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losing a cylinder, what happened?

Discussion in 'Bling and Appearance' started by kyan, Feb 22, 2008.

  1. I have a Suzuki Sv650 and today I pulled out of my drive and for the first few seconds I seemed to be running on one cylinder only and then the other one kicked in and it has been fine since.

    What could have caused this?


  2. Dodgy sparkplugs or coils.
  3. Was it wet?

    In my research before buying an SV i found that a common problem is water getting into the 1st cylinder's spark plug and stopping it from firing. Or something to that effect. The second generation have a little guard to reduce this apparently.
  4. nope not wet today. it is a first gen model though
  5. I should read more carefully next time. I thought it was pulling in after a ride.


    Trevor G
  6. do you have carbs or FI?
    on my old kawa when the carbs were stuffed, overnight one of the cylinders would flood so when I started it it would fire on one then after a while the other would kick in.
  7. It will have carburettors if it's a 1st generation.
  8. yep it has carbs.
    well i have been for a few more rides since then and all seems good. i'll pretend it didnt happen for now.
  9. mine was due to crap in the carbs. maybe put a carb cleaner (nulon) through it as a precaution
  10. Didn't leave the choke on a bit too long did we?
  11. havent had a need for the choke....
  12. and we have a winner.

    It's running way too rich on the idle jet and/or screw. Your fouling your plug at idle and it is clearing up with a bit of throttle.

    Has the bike any mods? How clean is your air filter? Original pipes?
  13. i dont really have much of a mechanical knowledge unfortunately. it idle's at just over 1000rpm. there are no mods. air filter looked pretty clean about a month ago. original pipes I believe.

    what should it be idling at?
  14. Not so much the speed (1,000 rpm sounds right) but the mixture setting. There will be a flat slot screw in each carb, flush with the body of the carb. That should be the idle mixture adjusting screw.

    I don't think it will be too rich, otherwise you would have trouble when the bike is hot, not when you are first pulling out of the drive when the engine is running at its leanest.

    If you want to play, here's how to go about it.

    1) Find out the current setting by gently screwing in until the screw seats slightly. Don't force it, you will damage the tip and it will not adjust the mixture the way it should after that. Count the number of turns eg 1.75. Both carbs will not necessarily be the same.

    2) Unscrew the same number of turns and go for a ride. When the engine is good and hot - say after 5 to 10 km - adjust each screw until each cylinder idles the smoothest.

    3) Do this several times (go back and check) and if the idle speeds up by more than 100 rpm, leave it. Do not try to adjust the idle speed unless you have vacuum gauges to complete the adjustment.

    4) Do not leave the bike idling for more than a couple of minutes while setting the mixture - it heats up in this time and you can achieve a setting which is not representative of the way the bike is used. If necessary go for a short ride (500m) and try again.

    5) If the idle mixture screw is on the engine side of the carb, screwing out makes it richer.

    If the idle mixture screw is on the air intake side of the carb, screwing out makes it leaner.

    6) If you really want to adjust the idle speed because things are going wacky, note which carb you adjusted for mixture when the speed increases. Adjust that speed screw just a little.

    If it idles slower after your mixture adjustments you have set the mixture wrongly!

    When you adjust the screw - slowly does it - turn it richer until it runs less smoothly or slower, then turn it back until it speeds up and runs smoothly again, and then continue to turn until it runs leaner and less smoothly again. In this way you go through the adjustment in both directions.

    Set it for smoothest running in the middle of the two extremes.


    Trevor G

    PS I really think you don't need to touch it. This is not going to affect your once-only misfire. If you don't want to fiddle, don't follow these instructions!

    PPS Adjusting the idle mixture does not really affect the running (lean or rich) elsewhere in the throttle range when riding on the road. Maybe up to about 1/8th throttle, but not after that.
  15. I'm thinking it's always been too rich, but not excessively so. Just enough so he doesn't need choke. So he has slowly fouled a plug, but not rich enough to notice a rough idle or poor off throttle response, once warmed, probably because it's always been that way.

    But it may be just a cactus plug.
  16. And that is quite possible, too! :)


    Trevor G
  17. i'll give it a bit of a turn and see how it runs a bit leaner.. cheers
    thanks for the tips