Seadoo 951 pop off questions

[Landen Koch]

I’ve got a 2000 seadoo xp, and I am installing 2.3 needle seats and 95 low speeds and 167.5 high speeds. The pop off on the pto carb was good-around 20 with the dull silver spring and dropped to about 10 and always held the pressure perfectly. The mag carb I am struggling with. I have the tester on the big 5/16 nipple and every other nipple capped off with a zip tie. It will not hold pressure (slowly leaks) and pops at about 15-18 usually and falls to about 5-10 and eventually loses all its pressure. I have tried different o rings on the needle seats but I’m pretty new to this so any info would be appreciated, thanks

 

[Landen Koch]

Would like to get it running soon so if anyone has any info that would be great.

 

[Grim]

where did you get the rebuild kit from, is it OEM? If it is OEM, I would disassemble and inspect each part for damage and inspect housing for damage. then I would submerge the carb and see if I could tell where the leak is coming from. if nothing is found I would buy another OEM kit and install it.

Also, review the carb rebuild thread to verify you are on track.

 

[azsxr]

Swap N&S see if the leak moves with it?

 

[mikidymac]

First off, why are you changing the jetting and needle and seat size?

 

[Landen Koch]

First off, why are you changing the jetting and needle and seat size?

Make it run way better, the head was flattened a very slight amount so compression will increase very slightly, and I think it will be healthier on the new top end because I made tuning much easier.

 

[Landen Koch]

Swap N&S see if the leak moves with it?

The needle and seat does not leak, I tried multiple different ones and confirmed good ones and the same thing happened with all.

 

[Landen Koch]

where did you get the rebuild kit from, is it OEM? If it is OEM, I would disassemble and inspect each part for damage and inspect housing for damage. then I would submerge the carb and see if I could tell where the leak is coming from. if nothing is found I would buy another OEM kit and install it.

Also, review the carb rebuild thread to verify you are on track.

The kit is all genuine mikuni parts and I have already inspected it all, but I never thought to submerge it so I will definitely give it a try, just soapy water would work?

 

[Grim]

The kit is all genuine mikuni parts and I have already inspected it all, but I never thought to submerge it so I will definitely give it a try, just soapy water would work?

yes, you could also get soapy solution and go over the carb areas to see if leaks show up, its a little harder to detect than submerging it!

 

[mikidymac]

Are you running the stock airbox?

With a new top end and just "flattening" the head there is no reason for the larger needle and seat and jets you have switched to. That 2.3 needle and seat are going to make it too rich.

Also keep in mind the 951 carbs use a different pop-off spring than all the other seadoo carbs and are specific to that engine.

 

[Landen Koch]

Are you running the stock airbox?

With a new top end and just "flattening" the head there is no reason for the larger needle and seat and jets you have switched to. That 2.3 needle and seat are going to make it too rich.

Also keep in mind the 951 carbs use a different pop-off spring than all the other seadoo carbs and are specific to that engine.

Have pro k filters and outerwears, and am using the dull silver spring that was in them to begin with.

 

[Landen Koch]

yes, you could also get soapy solution and go over the carb areas to see if leaks show up, its a little harder to detect than submerging it!

Appreciate you answering my question, if you have any other tips please let me know, thanks!

 

[Landen Koch]

Have pro k filters and outerwears, and am using the dull silver spring that was in them to begin with.

Also removed the choke assembly, installing a primer and removed the accel pump.

 

[mikidymac]

I would reach out to a specialty shop like Watercraft Magic on jetting.
You are going to be really lean with the aftermarket filters and no choke plates. The reason is that these carbs are really lean from the factory and when you pull off the stock intake and chokes you loose vacuum signal which makes them even more lean and even jetting doesn't always help at 3/4 throttle.
Also on a 951 which is prone to runaways removing the choke makes it very hard to shut down a runaway.

Here is a better explanation from Group K

Flame Arrestors – While the installation of aftermarket flame arrestors has been a very popular modification for many recreational pwc’s, we do not use or recommend them on our Swift Kit or Y2K Sleeper Kit. The technical reasoning for this choice is related entirely to the stock carbs used on the 951 engines. The carbs used on all 951s are the first generation of a carburetor that is designed as much for emissions friendliness as it is for performance. Among the most notable design features that make this difference, is the significantly increased distance between the butterfly and the “booster venturi” style fuel atomizer (aka “bombsight” atomizer). We cannot claim to know all the effects of this design departure, however we know a lot about one particular effect called “fuel delivery signal”.

In short, signal is the amount of vacuum within the inlet tract that helps to draw fuel from the metering circuits in the carburetor. The air restriction of the stock flame arrestor serves greatly to keep that vacuum very high. This high vacuum actually helps the quickness of throttle response at all engine speeds. When a free breathing flame arrestor is installed, this vacuum (aka signal) is reduced. The reduced signal means a slightly leaner fuel mixture through the entire range. This is normally not a dangerous issue for most pwc engines. However the emissions-conscious stock 951 carbs have an exceptionally weak signal at ¾ throttle opening. This means that a more open arrestor will cause the 70 – 80% throttle range become “a lot” leaner than the rest of the range. There is no jetting that can solve this problem (we tried). The “only” effective solution is to leave the stock flame arrestor (with the bolt on air horns) intact. Despite the restrictive appearance of the stock arrestor, it can easily pass enough air volume for excellent performance up to the 7140 rev limiter. The stock arrestor has received an undeserved reputation as “choking” the 951 into a bad rich condition. In truth, the rich condition is a correctable jetting issue, not an air access issue.

 

[Landen Koch]

I still haven’t really got the answer to my question, I know some people think this is a terrible idea but I have proof that it will work, I just need tips on finding a leak in my carbs because if I can’t find it with soapy water then I’m out of ideas, it’s my ski I’m gonna try it how I want it and if it runs terrible I’ll go back to stock, thanks

 

[mikidymac]

Fair enough.

If it won't hold pressure then the leak can only come from a few places and should be found with soap and water.
FIrst what carb is is, PTO or MAG?
If MAG your leak sources are..
1. Needle to seat.
2. Seat to carb body (o-ring).
3. Fuel pump cover.
4. Fuel pump body to cover or carb.
5. Fuel pump body to carb.
6. Brass hose fitting.

If PTO carb...
1. Needle to seat.
2. Seat to carb body (o-ring).
3. Fuel pump cover to carb body.
4. Brass hose fitting.

 

[Landen Koch]

Ok that’s perfect, I’m gonna go see if I can track the leak now, thanks for the help!

 

[mikidymac]

One more note, when you are testing pop-off you need to make sure the needle and seat are wet with some WD-40 every time it pops or you will not get a true reading. Cover it with a paper towel so you don't get it in your eyes.

 

[Landen Koch]

Yep, my pop off procedure is correct, the mag carb is leaking and I found that it was leaking in 2 spots-the one side of the valve block on the fuel pump side where it meets the carb itself (assuming it’s that bad shaped o ring) and the screws holding the whole fuel pump assembly side together, it was slightly leaking there also (probably that normal o ring on the top of the valve block). The last time the carbs were rebuilt was about a year ago, so I probably should’ve expected this when taking them apart and trying to use the parts again, they didn’t look bad at all but I will probably just order a new mikuni kit and hope it solves my problem.

 

[Boyd12]

I still haven’t really got the answer to my question, I know some people think this is a terrible idea but I have proof that it will work, I just need tips on finding a leak in my carbs because if I can’t find it with soapy water then I’m out of ideas, it’s my ski I’m gonna try it how I want it and if it runs terrible I’ll go back to stock, thanks

You will not have to go back to stock. Once you get it dialed in, it WILL run better than with the stock flame arrestor and you will not have a lean condition. I have had this set up for years on multiple 951's. You need to be very careful about water ingestion.
I would put the choke back on as Mikidymac is correct, 951's can run away and the choke will stop it. Good luck!

 

[Landen Koch]

I know the 951 are known for runaway, but if it does run away, I’ll smash the throttle and have something ready to cut the fuel feed line, and make sure my butterflies aren’t to far open, if all that is good I shouldn’t have a problem unless there is a leak somewhere else. What do you have your low and high speed adjusters set at

 

[Landen Koch]

I know the 951 are known for runaway, but if it does run away, I’ll smash the throttle and have something ready to cut the fuel feed line, and make sure my butterflies aren’t to far open, if all that is good I shouldn’t have a problem unless there is a leak somewhere else. What do you have your low and high speed adjusters set at

And yes I will pretty much always be the only one riding the ski and if anyone else does I will tell them to be very careful, I also have the outerwear’s which will help a ton hopefully.

 

[Landen Koch]

And yes I will pretty much always be the only one riding the ski and if anyone else does I will tell them to be very careful, I also have the outerwear’s which will help a ton hopefully.

Also on the video I watched it said that the choke plates will hit the little funnel shaped needle type thing on the pro k filters so the choke wouldn’t close anyway

 

[Boyd12]

I know the 951 are known for runaway, but if it does run away, I’ll smash the throttle and have something ready to cut the fuel feed line, and make sure my butterflies aren’t to far open, if all that is good I shouldn’t have a problem unless there is a leak somewhere else. What do you have your low and high speed adjusters set at

Low speeds are currently 1.5 out. I dont remember where I set the high speeds at. It may be around .5 out. This engine is not broken in yet so I dont know where they will end up. The previous boats were used at different elevations with other mods, so I don't think they would help much. I may have more info in the next few weeks. If I do I will share it with you.
Regarding the Pro K funnel, I think you can grind a little off to get the chokes to clear.
Outerwears are stupendous!

 

[Landen Koch]

just had a top end done, so mine won’t be broken in yet either, I’m running 12 gallon of 40:1 along with the oil pump and just gonna take it easy on that tank and then start to tune it up a little bit, but I’ll start there for the low and high speed adjusters, and as far as the choke goes I’m just going to go without it, on the first start I will make sure I know how to get it shut down if it does happen, either pin the throttle or cut the inlet fuel line, I would think that would kill it pretty quickly as long as the plugs don’t get to hot