96 GTX 787 Engine hard start and backfire

[650Guy]

OK, I just got this jet ski and now panic'n. Had it out twice and having a blast until now. Had small jet drive issue and now this.

Ran great for about 4 minutes. Then died. here is the scenario:

* Install new battery (old one was weak)
* Just topped off
* Fired her up and off we drove for about 4-5 minutes... then bla... she dies.

Pull it in and start the following:
* Switched spark plugs
* Switched to reserve tank (don't know... just trying anything!)
* removed the fuel filter bowl and check (found full of fuel and pretty clean)
* Got some starter fluid and she fired but rough
* once running full throttle gave it like 2000 RPM with backfire occasionally
* Pulled the front plug wire and not much changed
* Pulled the back plug wire and it died all together.
* Got it running again and with some feathering of throttle, got er up to about 4-5000 RPM and maybe 20 or 30 kts but must not let her idle, at Idle she backfires and sputters and eventually dies.
* Found the trick to starting was Full choke, Full throttle and crank the heck out of it.

I'm new to this jet ski scene and really am not sure where to start. Any suggestions would be simply awesome!

 

[jhjesse]

Sounds like you are running on one cylinder.
Pull the boots back on the plug wires and clip back about 1/4 inch Reinstall with new plugs (NGKBR8ES) and check. If no change check coil. (could be going bad)
Also check the plug wire connection in the box by the battery to make sure it is making good connection to the coil.
If it were me I wouldn't use starting fluid...could damage engine.

 

[650Guy]

Ya... was real hesitant to use the starting fluid i was desperate and dumb.

I was just reading another post, it said if the battery was low it could cause some misfire? do you know this to be the case??? Could it be so simple that my "New" battery was not fully charged?

 

[jhjesse]

Could very well be the case. Take to autozone and have it checked. It's a free service. Then if battery is good go from there with your checks.

 

[650Guy]

That would be way to simple, HA! I'm gonna put it on a trickle charge tonight and test at autozone. In the mean time, check the wires as you suggested. Thanks so much for reply'n!

 

[650Guy]

OK, so Battery is good, Ignition is good, now I'm leaning towards fuel and praying nothing with compression!

Anyone have any suggestions on how to check carboration and fuel??

 

[jhjesse]

If you still have grey fuel lines, replace them one at a time with black fuel hose from autozone 25 to 30 ft will do along with about a dozen clamps.

While replacing the fuel lines pull the fuel selector valve and clean it really good. Let it soak for a couple days or just buy new at the local Sea Doo dealer. $30.00

Remove the fuel filter and clean really good and reinstall making sure the O ring is sealing. (very important)

Pull the carbs off and carefully disassemble one at a time. Clean thoroughly...and I mean thoroughly. Replace or clean the small internal filters. They will be full of crap.

Re assemble the carbs and set the HSA and LSA to factory.

Crank it up and ride like hell!!!

 

[gsxgtxman]

Could also be a sync issue on your carbs. with the 2 seperate carbs they have to be sync'd perfectly for them them to work properly.

 

[650Guy]

OK, Really newby question, but I have a perfectly new battery that has been tested as fine. When I put the key on, i do NOT get the "CHERP CHERP". It kinda goes "click click" faintly? It will crank like gangbusters but just no initial chime?

I have not gotten to cleaning the carbs just yet but have removed the filter bowl and have replaced my lines from gray to black. Just now thinking that missing CHERP CHERP is a bigger factor then I thought leading to the electrical side? Maybe?

I really appreciate everyone's help and thoughts! its really helping me narrow it down and learn.

 

[jhjesse]

Mine never chirps anymore and I don't miss at all. She runs like a top.
When you get to the carbs you will see what all the fuss is about. Those internal filters will be full of gunk.
Make sure you clean the gunk out of the fuel selector valve, as well.

 

[650Guy]

Oh man, that's great to hear... I think? HA! Electrical seems tough to chase, carbs I can sink my teeth into. Plan to tackle them tomorrow or Fri.

 

[onebadcav00]

doesnt the coil on these fire both plugs at the same time?? if so he would know it with both plugs. its just a shot in the dark, they are high tec but not that high tec if anyone knows what i mean.

 

[650Guy]

If that is true, I could eliminate any electrical ideas. Tomorrow AM I'm planning on tearing into the carb and cleaning the RAVE. Once I find the problem, I plan to post it. I gotta say, having everyone's opinion sure does help.

 

[650Guy]

I think I found the problem. my motor is blown. Pulled the head off this AM and metal is everywhere, compression on front cylinder was ZERO!



Looks like my season is done.

Thanks for everyones advice. Now if anyone knows of a good place to get an engined, that would be cool.

 

[jhjesse]

no over till it's over

Hey 650,

Go to the SBT web site below. They will send you a new short block engine in a couple of days. Then you have 14 days to take your carbs etc. and put it on the new rebuilt engine. Then you send you old block in for a core.
simple as that. You will be riding in no time. My buddy has a yamahammer ski that He had done and he is riding as we speak. Last week He thought His riding season was over, as well. Give it a try.

www.sbtontheweb.com/

 

[650Guy]

I have heard Horror stories about SBT, I would love to go that route, but I'm not having good luck with motors and really don't want to have to be swapping them again. Does anyone have any SBT engine running... say a year later?

 

[roneagan@cfl.rr.com]

I have an SBT in one of my skis.. it's just been a year and it still runs great...
I would use them again if I had another problem... Go to the site and read the warranty they offer.. I belive Snipe said he has installed around 12 units from them with little or no problems.. They have everything you need to do the job...

 

[Browzee0080]

I have the same problem yet and compression is still good, any more suggestions????????

 

[Browzee0080]

My 96 gtx sea don't 787 has rebuilt carbs, good compression, new gas line, new battery, new fuel sock, new check valve invent line new 1.5 pound valve in vent line, fresh fuel, cleaned up fuel indicator nob. what els could make this waste of time and money continue to back fire?? If I start it and restart it will eventually run properly for along period of time, or until I turn it off and leave it set for a while.....

 

[ZeroTolerance]

Are your carbs adjusted correctly? A leak in your exhaust or small water leak near driveshaft? Check your ignition system with a dwell meter. "Did you check the spring, lever and needle valve in it to ensure it was the correct size for your motor?" - SeadooSnipe (referring to carburetor)

Rotary Valve adjusted correctly?

Can you please explain your personal problem more in depth as to what's happening.

 

[Browzee0080]

96' seadoo gtx w/backfire and bog upon starting. Needle and seat and spring were orderd from factory, Carbs were pressure tested and do not hold pressure, and all they are is a larger version of a weed whip carb. Are they required to hold a steady amount of pressure?? And how do you adjust the rad valve??? Thank you for your assistance...

 

[Browzee0080]

Pulled mag side plug wire still ran, pulled pto side plug it quit. Can't get any consistant good results out of tether.. Pushed start stop button 5 times for self diagnosis and no response.. How els do I test ignition???

 

[timmyboy76]

factory specs..

96' seadoo gtx w/backfire and bog upon starting. Needle and seat and spring were orderd from factory, Carbs were pressure tested and do not hold pressure, and all they are is a larger version of a weed whip carb. Are they required to hold a steady amount of pressure?? And how do you adjust the rad valve??? Thank you for your assistance...

1996 GTX 787 (2)/BN-40I, MAIN(jet)-142.5 PILOTjet)-70 1.5n/s, 23psi - 43psi LOW(low speed adjuster)- 1 HIGH(high speed adjuster)- 0

 

[ZeroTolerance]

Sounds to me like you have yourself an ignition problem and a carb problem :ack:. To test it you'll need a dwell meter. Carbs should hold pressure for a few seconds. Sometimes you have to manually bend the seat to get the needle valve to work properly.

Check fuel pump valves operation as follows :
Connect a clean plastic tubing to the inlet nipple
and alternately apply pressure and vacuum with
the mouth. The inlet valve should release with
pressure and hold under vacuum.
WARNING : Some fuel may be present in
fuel pump. Be careful not to swallow fuel
when under vacuum.

Repeat the same procedure at the outlet nipple.
This time the outlet valve should hold with pressure
and release under vacuum.
3, Diaphragm
PUMP DIAPHRAGM LEAK TEST
Using a suitable pump gauge tester, perform the
following test proceeding as follows :
– Install pump gauge tester (P / N 295 000 114)
on pulse nipple.
– Pump tester until it reaches 28 kPa (4 PSI).
Diaphragm must stand pressure for 10 seconds.
If pressure drops, replace diaphragm.

 

[Browzee0080]

So out side of a rebuilt fuel pump, is there any chance that the mag side crank seal could be leaking?? when I unpluged the pick-up from the housing case it let out a gasp, and from previous experience in 2-stroke motors when a crank seal goes bad before termination you are unable to adjust the carbs and fuel pump regulation is intermitent..