2008 SJ Stock Compression 180psi!?!?!?

cookerq62

cookerq62

Life's Been Good
Location
Upper Bucks, PA
I just finished breaking in my 2008 superjet and I checked the compression with my cheap gauge and got 180psi cold in both holes. Now this gauge read 145 psi on my ported (61x raised to 62t height) motor with a protec limited head. It also read 140-150 on a bunch of stock motors and 185 on a 61x with 35cc domes all cold. Is this normal?
 
stanton

stanton

High on jetskis.
Location
atascadero,ca
noone ever said anything about a power increase on the 08's

...did they?

i thought the 08 i rode ran great, this could explain it.
did you try it with a warm motor?
 
Officer Mike

Officer Mike

TJ / SJ / JJ
Location
Harveys Lake
could the more power be from the set back pump and large hub prop. not more power but more efficency from the motor? i never checked my stock compression i have ada head with 37s now. i was going to get my 08 head milled for another 701 project. we need to clear this up
 
D

DemianM

For comparisons sake:
I sold my 97 SJ to my best friend, and bought a 08 SXR (I know, we all make mistakes....). My SJ had a pipe, head and flame arrestors, solas prop.....WOT on glassy water had us EXACTLY even, we were completely even.

I now sold the SXR and got a 08 SJ. I did not spank it yet, only has 1 tank on it, but on a 10 second wot pull, I was a little ahead of my friend on the SJ. The ski feels VERY strong and very quick, and it isnt broken it yet! I will measure compression it as soon as I can (dont have a gauge yet) but it definitely feels like it has a lot more power than other previous years Superjets.
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
Different impeller, different weight balancing due to shorter pole and setback pump.

That has probably a lot more to do with it than increased compression.
The Yamaha website calls for regular unleaded.
The compression ratio of 7.2:1 has not changed since 07.
I doubt they'd have you run regular if they upped compression.

Of course, maybe their website is screwed up.
 
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Endo

Endo

Non-tree hugger
Location
Northeastern Indiana
What should Stock compression be? My 02 with several hours on it just checked at 170 per hole. Last time I used the gauge (last year) it seemed to read the same as my old gauge?
 
Officer Mike

Officer Mike

TJ / SJ / JJ
Location
Harveys Lake
DemianM said:
For comparisons sake:
I sold my 97 SJ to my best friend, and bought a 08 SXR (I know, we all make mistakes....). My SJ had a pipe, head and flame arrestors, solas prop.....WOT on glassy water had us EXACTLY even, we were completely even.

I now sold the SXR and got a 08 SJ. I did not spank it yet, only has 1 tank on it, but on a 10 second wot pull, I was a little ahead of my friend on the SJ. The ski feels VERY strong and very quick, and it isnt broken it yet! I will measure compression it as soon as I can (dont have a gauge yet) but it definitely feels like it has a lot more power than other previous years Superjets.
Click to expand...

i been telling you guys that they are quick. but as matt e said i think its alot to do with the pump and impellar. i cant say enough of the stock impellar. im dry piped and ada head and the impellar is still doing a great job. down low. middle. and top. i am side by side with my buddies 800. and he has.. 185 compression. b pipe. arresters. large hub 10/18 water box. and a lot of lightening..
 
D

DemianM

Officer Mike said:
i been telling you guys that they are quick. but as matt e said i think its alot to do with the pump and impellar. i cant say enough of the stock impellar. im dry piped and ada head and the impellar is still doing a great job. down low. middle. and top. i am side by side with my buddies 800. and he has.. 185 compression. b pipe. arresters. large hub 10/18 water box. and a lot of lightening..
Click to expand...


Mike,
are you running the type 9 pipe? How´s the bottom end? I want to install it alone (no head), how is it running on you? I am about to buy a B pipe but I am not sure, the only thing that puts me off the type 9 is cutting the brand new hood!
 
D

DemianM

I thought he was referring to the impeller when he said that the bottom/mid/top end were good. My question was a little more referred to how the dry pipe hits with the new pump and impeller, specially on bottom end. I know for sure the impeller is great on the 08 ;)
 
Officer Mike

Officer Mike

TJ / SJ / JJ
Location
Harveys Lake
Kennay said:
He's running a Type 4, and he just said the bottom end, mid, and top end is good.
Click to expand...



true. type 4. ... i can sit on the edge of the dock just off idle and gun it and it goes. no hesitationand no hit. just all linear arm wrenching ski. i also have the head tho. the type 4 also fits with out cutting the hood. the pipe you want i think makes a little better top then mine but the type 4 is better for all arond riding. theres also a mikuni jet in my stinger to restrict water into the waterbox which is big for low end take off. i like the dry pie vs the wet pipe. but im also comparing my dry on the yamaha vs the wet on the kawasakis. if you do alot of subs and stabs... and dont want dual exhasut, chack and make sure the wet pipe on yami doesnt load up like it does on kawis.. ask someone. i had a terrible time with that on my 750 and my buddies 800... so far so good with the sj. my opinon type 4 all the way. for all around riding..good luck
 
Matt_E

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
That's exactly the goof-up I had on my mind when I typed that.
So what does the manual say on what fuel to use?

EDIT: I just looked it up myself, the manual says 7.2:1, and 88 oct gas.
 
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