CR250 pistion question

Gerry MacNutt · Posted: Thu Jul 05, 2012 9:18 am Post subject: CR250 pistion question

On a 2002 cr250 motor with a very good low time "A" barrel is a OEM Honda 'A" piston OK for kart use? just wondering if it may be slightly on the tight side and possibly stick in this application. Or would it be better to run a "B" piston? Would prefer a "A" if it is safe to run.

Ian Harrison · Posted: Thu Jul 05, 2012 10:07 am Post subject:

Hi Gerry

An 'A' piston will be asolutely fine for kart use. The Honda 'A' pistons generally measure up at 66.32mm anyway so you should have 0.08mm (3.15 thou) of clearance with a brand new 'A' cylinder.

The 'B' piston is BIGGER and the Honda version measures up at 66.33mm, so until you get a fair bit of wear the A will be fine.

I have been told that some US Honda manuals seem to indicate that a 'B' piston is smaller . . . . that is incorrect.

All the aftermarket pistons are sized at:

A = 66.34mm
B = 66.35mm
C = 66.36mm
D = 66.37mm

I would stick with Genuine Honda, they are top quality and the sizing is consistent and accurate.

Best Regards

Ian Very Happy

_________________
Ian Harrison
Viper Racing UK
www.viper-racinguk.co.uk
sales@viper-racinguk.co.uk
+44 7984 225 564
+44 161 343 2009
Championship winning Superkart race team 1997-2012

Gerry MacNutt · Posted: Thu Jul 05, 2012 1:16 pm Post subject:

Thanks, yes mine did say the B was smaller.

John Michael Dillon · Joined: 26 Nov 2011 Posts: 64

Another piston question. Do the new pro x pistons that are coated require a little more clearence? I stuck one earlier this year. Had .0024" clearence. It siezed opposite corners. I believe I found the cause ('s) but just want to make sure before I put this one back together, Thanks