XR250 Clymer Manual spec check from another source please

As noted in another post my Clymer manual for my XR250 on page 74 states the compression should be :-


XR200, 1981-1982 XR250R,XL350R      199psi

XR250, 1984-on XR250R                     192psi

All other models                                 175psi

this isn't right is it. Does someone have the correct numbers please for a 1991 XR250R

Also, now its got me wondering about the valve clearance which have always seemed tiny to me:-

Intake - all models                    .05mm (.002 in)

Exhaust                                   .08mm (.003 in)

Can someone verify those please.

Honda service manual says compression for '86-'91 250 is 184.9 - 213.3 psi.

Valves are .002" intake and .003" exhaust.

Edited by Trailryder42

My clymers manual lists it at 199psi.



This is the version I've got

Yea there definitely are other  factors, one of the biggest being the cam profile and how much overlap is ground into it. That's why there sometimes different specs listed for static compression vs dynamic compression ratios.

And compression ratios(ie 10:1) and cylinder pressures (psi) are related but very seperate factors

Oh and btw those valve clearances are correct as well. To me they are a little on the tight side though so I always run .003 intake and .004 exhaust just be safe

> And compression ratios(ie 10:1) and cylinder pressures (psi) are related but very seperate factors

i think i unerstand - seems odd to quote a calculated figure, would be better for Clymer to give an indication of what should be measured.

Mind you the whole chapter is a bit generic as it goes on about checking cylinder and comparing values, and there is no mention of disconnecting the decomp cable.


Maybe we can get @Wild Alaskan to interject. He usually has some valuable input

Only way you will get valuable compression info is by measuring it with the exact same compression tester over time, if it running good starts easy and doesn't smoke test it. Test it again after 50 hours and see if it is any different. Do disable the Kickstarter decompress or stuff when testing.

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