Gixer SRAD hot starting/running issues?

[centaurus]

Hi guys,

I have a very strange problem with my '99 Gsxr750. The bike starts fine and runs smoothly, but once it gets over 80 degrees, the engine "sputters" and cuts off. If riding, it feels like when you've just ran out of fuel. If I try to restart it, it turns over as fast as when cold, but nothing happens. I even tried to crash-start it downhill and all I got was rubber marks on the road when I dropped the clutch. It's worth mentioning I still have lights and everything electrical when this happens.

If I let the engine cool down below 60 degrees, it starts fine.

This bike is new to me so I don't know if this problems has been before (the previous owner says - no). However, I have just cleaned and gapped the spark plugs, adjusted valve clearances, replaced the cam chain tensioner (it was getting a bit slack) and replaced the oil.

Does anybody know what can be the cause?

[DEATH_INC.]

I'd be wildly guessing, but I'd start with the engine temp sensor, make sure it's not still trying to run on the cold mixtures from the ecu. (tho the fact the gauge comes up may eliminate this....)
Next time it cuts out check whether or not it still has spark (you may need to pull 'er to bits first and run it 'till it cuts out) when it's hot (electrics can die with heat) and do a quick fuel pressure check (pull the fuel hose and see if it still pumps heaps), be carful, hot stuff and fuel isn't a great combo
Also, ask here http://www.gixxer.com/forums/forumdisplay.php?f=17

[actungbaby]

Hi also check your coolent system rad etc thinking water pump maybe

Hi guys,

I have a very strange problem with my '99 Gsxr750. The bike starts fine and runs smoothly, but once it gets over 80 degrees, the engine "sputters" and cuts off. If riding, it feels like when you've just ran out of fuel. If I try to restart it, it turns over as fast as when cold, but nothing happens. I even tried to crash-start it downhill and all I got was rubber marks on the road when I dropped the clutch. It's worth mentioning I still have lights and everything electrical when this happens.

If I let the engine cool down below 60 degrees, it starts fine.

This bike is new to me so I don't know if this problems has been before (the previous owner says - no). However, I have just cleaned and gapped the spark plugs, adjusted valve clearances, replaced the cam chain tensioner (it was getting a bit slack) and replaced the oil.

Does anybody know what can be the cause?

[centaurus]

Thanks for the suggestions, DEATH_INC. I tried as you said and I can still see fuel flowing from the tank, however there was no spark - not at all. After allowing it to cool down, I checked again and there it was - a nice healthy looking and strong spark.

I also discovered it is not a certain temperature. With the tank up, there was more fresh air flowing inside the bike and the engine died just after 100 degrees.

Given that this bike is electronic injection (and the ECU is under the seat - far away from heat), it must be wires, right? What else could it be that would kill the spark when hot.

I'd be wildly guessing, but I'd start with the engine temp sensor, make sure it's not still trying to run on the cold mixtures from the ecu. (tho the fact the gauge comes up may eliminate this....)
Next time it cuts out check whether or not it still has spark (you may need to pull 'er to bits first and run it 'till it cuts out) when it's hot (electrics can die with heat) and do a quick fuel pressure check (pull the fuel hose and see if it still pumps heaps), be carful, hot stuff and fuel isn't a great combo

[NinjaNanna]

It IS temp related, the general area doesn't get as hot with the tank up of off. That equates to a hotter engine temp to get the ambient temp hot enough to cause the failure.

[imdying]

Jump the test connector and see if it's throwing a code.

[centaurus]

Jump the test connector and see if it's throwing a code.

???

I suddenly feel inadequate - have no ideea what you've just said

Can you please repeat in simple English so people like me can understand too?

[imdying]

Typically an EFI Suzuki has a service port (which is a plug on the loom that goes nowhere) which you can jump the pins on with a paper clip). That makes the EFI light flash (on some models you get a code replacing the temperature gauge) in a preset sequence.

The workshop manual will provide a breakdown on what each sequence of flashes means, and detail how to jump the connector. I've never worked on anything that early, so YMMV.

Somebody on gixxer.com et all will be able to provide a link to download a workshop manual.

It may be that a sensor has failed and the code will tell you which one. Maybe not, but as it is free to try it's worth a look.

[MSTRS:Me]

Under the pillion seat is a little white block with 2 wires going into it (mine is on the left side). It has a black rubber cap covering the other side. Remove the cap and push the ends of a paper clip into the appropriate holes (the ones the wires go into the other side of). You may need to file down the paper clip to allow it to fit.
What will happen now, when you turn on the ignition is the digital readout for the temp on the tacho will have 3 or 4 dashes only. Run the engine until your problem shows up. The digital readout will probably now read 'C.... (the dots will be a number). Look up google for Suzuki fault codes to see what the number refers to.
That is what your computer is reacting to, but the problem is probably only a faulty sensor.

GXSR.com has this to say on the entire process

[centaurus]

I found the test connector, jumped it and ran the bike until it died. It showed C00 all the way (even after the engine died). I'm assuming this would mean the ECU and all the sensors are ok?

What is strange is that when the engine dies, it doesn't stumble, fluctuate on revs, bog down or miss a beat. It runs perfectly and stops suddenly, just like i have hit the kill switch, and even though the spark dies, no other electric component seems affected (dashboard, lights, signals, horn, etc...)

[MSTRS:Me]

No fault code suggests it is not a system monitored by the ECU that is breaking down.
Sign up to GXSR.com and ask on there. Someone will have had the problem and sorted it...

[imdying]

The tip over switch is mounted correctly? Not half hanging off its mount?

[centaurus]

The tip over switch is mounted correctly? Not half hanging off its mount?

Checked it and it it mounted correctly. I even opened it up to make sure the internals are good and I have the right way up.

[onearmedbandit]

Question. How long did you have it before it started playing up? Only just got it that afternoon? Or you'd had it for a few days? Weeks?

[centaurus]

Question. How long did you have it before it started playing up? Only just got it that afternoon? Or you'd had it for a few days? Weeks?

I've had it for a few months now but I bought it crashed so until the other day it hasn't been ridden - just started it briefly when brought it home to confirm it was running. Since then I did all the normal maintenance jobs (replace all fluids, adjust valve clearance, clean spark plugs, air filter, etc...)