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Help! '96 GSX R750 starting trouble.

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Yaro, Dec 13, 2010.

  1. Hi everyone.

    I just recently purchased a GSX-R750 as my 3rd bike (Kawa kz250 and cbr250r beforehand). Just got it on Friday. I'll just dot point relevant information, and if anyone at all can help me, I'll be super grateful.

    -shipped to me in Tas from Qld, took 3 weeks. Probably hasn't run for over a month.
    -When I go it, wouldn't start. Was very low on oil. The Drain plug was either stripped, or more likely, I stripped the thread trying to open it myself. Anyway topped it up with 10w-40 without draining old oil.
    -Bike STARTED and ran fine. occasional backfiring.
    -Bike has a bit of corrosion, dint in tank, with a bit of rust on it.
    -When I filled it up with petrol at servo (was low) noticed a tiny bit of corrosion in tank.
    -Rode it for 150km or so on Sat. no probs, just occasional backfire.
    -Sunday WOULD NOT start. Wouldn't even turn over.
    -Managed to start it by putting into 6th gear and rocking back and forth a bit, allowing it to turn over when starting.
    -Slight smell of petrol from bike/exhaust?
    -Today, won't start even with the rocking back and forth.
    -It turns over for a bit (after the rocking) then there is a slight bang noise and stops.

    -I have a service booked in tomorrow that I need to ride it to.

    Anyone; help?
  2. Wild guess would be a shagged battery from standing, and crap in the carbs, also from standing and from the corrosion in the tank.
  3. Pretty hard to strip a plug undoing it. Lots do putting them back in ... over tightening them.
    Don't mix any fluids. Specially coolant.
    Sounds like crab in the fuel system and a lot of neglect.
    Might pay to get a revs check on it to make sure its all legal.
  4. where abouts are you?
  5. Alright I got her started! Rolled her back and forth vigorously for about 3m each way then it was fine starting!

    I just hope it starts tomorrow :S
  6. I'm in Taroona, Tas. I suspect it might be leaking fuel into one cylinder. I've taken apart both a kz250 and my cbr before, but might leave this one to the pro's tomorrow and get back with the diag... if I can get it to the workshop.

    Also; doubt it's stolen as no-one would steal a bike like this and try to sell it on ebay:
  7. No they'd strip it for parts :)
  8. Sweetie no bike deserves that and certainly not the venerable T

    Sugarplum check the stator, it may need a rewind........
  9. spot on.

    Replace the battery and you should get a more reliable start.

    Put a liner in the tank before the rust gets an worse.

    Clean the bottom end of the carbies whilst you have the tank off.

    Sync carbies.
  10. Hi guys.

    Had the bike serviced, the rpm/idle is fixed. I told them not to touch the carbs as that'd cost me too much :)

    Runs really well, just a bit rough below 3k RPM and still locks up when starting.

    What I've figured is that it's NOT cold starts that make it hard to start, but starts after she's been standing around for a while.

    After some reading and all that jazz, I figured out it's suffering from Hydraulic lock because petrol is leaking into a cylinder when standing around.

    So tomorrow this weekend I'm going to check the fuel line for leakage, then clean the carbs. I've never cleaned carbs on a bike like this before, does anyone have a good guide? - I've got the service manual, but not sure if that'll be enough...

    Cheers and peace
  11. thatll be enough,

    just be careful removing the bolts, if they wont undo try giving them a gentle tap. an impact screwdriver may work or may stuff the bolt completely. make sure its a neat fit screw driver to head, other wise youll be running down to repco for an easy out kit. also if a o ring or gaskit is perished, youll need to replace it, otherwise it WILL leak fuel.

    youll need to sync your carbie and adjust idle mixtures after friggen around in there too. that will fix up your shit running at idle.

    edit: oh and by the way if hydraulic lock is occuring, your valves are leaking which is mondo baddo and your float level is ****ed, starter enrichment valve stuck on, etc etc etc. turn the fuel tap off before hitting the kill switch, when the idle rises abruptly (fuel starvation) turn it off. disconnect the fuel line if you think its required, leave something to collect the fuel, see if the tap is leaking. leave it for a while, however long you think it takes for this hydraulic lock to occur. reconnect everything, try starting it again. did it make any difference? im guessing not, that will eliminate that possibilty. what do you mean its locking up on starting? if you are saying what i think you are id be putting it down to a worn starter gear before hydraulic lock up. how many kays on the bike?

    PS the only time ive seen a bike experiance hydraulic lock up was when it literally went for a swim.
  12. hey monday disliker

    Firstly, i'm not at all familiar with the GSXR yet, I swear there is no fuel tap. Or I'm blind:

    Cheers for all the advice. The bike has 42,000km. Generally seems in good nick.

    Locking up on start up:
    (after standing around 1-2 days)
    first try:
    second try:
    I can feel the motor trying to turn, but can't.

    This is where I roll my bike back and forth vigorously while in 6th gear (looks like I'm screwing it). This I assume clears the cylinders. Then it starts fine. I really do suspect it's a bit of dirt in a float or something. That would explain it all? Just not really looking forward to the carbie maintenance, last time I did it, it was tedious shit.

    Edit; now that I think about it, it could be that the vaccuum fuel valve has a busted spring mechanism (or the like).

    edit 2; to clarify it's not super shit at low revs, just "fluffy" when powering under 3000. Idle seems almost regular after replacing plugs.
  13. I would suggest that your starter motor is stuffed. I would think that it would take a heap of fuel leaking in to the cylinder to cause a hydraulic lock. I cant really imagine that happening, and I would be looking at that way before hydraulic lock.
  14. But a starter motor problem would effect a cold/warm start as well as a cold start after 1-2 days. I'll add that to my checklist if it's not the valve or grimed carby
  15. Not necessarily. I don't understand how a valve or grimed carby would do this.... The cylinder would need to be basically half full of fuel to do this. The starter is a much easier thing to get checked out than pulling apart carbies, etc. The rocking of the bike could be helping to loosen the starter, therefore allowing it to work and start the bike. And I'm not sur how pushing the bike a little would clear out the amount of uel that would need to be in the cylinder to cause this problem.
  16. Most starter systems have the starter motor output shaft running against a gear with a 1 way clutch in it...I wouldn't be surprised if this starter clutch arrangement being worn or damaged is the cause of your problem.
  17. Crud in the carb float bowls is probablytrapped behind the float causing you fuel level to be too high for one cylinder. As a result you are probably flooding one cylinder. So no spark. It is therefore firing up on 3.

    Wip the float bowls off the carbs and give em a clean with kero, the rinse around the float and jets (a spray bottle filled with kero helps)

    Then wip out the plugs and dry them off. I bet one will be wet.

    Put everything back together and i bet it will start fine.

    Starter could be on its way out but i would want to be sure before i spent that kind of money.....if you have been cranking it a lot put the battery on a charger.....safer than a long ride that might leave you stranded
  18. Save the money & get someone to do it. If you are getting hydraulic lock from fuel very soon you may bend a con-rod costing heaps more for an engine re-build.
  19. I can.

    No it wouldn't. It only needs to have more fuel in it than the capacity of the combustion chamber at top dead centre. On a 750 I4 with a modest compression ratio, that's less than 20cc. Four teaspoonsful. Not much at all.
  20. ok, its flooding, yep it may well be doing so severely, which you could call hydraulic lock. it used to happen on my old storm occasionally, but i would have never used hydraulic lock, just badly flooded, same thing i guess. would struggle to turn over for a second then a massive bang, and shed start. does it make a noise when it starts like that? something in your carbies is allowing fuel to leak into your cylinder. drain the fuel bowls and leave it a couple of days, see if it does the same thing. my gues is either a float problem or the starting enrichment valve is stuck open.

    who told you rock the bike back and forward in gear???


    crankshafts are only designed to rotate one way, doing what you are doing will put a lot of strain on the drive train, big ends and camchain. i cant put it any clearer than that.

    if it floods, try this. remove the fuel pump fuse, leave the kill switch off, go to full throttle and engage the starter for at least 10 seconds. this is the flooded start drill, it should clear all excess fuel in the cylinder. try that and get back to us.

    i dont think you are going to have much choice other than having a good dig around the carbies. a perished slide diaphragm wont cause problems at idle, if anything it will cause it to lean out the further you go up the rev range for that cylinder. if its the spring, yeah it could be causing the slide to open up and dump fuel, if it is the spring it would be irrelevant how long its sitting around