I've recently acquired a nice knocking sound in my engine & decided its time for a rebuild. Does anybody know of a good set of oversized pistons to pick up if I bore the engine out to a 1200cc?

 

So, during the teardown, what did you discover that made the knocking sounds?

 

I think there were only two manufacturer's within the last couple years who did aftermarket piston kits for the VTR996, and only one of them who made an overbore set - they came in two or three sizes or something. But none the less, the final displacement after the overbore and installation was moderately under 1100cc's.
...I think the max' displacement with the largest kit came to like 1054cc or something.
Anyway, here is a link to JE Piston's site where they have a kit to raise the compression: http://www.jepistons.com/cat/je/powe...vtr_1000.shtml.
I don't remember who exactly did the overbore kit; maybe it was JE'. Perhaps someone else has some input.

 

Stoke bore and stroke is 98x66mm. A quick run-through on the ol' displacement calculation spreadsheet I found that it would take a 107mm bore to get close to 1200cc. That's +9mm, about 6mm more than the block can handle. In fact, I've heard mention that +2mm is pushing it. To get that kind of displacement you'd need to adjust both the bore and stroke. Factoring in the cost of the special pistons, special rods, crank machining (if possible to go that far), case machining, etc. etc. you are looking at several thousands of dollars. The net result based on the displacement increase alone would be maybe 25hp, so the $/hp isn't looking good. Some head work including oversize valves and cams would get you nearly that much increase for a fraction of the cost.

 

I haven't torn it down yet, but I'm suspecting that one of my valves is hitting the piston. I've never torn down a bike engine before but I can only imagine that it is just a more compressed version of a car motor.

I appreciate the help, and I have to say, its nice having a place to post a question and get some answers quickly. thanks guys.

 

So would it be realistic to install pistons from the SP1/2 at 100mm?

Because they're at 10.5 to one already, and are readily available as usable secondhand.

 

SP pistons have a different piston pin diameter. There is also the matter of deck height....

 

CP will make you an oversized piston, but I doubt you will get the capacity increase you want. Lighter weight, strength, and choice of compression ratio are the main advantages.

 

Hi i have the same problem. I will be having JE manufacture some overbore pistons 98,5mm for me. Only i have to buy 4 pcs, so i will be having two pistons for sale.
Anyone interested?

Greetings