Super Jet lost compression on front cylinder

[Polish jet pilot]

Hmm, 2 days ago it run fine, today wanted to fire her up and it wanted but couldn't... took plugs out, were quite wet. Placed my finger on the plug holes and noticed that the front does not have as much as the rear one... kinda strange - maybe a piston ring or something... I guess running high compression does not help either

So should I go to 84mm bore ? I was on 82.5mm but heard the motor comes alive around 760cc.... why do poor folks as myself alwyas need to face all this drama LOL

 

[Polish jet pilot]

maybe its just a busted head oring... need to take off the head and check but still think motor is done after 4 seasons...

 

[keith t]

Eh,....... could simply be a blown O ring - get the head off and see

 

[Polish jet pilot]

yeah, I hope its only that, but if not, them boring to 760cc - this time I will do case porting and more cyl porting...ehh, 4 years no real problems, I guess I should not complain too much..

 

[Superjetjim]

Bin that cylinder and get a DASA/XS on there!

 

[Polish jet pilot]

my cylinder is toast. Cracked sleeve, cracked sleeve and housing about 2 inches, dome is toast, not sure whats up with the lower end yet. F#$%k! Broken ring did that... Need a top end for sure.

Dasa would be great but not this season - budget is very tight, gas is expensive and summer is short...

 

[Sospikey]

Ouch! I would replace the crank while at it... 4 seasons plus mixed metal debris is a leathal mix for the bearings....

 

[Polish jet pilot]

the strange thing - the engine was not even loaded, it just wouldnt stay on longer than 1-2 seconds. I messedwith the fueling lines a bit before and thought there is air in them...so I tried a couple of times, and then found out the above....

 

[Freakrider]

my cylinder is toast. Cracked sleeve, cracked sleeve and housing about 2 inches, dome is toast, not sure whats up with the lower end yet. F#$%k! Broken ring did that... Need a top end for sure.

Dasa would be great but not this season - budget is very tight, gas is expensive and summer is short...

Sorry to hear that....here's a good quick option:

http://www.x-h2o.com/threads/106417-JetManiac-Blue-ported-Ported-Top-End-Kit-650

 

[Polish jet pilot]

I wonder how much for a core cylinder as the link above mentions a core....mine is cracked and it would cost some to send over to US...

 

[Matt_E]

Probably easier and cheaper to buy a core cylinder in the US and have it shipped to JM. Or see if has one.

 

[Freakrider]

I think he says add 100 bucks for core...

 

[Polish jet pilot]

will ask Chris if he has something..... darn motor pissed me off...

 

[stefan]

I got a JM/blue engine get the 760 cc ported cyl and you will bee a happy man.

 

[Polish jet pilot]

yeah looking for something in the 760-780cc range for a top end. I really think I squizzed all the juice out of that 727cc and after 4 seasons it gave up. Was running 210-215 psi (on Shell Vpower racing). It's not a secret that the motor was subbed a few times, it had a mag side seal leak and really needed a case port job anyways... Planning to port my bottom end (I have a ported Tim Judge motor here to have a reference on the case job).. hope to really do all the work in 3-4 days to be back on the water asap. Crap happens..lol!

 

[Polish jet pilot]

NOTE: 3-4 days once I have my top end )