Kawasakifreak Posted August 23, 2012 Report Share Posted August 23, 2012 I'm stumped & I don't like admitting it. My 1983 Kawasaki GPz750A1 appears to suffer from fuel starvation when using it's original fuel tank. It runs badly - only on prime & with choke !!? Once moving it runs ok but hates lower revs. Even when warm it'll stall at idle speeds without choke. The engine runs perfectly using a surrogate fuel tank off an old lawn mower so I know it's not the carbs at fault. The problem's with the original tank - I've already replaced the fuel tap innards with genuine Kawasaki bits, cleaned the fuel filter checked the fuel tap orifice is clear from obstructions without making any difference. Any advice appreciated. Link to comment Share on other sites More sharing options...
Taqman Posted August 23, 2012 Report Share Posted August 23, 2012 Obvious question - have you tried running the bike with the fuel cap open/off - I wonder if the vent is blocked so the tank is vacuming???? Link to comment Share on other sites More sharing options...
fran9r Posted August 23, 2012 Report Share Posted August 23, 2012 Is the tank breather blocked? Try runing it with the fuel cap off/open. Link to comment Share on other sites More sharing options...
VanWinkle Posted August 23, 2012 Report Share Posted August 23, 2012 could there be some way that you are either trapping or kinking the fuel pipe when fitting the tank on?. Link to comment Share on other sites More sharing options...
Conica Posted August 23, 2012 Report Share Posted August 23, 2012 We had this problem with the team north Bros, Stuck an NC30 fuel cap on the bros tank and it fitted perfectly, Brilliant, And then we spent weeks trying to figure out why is was being starved and just turned out the small vent in the fuel cap was in a different position to the hole in the tank! Link to comment Share on other sites More sharing options...
BudgetBoy Posted August 23, 2012 Report Share Posted August 23, 2012 Yep its the vent within the petrol cap by the souds of it. take it off and clean it up. Also blow through the pipe where the vent goes into. Link to comment Share on other sites More sharing options...
Kawasakifreak Posted August 27, 2012 Author Report Share Posted August 27, 2012 I've run the bike with the petrol cap open - makes no difference. The original fuel feed pipe from the tank to the carbs was awful. I've replaced it &added a vent pipe from one of the carb vacuum inlets - it still runs like shit. Link to comment Share on other sites More sharing options...
Kawasakifreak Posted August 27, 2012 Author Report Share Posted August 27, 2012 To clarify - I did all the above long before my original thread including improving the routing of the fuel-feed pipe. This problem has had two different mechanics scratching their heads so I know it's not just me being a fucktard. Link to comment Share on other sites More sharing options...
fran9r Posted August 27, 2012 Report Share Posted August 27, 2012 Erm, have you repeated the trick with the different tank set-up, just to check it wasen't a wierd result? Link to comment Share on other sites More sharing options...
VanWinkle Posted August 27, 2012 Report Share Posted August 27, 2012 To clarify - I did all the above long before my original thread including improving the routing of the fuel-feed pipe. This problem has had two different mechanics scratching their heads so I know it's not just me being a fucktard. well thats our joint mind reading trick fucked then!. Link to comment Share on other sites More sharing options...
Egg on Leggs Posted August 27, 2012 Report Share Posted August 27, 2012 I'm stumped & I don't like admitting it. My 1983 Kawasaki GPz750A1 appears to suffer from fuel starvation when using it's original fuel tank. It runs badly - only on prime & with choke !!? Once moving it runs ok but hates lower revs. Even when warm it'll stall at idle speeds without choke. The engine runs perfectly using a surrogate fuel tank off an old lawn mower so I know it's not the carbs at fault. The problem's with the original tank - I've already replaced the fuel tap innards with genuine Kawasaki bits, cleaned the fuel filter checked the fuel tap orifice is clear from obstructions without making any difference. Any advice appreciated. Have you done a physical fuel flow test? Are you absolutely sure the fuel tap parts are in the right way around. Link to comment Share on other sites More sharing options...
lorenzo Posted August 28, 2012 Report Share Posted August 28, 2012 How old's the fuel in the tank? Link to comment Share on other sites More sharing options...
fran9r Posted August 28, 2012 Report Share Posted August 28, 2012 Having thought about it, whats the chance of their being water in the tank? I'd try flushing and trying again. Link to comment Share on other sites More sharing options...
BudgetBoy Posted August 28, 2012 Report Share Posted August 28, 2012 Having thought about it, whats the chance of their being water in the tank? I'd try flushing and trying again. There's always a chance.. Done a few bikes with this problem. Take the tank off and drain it completely. While you are draining it make sure you get the outlets right for the fuel.. (res & main). Empty the fuel bowls as well. Refill with fresh pump fuel and switch to reserve.. And fire that baby up.. Link to comment Share on other sites More sharing options...
Kawasakifreak Posted August 29, 2012 Author Report Share Posted August 29, 2012 Emptied the tank & float bowels previously - no change. Had the fuel tap (petcock to the yanks) apart three times previously - super careful putting it all back together - no change. Ran engine with the fuel cap open - no change. Ran the engine using the lawn mower tank on two seperate occasions - runs lovely. Put the original tank back on each time - runs nice for 30 seconds or so & then runs like shit again. The bike's cursed. #11 Egg on Leggs - Physical fuel flow test ? No. I need to test a fuel pump on a ZX7R I'm resurrecting so I could do them both. Any suggestions on a good flow meter anyone ? Link to comment Share on other sites More sharing options...
Egg on Leggs Posted August 29, 2012 Report Share Posted August 29, 2012 #11 Egg on Leggs - Physical fuel flow test ? No. I need to test a fuel pump on a ZX7R I'm resurrecting so I could do them both. Any suggestions on a good flow meter anyone ? Get your lawn mower tank and time how long it takes to drop a litre out, do the same with the bike tank. No need for a flow meter. After that, run the bike tank to make sure the flow is constant. Remind me, is this a vacuum fuel tap? Link to comment Share on other sites More sharing options...
fran9r Posted August 29, 2012 Report Share Posted August 29, 2012 Seems odd it's OK at higher revs -you would expect any flow problem to be worse at high revs, not better. Still worth checking though. I'm wondering if it's possible the original tank is interfering with an ht/cdi lead somewhere? Link to comment Share on other sites More sharing options...
Kawasakifreak Posted August 31, 2012 Author Report Share Posted August 31, 2012 Seems odd it's OK at higher revs -you would expect any flow problem to be worse at high revs, not better. Still worth checking though. I'm wondering if it's possible the original tank is interfering with an ht/cdi lead somewhere? That had crossed my mind - the block connector under the tank has melted in one corner & the digi fuel readout stopped working. If it's that then I'll be surprised but worth a look. Get your lawn mower tank and time how long it takes to drop a litre out, do the same with the bike tank. No need for a flow meter. After that, run the bike tank to make sure the flow is constant. Remind me, is this a vacuum fuel tap? Good idea - thanks. Link to comment Share on other sites More sharing options...
fran9r Posted September 2, 2012 Report Share Posted September 2, 2012 That had crossed my mind - the block connector under the tank has melted in one corner & the digi fuel readout stopped working. If it's that then I'll be surprised but worth a look. Good idea - thanks. I bet you a digestive biscuit it's the connector. Link to comment Share on other sites More sharing options...
VanWinkle Posted September 3, 2012 Report Share Posted September 3, 2012 why dont you just go buy and fit another tank. Link to comment Share on other sites More sharing options...
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