high comp pistons

[grader]

by the end of this season i will have about 13000 miles on my 03 rx1. am thinking of installing weisco high compression pistons to boost the power and end the oil burning (13:1). is anybody running these? would i have to run premium or could i get away with 87 regular? any idea on hp with this compression?, thanks.

 

[RX1Jim]

I would not be so sure the new pistons and rings will end your oil consumption problem. I believe these engines are running too cool to allow proper combustion leaving the residue to gum up the rings and ring lands. I wish the seasn was long enough to try running different temp. thermostats and see what difference they make. The higher compression will put more heat into the combustion chamber so perhaps there we be less residue. I'd be interested in seeing what your pistons and rings look like when you take them out. Talk to Freddie at ECP about the HP increase, he is an expert, he'll know.

 

[RX1Jim]

Grader,

What is it going to cost you in parts to put the new pistons in? If i could find a used RX-1 engine it would be a terrific project to rebuild it withthe hi-comp pistons, some porting, cams and other mods.. I wonder how much HP is possible out of these engines without a turbo, NOS or a supercharger?

 

[Red2003]

At 13:1 you'll need atleast 91 octane. Power increase from compression alone would probably not be that significant. For the price of that rebuild, you could get more HP increase somewhere else. NOS maybe?

 

[grader]

the pistons are about 550.00 cdn complete. when new, the comp was 204 on mine and 205psi on black johns. the manual says spec is 179 min to 230. im thinking the 13:1 pistons should put it up near 230. i would like to keep it trailable and can run premium if i have to. i may have to pm freddy for more info, but was hoping someone else had allready tried it and could give me some feedback. they also make 12:1 pistons which is basically same as stock(11.8:1), but its the same amt of work so im figuring more bang for the buck.

 

[JDMCRX]

These motors run far from cool Well in me and other friends case they run warm lol. Bumping the comp will help some power, But i say some mild port work,exhaust and intake u will feel it.

 

[crazyyamaha]

I don,t know about the high comp pistons , but I do know that the 05 rings will end your oil burning. I replaced my rings about 4200 miles ago and it still doesn't use oil, and I drive very agessive ie like WOT across the turtle flowege wich is about 30miles across.

 

[RX1Jim]

Crazyyamaha,

What year is your RX-1? Did you replace the rings with the 2005 part numbers or did you have the dealer do the work? I beleive some members of this forum with 05 sleds also reported some oil consumption.

Thanks!

 

[crazyyamaha]

My sled is a 2003. I did the work myself with 2005 part numbers. I was using a quart every 300 mi before that ,now I don't have to check the oil every time I put gas in. Also, I am using Valvoline Durablend 5w30.

 

[RX1Jim]

Crazy,

Did you replace the pistons as well as the rings or reuse the 03 pistons? What did you find when you took out the pistons? Were the rings clearly stuck in the ring grooves? Does it look like carbon buildup is the reason for the increase in oil consumption? What did you do to hone the cylinders? I am thinking of helping out a couple of friends with sleds that are consuming oil but want to have a complete plan before I start. Thanks!!

 

[crazyyamaha]

I replaced the pistons, but I didn't think that I had to. I did it for peace of mind, they had 8400 miles on them. I was tearing the whole motor apart & what's $200 when you're spending $1400. The rings weren't stuck, but the pistons were full of carbon, mostly on top. Definitely burning oil! The reason that I rebuilt the motor was that I spun a bearing on the crank, because the oil drain plug fell out (it stripped out & I didn't realize it 'til it was too late.) Because the cylinders are ceramic lined and all of the honing marks were still on them and no wear was on the cylinder walls, I left them alone. I thought about honing them, but wasn't sure about doing it, since they were ceramic lined & didn't have any wear on them.

 

[crazyyamaha]

Oh, about carbon build up causing oil use. I believe that the '05 rings have more spring tension than the '03 rings. If you look at the rings, they look identical. I think the more carbon that you get on the pistons, the more oil that it uses because you get more blow by and you have higher compression now because you have 3/16" of carbon build up on top of pistons. As I said, the rings were not stuck. Also, the head & valve face had carbon build up, which would also increase compression. Being the rings weren't sealing, it would blow past the rings, pressurizing the crankcase, causing oil mist to go out of the breather hole & get resucked through the carbs. Vicious cycle, causing more carbon build up.

 

[crazyyamaha]

I apologize for all these posts, but I keep thinking of more things. When I rebuilt the motor it was almost a year ago. When I installed the piston rings I didn't offset them according to the manual which is about a quarter turn from each other. I did it the way I was trained I was an ASE certified mechanic for twelve years.The top ring was installed 90 deg. from piston pin .The second was installed 180 deg. from top ring. The first oil ring was installed back on the same side as the first ring but in the middle of the first ring gap and piston pin The oil expander ring is installed 90 deg. from the top oil ring on the same side as the first ring and top oil ring. The second oil ring is installed back on the same side as the second ring but 45 deg from the piston pin and top ring. Hope that makes sense. I am not saying that you have to install it this way, but this is the way that I did it and had good luck, so far.

 

[givemeaboost]

Where did you hear that the cylinders are ceramic lined ? They are nicasil coated from the factory just like many of the two strokes out there, Ken.

 

[crazyyamaha]

In my 2003 service manual it states that "newly formulated ceramic composite coating with increased silcone content for greater durabilty" .under the heading of cylinder /crankcase: . Thats is where I got my info from.