Topic: XL250S rebuild

[Sam Green Racing]

on a side note, does anyone know what piston is used to up these to 280cc ?

Scun, a 78mm piston would give you 276cc, a 79mm piston would come out at 283cc.
Just a matter of finding a piston of that bore with the right size pin hole, deck hight and valve reliefs.
Nearly all Hondas bore to +1mm in .25 increments, your +.75 gives you 253.6cc.
Did you find out what the funny smell was.

Sam.

[scunny]

hi Sam, no I haven't been stuck in the pub for a few days. the smell was the one you get when your motor is fubered, no sign of blow by or anything so the jury is out on that one, haven't checked the crankcase ventilation yet, who knows.
at the moment I'm sticking with the 253.6cc smallbore, it's a wicked slipper piston, sorry the camera hasn't recovered from it's last outing on the trail bike(got a bit wet when me and bikey went for an unplanned swim)

[scunny]

well citizens of the world, fitting this piston to the bore is driving me insane, I've broken 2 side oil rails and still haven't made progress. I must be losing my touch, never had a problem before.

[scunny]

well borrowed a piston ring compresser and the bloody piston snugged right in first pop, never got to use the compresser. onwards and upwards

[scunny]

yay were good to go, started second kick and ticks over nicely. now onto the 650.