Air Leak or Carb issues?

[GregM64]

2000 GTX 947 Fresh rebuilt engine, have already broke it in, but I seems to have an issue with either the carbs or an air leak. Problem; Set idle at 1400 RPM in water & adjusted Low & High screws, if you touch the throttle on the way out of the no wake zone the RPM will rise to as much as 2200 RPM & won't go back down unless you quickly punch it a couple of times then it will drop to 1600 RPM, I adjusted the idle screw again & it still does the higher RPM if you so much as touch the throttle. It has a little hesitation at first when you punch it but seems to run fine after that except for the idling. Also, when I pull it out of the water & rev it up to get the water out of the pump etc. it revs down really really slow.

 

[kmarts]

...when I pull it out of the water & rev it up to get the water out of the pump etc. it revs down really really slow.

i had this problem on my GSX. Turned out to be outer PTO crank seal was thrashed. It ran more or less ok in the water other than hard to start in water and the idle wouldn't always stay set. But the slow rev down on the trailer was the real indicator.

on my car engines when looking for an air leak id spray something like carb cleaner around the suspected area with the engine running and listen for a change in RPM. I wasn't sure how comfortable i was with that in a confined space with the seadoo so i made a set of block off plates and pressure tested my engine.

 

[JJinSC]

WD-40 works for finding leaks and will not be flammable or take the paint of off your engine.

 

[GregM64]

Thanks for the tip. Going to tear down the carbs again just to make sure all is good with them & then to a leak test on them & then the engine. Thanks,

 

[mwat65]

Yes definitely sounds like an air leak. Check throttle cable also. It may be sticking .

 

[GregM64]

Well, here is an update on the air leak. Carbs are tight, went thru them again & replaced all gaskets checked
pop off pressure etc., etc., installed carbs took it out to the lake & for whatever reason it could not get it to idle at all. I was even able to unscrew the idle screw to the point you could see daylight between screw end & throttle lever & no change, it was idling at 2350 in the water. So not sure where to go now, it has some hesitation & it it try's to die if you punch it out of the hole, but it runs good on the high end of the throttle. I didn't play with the low speed screw yet since I couldn't get it to idle. Help!!

 

[kmarts]

Did you remember to connect the pulse line on the carb? I never tried in the water but when i had my carbs on and off every other day messing around there was one time i forgot... Ski started instantly (which never happened before) and i couldn't control the idle either. Once i realized my mistake and connected it, everything was back to normal. But that only ever happened on the trailer, not sure it would start in the water like that.

Did you try and pull the choke to see how it behaved? I'd be real hesitant to run it much if you think you have an air leak you'll want to try and find it.

Did you try spraying some WD40 around the engine while it was running? without pressurizing the engine that will be your best bet to see if there's a leak. check the crank end seals.

mine behaved more or less like yours before i discovered the leak, seemed to run fine other than hard start when cold, low end hesitation/bog, would go WOT no problem, idle was always a little wonky and wouldn't stay consistent

 

[GregM64]

Yep the pulse line is connected. I guess I'll have to see about trying WD on the engine to see if it has a leak.
Not sure if I want to run it out of the water with a hose being that it is revving at 2350 in the water. Where was your leak at?

 

[mwat65]

Spray around the rv cover.

 

[kmarts]

Yeah you're probably right, out of the water it'll probably run away on you. Make sure to check that your throttle cable isn't too tight though.

You said it was a fresh rebuild. Did you do it or someone else? Because if it was really rebuilt, you should have new seals all around.

My leak was the outer crank seal, PTO side.

 

[GregM64]

Yeah, it is SBT engine, they said they do a leak test & that they doubted it was engine. What I meant about running it out of the water was that I thought it might over rev being that it wasn't in the water & I wasn't sure that a garden hose would give it enough water. I'll just keep it on the trailer & back it down the ramp.
MWat65- it doesn't have an RV cover it is a 951 engine.

 

[GregM64]

There is about a 16th of an inch play on the thottle cable. Any other suggestions?

 

[mwat65]

Sorry bud missed that . Double check all your fuel line connections and your base gaskets for your carbs. Lean runaway is a bitch and can be hard to chase down. Do you have an inline filter on it ?

 

[kmarts]

There is about a 16th of an inch play on the thottle cable. Any other suggestions?

I was told 2mm, you're not far off so it should be ok.

Yeah what I meant by run away is the engine reving up on its own cause it's lean and no load on the pump.

That's what mine did the first time I fired it up, scared the crap out of me because I couldn't get it to shut off. If it happens just pull the choke and hit the gas, it'll come back down. Doing it strapped to the trailer in the water works too. I'm just not close enough to water to make that feasible.

Good luck

 

[GregM64]

Gotcha, let ya know my findings

 

[GregM64]

Sorry bud missed that . Double check all your fuel line connections and your base gaskets for your carbs. Lean runaway is a bitch and can be hard to chase down. Do you have an inline filter on it ?

 

[GregM64]

No inline filter, going to take the carbs off again to make sure I didn't miss something.

 

[R-u-n2it]

If it starts to run away, pull the lanyard. Could the carbs be out of sync? Since your idle screw was backed all the way off maybe 1 butterfly is closed and 1 is not, get a mirror to look down the carb throat. You have 2 idle adjustments, idle speed with the screw on the carb/linkage and the low speed screw adjust idle fuel, sounds like they could use 1/8th turn open to test. Lee

 

[mwat65]

If the lanyard doesn’t kill it and sometimes it won’t with lean runaway pull the choke.

 

[R-u-n2it]

Sometimes the lanyard won't kill it? If that's true BRP would be liable big time since it's a safety lanyard to kill it if you fall off. A stuck throttle could be determined to be the owners responsibility but the lanyard/DESS is not mechanical or adjustable. You've actually witnessed a Seadoo keep running after lanyard disconnected?

 

[mwat65]

Absolutely. With lean runaway your burning gases not gas. I’ve pulled the lanyard and the plug wires and it will run wot until it burns the gases off. This is out of the water of course. You won’t get lean runaway in the water. If it’s happening in the water you have another issue. This is not just my opinion on killing it with the choke. Many on here will tell u the same thing.

 

[GregM64]

Well, I read an older message from 2017 that might be my issue. I removed the oil injection to go to premix so I didn't have to worry about it failing. What I believe possibly is that I have the throttle cable installed in the hole that the oil injection cable was installed in. I think it should be in the top hole not bottom. I will change it out tonight & fire it up, hopefully this was my problem from the get go. Fingers crossed!!

 

[Chester]

Sometimes the lanyard won't kill it? If that's true BRP would be liable big time since it's a safety lanyard to kill it if you fall off. A stuck throttle could be determined to be the owners responsibility but the lanyard/DESS is not mechanical or adjustable. You've actually witnessed a Seadoo keep running after lanyard disconnected?

Yes, when the engine runs away, even pulling the plug wires off will not stop it. You must pull the choke to kill it. It's called glow plugging and usually happens if the mixture is too lean. Hot spots in the combustion chamber ignite the fuel mixture and the disconnecting the spark plugs has no effect. It can occur (on any brand 2-stroke) if there is an air leak, bent throttle plate, misadjusted idle screw etc.
BTW, this only happens when the PWC is on the trailer, it will not happen in the water.

Chester

 

[R-u-n2it]

OK, You had me going there, The op had mentioned on the trailer and I was stuck on that I guess, or the retard.... I mean mentally challenged me escaped at the keyboard again. The self perpetuating kind, old school "dieseling".