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Hesitation from a stand still 787

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Jaxtoce1

Jaxtoce1

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I have a 96 GTX 787 and from idle (standstill) if you mash the the throttle it hesitates and bogs down for a good 2-3 seconds and then takes off... not really sure why it's doing this. Personally I don't mind having to butterfly the throttle a bit to get it going but for newer drivers like my brother he will end up stalling it a lot or getting so aggravated with it he doesn't want to ride. Other than the hesitation off the line the ski runs great. Once it's gets going throttle response is smooth and direct and top speed is about 45. Yes I know it should do 55 but the hull is pretty beat and the impeller could use a replacement so I'm ok with that speed.

Does anyone know how to fix this hesitation off the line? I'm assuming it's a tuning thing with the carbs? Also was told it could be an accelerator pump? Lmk what you guys think
 
Clean the carbs and install GENUINE Mikuni rebuild kits. Make sure to inject carb cleaner in the transfer port and be sure they are clean. They are a major cause of hesitation. Replace the needle & seats as well. If it still has the gray fuel lines, replace those too. Reuse the original springs on the fuel control lever and Check your pop off pressure. Continuing to run the ski as it is could result in a lean condition which could damage the engine. Check out the carb adjustments thread in the stickies at the top of the 2 stroke forum.

Also, the 96 GTX does not have an accelerator pump.
 
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I would also get that impeller fixed as it will also cause considerable hesitation off idle if it is bad enough to only get it up to 45 mph.
 
Carbs were rebuilt 2 years ago which was also when I replaced all the grey fuel lines, as far as the impeller, it's just a few knicks on the edges, the hull was reallyyy bad most of the keel had exposed fiberglass and dents and cuts and small holes everywhere... right now I'm in the middle of doing that all over. Should be done by tomorrow or Saturday. But I think that was the real cause of so much loss in speed.

Different question, is there a way I can get the RAVE valves out without removing the exhaust manifold ?

Thanks guys
 
A bad hull and a few nicks on the impeller will not cause a 10 mph loss in speed. You have something else going on.

Remove the spring clamp, top caps, threaded plastic cap and take the housing off the valve. Then remove the valve itself. The manifold does not have to come off.
 
mikidymac said:
A bad hull and a few nicks on the impeller will not cause a 10 mph loss in speed. You have something else going on.

Remove the spring clamp, top caps, threaded plastic cap and take the housing off the valve. Then remove the valve itself. The manifold does not have to come off.
Click to expand...

Good to hear, definitely was not looking to take that thing off again. Thank you! As far as the speed goes, like I said before I'm not to worried about it as I'm not a speed demon and the ski runs great other than this hesitation, but what else do you think could be going on then?
 
Also check the water injection controller on the water box. That can mess up the top end some. What kind of RPMs are you reaching? That will tell us a lot.
 
Jaxtoce1 said:
Also how do I check the water injection on he water box ?
Click to expand...

Just pull the cap off, looks like a rave cap. Then look at the diaphragm and springs to make sure everything is OK. This likely will not kill 10 mph though. But this and a bad wear ring or stuck rave could. DL a manual and it shows you everything on the water valve. 6800 rpm is the max you should get. If you get that at speed, then it is in the pumping side.
 
soccerdad said:
Just pull the cap off, looks like a rave cap. Then look at the diaphragm and springs to make sure everything is OK. This likely will not kill 10 mph though. But this and a bad wear ring or stuck rave could. DL a manual and it shows you everything on the water valve. 6800 rpm is the max you should get. If you get that at speed, then it is in the pumping side.
Click to expand...

Thanks I'll take a look tonight and report back later
 
If the rpms are getting up there & your top speed is that far off+hesitate off the line whats that wear ring look like? Is the hesitation as in you hit the gas, feel the rpms climb but dont go anywhere or simply hit the gas and nothing happens like its loaded up off idle?
 
I don't think it's the wear ring.. when you give it gas from a stand still, it just loads up and bogs a bit and then after about 2-3 seconds takes off and runs great... but if I come to a stop again and try to give it gas again, the same thing happens. It's always on take off that it bogs
 
Also took the raves out and cleaned them off tonight, also replaced the gaskets on both, looked at water box rave and everything looks good there too.. kinda stumped here as to what this could be? I still think it's tuning on the carbs, I think I might be running to rich.. could someone tell me the right carb settings for the high/low speed needles? Need it to warm up outside so I can get it back on the water to really test things out
 
The bog is either carb settings or dirty low speed holes in the carb. See the sticky. If you pull the choke out a little and hit it does it get better or worse? Again for the high end loss of speed, if you are hitting 6800 rpm, it is not likely in the motor side. At that point you are on the rev limiter.
 
soccerdad said:
This is a great read. http://www.mikuni.com/pdf/sbn_manual.pdf and the sticky for carb tuning at the top of this forum. http://www.seadoosource.com/carbreference.html is the carb settings. Note that the 97 motors have the PTO HS out 1/2. I did this on my 96 after I lost a PTO cylinder towing tubes. If you are just cruising, then the 96 setting of 0 on the HS is fine.
Click to expand...

Thank you, I am fairly certain on my 97 gtx i myself just set the highspeeds to 0. I was referencing a form from SBT forum with the carb specs. I will confirm and change this..we pull tubers :)
 
soccerdad said:
This is a great read. http://www.mikuni.com/pdf/sbn_manual.pdf and the sticky for carb tuning at the top of this forum. http://www.seadoosource.com/carbreference.html is the carb settings. Note that the 97 motors have the PTO HS out 1/2. I did this on my 96 after I lost a PTO cylinder towing tubes. If you are just cruising, then the 96 setting of 0 on the HS is fine.
Click to expand...

Since this ski is so old we tend not to tow anything with it to refrain from putting any extra strain on it... then again I do 180's and donuts all the time for extended periods of time which probably makes up for that strain... that being said, riding like that would you recommend keep the PTO, HS at 0? Or 1/2 turn out?

Thanks for all your guys help so far very informative
 
Get rid of your bog first. Then worry about the HS side. Both closed will likely be fine. Once it is running normal, push on it some, then do a plug chop and look at the plugs. If they are white, or if the PTO is lighter than the Mag, then open the PTO up some. You can't tune it until it is running correctly though. And is that GPS 45 or on the speedo? You have to use GPS for a real number.
 
Thats speedo for the speed. Hoping to get out on the water tomorrow, I will let you guys know how that goes then
 
You MUST use GPS to give us a real number. The Seadoo speedo is always incorrect. (check your paddle wheel to see if it is missing tooth or if it does not spin correctly). BUT still get us a GPS top speed.
 
This description isn't very clear.

Jaxtoce1 said:
I have a 96 GTX 787 and from idle (standstill) if you mash the the throttle it hesitates and bogs down for a good 2-3 seconds and then takes off...
Click to expand...

Does the engine bog down and try to die?
Or, does the engine rev right up and the Sea-Doo is slow to react?
These are two different symptoms that require completely different diagnosis and repair. You mentioned that you have a bad impeller and you lost top speed so I assume it's the latter. Repair your impeller and check the wear ring for damage, replace it if necessary. It's cavitating severely.

Chester
 
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