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  1. #1

    750 SS no start - no fuel?

    Hi all,

    I have a 97 Kawi 750 SS, single Keihin CDK II carburetor.

    I rebuilt the carburetor chasing a hard to start issue and it got me nowhere. Turned out it was most likely a worn out stator, however, after rebuilding the carburetor my "hard to start" became a "no start".

    I'm trying to diagnose this one. Spark plugs are brown and white now, indicating a lean condition. With the return line disconnected, I get small splatters of fuel, probably once a crank revolution.

    I have a pressure gauge between the fuel filter and pump supply port, and it's showing zero psi.

    At this point, I'm pretty much clueless about where to go forward. It feels to me like the fuel pump is bad, it's been rebuilt (which may be the crux of the problem).

    So, what I'd like to know is the following:

    1) How do I continue to diagnose from here?
    2) Should I *see* fuel down the throat of the carb while the motor is cranking? I'm used to 4bbl auto carburetors where you get a "pump shot" on throttle application so it's easy to tell.
    3) If it is the fuel pump, can I just cap off the pulse line and run a low pressure electric pump? (if so, how much pressure is this thing supposed to run?)

    Thanks much!

  2. #2
    Pain is fear leaving your body.... rlovebk's Avatar
    Join Date
    Aug 2008
    So. Cal.
    I have an older SS so I am not famaliar with yours but issues on mine were:
    I had to change all my fuel lines. They were gummed up.
    I had to pull the pick-up tubes and clean all of that stuff up. It had chrome on the plastic and the chrome was coming off and gumming up the works. It was plugged up all thru there big time. I emptyied my tank and cleaned it out also.
    If you try just a squirt of carb cleaner right down the venturi does it fire??
    Anyways you probably need to clean/change filter and seperator also.
    Pump on the Keilhin is internal corect?
    Hope this helps.

  3. #3
    My understanding is that they should be pretty similar.

    Yes, the pump is internal. It attaches on the opposite side of the carb body from the metering block.

    It'll start right away on starting fluid, and then die when the fluid has been used up.

    I'm somewhat confident it's a carb issue, as that was the change that took it from hard-to-start to no-start.

    I just wish I knew a good way to diagnose the pump. The service manual doesn't say much at all on hard start issues, other than "bad fuel pump" as a possible cause. No way to diagnose the pump.

  4. #4
    steve45's Avatar
    Join Date
    Feb 2008
    Welcome aboard, Shark Racer!

    A pressure gauge between the pump and filter won't read anything because the pump is sucking the fuel from the filter--it's below atmospheric pressure. DO NOT put an electric pump in this system, it's not designed for it and a leak could yield catastrophic results.

    No, you will not see fuel squirt into the carb when you squeeze the throttle because there is no accelerator pump. However, with the chokes closed, you should (eventually) see fuel spraying into the carb throat (there is a small hole in the choke plate and gas will spray around it).

    The way to make these engines start quickly is to install a primer. I use the hypodermic needle type that squirts fuel into the intake system. Some use the bulb type that go into the fuel line. I used to follow the instructions and remove the chokes, but now I've learned that it seems to work better if you leave the chokes in place.

    Sounds like you've got something together wrong, or the pulse line is split. I recently found this on a 750. Couldn't see it until I took the carbs off. The carb kits come with several springs for the float arm. You might try a softer spring.

  5. #5
    Thanks much, Steve. I think the pulse line was part of the problem. I hooked it up to a vacuum gauge and it was bleeding down quickly, so I replaced it. That got the fuel filter filling up much more quickly.

    Do you happen to know what pop off pressure is right for these? (and a good way to test it?)

    I tested through the pump port and got a number around the low 40s a few months back.


    I just went outside to test again. I took the fuel filter off, drained it, and put it back on. Key on and it filled up pretty quickly!

    So, I think the pulse line is good, and I'm fairly confident in the ability of the pump.

    That would leave pop off and mixture as the final piece of the puzzle, I guess.

    What is curious: I engage the starter for <15 seconds, then wait a minute or two and go at it again. The initial crank, I can hear the motor try to start and then nothing, it's just spinning the starter again.

  6. #6
    steve45's Avatar
    Join Date
    Feb 2008
    I don't know what the pop-off pressure is on these (I should).

    Have you put any gasoline down into the carb throats?

  7. #7
    Quote Originally Posted by steve45 View Post
    I don't know what the pop-off pressure is on these (I should).

    Have you put any gasoline down into the carb throats?
    I put a bit down, and that didn't get it started like the starting fluid. I'll check when I get back from the store - need lemons and limes for tonight's BBQ! (at least I can do something right!)

  8. #8
    I'm starting to think I have an electrical gremlin as well. That fast firing reminded me of a problem I had before I had the stator rebuilt: the wires would only show spark (with a timing light) as soon as the motor began to crank, then nothing.

    Testing my stator, it looks like I'm not getting good Vac when the motors running, <10Vac.

    Think the regulator is probably fried - do you know of a way to test it?

  9. #9
    steve45's Avatar
    Join Date
    Feb 2008
    I think you're grasping at straws. I don't think the regulator would affect spark. Are you referring to the ignitor?

    So, it will start, right? What is your battery voltage with the engine running?
    Last edited by steve45; 08-17-2011 at 08:50 PM.

  10. #10
    Hey Steve,

    No, it won't start, and you're right, I'm grasping.

    It's still maintaining this weird spark state. I'll get an ignition pulse or two when I first crank the motor, and then nothing.

    Stator is new, pickup coil checks out, same behavior on two igniters.

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