1996 GSX 787 slow cranking

[1993XP657]

I'm the 2nd or 3rd owner of this ski since it's had an issue and nobody has solved it. It will turn over fine with the plugs out, but you get about 3 seconds of cranking, then it acts like the battery is dead. Had an aftermarket starter and previous owner put in a new flywheel.

I get 2 beeps when lanyard is connected.
So far I have done as follows:
Ran a new ground from engine block to battery
Tried 2 different brand new AGM batteries as well as charged them.
Took off the aftermarket starter and put in a good used Denso OEM one as well as a rebuilt one that was also to the same effect.

When I pull the plugs out, I get a small mist of mixed gas as I should. I know what it's like when you have a bad needle and seat on an upright motor and you pull plugs and fuel shoots 6 foot in the air. This does not have this concern. No real oil coming out like a bad crank seal either.

I've even gone as far as swapping both battery cables from am extra ebox I had sitting around. All cables ohm less than .5 ohms.

What gives here?

 

[artr]

Try shorting across the top of the start solenoid with a insulated handle screwdriver. If it cranks normally for more than 3 seconds, replace the start solenoid.
If it is not the start solenoid, does it actually slow down cranking with the plugs out? If so, when it slows down, turn the engine over by hand at the PTO flywheel. It should spin freely. You should be able to feel if there is any internal binding.

 

[emspjay]

Bet that aftermarket starter is going bad. Get an OEM starter and a rebuild kit and rebuild it and put it in.

 

[1993XP657]

It will spin all day with the plugs out and turns freely by hand.

The starter is an OEM denso.

 

[1993XP657]

And I have tried 2 separate denso starters.

 

[mikidymac]

It is a pretty simple system so there is only a few things it can be.
1. Does the engine turn over all the way smoothly by hand with the plugs out?
2. Starter has to be good.
3. Battery has to be good, what is the voltage at rest and when cranking?
4. Solenoid has to be good, jumping the posts will test this.
5. Positive and negative cables have to be good, they go bad from the inside out.
6. Compression can't be too high, 150 psi is perfect.

 

[1993XP657]

Engine turns over by hand.
2 separate OEM good starters have been tried.
12.6v on both new batteries that were tried.
All cables have been replaced with known good ones from another ski.

 

[emspjay]

Ok I missed were you tried OEM's. Are you positive both OEM starters you tried are good?, and the rebuilt one was done properly? I once replaced a bad aftermarket starter with a "know" good OEM and it worked for a few weeks then it died (same thing cranked slow with plugs in). Put another OEM in (bench tested only) same thing, pulled that one out and did a complete rebuild including resurfacing the commutator and it has been working since then no problems.

 

[1993XP657]

Ok I missed were you tried OEM's. Are you positive both OEM starters you tried are good?, and the rebuilt one was done properly? I once replaced a bad aftermarket starter with a "know" good OEM and it worked for a few weeks then it died (same thing cranked slow with plugs in). Put another OEM in (bench tested only) same thing, pulled that one out and did a complete rebuild including resurfacing the commutator and it has been working since then no problems.

I'm the 3rd owner since it's had this issue. Previous owner threw 3 starters at it. I'm pretty sure its not the starter.

I did clean the 4 grounds on coil and it made it some better. Then the starter solenoid failed last night. Gonna replace it, and retest this evening.

 

[1993XP657]

I'm fairly well versed with electrical, this one has me stumped though. I did run a ground to the mag cover instead of starter ear, with no change.

 

[mikidymac]

What is the battery voltage when cranking?

 

[1993XP657]

What is the battery voltage when cranking?

Dropping down to 1v or so. I think the battery is dead from me cranking it last night.

With that said, it actually cranked and ran for about 3 seconds so we're on the right track after I swapped out the starter solenoid and cleaned the 2 small red wires as well as the battery cable ends with 1000 grit sandpaper.

 

[mikidymac]

At 1V that battery is junk.

I have seen brand new ones be bad also.

If the battery drops below 11V when cranking the coils will often not spark. These skis need a good strong battery and no jump starting or booster packs.

 

[1993XP657]

At 1V that battery is junk.

I have seen brand new ones be bad also.

If the battery drops below 11V when cranking the coils will often not spark. These skis need a good strong battery and no jump starting or booster packs.

It may be a rash of bad ones. I have used the diehard ones from advance on my other skis and they have been great.

 

[JMAN1]

My 96 GSX ski had a similar problem for a brief period as apparently the starter solenoid was on its way out. Apparently they can partially fail. It would crank perfect jumping across the terminals and showed the proper voltages but it would only intermittent crank from the start/stop button. Replaced that solenoid and everything works perfect now.

 

[1993XP657]

My 96 GSX ski had a similar problem for a brief period as apparently the starter solenoid was on its way out. Apparently they can partially fail. It would crank perfect jumping across the terminals and showed the proper voltages but it would only intermittent crank from the start/stop button. Replaced that solenoid and everything works perfect now.

That's what I'm thinking happened.

Side note, do the AGM batteries require a special charger on these?

 

[JMAN1]

yes your charger should say for AGM. however you could use a low charge setting for lead acid and get away with it.

 

[1993XP657]

Alright guys. I went and got a charger today with AGM capability and it showed the battery was at 80%. I also changed the starter solenoid the other day too. Cranking issue is fixed.

Still won't start though. I have spark, carbs are rebuilt and I have fuel and compression is 150 in each cylinder. I'm going to check rotary timing next.

 

[JMAN1]

check your small gauge ground lead from the start solenoid box to your battery. It will act like its going to start but won't without it. It may be an intermittent onnection at the ring terminal, I've had that.

 

[1993XP657]

check your small gauge ground lead from the start solenoid box to your battery. It will act like its going to start but won't without it. It may be an intermittent onnection at the ring terminal, I've had that.

I have had to put a new eyelet on it already. Seems ok. What's odd about this is none of the previous owners could get it to run either. I feel like I'm dealing with something deeper now. It will at least spin over until the battery is drained now with no issue.

 

[JMAN1]

I have had to put a new eyelet on it already. Seems ok. What's odd about this is none of the previous owners could get it to run either. I feel like I'm dealing with something deeper now. It will at least spin over until the battery is drained now with no issue.

sounds cliche but how deep have you gotten into carbs? your air/fuel ratio could could be very off idle. Also mine likes full choke, full throttle to draw fuel while it cranks for the first time in a day. The second its fires drop both the choke and throttle and she runs perfect (on mine). If it does die after that firing, I use choke till it fires, then drop it a feather throttle to a clean idle. Thats just for a first of the day startup.

 

[1993XP657]

sounds cliche but how deep have you gotten into carbs? your air/fuel ratio could could be very off idle. Also mine likes full choke, full throttle to draw fuel while it cranks for the first time in a day. The second its fires drop both the choke and throttle and she runs perfect (on mine). If it does die after that firing, I use choke till it fires, then drop it a feather throttle to a clean idle. Thats just for a first of the day startup.

Rebuilt with back to stock kits from OSD. New needle and seats as well. There is an obvious underlying issue here that nobody as addressed. That's why I'm thinking rotary valve.

 

[JMAN1]

does it flood the cylinders when cranking long? yes rotary is a decent thought since its been a long standing issue. but others would know better than I.

 

[1993XP657]

does it flood the cylinders when cranking long? yes rotary is a decent thought since its been a long standing issue. but others would know better than I.

Today I pulled carbs and rotary cover to check. I confirmed that the gear wasnt stripped.

I will say, this engine is kinda hard to turn over by hand with the plugs out. I'm wondering if the previous owner didn't rebuild the jet pump right.

 

[1993XP657]

Timed the rotary valve at 147/149* with margin of error.

When I spun the engine over with rotary cover off, alot of mixed gas seemed to have came from the ports like it was flooded. Cleared it and I'm charging the battery now.