piston size

[baz]

can any body tell me the std diameter of a 900 piston and a 1000 piston, read a thread about piston sizes not long ago but can't find it now (typical)
....cheers

[Big Fluff]

903cc = 66mm
1015cc = 70mm

[baz]

thanks fluff

[baz]

thats cleared that up, i've got 903 cylinders bored out to 1000 cc, if i fit these to a standard 900 engine do i have to change anything else.

[zman]

Good qwestion baz.
ive got the same set up and going to rebuild the head.Not sure if i should have to fit a 1000 head gasket

[Bob Todd]

I would fit an oil cooler, Bob.

[Garn 1]

Zman & Baz, after a 903 block has been bored for 1000cc, it is correct to use the Z1000 A1 head gasket set. No other changes are required except the usually carb jet changes.
As BobT suggests an oil cooler is a good idea,however, many do not require them unless constantly in traffic or an exceptionally hot climate.
Regardz.

[hanskloss]

Hi, regarding the oil cooler, I run 1015cc block in A4, screw in oil temp gauge fitted, most I've seen while stuck in London traffic on a hot day was 105 C, after fitting the oil cooler temp never went over 100 C in heavy traffic, although if you're moving oil temp is around 80-85 with or without the cooler, I think 1000cc is still efficiently cooled by the fins, coolers are more crucial on highly tuned machines