Super Jet head o ring failure ,piston wash pic ,what is going on here?

[yigaljet]

hello everyone
this motor is belong to a fraind of mine
61x cylinder
84mm la 5187b bb sleaves (installed witout any port timing at mind ),as is, and decked
wiseco dome top pistons
blowsion head
62t cases
engine is 2009
compression 190 psi ,gas pump
static timing at oem mark (no advance)
msd enhancer
hooker 9/15
v force 3 reeds
novi 3 single carb
now
the engine is runing rough at high rpm,somtimes the engine dies, while throtle released ,and will start up again
the engine done 20 fuel tanks
on friday after 2 tanks i dicovered the rear cylinder o ring leaking compression,next to the cylinder center(the pisser was spitting water)
bottom and is fair no dead spots but weak
i need some tuning advice
the piston wash looked rich to me ?
my feeling is the ignition timing is retarted way to much, but there isn't any overheating signs(like piston edge,or i am wrong, what do you guys think?

 

[Waternut]

Don't worry about piston wash. I've tried to adjust the tuning on my motor before thinking the piston wash was wrong and only made things worse. If the engine runs smoothly, leave it alone.

A blown o-ring can mean a few serious things but after only 20 gallons of fuel, I'm betting the o-ring was pinched when it was installed and then slowly failed because of it. Reinstall new o-rings and put grease on them so they stick to the head when it's upside down.

 

[Watcon]

Try installing a smaller return line restrictor in the Novi return line. Usually the Novi requires between a # 60 (more fuel) and a # 100 (less fuel in the carb). Just toss in the #60 and see if it cures the problem, then you can experimaent with different sizes. This pistons look rich, but thats a good thing...

Best regards,
Randy

 

[Tyler Zane]

i think he meant 20 tanks not 20 gallons. if thats the case you may need to change the o rings just because its time. they dont last forever. i dont worry about piston wash either, jetworks says that the cooling in jet skis is to inconsistent to worry with pistons wash. you will drive yourself crazy trying to get it right. i dont have any wash (they are all carbon coated) at all on mine and its been this way since day 3, so something must be right.

 

[kevbo]

Now you know why non-gasket, O-ring heads are a poor choice for yamahas. There is a low spot around the leaking dome. The O-ring keeps water from getting to the steel liner, it will not hold combustion pressure.