My 660 rator hasnt been rebuilt yet i dont know how long it will be before it does it dosent smoke or make noise and still feels spunkie but i didnt ride it when it was new either so i have nothing to compare it to it has a hotcam,R4slipon,jetting and a K&N filter when i do a topend rebuild i was thinking of putting the high compression piston in it 11:1 vrs 9:1 stock they say it will still run on pump gas the yfz has like 14.5:1 stock i think but thats gota be cam and head design that allows that anyway id like to know if anyone has put a HC piston in there 660 and if it was worth it, Also the 102mm? overbore that brings it up to 686cc same as the stock 700 rap as far as i can tell just buy the 102mm piston bore it and put it back together is that the deal..?is there any other mods to put that piston in? also does anyone know if the dual carb set up on my 01 is a primary/secondary setup like a four barrel carb?

 

all rappys have dual carbs that work in sync, cept new FI rappys and the high comp pistons do help a good bit i prefer either JE or Wiseco and the 686 kits really do wake the motor up specially since you got a cam for it too work with, but it wud be a good idea to always run premium(91-94 octane or whatever) and i know some people who use octane booster as well, and the 686 kits are just a big 102mm piston kit just bore and bolt in, no rod or crank mod, i think from wiseco you can get for about $160 or so, its called Wiseco high compression bigbore 11.1 piston kit.hope that helps

 

If it ain't broke, don't fix it. If you are happy with the power, then I would leave well enough alone. 4 strokes usually last forever if taken care of properly. But if you insist on a rebuild, a JE 11:1 piston is the way to go. I would stick with the stock bore or .20 over, you are going to gain all of the power from the higher compresion and lighter weight than you are with the oversize anyway. If you punch it out to 686 then you will max the cylinder out and will need a sleeve for the next rebuild. The carbs are both primary. The right carb feeds two intake valves and the left carb feeds one intake valve, so they both work together all the time.

 

<div class="FTQUOTE"><begin quote>Originally posted by: Raptor450

If it ain't broke, don't fix it. If you are happy with the power, then I would leave well enough alone. 4 strokes usually last forever if taken care of properly. But if you insist on a rebuild, a JE 11:1 piston is the way to go. I would stick with the stock bore or .20 over, you are going to gain all of the power from the higher compresion and lighter weight than you are with the oversize anyway. If you punch it out to 686 then you will max the cylinder out and will need a sleeve for the next rebuild. The carbs are both primary. The right carb feeds two intake valves and the left carb feeds one intake valve, so they both work together all the time.</end quote></div>



i would stick with the stock bore and you can go from 8:1 to 14:1 comp

 

Raptorguy2001
Mine was running just fine, just like yours. I thought about it, just like you are.
I thought, why not?. It's only money, right.
Went with 11:1 Wiseco, .020" over (stock bore was not that straight), Hotcam stage 2, Hotcam valve springs with titanium keepers, Kibblewhite valves (old ones were gone), and a K&N airbox eliminator kit (I only dune ride, no water crossings). While in there, I did some mild porting and intake port matching, then jetted up to 220 mains (5000 feet). I run premium fuel with no detonation.
After 2 dune trips I can tell you that I should have done this a long time ago. I won't get into what I'm beating in drag races because it will only cause arguments, but things are a lot different now.

I say, GO FOR IT!!!!

 

<div class="FTQUOTE"><begin quote>Originally posted by: DollarBillz

<div class="FTQUOTE"><begin quote>Originally posted by: Raptor450



If it ain't broke, don't fix it. If you are happy with the power, then I would leave well enough alone. 4 strokes usually last forever if taken care of properly. But if you insist on a rebuild, a JE 11:1 piston is the way to go. I would stick with the stock bore or .20 over, you are going to gain all of the power from the higher compresion and lighter weight than you are with the oversize anyway. If you punch it out to 686 then you will max the cylinder out and will need a sleeve for the next rebuild. The carbs are both primary. The right carb feeds two intake valves and the left carb feeds one intake valve, so they both work together all the time.</end quote></div>







i would stick with the stock bore and you can go from 8:1 to 14:1 comp</end quote></div>

Yeah, but then wouldn't you have to run race fuel? I've always been told most 4 stroke ATV engines need 115 octane if running over 11.5:1 compression?