JE FORGED PISTON 442CC BIGBORE KIT?

[g-force performance]

55mm +1 and 80+ hp race engines do not usually make good road engines. Available big bore kits are still quite expensive for just 4 piston and ring sets and the increase in capacity hardly seams worth the effort.

After a lot of research I have decided to save the money and spend it on fuel to ride as often as possible on reliable as designed by Honda NC30.

In general, I might agree with you. But, our 428cc race engines use ALL STOCK Valve Train. The heads are ported, milled and have performance full-radius valve jobs. The cams are also degreed. Some of that might decrease the low-end performance a slight amount, but we have such a gain over a stock engine that it just reduces the gains (but are still gains) at the lower end of the revs.

The image below shows two different 428 engines over a completely stock RVF400R. You can see that the power is increased everywhere. I don't know about you, but I would take the 428, 432, 440 or especially a 490 as a street bike any day. Although, our bikes do have the HRC NC-30 carbs with no airbox. So, you'd lose a bit on top, bet get even better low-end power and tractability with NC-35 carbs and an airbox.


Mike Norman
G-Force Engine Development
http://www.mngforce.com

[vfrman]

STOP! I have spent enough money...

[g-force performance]

STOP! I have spent enough money...

Sorry. I guess I am living up to my nickname.......

"The Divorcer"

Mike Norman
G-Force Engine Development
www.mngforce.com

[vfrman]

LOL! Maybe we can work something out on the side....You need a 98 900RR?

[g-force performance]

LOL! Maybe we can work something out on the side....You need a 98 900RR?

Uhm...not really. What I NEED is a Fuel Injected VTR250

Mike Norman
G-Force Engine Development
www.mngforce.com

[vfrman]

Can't help with that.

[Cammo]

Lots of injected vtr250's here in Oz

[magg]

New enthusiasm for a bigbore VFR leads me to resurrect this topic. Have received a set of FZR600 pistons and awaiting arrival of a set of piston pin sleeves to adapt the FZR pistons to VFR pins. Weight of complete FZR600 piston + VFR400 piston pin is only 8 grams more than complete VFR piston + pin. Same compression height for both piston and although crown of FZR piston is lower than VFR, larger bore should compensate. Final compression ratio to be determined.

Next step, should FZR pistons prove suitable, will be to acquire sleeves from Melling USA. My research so far says the sleeves will give the required 59mm bore for the std FZR pistons and also allow reboring to 60mm for fourth oversize FZR pistons. Std FZR600 pistons result in 460cc and 60mm gives 475cc.

[g-force performance]

New enthusiasm for a bigbore VFR leads me to resurrect this topic. Have received a set of FZR600 pistons and awaiting arrival of a set of piston pin sleeves to adapt the FZR pistons to VFR pins. Weight of complete FZR600 piston + VFR400 piston pin is only 8 grams more than complete VFR piston + pin. Same compression height for both piston and although crown of FZR piston is lower than VFR, larger bore should compensate. Final compression ratio to be determined.

Next step, should FZR pistons prove suitable, will be to acquire sleeves from Melling USA. My research so far says the sleeves will give the required 59mm bore for the std FZR pistons and also allow reboring to 60mm for fourth oversize FZR pistons. Std FZR600 pistons result in 460cc and 60mm gives 475cc.

8.0g = 534N (120lbs) of additional force on the pin, rod and bearings at TDC and BDC. That poor little rod is going to snap!!!!

I've heard rumor of someone possibly contemplating making a really really big bore kit to get 600cc, or close to it. It may be very expensive. But.....it would be a VFR600RR or RVF600R. That just might be one of the craziest things ever said on this forum Wait! Maybe not......

Mike Norman
G-Force Engine Development
www.mngforce.com
There is no such thing as "Too Fast"

[magg]

Heavier, yes, but compared to JE 58mm 444cc piston (148g) relatively a light weight. Also, engine intended only for road use.