All Things CR250

Mark Jauregui · Joined: 20 Apr 2004 Posts: 183

Hi,

I thought I saw a posting from Ian awhile back regarding piston skirts cracking/breaking, but couldn't find it here. What is the service life of a new Honda piston when being run with an aftermarket ignition? I had a piston skirt go through the engine. It was time for a rebuild, but I'd like to make sure that doesn't happen again.

Also, per a previous comment, it sounds like I don't need to worry about running B pistons with A barrels?

"So sizes are:

A - for 66.34mm bore size
B - for 66.35mm bore size
C - for 66.36mm bore size
D - for 66.37mm bore size

If your cylinder has been replated it could be any size, but without instruction most platers would finish to 66.34

As a by the way, Honda in their wisdom have discontinued their Flat Top A piston for the crankcase induction motor. However, we find the B piston runs fine even in a new 'A' barrel, and we don't suffer any seizures. It runs a clearance of just over 2 thou (yes Erik I was brought up on thous!!)."

Thanks,
Mark
_________________
Mark Jauregui

F125, 250 ICE/FE
NCK

Ian Harrison · Posted: Mon Apr 30, 2012 11:08 pm Post subject:

Hi Mark

We run pistons for 2 race meetings. In the interim if we get any bad detonation we change them as this will weaken the top ring land and make it liable to fall off!

Thre was a period when the flat top A piston was unavailable for the 2002-2004 and Honda were saying that it's OK to fit the B. (which in most cases it is, particularly if you are running leaded fuel).

The A piston for all types and years of motor 1992 - 2007 is now availale (although not shown on the 2002 fiche, it is on the 2004 fiche, so don't let a parts man fob you off) as follows:

Cylinder induction Flat Top 'A': 13101-KZ3-505
Crankcase induction Flat Top 'A': 13101-KSK-670
Crankcase induction Dome Top 'A': 13110-KSK-730

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

Mark Jauregui · Joined: 20 Apr 2004 Posts: 183

Thanks Ian!
_________________
Mark Jauregui

F125, 250 ICE/FE
NCK

Anthony Williams · Posted: Tue May 01, 2012 5:32 pm Post subject:

Hey Ian - I know this is slightly off topic BUT does that also apply to Honda CR 125 engine - is the A pistons now available?

Ian Harrison · Posted: Wed May 02, 2012 4:52 pm Post subject:

Hi Anthony

It depends what year you are looking for:

For instance they only make the 1999 in an A, 13110-KZ4-506 , and they only make the 2001 in a B, 13120-KZ4-A90 and they make the 2005 in both, 13110-KSR-730 (A) and 13120-KSR-730 (B)

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

Anthony Williams · Posted: Wed May 02, 2012 9:31 pm Post subject:

Thanks Ian - you are the man! Very Happy

John Michael Dillon · Joined: 26 Nov 2011 Posts: 61

Ian is the man.

Ian Harrison · Posted: Wed May 09, 2012 9:55 am Post subject:

Anthony Williams · Posted: Wed May 09, 2012 2:10 pm Post subject:

Hey Ian Thanks a lot I really appreciate the information!

Roger Miller · Posted: Mon Sep 03, 2012 9:14 pm Post subject:

Have been getting ready for Laguna, and due to a bit of an issue at Buttonwillow, have been doing up a set of cases for one engine.

Interesting discovery - what is the difference between the 2002 cases and the 2003 cases?

Hint, has nothing to do with the combustion chamber.

Larry Dobbs · Posted: Tue Sep 04, 2012 6:33 am Post subject:

Different size or location of the motor mount points?! I am guessing!

Roger Miller · Posted: Tue Sep 04, 2012 9:15 am Post subject:

BZZZZ Incorrect.

OK, here ya go... I thought I had a flock of 2003 engines, so I ordered the 2003 cases... During reassembly found something didn't match up.
Seems Honda changed the size of the bolt holding the "Guide Plate" which is involved with the gear selector drum. In 2002 the three bolts are 6mm, and in 2003 they are 8mm. So it was an interesting moment when this was discovered.

Darryl Bertram · Posted: Tue Sep 04, 2012 2:12 pm Post subject: Honda Piston Number

Anyone know what the Honda piston number 13100-KZ3-880 is supposed to be. It's a dome 250 piston, two rings and measures 66.36mm

On the subject of pistons I bought a Prox piston and it's an Art manufactured piston looking a whole lot like the Honda ones?

Maybe I should stay off E Bay????
_________________
Australian American Racing

Aussies in Texas

Chris Reinhardt · Posted: Tue Sep 04, 2012 2:14 pm Post subject: Re: Honda Piston Number

Ian Harrison · Posted: Wed Sep 05, 2012 1:05 am Post subject:

Hi Guys

Chris has it bang on the button.

The piston fit's is the O/E spec for 1986-1996 crossers (in fact any '86 to '01 motor) if you want to use a dome top.

At that part number it's an 'A' and should measure 66.34mm Should also have a zero or 'A' stamped on the dome.

So Daryl, perhaps you need to search for a new micrometer off Ebay Wink

The Prox pistons for the 1986-1996 (dome top) and for the 1997-2001(flat top) are manufactured by ART (who also cast the Honda O/E pistons).

Prox Pistons
The 1986-1996 is full O/E quality
The 1997-2001 has just changed. The casting is not quite O/E quality and now has a bisulphide coating (still seems a good piston (so far)
The 2002-2004 is now no longer ART (I wouldn't put it in a kart motor)
The 2005 to 2007 (single ring, dome top) is not an ART (I wouldn't put it in a kart motor)

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