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  1. #1

    Smile Uggh 94 SL750 3650RPM

    Hey;
    I got a 94 SL750 that is having problems. It will only hit 3650 rpmís and itís lagging at that. I am a newbie sort of and yes, I have read almost every post I can before putting this up. I appreciate any advice in advance. Oh, I also downloaded the manual and read most of it including troubleshooting.

    What I have done so far:
    1) Replaced fuel pump with 3-line Mikuni
    2) Tested compression, all show 120
    3) Replaced fuel filter
    4) removed auto-cock thing
    5) Replaced spark plugs bpr7es (sparks on all 3)
    6) Kicked and screamed a bunch, talked to it german, French and English, no luck there either

    Here is what happens:
    1) It starts with choke on, smokes a bit
    2) If I give it full throttle it usually stalls
    3) Will restart if I choke it

    Here are some other notes:
    1) When I remove the flame arrestor cover there isnít anything in it, just the carb openings, is this right?
    2) The lcd screen works
    3) If it stalls I need to choke it again to start it
    4) I still believe itís a fuel issue but I am getting into areaís I donít know much about

    What else to check. Don't know much about the electrical but I am sure I could figure it out.

    Thanks
    JoN W


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    My guess is that you need to pull the carbs apart and clean them up inside.

    Replace the rest of the fuel lines, including those inside the tank.

    Reset the carb adjusting screws to factory specs.

    While you have the carbs off, check the condition of all the reed petals. Also check the crank index, just to be sure that isn't out of whack.

    There should be a flat metal plate, full of holes, covering the bottom of the flame arrestor over the carb openings. It is the metal plate that stops a backfire flame from getting out into the hull interior.

  3. #3
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    You should change the fuel hoses, inspecting those inside the fuel tank if applicable. Also inspect the fuel shut off valve for restrictions. Definately sounds like fuel starvation, carbs should be disassembled and thoroughly cleaned and inspected.. DON'T run it until you get it sorted out. Otherwise a holed piston is soon to follow.

  4. #4

    Smile Thanks - Couple more questions

    Thanks for the quick response.
    I pulled the fuel lines from the separator and the switch and the main fuel line looks dry as a bone but the reserve seems like fuel may have passed through it at one time. Before I start rebuilding carbs (yeah I should do it anyhow) I wanted to track the easy stuff first.
    1) Where can I get the following
    New fuel switch
    Gas tank thing (sorry donít know the name, but the thing that has all the lines in it)
    A throttle control for the handle (the one on the 95 broke)
    2)Replacing the fuel filter with a standard 1/4Ē fuel filter is fine? Or do I need a special version?
    I appreciate the help, I am reading the manual as well as the forum and am grateful for the knowledge that you all share.

    Thanks
    Jon

  5. #5
    seaobin's Avatar
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    Thanks for the quick response. Your welcome

    I pulled the fuel lines from the separator and the switch and the main fuel line looks dry as a bone but the reserve seems like fuel may have passed through it at one time. Before I start rebuilding carbs ( do this first, at least open and look)
    (yeah I should do it anyhow) I wanted to track the easy stuff first. By Pass the switch to the reserve line (deepest fuel line)
    1) Where can I get the following
    New fuel switch (You can use the sea doo, but try to clean yours first) Ace Hardware might have the o-ring. Very basic design, just dont want air to come through there. Put a little white lithium grease on teh oring to help seal.
    Gas tank thing (sorry donít know the name, but the thing that has all the lines in it)
    A throttle control for the handle (the one on the 95 broke) Check ebay or WATCOM
    2)Replacing the fuel filter with a standard 1/4Ē fuel filter is fine? Or do I need a special version?no standard fuel line form ACE or where ever
    I appreciate the help, I am reading the manual as well as the forum and am grateful for the knowledge that you all share.

    also: Check the seperator bowl and make sure you have no air in it, when you crank, does it draw down and refill? If yes good if no bad.

    Do you have solid/consistent spark

    Is your battery charged all the way

    Where are you?????

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by jwubbena View Post
    Thanks for the quick response.
    I pulled the fuel lines from the separator and the switch and the main fuel line looks dry as a bone but the reserve seems like fuel may have passed through it at one time. Before I start rebuilding carbs (yeah I should do it anyhow) I wanted to track the easy stuff first.
    1) Where can I get the following
    New fuel switch
    Gas tank thing (sorry donít know the name, but the thing that has all the lines in it)
    A throttle control for the handle (the one on the 95 broke)
    2)Replacing the fuel filter with a standard 1/4Ē fuel filter is fine? Or do I need a special version?
    I appreciate the help, I am reading the manual as well as the forum and am grateful for the knowledge that you all share.

    Thanks
    Jon
    You can use the Sea Doo petcock from WSM ($15) or clean/inspect your stock one. You're looking for the rubber folding over and restricting fuel flow. No flow = bad news

    John Zigler would have the fuel sender. Also look for the updated aluminum threaded cap. The plastic ones were prone to cracking.

    Try John again for the thumb throttle. Also I think he has some new finger throttles as well. You can also look for guys parting skis out.

    Any 1/4" plastic fuel filter should be good, but they do have higher flowing filters if you have a modified engine. Polaris filters would be recommended though.

  7. #7

    When you say bad news

    I tend to hope for the best and expect the worst, so when you say bad news, what is the worst case?

    I am in Atlanta, GA btw.

    The sep was full, I took it off and emptied it but haven't tried starting again until I looked over everything.

    Following the instructions and manual we could remove the auto-petcock on the 94 series? a clear tube is left that I read can just hang but block it, is this the case or do I need to put the petcock back on it? right now I got the mikuni 3 line going to each carb, the pulse line from the engine and the inbound from the sep.

    (I was going to bypass the switch but wasn't sure if I could bypass the sep for testing?)

    I have 7es plugs and checked the gap, it was way off, something like .40 so i brought them down to .28.

    Looking at the fuel pickup, I have two lines (res and reg), one other dangling thing and another line (I think that's right, I would have to look).

    How do I measure pressure?
    Is there a way to check each step, from the tank to the switch, switch to the sep, sep to the pump, pump to the carb? After it goes into the carb, it's over my head...

    Engine 101 - Correct me where wrong -
    Compression on the engine pushes pressure on the pulse line at the same time pulls gas through the pump and carb?

    I haven't checked all lines as of yet.

    Thanks again, boy isn't this fun!! At least I have one running or I would pull my hair out!

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by jwubbena View Post
    I tend to hope for the best and expect the worst, so when you say bad news, what is the worst case?

    I am in Atlanta, GA btw.

    The sep was full, I took it off and emptied it but haven't tried starting again until I looked over everything.

    Following the instructions and manual we could remove the auto-petcock on the 94 series? a clear tube is left that I read can just hang but block it, is this the case or do I need to put the petcock back on it? right now I got the mikuni 3 line going to each carb, the pulse line from the engine and the inbound from the sep.

    (I was going to bypass the switch but wasn't sure if I could bypass the sep for testing?)

    I have 7es plugs and checked the gap, it was way off, something like .40 so i brought them down to .28.

    Looking at the fuel pickup, I have two lines (res and reg), one other dangling thing and another line (I think that's right, I would have to look).

    How do I measure pressure?
    Is there a way to check each step, from the tank to the switch, switch to the sep, sep to the pump, pump to the carb? After it goes into the carb, it's over my head...

    Engine 101 - Correct me where wrong -
    Compression on the engine pushes pressure on the pulse line at the same time pulls gas through the pump and carb?

    I haven't checked all lines as of yet.

    Thanks again, boy isn't this fun!! At least I have one running or I would pull my hair out!
    Worst case scenario would be a holed piston, maybe cylinder damage, or even the crank bearings could fail. Like I said, bad news....

    DEFINATELY remove the autocock!!!!! Cap any hose going to it that can't be eliminated.

    You should have a petcock should you need to shut off fuel supply, but you can bypass it for testing.

    You can also bypass the water/seperator for testing as well. Not sure why, but you could.

    Get yourself a set of BPR8ES plugs, the 7's are actually hotter, increasing the chances for burning a hole in the pistons.

    You should have a reserve pick up, a main pick up, a return nipple and a vent nipple (hanging thing is a check valve) It allows air in to build a slight pressure inside the fuel tank, helping to push fuel into the fuel pump. At the top is a pressure relief valve that opens at 1.5 psi should it build too much pressure.

    You'll need a pressure gauge to measure fuel pressure.

    Really no way to check each step per say. Just make sure the lines are clear of restrictions.

    There's a vacuum applied to the sending hoses to the water seperator and fuel pump. From there it's pressurised to go to the carbs. That can be measured with the gauge. Place the gauge between the fuel restrictor (return hose going back to fuel tank) and the carbs. Should get around 1-2 psi at idle and around 4 psi at WOT.

    Fuel pumps operate from the engine pulses. Vacuum is applied opening one check valve to pull fuel into the fuel chamber of the pump. Then the piston down stroke creates a + pressure, pushing the diaphragm the other direction. This closes the opened check valve, and opens the other. Forcing the fuel in the fuel chamber out the nipples and into the carb fuel rail. This happens many times a second, that's why pressure should rise along with RPM.

    There's a restrictor inside the return hose of some models (780's have them integrated into the carbs) which prevents fuel from flowing back to the fuel tank. This creates fuel pressure.

    Definately check your fuel hoses. I'd replace them because of age. Also look for the restrictor and make sure to re-install it into the new return hose.
    Last edited by xlint89; 07-24-2008 at 11:25 PM.

  9. #9

    Thanks again, update

    Yet again, more questions... I continue to read everything I can about those having similiar problems but none quite match mine.

    Alright, i tore it all back down (fuel lines and such) and replaced them with the clear type. I need to find that restrictor, not sure if I replaced that one or not. Once replaced, I tried to turn it over to see what happens and then nothing. I walked away, went out on the other working ski, and came back and for giggles tried to turn it over again. This time I noticed the fuel start to pulse through the lines. They have air in them still, not sure if that is a problem. (It appears at IDLE to be a couple times a second?)

    My battery died after all that so I will have to charge it.

    My questions -
    1) Going from carb to the tank (if I remember correctly), it connects to the nippled one with the thing hanging in the tank or the one with nothing? (I re-read your answer and I beleive this is correct)
    2) Before I take the carbs out, can i blow the "carb filters" out somehow, I read this on another post that he blew air through the return?
    3) The tank releif valve will blow at 1.5 psi and this would be in the handle?

    3.5) There was a clear tube coming from the bottom of the first carb going to the original auto-cock, what does it do and I read to cap it and let it hang.

    4) Proof that I shouldn't be working on my own engines I can't find removal instructions for the carb's anywhere, I beleive the 94 SL750's are Mikuni carbs? I want to make sure I can remove the carbs without loosing something, it would be a lot easier to work on, there are the bolt's at an angle going into the case and then two other bolts from the bottom (per carb), which ones do I remove in order to pull the carbs and not loose anything too important.

    So, here is where I am at now -
    1) Res and regular line going to switch, separator and then intake of pump (the intake on the side, not the top one)
    2) Each line out of the pump goes to each carb and the other side of the carb intake line is capped
    3) Going from the return line (on the carb's it's the top rail), I replaced each of the connectors and the line going back to the tank
    4) I replaced the pulse line going from the crank case to the pulse line on the pump
    5) I tightened everything down

    I did not replace the vent line going from the tank up into the handle bar area.
    Last edited by jwubbena; 07-30-2008 at 01:41 PM.

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by jwubbena View Post
    Yet again, more questions... I continue to read everything I can about those having similiar problems but none quite match mine.

    Alright, i tore it all back down (fuel lines and such) and replaced them with the clear type. I need to find that restrictor, not sure if I replaced that one or not. Once replaced, I tried to turn it over to see what happens and then nothing. I walked away, went out on the other working ski, and came back and for giggles tried to turn it over again. This time I noticed the fuel start to pulse through the lines. They have air in them still, not sure if that is a problem. (It appears at IDLE to be a couple times a second?)

    My battery died after all that so I will have to charge it.

    My questions -
    1) Going from carb to the tank (if I remember correctly), it connects to the nippled one with the thing hanging in the tank or the one with nothing? (I re-read your answer and I beleive this is correct)
    2) Before I take the carbs out, can i blow the "carb filters" out somehow, I read this on another post that he blew air through the return?
    3) The tank releif valve will blow at 1.5 psi and this would be in the handle?

    3.5) There was a clear tube coming from the bottom of the first carb going to the original auto-cock, what does it do and I read to cap it and let it hang.

    4) Proof that I shouldn't be working on my own engines I can't find removal instructions for the carb's anywhere, I beleive the 94 SL750's are Mikuni carbs? I want to make sure I can remove the carbs without loosing something, it would be a lot easier to work on, there are the bolt's at an angle going into the case and then two other bolts from the bottom (per carb), which ones do I remove in order to pull the carbs and not loose anything too important.

    So, here is where I am at now -
    1) Res and regular line going to switch, separator and then intake of pump (the intake on the side, not the top one)
    2) Each line out of the pump goes to each carb and the other side of the carb intake line is capped
    3) Going from the return line (on the carb's it's the top rail), I replaced each of the connectors and the line going back to the tank
    4) I replaced the pulse line going from the crank case to the pulse line on the pump
    5) I tightened everything down

    I did not replace the vent line going from the tank up into the handle bar area.
    Q1: return goes to the plain old hole. Check valve hanging down is for the vent to the handle bars area.

    Q2: Filters need to be removed to be cleaned. Blowing air through the return will do nothing.

    Q3: yes

    Q3.5: Most likely a vacuum hose. Cap it off air tight.

    Q4: Remove the 2 nuts per carb (6 total) to remove the carbs.

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