Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

XVS650 hunting @ idle

Discussion in 'Technical and Troubleshooting Torque' started by Darrin Hodges, Jul 19, 2015.

  1. #1 Darrin Hodges, Jul 19, 2015
    Last edited: Jul 19, 2015
    I rejetted the carbs and adjusted the air/fuel mix (it has v&h pipes + spike airfilter now). It runs well and there is no popping (was some before) BUT it won't settle on a steady idle speed, I've sync'd the carbs but the issue remains. It seems to vary between about 800 - 1100 RPM and actually stalled once at the lights. I've read it can be caused by the idle circuit being too rich or there is an air leak somewhere - any hints on what it may be?

    Edit: Forgot to mention that the needles were shimmed up as well.

  2. Hi Darrin, don't know about your bike specifically but usually hunting is simply a mixture problem down low, most often being too lean, am guessing since you have changed the airflow system with pipe & cleaner it just needs richening up in the off idle area, usually with carbies the jets don't affect off idle mixture much, it is often remedied by lifting the needles a small amount so you richen up that area of the circuit a bit, the needles have a taper on the bottom section so lifting them opens up the volume for more fuel to be sucked through, also lifting the needle helps richen up the low to midrange area as well, the needles are often held in with circlips around a groove & there are usually a few extra grooves up & down needle to adjust this. I am only guessing but hope this helps.
  3. Thanks coljon, I did shim the needles up as well, forgot to mention in the OP. It was a bit rich initially (was popping like mad & plugs were sooty) but the idle was good. So I re-adjusted the mixture screws and the popping has gone away but idle is off, maybe tweak them out a touch more?
  4. Get it running, and while running spray some water over the carb bases, hoses etc and if there is a vacuum leak, the engine will start to splutter.
    It's even better if you spray some white spirit, because the engine rpm will increase, and that may be easier to notice if it's having trouble idling.
  5. Yes, try out a bit more, sometimes in can be the opposite way needed but I think unlikely. Lots of luck.
  6. Have you checked your water pump? last time I had a vehicle hunting at idle that was the problem.
  7. How on earth would the water pump affect idle? The only way is if water is leaking into the combustion chamber, and that would be via a head gasket or cracked head problem.

    I don't think that the water pump will be the issue on an XVS650 ;) because they don't have one lol
    • Like Like x 2
  8. It's the rare water pump driven air cooling system (y)
    • Like Like x 3
    • Funny Funny x 1
  9. With overhead underhang!
    • Like Like x 2
  10. I dunno, I never bothered to look up the bike specs but if it's air cooled then you may also have some weak spark somewhere.

    Don't ask me how - when the water pump failed on this car it was hunting idle pretty bad, I even have a video of it. I tried absolutely everything else until that point.
  11. Anybody know if there is a trick to adjusting the idle mix with the engine running, the adjusters are kinda hidden behind the intake manifold, which needs to be removed as well as the tank
  12. I have never worked on your model before, but I am assuming the mixture screws were plugged, and you have removed these blanking plugs.
    Starting adjustment somewhere around 2,1/2 to 3 turns out should do.
    This will vary depending on many parameters.

    A remote fuel tank is the way to run the motor without your main tank on. To adjust idle air mixture while running, you need the full intake and filter assy on. Is it possible to temporarily install the snorkel upside down? Wrap tape around to seal for leaks. Otherewise it's remove, adjust, replace, test,repeat.
    • Like Like x 1
  13. Thanks, didn't think about trying the snorkle upside down, will see if it can, otherwise yeah, its remove adjust replace.
  14. Ok, so set the mix screws out 2 3/4 turns, but the idle didn't seem to improve, in fact seemed a bit worse. It does seem to idle well when cold, but deteriorates as the the engine get warm. Will work on it more this weekend but if I can't get the idle right, might book it in for a tune.
  15. Hi again Darrin, maybe your setup requires different tapered needles as just lifting your standard ones may over richen the bottom end circuit too much, on my old Fireblades i had this problem so purchased a jet & needle kit which was tailored for my carbies specifically, anyway, may not be your problem but was a thought.
  16. #16 Darrin Hodges, Jul 24, 2015
    Last edited: Jul 24, 2015
    HI Coljon, was wondering about that last night. With the shimmed needles I guess additional fuel is being drawn at idle through the needle jets?

    I suppose I can drop one shim or turn the mix screw out just 2 turns (or so)?

    Edit: Apparently the factory setting 1 1/2 turns.
  17. Yes, image just lifting the standard needles combined with the larger jets could make the bottom end including idle/off idle overly rich, are you able to purchase after-market needles/jet kit to match your carbies? Would think they would be a better solution so the fuel/air ratio would be more consistant in the lower range. Maybe the jet/needle kit comes with other jetting/air bleeds to facilitate correct low range fuel air ratio also, been so long since I have played with carbies but remember how important & tricky it is to get bottom end/off idle circuit sorted so you don't lose unnecessary torque off idle.
  18. Thanks to valfar's suggestion, I assembled the air intake upside down, with the tank on a table next to the bike, I was able to easily access the mix screws:


    I set the screws to 2 turns out, I tried 3 but the idle deteriorated. Seems to idle better now, though sometimes it dips a bit. I also removed one shim from the main needles, as the 2 shims put the needle on what would be past the fourth notch, now it sits a tad under 4. The rev limiter kicked in at the right time so it seems about right.
  19. OK, went for a longer ride today, seemed to have lost a bit of poke at the top end, so will put the shims back. Looking at the plugs, seems to be a bit on the lean side, going to check the fuel level to see if the floats need adjustment. The manual specifies 2 1/2 turns out, so I'll start again from there, so much easier now I found the intake can be installed upsidedown, I can get to the mix screws with the engine running.
  20. When I had the 650 tuned to suit the new exhausts etc they had to increase the size of the idle jet to get the mixture correct.
    The mains only needed a little tweak.