Overbore; Ensuring the right stuff


Post Reply
User avatar
cbx6ss
ICOA Member
ICOA Member
Posts: 350
Joined: Tue Apr 26, 2005 9:17 pm
Location: Virginia Beach, Virginia
Location: Virginia Beach, Virginia

Overbore; Ensuring the right stuff

Post by cbx6ss »

So I'm somewhere in the middle of an overbore, and valve job. I am preparing to farm out the overbore and hone. I just received a set of brand new 1st over (.025?) pistons from Honda. The original pistons measured as follows:

ORIGINALS
2.5383
2.5384
2.5383
2.5385
2.5385
2.5385

When I measured the new ones I got:

NEW ("25")
2.5480 (all)

Increase of .010 diameter from original

I expected 2.538 + .025 = 2.563

What gives?

Is this right? Am I missing something?

/r
Brad

EMS
ICOA Member
ICOA Member
Posts: 10151
Joined: Wed Mar 05, 2003 7:55 am
Location: North East OH, ICOA 3904

Post by EMS »

I am a little confused by all these numbers, especially as you mix metric and standard measurements. The Honda CBX is a metric bike. The piston oversizes were usually identified by mm oversize 0.25mm, 0.5mm,0.75mm and 1mm. I don't know where you have the 0.025 (inch?) oversize dimension from.
Your old pistons measure 2.535 inches = 64.46mm
The new ones are 2.548 inches = 64.72mm
Difference = +0.26mm = 1st over

User avatar
cbx6ss
ICOA Member
ICOA Member
Posts: 350
Joined: Tue Apr 26, 2005 9:17 pm
Location: Virginia Beach, Virginia
Location: Virginia Beach, Virginia

Post by cbx6ss »

Got it! I went back to the parts web site to check and sure enough they offer:
.25
.50
.75
1.00

Maybe if the U.S. had gone metric (in the 70's?) like we were supposed to, that would be one less thing confusing me today. Instead we have both measures on everything today.
Thank you all!
Regards,
Brad

-----Original Message-----
From: The Becks [mailto:T_CBECK@Charleston.net]
Sent: Wednesday, September 10, 2008 8:38 PM
To: Brad Eyre
Subject: Re: Overbore continued...

0.25mm, or about .01 inches.

Tony Beck
-----Original Message-----
From: owner-cbx@ucdavis.edu [mailto:owner-cbx@ucdavis.edu] On Behalf Of XCBMW@aol.com
Sent: Wednesday, September 10, 2008 8:20 PM
To: eyrepb@comcast.net; cbx@ucdavis.edu
Subject: Re: Overbore continued...


In a message dated 9/10/08 7:54:55 PM Eastern Daylight Time, eyrepb@comcast.net writes:

<<I>>

Sounds like the 2.538 is inches and the overbore is .25mm

Paul
NJ

Don #6141

Post by Don #6141 »

I remember once long ago reading a review on a new phono cartridge. It had a tracking force measured in grams, an antiskating force measured in dynes per centimeter squared and mounting holes 1/2 inch apart. I think the reviewer said it best - "Only in America!"

Don

EMS
ICOA Member
ICOA Member
Posts: 10151
Joined: Wed Mar 05, 2003 7:55 am
Location: North East OH, ICOA 3904

Post by EMS »

Don #6141 wrote:I remember once long ago reading a review on a new phono cartridge. It had a tracking force measured in grams, an antiskating force measured in dynes per centimeter squared and mounting holes 1/2 inch apart. I think the reviewer said it best - "Only in America!"

Don
A Shure?

Rick Pope
ICOA Rally Director
ICOA Rally Director
Posts: 2270
Joined: Wed Sep 03, 2003 3:16 pm
Location: Lawrencburg, IN
Location: Lawrenceburg, Indiana

Post by Rick Pope »

Sheesh. Got 'em on both of my Dual turntables.. We really are old.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.

User avatar
alimey4u2
ICOA Web Video Director
ICOA Web Video Director
Posts: 5093
Joined: Fri Aug 11, 2006 1:03 pm
Location: Uphill, WsM, United Kingdom

Post by alimey4u2 »

"Dual" deck & "Precept" cartridge here, just purchased two styli for a kings randsom which should last me in my dotage. Not being selfish, I left one ( the last) for someone else to buy.... :wink:
ICOA # 656

Post Reply

Return to “ENGINES: Maintenance, Performance, Parts Sources”