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  1. #1

    Post 787 wont turn over with spark plugs in (96 GTX)

    Hi all,

    Some Info:
    I have almost given up on 2 strokes due to this troublesome ski!!..
    I recently rebuilt the carbs as the needle and seat were leaking and causing my engine to bog / hesitate. I have also changed all fuel lines.

    Specs:
    Compression test shows 150psi on MAG and 147psi on PTO. (Full throttle, and the other plug out).
    I have tried 2 batteries (one brand new), and have tried jumping it from my car for extra power (with car off).. even my worst battery can start a mates GSX 787..
    I have dremelled the connections of all leads, so they are great connectivity (except in the rear electrical box).
    Rectifier was good last time i checked - disconnected the red wire and it didnt change the performance..
    Stator was also fine and matched up to all seadoo service book checks,


    Problem:
    Engine wont turn over while the spark plugs are in.. even if they are only half in!..
    When both plugs are out, i can easily turn the engine over by hand, and it doesnt feel like its got a bad bearing or anything.
    With the plugs out, the starter easily spins the engine over and maintain a fast crank speed, you can see a vapour exiting each piston.
    With spark plugs in, it cranks (half a rotation or so) and then doesnt have enough power to continue cranking.. and have tried many batteries / jumping leads.





    I have no idea on what to do, and dont know where to look.. it seems the stater is fine, battery is perfect, starter solenoid is working as it should..


    Any ideas??..
    Thanks Tony.


  2. #2
    95spi w\factory pipe/96xp Diggler's Avatar
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    I "had" a 97 xp that when I didnt use it for a couple weeks, it would do the same thing,thought it was vaper lock. I thought it must have been from vapor in the crankcase because all's I did was poor a cap full of gas in each plug hole, put them back in and the sob fired off like charm. Another thing thing that I fixed was one of the tiny balls in the one way valves for the accellerator pump would get stuck so it would get air in the small lines for that. Cleaned that and if anyone knows they have an accelerator pump setup on there 787, you can use it like a primer to start it up way faster when cold, than using the choke so much. Just pump the gas a few times till you hear fuel spirting in there and it should fire up much more faster.

  3. #3
    i had the same problem with my 97 gsx and i had to take the rotary valve off and tip the ski on it side. it had a bit of water in the bottom end and it would not turn over. the best way to check that i found was take the plugs out and turn it over if there is a white look gunk comes out of the plug hoels then it is more than likely water. to get the rotary valve off you have to take the carbs off and the covers is in behind them. if that is your problem then when you do take it off take and mark where the valve is on the shaft. my valve was all pitted so i went out and got a new one for around $50. my thing is if i am going to go and rip it all apart it should be a new on going on so i dont need to get a brand new cover because i didn`t want to spend $50. then when i got it all back put back togeather i put some sta-bil marine formula in the gas tank and run it. it took a few times of turing it over to start but it did.

  4. #4
    96XPSS's Avatar
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    Hey Tony, when you say you dremelled the ends of the wires, did you remove the heat shrink tubing over the crimped part of the connector to confirm it isn't corroded under there?

    1. It's either wires, solenoid, or starter brushes. Jump the large terminals with a screwdriver to confirm the contacts are still good, on the solenoid. It's in the rear electrical box. If it does the same with the plugs in, it is good.

    2. Use a set of jumper cables and parallel them with the wires from battery hot to the solenoid, and battery ground to a good ground on the engine. The wire corrodes on the ground wire, under the engine, under the heat shrink tubing. If she spins over fine then take off a jumper at a time to confirm which one is bad.

    If 1 & 2 doesn't identify the culprit then the starter brushes are worn out. You can disassemble and relace the brushes without having to buy a new starter, it's much cheaper this way.

    The reason why it spins with no plugs in is there is no real electrical load on the starter. When you load the electrical circuit by installing the plugs, the weak part of the circuit cannot allow full voltage to pass, and thus the engine will not turn over.

    Robert

  5. #5
    planiack's Avatar
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    Take a voltage reading at the battery with the plugs in and turning it over. Then take a voltage reading at the starter terminal turning it over with the plugs in. The reading should be the same. If not, you have a faulty connection. It is breaking down under the load. Also take a voltage reading with the meter hooked up to the battery positive and the starter case. Again, the reading should be the same. If not, again a poor ground connection. Good luck.
    Mike

  6. #6
    Thanks for all the responses.. kind of gives me hope!...
    my 787 doesnt have an accelerator pump, and the carbs have just been rebuilt


    Quote Originally Posted by 96XPSS View Post
    Hey Tony, when you say you dremelled the ends of the wires, did you remove the heat shrink tubing over the crimped part of the connector to confirm it isn't corroded under there?

    1. It's either wires, solenoid, or starter brushes. Jump the large terminals with a screwdriver to confirm the contacts are still good, on the solenoid. It's in the rear electrical box. If it does the same with the plugs in, it is good.

    2. Use a set of jumper cables and parallel them with the wires from battery hot to the solenoid, and battery ground to a good ground on the engine. The wire corrodes on the ground wire, under the engine, under the heat shrink tubing. If she spins over fine then take off a jumper at a time to confirm which one is bad.

    If 1 & 2 doesn't identify the culprit then the starter brushes are worn out. You can disassemble and relace the brushes without having to buy a new starter, it's much cheaper this way.

    The reason why it spins with no plugs in is there is no real electrical load on the starter. When you load the electrical circuit by installing the plugs, the weak part of the circuit cannot allow full voltage to pass, and thus the engine will not turn over.

    Robert
    96XPSS - No i only dremmeled the ends - didnt think of doing under the wire connection.. I will confirm if the wires are bad by connecting jumpers directly to the starter and also doing voltage tests as Planiak suggested.

    I think all the posts are logical and could be any one of them.. i doubt its hydrolocked though.. when this used to happen, i use to just take the plugs out, crank, and then put the plugs back in, and it would turn over and start..


    If i find the starter is bad, im more than confident to rebuild it... im into electric RC cars, and have done brushes and general maintenance many times..

    Thanks for the help, i'll go outside soon and work on it.. i'll post my results later today.


    Tony.

  7. #7
    voltage drop at the battery is down to 7.5v while cranking.. this is the same at the starter terminals, and all other methods..


    jumping the starter directly (took half an hour to manouver into getting the positive) did the same thing.. however it did turn over the once (rather than just half).

    So now i think its the starter.. looks like a "@#[email protected]#$" to remove!

  8. #8
    i had to redo mine and it was a pain in the a$$ but take ur time and you can get it there in one right up on the the bottom of the engine and when you go to put it back in make sure you put the ground wire on first because if you dont it is a big pain to get it on after

  9. #9
    Finally got the starter off..

    When manouvering with the positive cable, i noticed it wasnt a solid post on the starter.. after twisting it a little by hand, it all of a sudden went loose.. after opening up the starter - which looked like a bombsite, i realised that this connection goes to the brushes... so i'll definantly need one of those..

    Heres what the starter removal looks like:


    Ignore that Rotary Valve in the background - that is a paper one printed from the service manual.




    Teeth look like they have had a beating on the edges.. and a yukky paste of grit and grease on the walls






    (This was after i brushed it clean a little).. it was a dry dry bombsite.. SOOO much dust came out of the starter!




    Does the below photo look fine?.. i am worried about the lack of coating on the thick wires?





    You can see how i ruined the positive thing.




    Im just about to clean it all with electric motor cleaner spray. (i got some from my electric RC cars.
    I pulled the starter yoke out of the magnets, and they are all intact and none are broken (common problem on my RC cars)

    Is my starter salvagable?.. If so, what parts should i go and buy?..

  10. #10
    96XPSS's Avatar
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    That starter has been full of water before. If the bronzite bearings have no play in the ends, go get a brush kit and try her. Inspect windings for hot spots that would indicate a short, otherwise, you should be ok.

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