2000 SeaDoo GTX - Stalling and Hesitation at low speed

[Big Fish]

Hi All,

I've posted in the past about this issue and taken some steps but I'm still having issues so looking for some advice. I have a 2000 GTX with the 951 engine, duel Mikuni carbs and an accelerator pump. The compression is good in the ski and it runs very strong with a few very specific issues.

Scenario:
First, if I'm going fast (3/4 or above throttle) then let off the gas completely the ski stalls quickly but can start right back up. If I feather the throttle I can sometimes get it to not stall but its tough. Second, not always but if you punch the gas from idle it will bog down and stall most times unless you feather the throttle to get it going. Third, if you hang right around 3500 RPMs you can almost pinpoint that spot as to where it has some hesitation. Meaning if you go a little below or above that mark you can feel it hesitate. Finally, if you snap the choke before hitting the gas in scenarios 1 & 2 above the ski will take off without hesitation. This condition has existed for the 3 years I've had the ski.

Here is what I've done in this order:
1. Last year (2018) replaced the MPEM last year due to some other no start condition. Likely not related to my hesitation issue.
2. Last year (2018) replace rear ignition box, ignition coils and wires due to a gasket leak in that box. Likely not related to the hesitation issue.
4. This year (May 2019) took off air filter cover and while ski was not running held a mirror in front of carbs and hit the throttle a few times and saw spray going into both carbs. I'm told that is the test to see if my accelerator pump is working so I assume it was so I didn't replace the baffle (or whatever is inside the pump).
5. This year (May 2019) rebuilt carbs including new needles and seats and Mikuni OEM rebuild kit. Tried spraying carb cleaner in the small holes (that I assume were low speed holes) but I don't recall if I had no flow before and flow afterward. As I recall it was tough to see if me spraying them had any impact at all since they were so small.

I was hopeful the carb rebuild and clean would solve the hesitation and stalling problem but it is exactly the same after the re-build so I'm now at a loss. I assume it has something to do with the low speed jet since the ski hauls above 1/2 throttle with no issues. Also since if I hit the choke quickly and it responds I assume the problem is that I have a lean condition that becomes richer instantly when I snap the choke cutting off the air and increasing the ratio of gas to air.

Not sure what steps to do next so looking for advice. Am I now in a place where I can make some adjustments to the low speed jet and if so does that require I pull the carbs back off? Let me know your thoughts. Really appreciate your assistance.

 

[funsummerahead]

What do you have your air mixtures screws set to? The stock settings have always worked for me and then the usual check/adjust of the accelerator pump and setting of the idle.
Does it start and idle by itself or does it die?
What is the ski's idle rpm?

 

[mikidymac]

So the 951 is a really strange bird in the fact that it was jetted really lean from the factory from emissions but it should still run really good on the sock settings.

First make sure your accelerator pump is squirting an good stream in both carbs since the exit nozzles get plugged really easy.

Next make sure your little holes int he body of the carb below the throttle plate are really clean. Spray into the pilot jet hole with cleaner and compressed air and make sure the low speed screw is in so you get full pressure through these holes.

Next make sure you have the correct needle arm spring installed as this is specific to the 951 and will not work with any other spring.

Finally check pop-off and then once the cover and diaphragm are on check to make sure the carb holds 10psi.

If the ski has higher hours you might want to check the reeds for chips but I would suspect the carb first since pulling the choke makes it run better.

 

[Big Fish]

What do you have your air mixtures screws set to? The stock settings have always worked for me and then the usual check/adjust of the accelerator pump and setting of the idle.
Does it start and idle by itself or does it die?
What is the ski's idle rpm?

Thanks for the response. I have never touched the mixture screws so I was looking for some advice on how to do that and if I should given whats already been done. Yes is starts and idles perfect. Not sure on the idle but I think maybe 1300 in the water. It never dies at idle only when you come off high speed throttle quickly and occasionally when going from a stop to hard acceleration.

 

[Big Fish]

So the 951 is a really strange bird in the fact that it was jetted really lean from the factory from emissions but it should still run really good on the sock settings.

First make sure your accelerator pump is squirting an good stream in both carbs since the exit nozzles get plugged really easy.

Next make sure your little holes int he body of the carb below the throttle plate are really clean. Spray into the pilot jet hole with cleaner and compressed air and make sure the low speed screw is in so you get full pressure through these holes.

Next make sure you have the correct needle arm spring installed as this is specific to the 951 and will not work with any other spring.

Finally check pop-off and then once the cover and diaphragm are on check to make sure the carb holds 10psi.

If the ski has higher hours you might want to check the reeds for chips but I would suspect the carb first since pulling the choke makes it run better.

mikidymac:
Thanks very much for the response. As for the lean condition I'd obviously like to explore any option that makes sense before having to take the carbs back off. I'll do it if that makes sense just wondering if there is an adjustment to the low speed jet that I could or should try before taking the carbs back off. Let me know if any adjustment could potentially be made before I take the carbs off if you know of any.

I did check the squirting of the accelerator pump with a mirror and it seemed to be squirting steady into both carbs. I can check again this weekend when I'm up north with the ski but I think that is good.

As for the holes in the carbs I "think" I cleaned them well but didn't pay particular attention to those holes to see if my carb cleaner went through them. Do you happen to have a picture of what those holes look like? I never took out any jet screws so the low speed screw was definitely in when I hit it with the carb cleaner but should I see that coming out somewhere else on the carb? I can say that the screws on the plate were rusted pretty bad. I hit them with carb cleaner and tried to remove as much of it as I could.

Needle spring I kept the original one that was on the carbs despite having the new ones with the rebuild kit because I didn't want to mess that up and was told that I should just reuse the old one.

As for pop off pressure I did not do that test because I simply replaced the old spring and arm. Also I wasn't very clear on how to do it. If that's very important I can certainly try if I have to get the carbs back off.

Ski has 130 hours on it. Not sure what the reeds are. That's a new one for me. I've done a lot on my 2 skis but never heard of those. Can you advise how to check?

Thanks again.

 

[mikidymac]

Here is a picture of the 3 small holes next to the #8 and the big one at about 7 o'clock.


Also please read my carb thread here....Carb Rebuild Thread

The reede are in the intake and act like an intake valve opening and closing thousands of times a minute.

 

[POPPS]

Had a 951 with similar problems. I like to eliminate a faultering fuel pet cock, so I ran the fuel in line to the carb straight from the fuel pickup, which solved the issue and saved me pulling those carbs off.