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Old 05-10-2012, 09:15 AM   #5
DiabloADV OP
Joined: Oct 2010
Location: Nor Cal, USA
Oddometer: 2,326
My caliper is accurate to withing +/- 0.1mm. Not good enough for machine work, but good enough to know these aren't stock R90/6 cylinders and pistons. Measuring at the middle ring, I get 93.4 on the piston. The bore is 93.7 in several spots. That's too much gap...

The rings all have end gaps in spec. Seems that if the bore was too big, the end gaps would be wider. Piston sides and skirts show no wear other than very slight marks up/down. The original machining marks are still on the piston sides.

But -- these pistons/bores are too big to be 90/6 overbores, and too small to match any of the 100 specs. I'm gonna have to take them in to a machine shop for proper measurement. The piston/bore gap should be ~0.04, not 0.15.

Off to see Ted with these in hand.


Here's pics of the markings on the cyl and piston:

I scrubbed a bit on the top of the piston...

That would be the spec for an R100 piston. I must not be getting a good measurement. Will have them checked out.
1974 R90/6 motor w/1050 kit; twin plugged; installed in...1970 R60/5 frame; RM125 front end; KZ1000 Police Tank.

DiabloADV screwed with this post 05-10-2012 at 09:38 AM
DiabloADV is offline   Reply With Quote