XR 250 RY compression

[Hotdoggen]

Does anyone have a compression figure for a xr250ry Haynes is quoting 185 to 213 psi but I'm recording 100psi, Not long since a rebore so maybe I have a valve problem.

[XR Mad]

Drop of oil in through the spark plug hole then check the compression again if its higher then its the rings if its the same it's as you say the valves

[416cc]

If the head was off while the barrel was being rebored was the head not checked for valve seating or a decoke while the barrel was being done??

It may well be that the piston rings on the new piston may well need a few more miles so's to bed them in a bit more. Did you do the compression check when the engine was hot??...or when cold?? It can make a big differance to the readings. Don't forget that the compression ratio is a bit higher as standard, so i'd be looking for the upper end of the figure from Haynes on a fully prepped engine.

[taggkent]

what year is an ry?

Does it have the centrifugal camshaft mounted decompressor?

are you testing it with the throttle fully open and the choke open?