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Identifying startup and idle stall issue

Discussion in 'Technical and Troubleshooting Torque' started by Zir0138, Aug 21, 2016.

  1. Hey Guys,

    So I have a 2010 hyosung gt650r, yes I know....I know! Haha so lets skip the usual please.

    Thus far I have fixed and upgraded everything myself, including a new Mosfet regulator, new stator, I have serviced it regularly but being a hyosung theres always something,

    My something this time is startup and idling, I recently rode from Coffs harbour to syd with no problems, bike started up first go, idled perfectly (for what it is) and everything was working, the next day it got alittle hard to start, took a few turns and finally caught, then while riding holding 4k revs she randomly surgs, revs seemed to stay the same but she jults as if I accelerate and let off over and over, and then acouple of times that day when stopped at the lights she stalls on me, then start up fine.

    Eventually it got worse and worse the next day, to the point where starting her causes backfire and popping, takes anywhere upto 30sec of turning over to get started, but when I apply acceleration she pops and backfires

    If the heavens forbid I get it started I need to maintain 3k plus revs or she will likely stall (not always, sometimes its like nothing is wrong and she idles nicely, then BAM! Random Stall) while she is running above 5k she runes fine, nothing to worry about, but when I need to slowdown or stop is when the problem appears.

    I pulled the rear Spark plug and it was foul, wet and black, replaced it, that helped alittle, new sparkplug indicaces its running lean, has white tips and is dry now.

    I have checked...
    Coils (4.4 ohm)
    Vacuume leaks
    Fuel for water
    Battery level

    The only thing I can think of is the injectors are slightly clogged.
    Mechanics have told me over the phone that it sounds like valves are burnt and need to be rebuild aswell as clearances, does that sound right?

    Otherwise I really hope someone out there knows whats wrong.

    Thanks in advance.

    The idiot who bought a hyosung :p
  2. Injectors clogged try some of the aftermarket fuel cleaning detergents if you can get it to run long enough. Did you get fuel just prior to these problems starting, was it from a station you don't usually use? Dirty fuel is perhaps a candidate or water in the furel although you say you have checked this?

    Burnt valves, possible I suppose, it would need to have been running very lean. Check the colour of the exhaust outlet ot give you an idea if it has been running lean for long periods?
    Has the F1 fault light come on?
  3. Yeah I checked and there was no water or impurities in the fuel, I have also filled up with 91, drained mostof it and filled with 98 now.

    Dosnt seem to be any colour to the exhaust, if anything it feels sort of wet, like my fingers will get slightly damp, but that I assume is normal, its not over the top.

    Iv read that injector cleaners are only good to prevent clogging not fix it once its happen, so would that still help,otherwise how difficult would it be to clean/check them?

    And nah no Fi light :(
  4. Does it have starting/cold mixture enrichment? Maybe that isn't working effectively.
    Do you have a workshop manual for it?
  5. Not that I know of, what is it, like additives in the fuel or something?

    Nah no manual for it, someone at hyosung thought up the bright idea of not making a manual for this one :(

    I think ill try removing the injectors tomorrow, and try clean them
  6. The fuel injection equivalent of a choke is what I mean.
    Perhaps an ancillary injector that only fires during cranking or under a certain temp, or a system to squirt more fuel through the standard injectors during cranking or under certain temps.
    Since the issue appears to be starting and idling I'm thinking that something has stopped working during/after your ride to Sydney.
  7. Pull injector out while it's still connected and turn ignition on and see what sort of flow are coming out of them
  8. Oh ok, I dont think it has anything like that, the ecu will push more fuel in at start up and slowly setle to idle, that still happens if I get it going.

    Oh yeahh good idea, ill try that tomorow :D
  9. THIS PDF covers a range of the 650 engine both carb and fuel injected. May help.
    • Winner Winner x 2
  10. That PDF workshop manual Chris has linked too is just what you need.
    Page 17 starts the diagnosing fuel injection system section.
    List of sensors and so on so you can test each and rule them out as the cause of your problem and so on.
  11. Ohh awesome! I was only awear of the older 650 carb engines, didnt know it covered EFI.

    Ill have a read through and start on the injectors in the morn.
    Thanks guys :D

    Also today I noticed one of the relays under the back seat started clicking erratically when it stalled today, is that a normal thing? Because it was an unexpected shutdown or is it something I should be looking into?
  12. I would try and identify the relay and what part of the circuit it is in. It could be a symptom of your problem. If it is the fuel pump relay for example fuel starvation may be an issue.
    • Agree Agree x 1
  13. Sounds like it's erratically running quite lean. Have you checked fuel filter, fuel regulator, fuel pump, fuel hose and corresponding wiring/fuses/relays? Done a fuel flow rate test? I think it's typically 50mL+ for 3 seconds. Cheap bikes tend to have cheap waterproofing and the interconnects are the first to go.

    Only way to really clean the injectors is a proper ultrasonic bath and then a flow/spray test. I'd be looking at just about all other options before the injectors really, they're not as prone to abuse or environmental factors like the rest of the system.

    Damaged valves or out of spec clearances are a possibility, but exclude the easier stuff first. Could probably buy yourself a cheap ebay USB endoscope with a 45deg mirror if you suspect valves afterward.
    • Agree Agree x 1
  14. Ok ill look into the fuel tomorrow instead of injectors.

    Yeah Spark plugs seem to be showing its running lean, this bike dosnt have a fuel filter, thus I thought injectors might be clogged, but fuel starvation would sound right but it runs perfect after 5k, revs up high no problem, thus im stumped!
    Its only low end :(
  15. Sounds electrical if thats the case. TPS, air flow/pressure, air temp and coolant temp sensors. If no reading is present the ecu tends to pick a failsafe value to limp you home. Corrosion can increase resistance and give an inaccurate value to the ecu or one of them could have given up altogether. The self diagnosis is usually pretty good at telling you if a sensor outright died or got disconnected but don't rely on it. Looks like you need a special tool to diagnose though.

    WOT usually has its own paeameters ignoring some sensors. If it's restricted though who knows what happens in the depths of the ecu.
  16. It will have a fuel filter, perhaps a bag type over the pump inlet in the tank or similar. But clogged filter is more likely to create issues at high load and revs than at idle.
    Just work through the troubleshooting steps in the manual and eliminate things one at a time.
  17. Well I did change the tps about 2 weeks before, but I changed it back to original setting and no difference.

    Well with the sensors that sounds more reasonable, iv called around for a compression test, but after quotes i figured its better to buy the kit and do it myself, should get it in a few days,

    I have been through fuel and it seems to be pumping fine, high end still works withough hiccups or anything, so im leaning towards a sensor.