SJ 650 issues

[MB465]

Looking for some direction with this.
When you are half throttle to full the ski only gets to about 10 mph. It surges up and down not gaining any speed. If you jump the ski out of the water it takes off and runs fine until you let off the throttle and it'll go back the same thing. first we thought it was fuel so I cut out any places there might be any leaks fuel switch, primer, did a rebuild kit on the carb changed the fuel filter and checked the check valve. compression 150 each cylinder
its got a b pipe, and port work.
jets are 120, 162.5 main and 2.5 needle I understand those are big but its what was in it originally when I got it.
Anything helps thanks guys

 

[Bocaj88]

Might be bad crank seals. I had a js550 that would never get on plane no matter how much throttle you gave it. If you could get the pump to unhook it would rev and eventually you might get it on plane I had really leaky crank seals and after replaced it ran much better. Any idea if the bottom end was ever rebuilt? You can try to pressure test the engine. Found this on PWC today on how to test it
http://www.pwctoday.com/showthread.php?t=166854
Just my 2 cents, I'm just a kid so I'm probably wrong just figured I throw it out there

 

[MB465]

did not do a pressure test but sprayed some starter fluid on any possible spots (not front crank seal) and didn't hear anything. If I have a solid vacuum on the carb line wouldn't that mean I probably don't have a system leak? not sure what that third line on the carb actually does.

 

[jonolove]

did not do a pressure test but sprayed some starter fluid on any possible spots (not front crank seal) and didn't hear anything. If I have a solid vacuum on the carb line wouldn't that mean I probably don't have a system leak? not sure what that third line on the carb actually does.

Pulse line. your jetting is way rich imo

 

[MB465]

Pulse line. your jetting is way rich imo

for sure it is but the top was good before and the pilot is I think around stock and it was gutless on the bottom

 

[JetManiac]

Looking for some direction with this.
When you are half throttle to full the ski only gets to about 10 mph. It surges up and down not gaining any speed. If you jump the ski out of the water it takes off and runs fine until you let off the throttle and it'll go back the same thing. first we thought it was fuel so I cut out any places there might be any leaks fuel switch, primer, did a rebuild kit on the carb changed the fuel filter and checked the check valve. compression 150 each cylinder
its got a b pipe, and port work.
jets are 120, 162.5 main and 2.5 needle I understand those are big but its what was in it originally when I got it.
Anything helps thanks guys

Why not replace the jets and n&s to correct size for your ski and setup? That is a huge amount of fuel for a 650 to swallow.

 

[MB465]

Why not replace the jets and n&s to correct size for your ski and setup? That is a huge amount of fuel for a 650 to swallow.

not sure what to put in there, It makes me nervous that it ran good before with that main and still does on top if you unload it and get it going. I think I should probably just go halfway back to stock and see what it does? also found out last night that my pop off pressure was off of what it was supposed to be so I fixed that.

 

[JetManiac]

not sure what to put in there, It makes me nervous that it ran good before with that main and still does on top if you unload it and get it going. I think I should probably just go halfway back to stock and see what it does? also found out last night that my pop off pressure was off of what it was supposed to be so I fixed that.

What mods from stock do you have?

650 motor with stock pipe? head? flame arrestor? etc?

 

[MB465]

What mods from stock do you have?

650 motor with stock pipe? head? flame arrestor? etc?

Just a b pipe and some port work. other thing is that this all happened about 30 minutes after I messed with the b pipe setting but I put it back to what it was don't know if I could have got the motor too hot and wrecked ship.

 

[MB465]

update lowered the pop off pressure and it started to run a little better now I can roll into the throttle and its fine but if I wack it it does the same surge until I back out and roll back into it.