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2003 Xr80r No Compression

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Hey guys.. Been a while since posting on here.. Been Pretty busy in the shop..

I have a stupid question that I should know the answer to but im at a loss and gonna ask it anyway..

I just rebuilt my sons 03 Xr80.. I got the bike for a steal and my son was ready for a clutch and the xr80 being the

perfect size I thought why not.. Now having built several Xr's in the past, (a 97 200 for my older son) Im pretty well

up on the xr motors from top to bottom.. And just four strokes in general... But this one is really bugging me.. When it was tore down, the timing chain was broke for one and the head was junk.. (Journals were trashed) So I plunked down the cash and bought a New OEM Head, Cam, Cam Chain, Valves And Springs.. The Cylinder was pretty rough so I sent it of to Powerseal USA to have it Bored..; Ended up at 48mm.. So then I ordered A 48mm Wiseco Piston Kit to put in it.. All went well in reassembly.. End Gaps are good, Piston to Cylinder wall Clearence is good, Put the Head on Timed the Cam, Adjusted the Valves (Both at .003 Thou) I always go a little above the Top spec on the Hondas, Buttoned it all up, put it back in the frame and Damn.... Not a bit of compression... None what so ever.. I haven't done a compression test on it to get the exact psi but I cant see it being more than maybe 50psi.. No air leaks in the intake boots, I have been over this and over this and can't seem to put my finger on why there no compression.. I haven't taken it back out of the frame yet before posting this.. Any suggestion would be greatly appreaciated..; Im sure im over looking something here but maybe someone could think of something I missed... I even second guessed my ring order on the piston but I Miked the top two rings to be sure I didn't get them mixed up.. Narrower ring is on top with the inside beveled edge.. Piston was installed with the arrow pointing toward the exhaust.. Thanks for any help you guys can give me..


I just thought of something.. I didn't lap the valves when I put them into the new Cylinder Head.. Could this be where my compression loss could be coming from?? Didn't do a leak down test by putting water down the intake and exhaust ports before installing the head?? Bike started but will not idle below 1800 to 2000rms without dyeing..

Edited by Nathan Stiltner

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