02 Cr125 is fast-revisited

[marcusgunby]

01 Honda Cr has it right.

 

[<HONDA>]

Why would u do that? it makes no sense putting a piston for husky in a honda because the airflow would be different. Is that not correct?

 

[marcusgunby]

Honda dont be too quick to dismiss the idea-heres some background info-
a piston is used to compress the mixture in the combustion chamber,if the top of the piston is the right height from the guedeon pin holes then it probably can be used in any engine with the same dimension-say 54mm bore(like all the 125s have)and say 25mm from crown to pin hole.Now different pistons have different styles-some have windows in the intake side and some have lightening areas around the pin hole.We can use these different designs to tune the engine to our needs.The std Cr piston has a big window in the back-this give more midrange power-but this is where the CR odesnt need more power-it needs more bottom and top.A piston without the window may give a boost to the bottom by moving the power from the midrange.Also the lightening pockets around the pin area arnt there on the vetex and this will boost crancase compression.

Eric Gorr uses 1 piston on all the 144cc conversions no matter what brand it is-KTM/KX/YZ/RM/Older CRs.

Ive known a GP kawasaki team to modify the engines to use Cr pistons.
Also i beleive a hot set up for some tuners is to use a RM piston in the CR.
The thing to be careful is when swapping piston from a domed crown to a flat top-head mods have to be done.

Eric gorrs website has alot more info on this-read up and be wise;)

 

[NO HAND]

Would the wiseco equivalent be as good? I found in the wiseco catalog a few pistons that don't have the rear port window. One is the 707- no port window and the ring pin is in the center at the back, same height/timing. But the best looks to be the 762- no port window, center ring pin, longer skirt and thicker crown, but same height/timing... The wiseco husky piston is the 760 it's too bad they don't describe that piston, it should be similar to the 707. It's really really too bad they don't make any of those in 56 mm either:ugg:
For the RM piston, Eric explained once that there is a need to modify the head to use it.

Originally posted by EricGorr
The 2000 RM125 piston is 1.5mm shorter on the timing height. This piston will advance the port timing and increase the duration of the transfer and exhaust phases. The ring centering pins on both pistons are directly on center with the rear boost port. That enables the rear transfer ports to be widened even further for more overrev... RM Piston, Stock Exhaust
Turndown the gasket surface 1.25mm up to the squishband so the entire 54mm of combustion chamber protrudes past the gasket surface. The RM piston has a shorter timing height and this mod will compensate for the distance between the piston and head.

 

[marcusgunby]

NO HAND i would think the wiseco will work very similar.You will soon be taking over my job and taking my pay-BTW Rich wheres is my pay its been years now and still no check-no doubt it got lost with the postal strikes;)

 

[NO HAND]

Marcus, If I'd be you I wouldn't worry. I've never even held a grinder in my hands. I'm just trying to be a good student. You can't believe how much I learned here in the last year. I really didn't choose the right job in the first place. Do you know what it looks like a social worker with black oil stains under the fingernails..:think:confused:

 

[marcusgunby]

No Hand i hope i havnt given the impression i do my own porting-i left it to a Uk tuner that works to EG specs(as do alot of tuners BTW)porting is skilled work and easy to do badly so i decided not to try as im better at bolting things on;) BTW my Kidney patient dont appreciate me turning up with filthy hand either:confused:
I leant alot of things from this board and also having a friend who got given parts to try for free(because he was fast-a lot faster than me :()

 

[marcusgunby]

No Hand has the wiseco got lightening holes around the piston pin area as this is one big difference if it has-i would go for the vertex if the wiseco isnt the same.

 

[NO HAND]

I'm pretty sure that the 707 and 762 do have lightening holes. Wiseco listed the differences between their product and the stock piston and they said nothing about the lightening holes. The 760 has chances to be like the Vertex but I'm not sure. It is intended to be a stock replacement for the husky cr125. Then it is probably safer with the vertex. Does anyone knows if Vertex has a 56mm husky 125 piston?

 

[marcusgunby]

Seb the husky piston is a vertex if i remember right as is the KTMs.
They list 4 different types of 56mm pistons so you will need to match up the crown heights etc.
I just noticed the piston i have is listed as a CR/WR 97-00 this is the one i have but mine on the box goes from 97-01 because the list is only up to 2000
So the piston i use is the 726-729 so make sudco happy and order away with confidance.

 

[WorldWideRacer]

Marcus (or anyone else, for that matter)-
I am looking for a piston from a common motocross bike that will fit my NSR 250 (Wiseco does not list it, but I want to see if they make one that will fit). Could any of you who have old pistons that are still in decent shape mail them to me so I can take some measurements? Or if any of you out there already know of an interchangeable piston on this bike, let me know.
Thanks,

 

[marcusgunby]

WWR i dont think mailing them is the answer-it would cost as much as a new piston-i can take measurements if you want?

 

[WorldWideRacer]

Marcus,
If you got the time, I would really appreciate it. Just shoot the specs to me in an email at p-d-herr@yta.attmil.ne.jp .
Thanks,

 

[marcusgunby]

Paul i will take a piston to work to measure it as i have better tools-this will be on Thursday.

Seb ive been thinking-you should use the pistons you have available as i dont beleive you will have any power worries once you get the red beast up and running.:cool: