KX Riders

Maintenance & Technical => KX500 Original => Topic started by: lsampson on April 09, 2013, 02:56:04 AM

Title: Anyone heard of an OEM "C" piston??
Post by: lsampson on April 09, 2013, 02:56:04 AM
I recently tore down my top end on my 1991 KX 500 to freshen things up. I installed a wiseco STD piston, and it ran great but rattled ALOT. I tore it back down, and inspected the old and new pistons extensively. The old piston measures 85.94 mm and the wiseco measured 85.84mm, at least using my caliper. I'm aware that the wiseco is slightly smaller for thermal expansion. I'm borrowing an inside micrometer today, so I should be able to get the bore measured up tonight.

The old piston has a "C" stamped on the crown.

Has anyone heard of a "C" piston size?? All I can find online is 0.50 mm over sizes in Wiseco for over-bored engines, and all I can find in OEM is 1 size, part number 13001A (13001A: PISTON-ENGINE,B) but NO C pistons. With the dealer its the smae OEM number, 13001A: PISTON-ENGINE,B

I know my YZ 250 had different bore sizes, but I'm not sure how much difference it really makes, and I'm not sure why they would call it PISTON-ENGINE B if there wasn't a "C"  :? :? :? :? :? 
Title: Re: Anyone heard of an OEM "C" piston??
Post by: serafin on April 09, 2013, 07:32:05 AM
I think its PRO X that has A B C sizing. 

S
Title: Re: Anyone heard of an OEM "C" piston??
Post by: Motorrad on April 09, 2013, 08:16:23 AM
Quote from: serafin on April 09, 2013, 07:32:05 AM
I think its PRO X that has A B C sizing. 

S

I was thinking the same thing.
Title: Re: Anyone heard of an OEM "C" piston??
Post by: lsampson on April 09, 2013, 08:37:22 AM
looked them up, A is 85.94mm, B is 85.95mm. no C.
Title: Re: Anyone heard of an OEM "C" piston??
Post by: lsampson on April 15, 2013, 02:24:25 AM
Just for anyone's future use, the "C" stamped on my piston must be for cast, as the piston measures like a normal OEM piston.
Title: Re: Anyone heard of an OEM "C" piston??
Post by: alward25 on April 15, 2013, 04:28:45 AM
Maybe they wanted to label the compression end :lol:
Title: Re: Anyone heard of an OEM "C" piston??
Post by: Motorrad on April 15, 2013, 04:32:36 AM
Quote from: alward25 on April 15, 2013, 04:28:45 AM
Maybe they wanted to label the compression end :lol:

Or it stands for "cupcakes". And your supposed to flip it over and bake cake in it...    Hmm that gave me an idea for the getting baked thread....
Title: Re: Anyone heard of an OEM "C" piston??
Post by: Goat on April 15, 2013, 11:46:45 AM
Quote from: Motorrad on April 15, 2013, 04:32:36 AM
Quote from: alward25 on April 15, 2013, 04:28:45 AM
Maybe they wanted to label the compression end :lol:

Or it stands for "cupcakes". And your supposed to flip it over and bake cake in it...    Hmm that gave me an idea for the getting baked thread....

LMAO!!! Thanks for the good laugh. I needed that today.
Title: Re: Anyone heard of an OEM "C" piston??
Post by: lsampson on April 16, 2013, 02:24:44 AM
Quote from: Motorrad on April 15, 2013, 04:32:36 AM
Quote from: alward25 on April 15, 2013, 04:28:45 AM
Maybe they wanted to label the compression end :lol:

Or it stands for "cupcakes". And your supposed to flip it over and bake cake in it...    Hmm that gave me an idea for the getting baked thread....

 :-D :-D