Cannot get proper pop off

[BrianJV]

Hi all, I rebuilt the carbs in my 99 GTX 951. I cannot achieve the proper pop off when testing. I used genuine Mikuni kits and installed new dull silver springs. I'm only getting around 14 psi. I tied bending the arm slightly, but only get slight increase. Tried the old spring i got 15psi.Tried another new spring only 13psi. Both carbs same thing. Tried a different gauge same thing. Out of frustration i stretched an old spring, that got me about 23psi. I know thats not the proper way to do it. Any ideas? (very frustrated) Thanks!

 

[BrianJV]

Well i took a couple new dull silver springs, 95 gr. i believe, gently stretched them little by little until i got close, about 19 psi. then very little adjustment to the tang arm till i got 20 psi. Book says 19-23 psi. I'm gonna go with it, hope it works.

 

[MoDawg73]

What is the pop off you are striving for?

 

[MoDawg73]

I have heard that the book is incorrect for a 99 GTX limited with 951. I got mine to about 40.

 

[BrianJV]

Its all stock. 2.0 needle seat. Mikuni chart says 19-23 psi.

 

[mikidymac]

The 951 takes a special spring that is different than all other Mikuni carbs.

You can only use the one from the Mikuni 46i carb kits.

Never stretch, cut or modify the springs.

 

[BrianJV]

Thats what cant figure out. I used genuine Mikuni 46i kits. With that spring only got 14 or 15 psi. Wet wirh wd40 each time i checked.

 

[tmclark4209]

You sure the gauge is reading correctly ?

 

[BrianJV]

That was my thought also. Changed it to a new one, exact same readings.

 

[POPPS]

Is the O ring at the seat leaking?

 

[BrianJV]

yes. no bubbles at all. Then pops.

 

[POPPS]

I am not aware of a different pop off spring for the 951. Are there more than 4 different springs? When I go thru a customers carbs, with my pop off gauge, it's for 2 reasons. 1, to see if there are any external leaks, and 2, to see if the O ring on the seat is leaking. On my race boat, I am trying for equal pop offs, yours is stock, the settings all have built in variances, on mine,the 2.3 seat and gold spring (115), with my pop off gauge is 26, the mikuni
manual states that this combo would be 22.

I would check for external leaks , and then, that the seat O ring does not leak.

 

[BrianJV]

seat o ring is good, no leaks, I will check for external leaks. Spray with soapy water? Thanks.

 

[R-u-n2it]

Are you correcting a problem or just going through the carbs and trying to get them "right"? Using a different size N&S will change pop-off range.

 

[BrianJV]

Just got them. Carbs never off. They sat for a few years, so going over everything before i put them in the water. They did run well before. on the trailer. I ordered the 95 gram "951 only" springs. just to see if that helps. Havent had time to work on it lately.

 

[BrianJV]

Update! Finally found time to work on the ski again. Installed new 95 gr. dull silver springs. Still low. Pulled the newly installed needle and seat. Grabbed the rebuild kits i bought for the other GTX to borrow the needles and seats from. I then realized even tho i purchased genuine Mikuni rebuild kits, the needles and seats were aftermarket! I put them in anyway, and got a little higher pop off. Then i started swapping needles, arms, even the pins for the arms, back and forth and finally got solid pop off readings of 19 psi on both carbs. Got it all back together, hopefully will get it in the water on the weekend. Lesson learned- Make sure ALL carb parts are genuine Mikuni! I cant believe the huge variations i was getting from 2.0 seats, from 14 psi to over 25 psi just by swapping parts around. Thank you everyone for the help!