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Engine miss / stalling issue Hyo GT650R

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by zeddicus, Oct 19, 2008.

  1. So a little background first.

    I have an '08 Hyosung GT650R with currently around 7k on the odo. Several weeks ago I noticed that it would occasionally miss very badly while riding along at 60 or 70km/h, from memory between 5 and 7krpm. The first time this happened my first thought was out of fuel, though I couldn't see how as the fuel gauge said I had plenty left and I'd only done 170km on the odo since last fill (normally get at least 250km). So I stopped on the side of the road for 30 or 40 min until my mate turned up with $5 worth of fuel. No missing after that for the last 5 or 8 km in to work.

    The next time or two it happened I rode through it rather than stopping. After a few min of missing very badly it seemed to go away however in both cases I was most of my way through a (say) 50 min ride when it started to happen, so maybe it was still an issue but I simply reached my destination.

    At this point I booked it in for a service (6k service). Basically they did the service but couldn't find anything which could cause the missing.

    The next time it happened there was a twist: it started stalling taking off from the lights. It did this three times in one trip on the way into the city. Also when you blipped throttle going into 2nd/1st it would make a sort of burp sound (not a pop) and the engine would miss.

    At this point I booked it in again and left it over the weekend. Come Tuesday it would not crank at all (think the same sort of thing you get when you leave the kill switch on). I tee'd up the dealer doing the work to pick it up for me at no cost and they came out on the Wednesday and picked it up.

    After being in the shop for a week (mostly because they didn't work on it for three or so days when they should have) the verdict was 'dirty/bad fuel'. Apparently there was carbon on the sparkplugs and they took a bunch of bad fuel out of the carbies, as well as carbon (iirc) in one of the jets. No crank issue was a faulty sidestand switch. End result, I had to pay for this work.

    Two days later the missing issue happens again on the way in to work. I've booked it in for tomorrow and AFAIK am at least getting a decent loaner bike while they try to fix it again. I'm also thinking about getting my $ back given that I paid for them to fix an issue and they have not done so.

    In summary:

    1. Always happens a decent way into the tank of fuel (least km's was 130 on the odo).
    2. Went from missing to stalling.
    3. Carbies have been stripped and cleaned, fuel was 'guaranteed good' at least the last time it occured, new spark plugs.

    Thoughts on possible causes?
  2. Seen a few dodgy CDI's on those here and there.
  3. A cdi being effected by heat seems about right. The fact they clean the carbies makes the float needle an unlikely culprit.

    The fact they had it apart combined with the dirty plugs makes fuel and vacuum lines unlikely. Still you could have a crack in a vacuum hose they didn't notice.

    the dirty plug also makes tank vent unlikely, but check that it is clear anyway.

    Could also be leads or plug caps.

    They are in bed with the islamacs and making WMD to take us all out

    Paylin 08 4 eva
  5. Update:

    Took it in this morning and spent 35 min trying to get them to do something. They suggested 'isolate the sidestand switch, you take it away and see if it happens again'. At this point I mentioned they replaced the sidestand switch last week. 'Oh well we'll try it anyway'.

    Ahh... no, no we won't.

    I explained this always happens a good way into a trip (say the 40 min mark) and that (for example) on the way to dealer this morning (a 5 min ride) it was fine, despite playing for the last part of my trip home on Friday. They flat refused to allocate someone to ride it for the length of time I've told them it requires before the problem manifests. Given they've also refused to do much until they can replicate the problem I don't see this ending well.

    Did I mention they also argued about a refund for the last lot of work? Apparently paying to have a problem fixed and the problem NOT being fixed, doesn't seem to qualify as refundable. They ended up saying 'Let me think about it and we'll talk tomorrow'. At which point no doubt I'll have the same argument from them.


    And as to supporting North Koreans... heh, well you know I _could_ have borrowed a certain person's CBR1kRR while he was away but then he went and put it into the side of Bambi at 60Km/h while riding the Nasho :p
  6. I had a similar problem on my 06 GT650R. turned out to be a rusty terminal on the rear coil and the coil itself. hope this helps!
  7. Update:

    Went for a ride up the Old Pacific Highway today with a friend. Bike started missing (power surge/drop/surge/drop) while still on Pennant Hills road, less than 20 min into the ride. Stopped, filled the tank with fuel and took off. Issue reappears after less than 10 minutes.

    At two or three points I stopped, switched bike off, popped the fuel cap open, closed and started to ride again. On one of these occasions I had the issue with near stall on take-off (and yes I was in first :grin: ). On all three occasions I was seeing the miss issue within 2 minutes of popping the cap and re-starting my ride. On no occasion did I hear a hiss.

    Does it in several gears, across a decent rev range (4 - 7krpm today... my bike is restricted still so it's fairly useless going above 7k hence I normally dont) and at varied speeds.

    It's been a hot day (26 or so) but the temp bars were at between 3 and just over half (or or two bars over) when it was occuring so there's no specific temp it is occuring at.

    Riding back it was missing the entire way on and off from north of Asquith through to North Parramatta.

    One thing of note: the bike smells like it runs rich yet the dealer specifically told me they tuned the mixture via mixture screw when they did the carbies.

    I'm going to put the stock exhaust back on tonight and see how we go this week. Hopefully the issue continues and I can then categorically state it is not the exhaust (despite said new exhaust being fitted for at least a month or two before the issue started).

    - Fuel level makes no difference.
    - Rev range and gear no difference.
    - Speed no difference.
    - No audible hiss from popping fuel cap.
    - Temp (at least via gauge) is variable.
    - Bike smells like it runs rich (my mate riding behind me complained!)

    If putting the original exhaust back on doesn't fix it I will be cancelling a trip I have planned for next weekend (long weekend for me) and spending the Monday riding around to make the problem appear. Once it does I'll be taking it to the dealer and asking they put a mechanic on it right at that moment to ride it for 30 min. Hopefully this should guarentee they finally experience the problem and do something which fixes the damn thing.
  8. Any news on how this went in the end?
  9. I've put the old exhaust back on but have not had a chance to properly test it yet unfortunately :/ At this stage it looks like it will have to wait until I return from holidays in December, at which point I'll be de-restricting it prior to doing any further testing.


    The stock exhaust has been on for about a week and I have been riding to/from work. The first day with stock installed I saw the issue however it has not appeared since then. Interestingly though, there has been no similar weather to compare it with. Also I've not had a chance to really push it along for a few hours to force the issue.

    I went through some of the work logs the dealer did as part of troubleshooting. It appears they replaced the spark plugs at the 6k service and then replaced them again less than 2 weeks later while troubleshooting this issue for the second or third time. Assuming they are simply lazy (not checking work history of the bike) rather than silly (replacing spark plugs which are brand new, making it the THIRD set I've had the problem with) I can only assume this was because the colour of the plugs indicated it was running too rich? Given that they apparently adjusted the mixture screw (internal to the carbie AFAIK, as opposed to the idle knob on the outside of the bike) to adjust mixture, I'm thinking perhaps it's got something to do wtih the new exhaust.

    If it is a fuel issue caused by a different exhaust (Screaming Demon shorty) I'm assuming it will require a re-jet to fix. I assume it would be a waste of time to do this with it still restricted so as I mention above, I'll de-restrict in December and re-start the testing process. In the mean time I need to learn more about how the fuel system works, how back-pressure from exhaust and air-flow from airbox interact with the fuel supplied by the jets, how variations affect the system etc etc and how to read the plugs to tell where you are :p
  10. It is possible to ruin a set of plugs in less than two weeks if they are fouled, you can clean them, but for ~$3ea, I wouldn't get too worried about it.

    Have you raised the coil problems as sugested by Rooz with the dealer?

    It could be many many things, but I suspect the exhaust has nothing to do with it. (Although you should get it re jetted to suit the new exhaust)

    Sounds like the dealer is not taking you very seriously, maybe there is someone higher up in the business you can have a calm word with, point out your problems & your proposed solution.

    Good Luck!
  11. I'm not all that familiar with the 650 Flungdung, but I recall reading over on www.korider.com/forums that there have been similar issues with other GT650R's. Something to do with vapour lock and the fuel cap?

    Have a root around on that forum (if you can get past all the 10 year old childrens posts :roll:) and I'm pretty sure you'll find your answer. Let me know how you go.

  12. Update:

    Am certain it's not a tank suck issue as the problem continues after an open/close of the tank lid.

    I have had the bike de-restricted and so far have not had any issue with it. I'm waiting for a hot day to take it for a run as it seemed most prevalent in hot conditions. It would be nice if the problem simply 'went away' now that it's de-restricted... then I could concentrate on leaning out the mixture a bit. Right now I'm lucky to get 220km/tank :/

    Will leave this thread for now and post only if I have further relevant info (i.e. it starts happening again).
  13. are you sure its not the sidestand switch? common fault in the hyo. lots of switches are effected by heat when they are on the way out.