Heavily modified gpr 1200 piston situation

[srjrinc]

First of all, thanks to those who advised me to just tear down this ski from my prevous post!!!
GPR 1200 on pre-mix with head, triple pipes, Novi's, Skat pump ect. to much to list.
PSI @ 170 on 1 & 2 , # 3 was at 110. This is what I found, what do you guys think?

[thatdude596]

That's a gp1200r? What triple pipes?

[srjrinc]

Enlighten me! Dick

[Screamin'SLX]

Like looking in a mirror...my engine compartment looks just like that. Speedwerx pipes are awesome! It's hard to tell from the pictures since my laptop sucks but is part of the piston sheared off and the rings are sticking out? How is the rear cylinder? Any places that you can catch your fingernail on?

[srjrinc]

The pic here is the #3 piston.....its not sheared off, its ...........very hard to explain.
Looks like a combination of melted & as if it were sand blasted off.

[JIM'S PERFORMANCE]

what kind of fuel are you running with 170 compression. that is some extreme heat on the exhaust side. Also no piston wash at all.

[Screamin'SLX]

what kind of fuel are you running with 170 compression. that is some extreme heat on the exhaust side. Also no piston wash at all.

Jim's right...this was my next question. With 170lbs. you must be using the race gas domes since my pump gas domes give my speedwerx ported 1200 140psi in all 3.

[srjrinc]

I was using 91, with Castol racing pre-mix.

[JIM'S PERFORMANCE]

I was using 91, with Castol racing pre-mix.

By looking at that piston i would say higher octane and more fuel needed.

[srjrinc]

wow. I'm running Novi's. 105 or 110 octane?

[JIM'S PERFORMANCE]

wow. I'm running Novi's. 105 or 110 octane?

novi's are great carbs. just rejet them, with triples go 110

[srjrinc]

What would you recommend for re-jett?

[Pistonwash]

It's running too lean..make sure the carb on #3 has one jet size higher than the other 2. There's a guy that posted this years ago about NOVI's and their peculiarity :http://www.greenhulk.net/forums/showthread.php?t=52303

With the head at 170lbs. you can comedown on CR and squish and will NOT affect your speed too adversely. Does the Speedwerx head have domes? I can't remember...anyway, go down on your compression by -15lbs. or so...you will be just fine.

[thatdude596]

91 octane is way too low for 170 psi. thats race guy bro, not 91 with ethanol in it. those pipes are funky how they are routed compared to my factory pipes. that and the odd head through me off a bit. like the guys said needs more fuel with higher octane

[bigrob]

That looks lean with detonation. While its apart pressure test your pipes, a leak in the pipe can cause this to happen as well. If pipes are ok switch to 50/50 110 and pump gas, and richen up the rear cylinder