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Suzuki GS500 Hunting at 100k's

Discussion in 'Technical and Troubleshooting Torque' started by i_happen, Aug 18, 2009.

  1. I have a reasonably new 09 GS500 and at night while at 100 the bike seems to hunt a bit with the rev's. Its ok when the weather is warmer (above 10-15 Celcius) but below 10 it hunts. Feels like a loss in power then it comes back. When the engine is cold and the choke is off it is fine. It's only after about 10 minutes at 100 the prob starts. Does anyone have any idea's before I take it back again to the shop. I run BP Ultimate in it and have drained the Carbs a few times but no fix as yet.
    Thanks in advance for any advice
    Regards Brian

  2. Hunting is often a sign of a lean mixture. The fact that it happens at low air temps supports this as cold air is denser and that makes the mixture a bit leaner. Next time it happens try putting the choke on while you're cruising at 100 and see if the hunting stops. If everything in the carbs is in good shape and clean, then maybe you'll need to get the carbs tuned. (Different jets or needle). If its under warranty, get the dealer to fix it.
    Does it happen at higher speeds?
  3. Thankyou the mole
    I will try the choke tonight. I haven't tried it above 100 as I'm not a fan of the higher running cost the police seem to add for me (I seem to be the one that get caught). I might just drop it back a gear and see if it changes as well. The bike has only 1600 on the ODO but your hint at lean running does add up so will chat again to the shop. They might be avoiding the idea of re-jetting
  4. I turned the choke on when the engine started to hunt and it made it slightly worse. Another thing that happens is it gets worse as the tank gets lower. From full it's almost not there. Half a tank and it's annoying and when the tank is lower it's a real concern.
    I think it might have something to add to this. After riding nearly 30k's last night with the issue happening I switched fuel tap over to reserve as I lost all power. Fuel was low and the problem disappeared. I filled the tank at the next BP with BP Ultimate (Only Fuel I ever put in it) and rode on. Switching back to ON the problem was gone but then again I wasn't on open roads anymore. I will switch from "On" to "Reserve" the next time it happens. If it does it's definatly between the fuel tap and the tank. It's getting somewere.
  5. The money you save running quality 91 fuel you can spend on fixing this issue.

    Another thing to try is popping open the fuel cap when its hunting as the system may not be breathing as it should.

    Seriously run it on 91 though.
  6. I will try the Fuel cap. You are the only one to say run it on 91. Why do you suggest it over the BP Ultimate. I work with about 30 mechanics and they all say BP Ultimate over any other fuel for engine care. All say (including the bike shop) say stay away from Shell Optimax. They also add only fill on BP or Mobil for normal RON fuels if BP Ultimate isn't available.
  7. I said a "quality" 91. You don’t run a high enough compression ratio to warrant 98. You're 30 mechanics should have mentioned that.
    By all means run an occasional tank for the detergent benefits but there's no performance gains.

    Have a look at the Shell website and stop spreading that urban myth. What may or may not have been half true once doesn’t apply for modern engines.
  8. In addition to what 2wheelsagain says, check what fuel your bike manual says you should be using, and then use that fuel.

    I doubt you would need 98 octane fuel. 95 octane at most, but as 2wheelsagain suggests, I run 91 octane, from any quality supplier. Which includes Shell by the way. I find there is less of a difference between 91 octane fuels than there is between 98 octane fuels.
  9. The GS500 only needs 91 fuel, any more is a waste. Have a look at the GS500 forums at http://gstwins.com/gsboard/ for advice - they will all say the same thing and may be able to help with this issue.
  10. Ok. I know the book and everyone else says 91 fuel (Book says 91 or above or to increase if there is knocking) but getting back to my original issue. Would the BP ultimate be causing the bike to hunt. I haven't been able to crack the fuel filler while riding as it's been raining everytime I have been out on it since I read the post and I'm not going to risk water entering the system but I will post what occurs when I do it.
    Also I have repeated switching the Fuel tap from ON to RESERVE and the issue did continue to my one lead has been removed.
  11. I will throw my 2 cents in... I'm rididing a 650 single carburated bike same roads every day... I get a regular 240km out of a tank using 91 but I get 260km if I use 98, (eather Mobil or BP). If I use the ethenol blend from my local independent my bike runs bad and I get a misrable 170km... I also have a shell station near and I though I'll test it out... 210km on their unleded and Optimax.

    I'll stick with the BP Ultimate.. Optimax is "thicker" and I know from past expiriances there are car and bike fuel pumps that just cant deal with it..

    I'm expiriencing hunting as well and always had on this bike.. I have uped the pilot jet by 1 and main by 2 and the nidle is 1mm higher... I have had the bike tested on the dyno (after the rejeting) and it is running slightly rich. The end result is better but not ideal.. my mechanics sugest some sort of air leak eather into the air box or even the exhaoust.. If the bike is under warranty get the mechs to look at it.. if it is not than you might be up for $$$
  12. My thoughts exactly.

    My cbr929 runs 100% perfectly on 91 (as suggested in the users manual).

    Try 91 and see if the problem fixes itself.
  13. Ok.
    The bike is now fixed. After going through every tip I was given the shop finally found a loose connection to one of the carbies. It was causing an imbalance once I was at speed. The bike is now fixed and running really good.
    Now when it comes to the debate between BP ultimate and standard BP (I'm keeping it to one brand for ease right now) I will stay out of it. I have my reason's for running it and I very happy with my reasons.

    Thankyou to everyones input as all the things I tried helped the bike shop to narrow the problem down.
    Regards Brian