Bike cuts out | GTAMotorcycle.com

Bike cuts out

M

Merkid

Well-known member
2012 Suzuki GSX1250FA (Bandit)

When warmed up and with a low fuel level in the tank the bike would not make it over 3000 rpm. It is better when cold, but I can barely get up to about 5000 rpms.

When the tank is full and the bike is warm, I can get to about 5000 rpm before it cuts out . It feels like the rev limiter kicks in.

It starts fine all the while.

I replaced the fuel pump and it temporarily helped but now no change.

Does this sound like a fuel delivery issue?
 
Sure sounds like a fuel pressure issue, check for leaks on all of the hoses inside the fuel tank and the fuel filter.

.... you already replaced the fuel pump! are you sure the original one was done or was that trouble-shooting this same problem?
There is likely a fuel pressure regulator in there somewhere too.
 
Have you looked inside the fuel tank when it's running, watch for fuel spray or turbulence where it does not belong.
 
When you "replaced the fuel pump" did you replace JUST the pump (thus having to disassemble the sending unit in order to do so) or did you replace the entire sending unit with its integral pump with a new assembly (expensive) or used assembly (but is it known good)?

If you replaced just the pump, did you also replace the suction filter? Did you back flush the secondary (generally non serviceable) filter inside the sending unit?
 
As usual it would be So easy to trouble-shoot if you only had 2 identical bikes :whistle:
 
Brian P said:
When you "replaced the fuel pump" did you replace JUST the pump (thus having to disassemble the sending unit in order to do so) or did you replace the entire sending unit with its integral pump with a new assembly (expensive) or used assembly (but is it known good)?

If you replaced just the pump, did you also replace the suction filter? Did you back flush the secondary (generally non serviceable) filter inside the sending unit?
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Just the pump as the entire assembly was a crazy price.
 
Thanks for the feedback guys.

I do suspect that there is leakage in the entire unit so will take it out and pressurize it on the bench, trace the fuel line for loose fittings too.
 
First time I had a problem like that it was the metal fuel filter that split, second time was when a rubber hose inside the tank rotted away.

Did your fuel filter ever have water in it? Did you drop your bike into the lake like I did once? Water destroys the filter paper in the fuel filter preventing it from allowing fuel to flow as freely through it, that will starve the engine for fuel same way. <- if your fuel intake is sucking air when the fuel tank level is low that would do it, although the system might bleed itself out much easier then a diesel which typically has a mechanical injector pump.
 
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Trials said:
First time I had a problem like that it was the metal fuel filter that split, second time was when a rubber hose inside the tank rotted away.

Did your fuel filter ever have water in it? Did you drop your bike into the lake like I did once? Water destroys the filter paper in the fuel filter preventing it from allowing fuel to flow as freely through it, that will starve the engine for fuel same way. <- if your fuel intake is sucking air when the fuel tank level is low that would do it, although the system might bleed itself out much easier then a diesel which typically has a mechanical injector pump.
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Nope, no exposure to water. There is only a small filter that is pressed in place and fixed on the fuel pump assembly unit. It resembles a tea bag. At first I thought it was clogged up causing fuel starvation but it was fine when I replaced it.
 
Merkid said:
Nope, no exposure to water. There is only a small filter that is pressed in place and fixed on the fuel pump assembly unit. It resembles a tea bag. At first I thought it was clogged up causing fuel starvation but it was fine when I replaced it.
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That would be slightly unusual, fuel filter on any Fi motor I have seen is a metal canister on the high pressure side of the pump ymmv.
... you never want to starve an electric fuel pump located inside a fuel tank, that could make it go boom!

Edit: looked at the parts fiche, your pump shows a strainer and no filter, that's not going to do much to stop water or dirt particles that are big enough to plug your injectors. Check your injectors.
 
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Have you checked the simple stuff first before assuming expensive stuff?

Like the kickstand switch?

At a certain RPM the engine may be making just a perfect resonance frequency through the frame to sporadically trigger something like a wonky kickstand switch or tip-over switch which I believe the bandit has like it's GSXR brethren.
 
PrivatePilot said:
... simple stuff ...
... perfect resonance frequency through the frame to sporadically trigger something like a wonky kickstand switch or tip-over switch...
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:LOL:
 
LOL all you want.

Kickstand switches cause people grief all the time,

Simple things cause people grief all the time.

I’ve seen people spend thousands of dollars replacing expensive bits on cars because their buddy’s third uncles sisters son told them that was their problem, only to find out the problem is still there and the actual issue was a chewed wire.

And perhaps you’ve never dealt with a vibration triggered issue, but yeah, perhaps you haven’t spent much time under the hood of a car.
 
I have no doubt that safety cutout switches are a leading cause of failure, but if harmonic vibrations are enough to make it toggle, you probably don't have a strong enough spring on the switch lever. Replace that stupid switch on the side stand with a chunk of rubber on the end of the side stand foot and you have a simple device that does the job of an overly complex one.
21shczin9NL.jpg


Tip over-switch :/ is a mercury switch, it's not going to make contact unless you tip it upside down, gravity and liquid mercury is very predictable.
 
Trials said:
Tip over-switch :/ is a mercury switch, it's not going to make contact unless you tip it upside down, gravity and liquid mercury is very predictable.
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Tipoover switch may have been a mercury switch in the past, but I would be shocked if it is today. Probably some stupid MEMS sensor now. Cheaper, no environmental concerns and no moving parts.
 
GreyGhost said:
Tipoover switch may have been a mercury switch in the past, but I would be shocked if it is today.
Click to expand...

They're not.


I'm not saying it's 100% likely to be either of my suggestions...but hey...always check the simple stuff first.
 
Hence why you check the simple stuff first, especially if you're experiencing these issues while the bike is sitting already at an angle on the kickstand. Maybe the tipover switch got knocked off it's correct mounting position and the bike thinks it's headed for it's side when it's actually not...for example.

Heck, it could be a loose wire on the back of the tip over switch (or to be clear, anywhere else) that's causing the issue as vibrations build.
 
On the Montesa it waits 5 seconds before it does anything. You have to be crashed.
or falling a heck of a long way upside down.
 
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