2012 limited race superjet, keeps seizing pitons :/ Help needed!?

Christian_83

Christian_83

Xscream
Location
Denmark
Hi Guys,
A good friend of mine, is racing a '12 SJ, its a limited setup. This machine, has sized around 10 pistons.

First of, he bought the ski, with very little use. He put on a b pipe and a hooker 9/15. nothing else.
This sized the first piston.
std setup.jpeg

After this, he tried almost everything to keep the engine running without seizing again.
Msd Enhancer cdi with RPM limit from 7500-8000rpm
ADA head with domes ranging from 150 - 180 psi.
stock dual 38 carbs with 150H and 75L jets (AM air filters) with external fuel pump.

Water routing is single cooling, starting in B pipe manifold, head to bottom of head pipe, top of head pipe to T, running in to stinger and overboard pisser. (we are in cold water in Denmark, our water temp at the moment is 15deg Celcious) and the last pistons sizure happened this weekend in training for Danish championship. He is running 95 octane pump gas and have tried 4 types of oil, currently running Castrol Power 1 fully synthetic.

There is no pattern in when or why the seizing happens, sometimes its the front cylinder, sometimes its the rear.
This is obvious really frustrating and a bit expensive, he is riding the ski pretty hard on the track and most of the time he is WOT.
It has also sized pistons in another cylinder, that was "flowed" no change to port timing.

We really hope you guys, who are racing limited Superjets, can help us or just some really sharp mechanics.


IMG_5401.jpeg IMG_0665.jpeg

Andreas and Christian
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
95 octane in Europe is not the same as here.

I raced limited from 1999 until 2002 on my superjet. had one or two seizures. Mostly my fault. I do not think the hooker is to blame. That is the lowest pitch of the Hooker line. Should be fine for this application. I am going to say it is more of a jetting issue or the static timing is advanced to much. Some heat has been built up.
 
S

SVTPete83

Location
Chico, Ca
Ringlands are melted. I would say some serious heat buildup. I have run a 180 psi limited setup for years and never lost a piston using 91 octane and riding it like a raped ape. Dual cooling, the right tune, and make sure rpm and timing are gtg.
 
Christian_83

Christian_83

Xscream
Location
Denmark
Please read the entire post, the first time he seized a piston. the engine was STOCK and almost brand new, only mod was b pipe and hooker prop.
after first seizure, he got it bored first to 0.08mm clearance and later 0.12mm clearance. They did not check ring gap. New pistons were Pro-X

He hasnt checked the static timing, so he will be checking that tomorrow.
@Big Kahuna what setup did you run, back in the day? any idea on what jetting you ran?
@DAG he hasnt measured the temp, but the engine docent get so hot, that you cant keep your hands on it. But will check the temp, when its rebuild.
 
DAG

DAG

Yes, my balls tickled from that landing
Location
Charlotte, NC
If you can keep your hand on the cylinder your piston is expanding into your cylinder walls. Restrict your cooling to get around 50C off the head
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
Christian_83 said:
Please read the entire post, the first time he seized a piston. the engine was STOCK and almost brand new, only mod was b pipe and hooker prop.
after first seizure, he got it bored first to 0.08mm clearance and later 0.12mm clearance. They did not check ring gap. New pistons were Pro-X

He hasnt checked the static timing, so he will be checking that tomorrow.
@Big Kahuna what setup did you run, back in the day? any idea on what jetting you ran?
Click to expand...
Started out with just BPipe, Flame Arrestors, Solas J pitched down some (This prop was really steep, way beyond specs), MSD enhancer, Later Added Dual Cooling and ADA Head. Tried an R&D head and smoked a piston, head had a defective dome. Ran jetting per FPP site for Limited Chamber. Rode it like I stole it.
 
OCD Solutions

OCD Solutions

Original, Clean and Dependable Solutions
Location
Rentz, GA
It certainly looks like cold seizure.

A cold seizure is the result of the piston expanding too fast with respect to its cylinder.

Your engine is constructed on many different types of materials all housed together and designed to work as one system. All internal engine components, when heated (running engine) will expand to some extent. This expansion is normal and unavoidable. Different components will expand at different rates and will expand to different extents.

When you fire an engine after it has been able to completely cool down to a state where all internal components are at their “NEUTRAL” state.. meaning they are in no state of any expansion due to heat, these components will begin their expansion all over again. It is THIS expansion rate differences that will cause an engine to “Cold Seize”. So, you have an entire engine that is being heated and, as a result, ALL of its internal components are expanding at different rates. This INITIAL expansion is what you need to be mindful of to avoid a cold seize. Once these engine components have reached their full expansion, then the engine should be operating in its design spec and safe to run and run hard. If you choose to fire up a cold engine and immediately pour large amounts of heat into the components (i.e. high rpm) you RISK having these varying expansion rates collide and seize. Make sense??
Click to expand...
 
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