Eric? Wiseco Piston kit

[Motolaw]

Eric, or anyone else that knows;

I have a 2000 CR250 cylinder with Eric's overbore kit, (270). I need to know what Wiseco piston kit to use when doing a top end. I looked for my receipt but I can't find it.

I also need the gasket kit (Cometic?), number that goes with it.

Thanks

 

[marcusgunby]

If you goto www.wiseco.com i think they list all pistons made by them.Yours is 2mm oversize.

 

[Motolaw]

I've tried that but there appear to be different part numbers. I am fairly certain that it is a specific part number for the kit, but I can no longer find it.

Mike F.

 

[Rich Rohrich]

CR270 1997-2000 Models
FSB: 68.520
PISTON KIT: Wiseco #723P8
GASKET KIT: Cometic #C7116
HEAD MODS: 68.5 diameter, .5 recess, 4 degree squish angle

 

[bclapham]

Rich: you are an overflowing mountain of facts my man! :worship:

you might be able to answer a couple of questions for me! :thumb:

1) wiseco offers a different piston for both the 99-01 YZ250 and the 02 YZ250. do you know what is the difference? (both are 66.40mm) can an 02 piston be run in the 01? i was of the understanding that the engines only differed in porting, but this suggests otherwise.

2) Wiseco offers a 2.1mm oversize piston (68.50mm)for these bikes, which by reconing gives a 265cc big bore. However, Rick Peterson is offering a 285cc big bore kit for these YZ's with the standard stroke and a 71mm piston. Do you know what piston they are using for this setup? is going the extra 35cc to far? and does changing the bore - stroke ratio so dramatically change the power output / powerband for good or bad?

thanks in advance ;) ....hopefully eric himself might chime in at some point, havent heard from him for a while, i expect he is a very busy many.

 

[Motolaw]

Thanks Rich,

At the risk of being perceived as a dumb *ss, (like that has ever stopped me before), I will sheepishly ask:

Is there a different kit for a 2001 CR 250 cylinder? After I posted I started second guessing myself as to whether it was a 2000 or 2001 cylinder. I traded in a 97 Cylinder for one of Eric's overbored cylinders complete with porting and I'm waffling on which year he sent me.

Although I didn't think Honda changed the cylinder until it went with the case reed set up in 2002, so maybe the 2001 is the same as the 2000 anyway?

My humble thanks again.

Mike F.

 

[EricGorr]

The correct number for the flat top 2mm oversize Wiseco is 702MO6850 and the CR250 Cometic gasket kits are already opened up to 68.5mm

 

[Rich Rohrich]

Originally posted by EricGorr
The correct number for the flat top 2mm oversize Wiseco is 702MO6850

Eric - Does that replace the Wiseco #723P8? :eek:

 

[bclapham]

any feed back on the yamaha pistons, gentlemen?

thanks

 

[Rich Rohrich]

Bruce - Rick Petersen has some of his pistons made custom so you are forced to buy them from him directly at whatever markup he chooses to add (read HIGH) . When you start moving the bore that far into the existing transfer ducts you risk compromising their ability to flow . I don't know enough about the design in question to tell you whether or not this is the case at 71mm. Eric can probably tip this in.

 

[bclapham]

Thanks rich, it seems that cc's go up exponentially in price and you rapidly come into trade offs! with my limited experience, i never even considered port ducting and flow, but rather i wondered of the effect of bore to stroke ratio and how that changes things (i assume that yamaha changed from the shorter stroke to 72x66.4 for a very good reason!

its not soemthing i am considering right now anyway, since a well setup puch maxi would have enough power for me!!, just trying to learn about my engine etc. i have to get past this funny looks of other riders thing with my magie fuel brews and coolbox first also!:) hopefully eric may share some of his experience. thanks

 

[r_rider28]

Originally posted by Rich Rohrich


Eric - Does that replace the Wiseco #723P8? :eek:

Yes, and also replaces the 702P8 which was also used for this kit.

 

[Yz250rider]

What is your opinion on using a Wiseco piston in a stock 02' YZ 250? This will be the first top end rebuild.

 

[bclapham]

go for it! just remember to do 3 heat cycles

 

[Rcannon]

Originally posted by Rich Rohrich
Bruce - Rick Petersen has some of his pistons made custom so you are forced to buy them from him directly at whatever markup he chooses to add (read HIGH)


I would imagine. Have you checked out his regular, advertised prices?? Wow!