Pop off pressure

[Water sports]

1999 Seadoo speedster 787 2 stroke jet boat

Hi

Well finally got to do my pop off and I am getting a pop off around 42 psi. Question is this correct and does this apply to both carbs.

 

[mikidymac]

That is a little high but should be fine, you want both carbs to be as close to the same as you can get them.

 

[Water sports]

That is a little high but should be fine, you want both carbs to be as close to the same as you can get them.

Thanks ok if thats ok then i will carry on assembling the car totally see below what is in the manual which I don't quite understand are they asking to add these numbers together and is that the pop off under psi

 

[mikidymac]

THey are saying that it should be 38 psi but it could be 38-12 = 26 or 38 +12 = 50.
The seadoo specs are way off though. To get the correct test pressure use the Mikuni chart using your correct needle and seat size and spring. Mikuni makes the carbs and carb parts so I have no clue how seadoo ever got such strange numbers that they call for on their pop-off when the Mikuni combinations can't possible match what seadoo claims.

 

[Water sports]

THey are saying that it should be 38 psi but it could be 38-12 = 26 or 38 +12 = 50.
The seadoo specs are way off though. To get the correct test pressure use the Mikuni chart using your correct needle and seat size and spring. Mikuni makes the carbs and carb parts so I have no clue how seadoo ever got such strange numbers that they call for on their pop-off when the Mikuni combinations can't possible match what seadoo claims.

Okay so now I have tested the other carburettor and this is popping off at 32 psi and the other over 50 what is my best option here

 

[Water sports]

To get a carbs the same which part of the aim do i bend see photo below
Please note I have used the original springs however I don't know if these were ever changed from the previous owners

 

[FlyboyX]

your screw heads are shanked up pretty good in the first pic. i suppose as long as you can get them in and out you will be ok. like most of these carbs, yours also seem to have suffered a good deal of corrosion. my boat also sat for a long time and had this issue. i rebuilt mine 3 years ago following miki's DIY thread. even though i always put fuel stabilizer in my gas every time i fill up, i was starting to have problems again this season. i took the carbs apart again a couple weeks ago and i once again had a good deal of corrosion. my point is that over the course of time, it will come back and cause issues.

as to your pop off pressure, as mentioned, they should be the same for both. you have a large difference between yours. i don't know if you can bend anything enough to compensate. the only thing in there that is a little bit adjustable is the sheet metal tab that connects your spring to the needle. it really should be flat though when the needle is closed. at this point, i would suggest trying the springs that came with your kit.

 

[mikidymac]

You can't make up that difference bending anything.

Either something is up with the springs, needles or arms to cause that big of a difference.

 

[Water sports]

You can't make up that difference bending anything.

Either something is up with the springs, needles or arms to cause that big of a difference.

So Do you think I should use the springs that came with the kit which is a original carb kit

 

[Water sports]

your screw heads are shanked up pretty good in the first pic. i suppose as long as you can get them in and out you will be ok. like most of these carbs, yours also seem to have suffered a good deal of corrosion. my boat also sat for a long time and had this issue. i rebuilt mine 3 years ago following miki's DIY thread. even though i always put fuel stabilizer in my gas every time i fill up, i was starting to have problems again this season. i took the carbs apart again a couple weeks ago and i once again had a good deal of corrosion. my point is that over the course of time, it will come back and cause issues.

as to your pop off pressure, as mentioned, they should be the same for both. you have a large difference between yours. i don't know if you can bend anything enough to compensate. the only thing in there that is a little bit adjustable is the sheet metal tab that connects your spring to the needle. it really should be flat though when the needle is closed. at this point, i would suggest trying the springs that came with your kit.

Thanks for your reply and advice yes these carburettor's have been through a sonic machine and soaked in cleaner looking at those photos make it look really dirty it seems a bit strange why I am getting this variation I could try the springs that came in the kit but have been told not to use them for some reason which I don't know why especially if they are genuine carburettor kits I haven't even looked at the other two calves yet on the other motor

 

[FlyboyX]

normally unless the springs are rusty or incorrectly replaced, they should be the correct tension. its hard to say what springs come in the kits, but be sure to buy only oem mikuni parts.

iirc, there are 2 or 3 different springs in the rebuilds. i would try one in your carb and then check the pop off to see what you get. if you don't like the results, try another one.

 

[Ridley]

Just rebuilt mine following miki's thread too, 97 Challenger 787. Both carbs pop-off at 42 psi. Found some conflicting information on different forums and threads. Re-used the existing springs and genuine Mikuni parts kit for the rest.

Think i'm going to leave them as is and not try to adjust the levers.