin can anyone confirm if this is normal? I’m getting some side to side play but have been told that could be normal on older designed bikes , this motor has apparently 75 hrs . I do have a video but can’t upload it
Next thing is the timing didn’t quite line up between the cam markings and timing peep hole by the rear brake ( I checked clearances with the cam in the right place )
Thanks for any input .

The timing marks rarely seem to line up perfectly to my eyes. Before I unbolt the cam sprocket for the first time, I get those marks perfectly spot on and open the right side inspection hole and make a punch mark on the inner assembly where I think things line up.

Slightly tight tolerances are perfect, but Honda wanted to make the specs owner-proof. On a 450, where the spec is .006 and .011, I aim for .0045 and .009. That has the effect of quicker and longer duration valve opening, as well as setting the valves down slight softer.
The exhaust valves are generally not the problem child that the intakes can be. I change to stainless steel soon, trading absolute red line performance for better longevity and durability.

I haven't been around a decompressor pin that is out of spec, someone else will have to chime in.

Thanks for reaching out and sorry for delayed response .
do you reckon a sloppy decompression pin could cause the exhaust valves to be open too long causing low compression? Carried out a compression test this evening following factory instructions, bike fired up after 8-10 kicks for warm up but only read 25-ish psi during a compression check, seems odd that it started with such low compression , wondering if the sloppy pin has something to do with the low reading. Bikes at 74 hrs of trail riding so wouldn’t be totally out the question that it needs a top end .