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Suzuki GSF250 stalling

Discussion in 'Technical and Troubleshooting Torque' started by voondar, Jan 11, 2011.

  1. I have a 1997 Suzuki GSF250 that is having some running/starting problems. When I start it up with the choke fully engaged, the bike barely revs at 2000. It also stalls when I brake with just a moderate amount of force. Occasionally when I turn the throttle there is little to no response. My initial guess is a problem with the carburetor but don't know where to start. Any suggestions?

  2. Under each carb there should be a small screw that allows you to drain them. Make sure the engine's off and the fuel tap is set to on (not prime), and drain each one checking firstly that the fuel is clean (ie no sign of brown rust), and that you get a roughly equal volume of fuel from each. This will show if there's any problem with fuel getting to the carbs.

    Next, set the fuel tap for prime and see if any more fuel drains from the carbs, if so it's a sign that the needles are worn and not sealing properly.

    While you're at it I'd suggest replacing the fuel lines and fitting a clear inline fuel filter (usually only a couple of bucks from an auto store). Not only will this prevent crap in the tank damaging the carbs if the tank filter fails, but it also gives you a good visual indication of how much fuel is flowing to the carbs.
  3. stalling under brakes is always a tough one. I've had it electrical and fuel.

    This isn't right. The drains are on the bowl side of the float needle so with the tap on prime all you will get is fuel.

    Switching the tap to 'on' should stop the fuel if it doesn't then you know you have a problem with the tap. This problem, however, is that is unlikely to be the cause. Still good to know.

    Firstly I'd be looking for a float needle not seating. Draining the bowls as JD suggests may fix this. Unfortunately it is more likely the bowl has got to come off and the bottom of the carbies cleaned.

    You can check which cylinder is getting too much fuel by putting your hand NEAR each header pipe. It will show up in riding by bogging down and then clearing as revs rise. If this last thing isn't happening it is unlikely to be a float needle.

    Also the idle on these thing should be about 2000rpm.

    As to the choke, too much choke can prevent an engine from revving, especially at this time of year. Come back to half choke.
  4. Yeah you're right, my mistake. Had other things on my mind when I wrote that and wasn't thinking clearly.

    My suspicion is that the likely cause is rust or something from the tank gunking up the carbs and restricting fuel flow.
    Also possible there might be a leak in the rubber couplings between the carbs and the engine, as these tend to get brittle with age, especially if the bike's been exposed to the elements (ie grey import).

    Oh and 2,000 is too high for these engines, fairly sure the recommended setting is more like 1,800.
  5. Lets look at your starting procedure. How long do you keep the choke on for after starting? Is the problem happening with the choke on or with it off... or both?

    It sounds like you could just be overusing the choke.

    - boingk
  6. Thanks for all the replies. I emptied 2 of the drains from the carb (I could only get to 2 with the tools on hand) and the fuel looked pretty clean with a slightly purple tint to it. There was ~100 mL of fuel in each one. When I turned on the primer fuel flowed out of the carb drain.

    I will have a look at the ignition tonight. At the moment, I can't even get the bike to start up. I doesn't sound like the engine is turning over.
  7. It isn't cranking? If so, be carful as the 'sump' me be full of fuel.
  8. Is there any easy way to check this? I also have the service manual for a GS400 which is mostly the same as far as I can tell that I have been following.
  9. Pull the oil filler cap and have a sniff. try turning the engine with the back wheel. Higher gear helps.
  10. Is you battery fully charged. Number one fault going around... and its easy to fix, too.

    Cheers - boingk
  11. Battery seems to be OK. Have full lights, etc. and ignition motor sounds like it is going with little dimming of lights, just no engine turnover. I'll check it with a meter while its trying to turn over.
  12. ibast - I had a sniff and could not smell any gas but I did have some on me from draining the carbs.

    I tried giving it a running start and it turned over about 3-4 times before dying. I am thinking maybe the spark plugs are bad.Does that seem probable for the symptoms? Do you if I need remove the gas tank to remove them and what size sprocket I need?
  13. The plugs are one of the standard spark plug sizes, I forget which exactly but any of the cheapo sparkplug socket sets at an auto store should do the trick if you don't already have sparkplug sockets (used to be able to get a ratchet handle and assorted sparkplug sockets at Supercheap for around $10).
    It is possible to remove the plugs without removing the tank, but it is easier if you at least loosen the back of the tank so you can lift it up if needed.
  14. One tip for you: once you get the plugs out take one with you when you go to buy more! Theres nothing worse then getting there and seeing an armada of different sizes and, of course, motorcycles aren't in the damn reference guide.

    EDIT: You could probably get away with simply cleaning them. A rag with methylated spirits or petrol on it will work well, just get a single layer of cloth between the electrodes and rub each of them well. 400 to 800 grit sandpaper would also work, just take it lightly if you use it as it doesn't need much

    Cheers - boingk
  15. But don't try and ride on 3 cylinders ;).
    NGK make plugs to fit the GSF250 but they are motorcycle specific, so you'll have more luck at a bike shop than an auto store.

    Edit: Oh and Boingks suggestion of giving them a clean is a good one, though at only something like 5 bucks a plug up to you whether you think it's worth the hassle or not. If you do clean just make sure you check the gap before putting them back in, just in case you accidentally changed it.
  16. Still read like you are getting too much fuel.

    Try holding the starter button and slowly winding open the throttle to get it started