265 or 270?

[ZSNOW]

i just got a 1986 250r, the guy i got it from said it was a 270? im kinda thinkin he just rounded off a 265? its a paul turner motor

[deathman53]

whats the bore at?? 68mm is an 263, 69mm is an 270

[matt250r21]

Do you know if you have a short rod crank in your 86? I can tell you the long rod 87-89 cranks (72 mm stroke) with a 68.5 mm bore is a true 265.3 , a 69mm bore and the long rod crank is 269.2

I am not sure if the old short rods have the same stroke as the long rods. I'm sure someone will chim in.

[ZSNOW]

its a 1986 so im guessing a short rod, its a paul turner motor, i dunno if that means anything? i have never pulled this thing apart so i dunno what the bore is.

[ZSNOW]

well wouldn't that have something to do with the bore?lol was there certain sizes that paul turner made or were they all different?

p.s i just want to know so i can race the last race with it

[atvmxr]

is there a spacer plate between the jug and crankcase? If not you probably have the 86 crank. stroke is the same, same displacement on the long and short rods. the piston pin location is changed.

[Aceman]

Following what Deathman said, you don't know your motor size without knowing your bore size. If you want to know, pop the head off and measure the cylinder.

[deathman53]

keep in mind also, does it have a stroker crank??? You will be able to tell this based on the thickness of the spacer plate or if the head look machined. Post a picture of it as it is now and tell us the size of the piston, also size of the spacer plate(if there is one). That will tell us the displacement of your motor. I have a stock 88/89 crank, 72mm 85/86 piston, and 4.5mm spacer plate, it comes to 293cc's. Most stroker cranks use a spacer plate of uncommon sizes. Also Paul turner liked using yz250 pistons, they are 69mm and to use them a 3mm spacer plate is required. A picture and some info tells alot.

[ZSNOW]

no spacer plate, but it does have a realll tall what looks like a cool head but real thick, once i get a gasket kit ill pop the head should be by the end of the week, so chances are its a yz250 piston?

[brandon72396]

It will not be a yz piston. There would have to be a spacer plate. It will be the 86 stle 250R piston. 68.50 is the bore of the 265 if that is what you have

[deathman53]

it would need a 3mm sapcer plate for that piston, I know they used that setup in the past.