Seadoo 1996 GSX 781 wont turn over with plugs in
- Thread starter Andrewdinsdale
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- 1996 781 gsx seadoo won't start
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Cliff787
Active Member
You won't need to pull the engine out to look at the flywheel and woodruff key.
Loosen the two 13mm bolts ON TOP of the two front motor mounts and NOT the two bottom bolts that hold down the motor mount on top of the shims.
Slightly lift up the motor and place a piece of 2"x4" wooden block under the front of the motor to keep it elevated. At this point. You can take off the 10mm bolts(M6?) and use a wide tipped screwdriver to pry the stator cover off and ¡VIOLA! The flywheel and woodruff key are now exposed and can be inspected. You don't have to remove the flywheel to inspect the woodruff key. Both components are just behind the stator cover!
You can check the condition of the woodruff key, flywheel and timing hole to magneto cup. The magneto cup has a piece of flat metal on it. The edge of one of these flat pieces of metal should be placed near the punch mark(looks like a dot in the flywheel) for proper timing.
Moving on...if you removed the rotary valve cover. Did the rotary valve come off with the cover? If so, you'll need to re-time the valve or serious back firing will occur and the engine will NEVER start.
As far as the condition inside from the pictures...they look okay to me.
There is some light scraping on the Case where the rotary valve spins on. I don't know if that's an issue or not. But I think all looks good inside from the pictures.
If the valve and cover are still off. Can you grab the rotary shaft gear and turn it left and right without it spinning 360*?
Loosen the two 13mm bolts ON TOP of the two front motor mounts and NOT the two bottom bolts that hold down the motor mount on top of the shims.
Slightly lift up the motor and place a piece of 2"x4" wooden block under the front of the motor to keep it elevated. At this point. You can take off the 10mm bolts(M6?) and use a wide tipped screwdriver to pry the stator cover off and ¡VIOLA! The flywheel and woodruff key are now exposed and can be inspected. You don't have to remove the flywheel to inspect the woodruff key. Both components are just behind the stator cover!
You can check the condition of the woodruff key, flywheel and timing hole to magneto cup. The magneto cup has a piece of flat metal on it. The edge of one of these flat pieces of metal should be placed near the punch mark(looks like a dot in the flywheel) for proper timing.
Moving on...if you removed the rotary valve cover. Did the rotary valve come off with the cover? If so, you'll need to re-time the valve or serious back firing will occur and the engine will NEVER start.
As far as the condition inside from the pictures...they look okay to me.
There is some light scraping on the Case where the rotary valve spins on. I don't know if that's an issue or not. But I think all looks good inside from the pictures.
If the valve and cover are still off. Can you grab the rotary shaft gear and turn it left and right without it spinning 360*?
Andrewdinsdale
Member
Ok thanks for the info on checking the woodruff key, I will give that a go tomorrow, sounds easier then I thought.
With regards to the rotary cover, I was extra careful to not disturb the rotary valve and luckily it stayed in place, until I knocked it off 5 minutes later and had to quickly learn via youtube how to make a tool and re-time it at the correct angle.
I had a suspicion that it was over fueling or has excess fuel in the crankcase as the plugs come out dripping every time I spin the engine- I dipped a bit of clean fuel hose into the bottom of the crankcase via the inlet valve and there seemed to be about an inch of liquid (fuel) at the bottom.
Obviously thats not suppose to be there? So with a primer bulb and some fuel line I tried to suck out as much as possible and only got about 50ml. Any idea how I can get any more out? Unless I'm being a rookie I thought it was a bid odd...
Thanks again
Andrewdinsdale
Member
I thought the same, its not the camera thats how it looks in the first pic, (front cylinder). I'm guessing when it was rebuilt they decided this would be OK to leave as is, its not too bad just slightly damaged I think.
Cliff787
Active Member
If the plugs are dripping wet with fuel. Then it sounds like the seals might be bad. Unless the carb needle & seat valve(s) are leaking that much fuel past the o-ring seal in those valves. I would guess that the crank seals are bad. I know that isn't what you want to hear. But if that amount of fuel is collecting in the bottom end. Then obviously. Something is a miss and failing.
Andrewdinsdale
Member
The latest I'm getting is I still have the carbs off, i pulled the front cover to check the flywheel key and stator etc.
The stator was very dirty so I cleaned it till it looked like new, the contact points were all black.
I thought, hey this must be it, it's getting a weak spark. But stuck it all back together and it's the same.
Anyway. Now when turning it over (still have the carbs off) I put my hand over the RV and presumed I'd feel sucking as it's the inlet. But it's the opposite it's blowing out.
Does his mean I put the RV back 180 degrees out or is there something wrong with the engine?i don't think the brass gear on the RV has gone as I can't move it and if you turn the RV by hand with the plugs out (takes some doing) it spins the engine over.
Completely at a loss with this thing.
Andrewdinsdale
Member
I've left the carbs off now for a good few turns over of the engine so no new fuel is getting in there, it's eventually stopped getting the plugs soaked now so I'm hoping there's no issue with my crank seals etc. I don't fancy another engine rebuild*
Andrewdinsdale
Member
Latest update;
Today I removed the flywheel to triple check there was no fault with the woodruff key. (It was fine).
I put it all back together, everything now clean.
It was exactly the same, not starting -still sparking but not starting.
I decided to run a new earth wire to my front mpem box as I had to try something new - maybe I was getting a weak spark and the MPEM wasn't getting a good earth? Anyway, as soon as I ran this wire it fired, (full choke no throttle). Then it did the same again, fired but didn't run more then a cough.
After this it wouldn't start at all but my new diaphragms SHOULD turn up tomorrow for the carbs so hopefully this is my final issue. I don't know if my new earth wire fixed a weak spark or I got lucky?
Who knows. Will update when I put my new carb kits on and chuck my carbs through the ultrasonic cleaner.
Today I removed the flywheel to triple check there was no fault with the woodruff key. (It was fine).
I put it all back together, everything now clean.
It was exactly the same, not starting -still sparking but not starting.
I decided to run a new earth wire to my front mpem box as I had to try something new - maybe I was getting a weak spark and the MPEM wasn't getting a good earth? Anyway, as soon as I ran this wire it fired, (full choke no throttle). Then it did the same again, fired but didn't run more then a cough.
After this it wouldn't start at all but my new diaphragms SHOULD turn up tomorrow for the carbs so hopefully this is my final issue. I don't know if my new earth wire fixed a weak spark or I got lucky?
Who knows. Will update when I put my new carb kits on and chuck my carbs through the ultrasonic cleaner.
Andrewdinsdale
Member
Right so here we go again, carbs off and apart. Waiting for the postman currently.
But..!
On inspection one of the carbs has a (ever so slightly) bent butterfly. It was holding it open slightly so the carbs weren't even close to balanced. I've managed to get it back to how it should be, closing at least. So when I balance them next time that should be OK.
With regards to the needles and seats, I trawled the internet, phoned local seadoo dealers and I can't get needles/seats here in the UK without ordering them from the US.
They look good (but I know you can't tell) I'll order some if the new diaphragm kits don't work.
Any idea of the carburettor settings?
I noticed theres two mixture screws per carb.
Thanks
jhjesse
Well-Known Member
High speed (upper screw) - 0
Low speed (lower screw) - 1 turn out
Pop off 23 -34psi use old spring if possible.
http://www.seadoosource.com/carbreference.html
Low speed (lower screw) - 1 turn out
Pop off 23 -34psi use old spring if possible.
http://www.seadoosource.com/carbreference.html
Last edited by a moderator:
Cliff787
Active Member
Good find on the bent butterfly!
OSDparts.com is where I get my Mikuni parts as well as other OEM Sea Doo items. They are here in the USA(Ohio). I don't know what shipping would cost You. But worth it to get back on the water in my opinion!
They have carb kits that include the base gaskets, needle & seats with either aftermarket tips or Viton tips & hex head stainless steel screws included in their kits. Nice!
Carb settings are:
Lows - 1 1/4 turns out
Highs - 0 (Closed)
OSDparts.com is where I get my Mikuni parts as well as other OEM Sea Doo items. They are here in the USA(Ohio). I don't know what shipping would cost You. But worth it to get back on the water in my opinion!
They have carb kits that include the base gaskets, needle & seats with either aftermarket tips or Viton tips & hex head stainless steel screws included in their kits. Nice!
Carb settings are:
Lows - 1 1/4 turns out
Highs - 0 (Closed)
Andrewdinsdale
Member
Ok so to everyone interested this is now the latest.
Finally I have got the blooming thing to run!
After rebuilding the carbs, it still wouldn't go and my needle valves/seats need replacing as the engines flooding every time. I ordered some genuine Mikuni ones from the UK in the end £48 including postage for two should be here Friday.
But anyway. It still would't run and I was scratching my head and spoke to a friend who deals with PWC and said I should try another coil if I had one- and I did. A Yamaha 40hp Outboard Coil from the 90s- It was worth a shot?
Stuck that coil on with some bodged wiring and it fired right up.
I must have just had a weak spark, but as it was flooding I disconnected the fuel and let it run with what it had left in the carbs for a good 15-20seconds. Revved up lovely, now I need to source a coil (can't get a new one in the UK easily) and fit my new needle valves when they turn up.
Thanks for everyones help.
Finally I have got the blooming thing to run!
After rebuilding the carbs, it still wouldn't go and my needle valves/seats need replacing as the engines flooding every time. I ordered some genuine Mikuni ones from the UK in the end £48 including postage for two should be here Friday.
But anyway. It still would't run and I was scratching my head and spoke to a friend who deals with PWC and said I should try another coil if I had one- and I did. A Yamaha 40hp Outboard Coil from the 90s- It was worth a shot?
Stuck that coil on with some bodged wiring and it fired right up.
I must have just had a weak spark, but as it was flooding I disconnected the fuel and let it run with what it had left in the carbs for a good 15-20seconds. Revved up lovely, now I need to source a coil (can't get a new one in the UK easily) and fit my new needle valves when they turn up.
Thanks for everyones help.
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