Suzuki S40 starting problem - Page 2
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  1. #16
    Super Moderator

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    Quote Originally Posted by Phil41 View Post
    and my daily ride is a 2008 Suzuki C90T which is unmolested except for Mustang seat and 4 inch handle bar risers. Will post results soon. Thanks again!
    Good for you.

    This is an ENTIRELY different situation than those who tear apart their only ride and then cry when it doesn't run right anymore.
    Don't believe everything that you think.

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  3. #17
    Newbie
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    2008 Suzuki Boulevard C90T
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    North Carolina
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    Ok, got the proper mixture screw. Of this I'm certain. The original had like a two step tip. Anyway, it still just tries to fire upon starting with black smoke from the exhaust. I only have the mixture screw turned out 1 1/2 turns. Factory spec is 3. All stock jets are back in the carb. Not getting enough air flow through filter? And opening the throttle still kills it.

  4. #18
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    Quote Originally Posted by Phil41 View Post
    with black smoke from the exhaust.
    Mixture WAY too rich.
    Try it with the air filter OFF and see what happens.
    Could be float too high, allowing too much fuel into the bowl.
    Could be a gasket leak or a crack in carb body allowing raw fuel into the throat.

    I think I even remember hearing about a failed diaphragm in an "automatic" petcock allowing gas directly into the manifold.
    Don't believe everything that you think.

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  6. #19
    Newbie
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    2008 Suzuki Boulevard C90T
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    Quote Originally Posted by Easy Rider View Post
    Mixture WAY too rich.
    Try it with the air filter OFF and see what happens.
    Could be float too high, allowing too much fuel into the bowl.
    Could be a gasket leak or a crack in carb body allowing raw fuel into the throat.

    I think I even remember hearing about a failed diaphragm in an "automatic" petcock allowing gas directly into the manifold.
    thanks. that's what I'm thinking. weather here has not allowed me to tinker much except in the garage, so taking it out to start has been limited. i'll check the air filter first of course and let you know what I find. I do know float height is correct.

  7. #20
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    Quote Originally Posted by Phil41 View Post
    I do know float height is correct.
    Famous last words !!

    The needle valve might not be closing good.
    And the old brass drum floats would sometimes leak and "sink" instead of float.

    Just rambling.
    Don't believe everything that you think.

  8. #21
    Seat Tester
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    2002 VS800
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    In agreement with the points that Easy Rider is making. Am running way behind here but will offer some possibles before getting on with the day.

    Checking the air filter is a good place to start as mentioned. A blocked air filter can obviously reduce the amount of needed air for the proper air/fuel mixture. And on these bikes with the EPA gear, it's not uncommon for folks to find that the air filter is saturated with oil. You're correct that black exhaust smoke indicates too fuel rich. Oil smoke is usually grey, but if the oil were excessive, the exhaust smoke would be a blue/black color.

    What do the spark plugs look like ? Black, wet & a smell of gas ?

    Also as mentioned, if a gravity feed petcock is left open, fuel can continue to enter the carb while the bike is off and eventually find it's way thru the intake and into the combustion chambers. A "vacuum actuated" petcock is only supposed to allow fuel flow either when hitting the starter button or while the bike is running. These types of petocks can sometimes fail and essentially act the same as an open gravity feed type. I forgot to shut off a petcock one time (after that experience, one tries to insure that it doesnt happen a second time). Wasn't getting black smoke, but it did fuel wash the cylinder bores and the excess fuel got into the crankcase, which diluted the oil. Potentially disastrous situation unless caught in time. You could probably remove the oil filler cap and see if you get a whiff of gas or not.

    I realize that we touched on possible choke probs earlier in the thread and we both agreed that the choke seemed to be working properly. We might want to revisit that as a possible at least.

    As Easy Rider points out, the needle valve might not be cutting offf the flow of fuel into the float bowl. Also not uncommon if the needle valve seat o-ring has deteriorated.

    This is a real long shot.........the old Triumphs have a main jet holder that's removable. Had one vibrate loose completely, which essentially negated the main jet. Point being, it's rare, but at least possible for jets themselves to come loose. If by chance the pilot jet were loose, one can imagine how much more fuel could be getting dumped into the mix.
    Riding Ain't A Hobby, It's A Lifestyle

  9. #22
    Newbie
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    2008 Suzuki Boulevard C90T
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    North Carolina
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    Ok, pulled the carb again, dismantled, cleaned again. Checked the plug. Had some carbon but nothing close to fouled. Cleaned it. Now I can get it to idle fine, but choke needs to be pulled out to first click to run. Starts fine with choke all the way out. Dies if pushed all the way back in. First notch while pulling back out, it will keep running. No more black smoke. I suspect that the fuel level in the carb bowl is too low. Raising fuel height is my next course. Am I assuming correctly?

  10. #23
    Newbie
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    2008 Suzuki Boulevard C90T
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    North Carolina
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    Oh yeah, still dies if throttle is rolled opened

  11. #24
    Ditch Magnet
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    don't want to beat you up over this, but when you clean the carbs do you blow carb cleaner thru all the passages and can you see light when you hold the jets up and look thru

  12. #25
    Newbie
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    No prob. Yes to all. I don't skimp on the carb cleaner.

  13. #26
    Ditch Magnet
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    https://www.partzilla.com/catalog/su...650/carburetor i looked on partzillafor a 2007 s40. the parts diagram says for part #18 pilot jet it's 52.5 and the main is 45. in your previous posts has 55 pilot and 150 main.your having problems in the low rpm range but if it runs better with the choke one quarter out and i'm suggesting your pilots to rich doesn't make sense. the other thing is i'm not an expert on carbs so here it is, wouldn't a low float bowl affect wide open throttle where the demand on fuel is greater than low rpm's

  14. #27
    Seat Tester
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    This is interesting. Before pulling/cleaning the carb this last time, it seemed like the symptoms indicated a too rich condition. Now it appears to be a bit on the lean side. If you removed then re-installed the choke plunger during the carb cleaning, guess it's possible that the choke plunger might have been off somehow and it got corrected during re-installation ?

    You're right, Nick, about the float level having more fuel demand at higher rpm's altho' at idle there would be at least some demand for a proper idle. With the bike running, the vacuum pulls fuel into the venturi, creating a mist for the air/fuel ratio. Lower rpm's, less vacuum, demanding less fuel. Higher rpm's, higher vacuum, demanding more fuel. Would think that if the float level is at factory spec, that part would be good to go.

    Your stock jetting of 52.5 pilot, 145 main should be fine. Having to open the choke 1/4 way out would indicate a need for more fuel. Also, when you open the throttle, it lifts the slide/piston inside the carb body which allows more air into the venturi. More air when it's possibly too lean to begin with may be causing the prob when opening the throttle.

    Earlier, you mentioned that the air/fuel mixture screw was 1 1/2 turns out, with factory spec calling for 3 turns out. You might try turning it out to factory spec to see if that provides the needed fuel that the choke is currently compensating for. It might also allow the proper amount of fuel to balance out the mix when opening the throttle and having the slide allow more air in. You're CLOSE and might nail this down soon. Keep up the good work!
    Riding Ain't A Hobby, It's A Lifestyle

  15. #28
    Newbie
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    I've gotten pretty good at pulling the carb. Lol. I just pulled it off again, took it down to everything that can come off, clean it out, every passage and orifice. One of the jets up top, under the diaphragm may have been clogged. Looks like a new carb now. Checked float height at a hair over 1 inch. In spec. With clear tubing, checked fuel height. Just under top of bowl. Within 1/2 cm. Fuel flows freely through petcock. Everything is totally back to stock. That's where I quit. Will see what happens tomorrow. This has been a real head scratcher. Thanks for all the input..

  16. #29
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    Quote Originally Posted by Phil41 View Post
    Will see what happens tomorrow. This has been a real head scratcher. Thanks for all the input..
    Sounds like you have now gone from WAY rich to a bit lean......which is normal for late model bikes.

    First, be sure you have the air filter ON, that there are no manifold vacuum leaks, and let it warm up good before you convince yourself that there still is a problem.

    It is normal to need one click on the choke for it to idle cold......and maybe another click if you want to actually ride it before it warms up good.
    Don't believe everything that you think.

  17. #30
    Newbie
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    2008 Suzuki Boulevard C90T
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    Yesterday when I could get a good idle, I let it run for probably 5 minutes. Good and warmed up. Still wouldn't run if the choke pushed all the way in. Anyway, gonna try again today


 
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