I heard a POP today

[peb]

I pulled into the parking garage at work this morning and as I was backing the bike into the parking space (engine idling)I heard a pop. The pop made the same sound as when my daughter dropped her bicycle helment in the garage. There was someone close to me in the garage and heard the sound also. They said it was POP and not a backfire sound. After the pop sound the engine started idling rough and I could smell gas. Not a strong smell, but I could smell gas. I rev'd the engine and the roughness was there also. The bike has 124K on it. Any thoughts about what has happened?

[dirtrider]

Hi Peb

 

Sorry not much help without further information.

If the gas smell is in fact from your bike then look for signs of gasoline dripping down from the right side of your bike, if so suspect a fuel line popped off or if your bike has quick disconnect added maybe a failure in that area.

 

When you get off work see if the gas smell is still there, look for gasoline leakage, see if the engine still misses.

 

If you can give us a little more info maybe we can help.

 

 

[peb]

I went back to check on the bike and there is no fuel smell or fuel puddle near the bike. I think the fuel I was smelling was from unburned fuel that was being injected into the engine. My gut feeling is that a cylinder shut down, but I am not a technician so I could be way off base on this.

[dan cata]

Check for spark at the spark plugs and increased oil level

[Joe Frickin' Friday]

A popped-off fuel line should kill the engine completely if it's upstream of the pressure regulator, since you'd lose all pressure to the injectors. One that's merely ruptured would have to leak a lot of fuel to affect fuel pressure at the injectors.

 

A line downstream of the fuel pressure regulator shouldn't rupture since it's supposed to be at zero pressure. If it was somehow under significant pressure, then the bike should run like crap, and then start to run better if it ruptured. Moreover, this would result in a steady stream of gasoline draining from the tank - even with the bike shut off - as there is no backflow checkvalve on the line from the regulator back to the tank.

 

Possibly the fuel pressure regulator itself has broken? If the diaphragm inside it ruptured, that could explain:

 

-the "pop" sound

-the rough idle (low fuel pressure due to improperly-functioning fuel pressure regulator leads to fuel starvation)

-the smell of fuel (fuel leaking out through the ruptured diaphragm)

 

If you're smelling unburned gasoline from somewhere other than the tailpipe, this may be a dangerous condition (depending on leak rate) that needs to be fixed ASAP.

 

If there is in fact a leak, you may be able to identify its location by turning the key on with the kill switch set to "run" and the sidestand up. This cycles the fuel pump for a second or so to pressurize the fuel system. If the leak rate is small, you can run the fuel pump for additional 1-second bursts again and again by cycling the key, the kill switch, or the sidestand. In this way you can leak enough fuel to identify the leak location.

 

I would suggest doing the above with the tupperware off the bike, and the bike parked out in the open.

 

Alternative explanation might be an electronic item that "popped" and is causing problems with engine control. Some kind of short within the TPS (or O2 sensor) that wrecks it, and now the ECU has trouble determining the right mixture?

 

Some clues might be gained by checking the ECU for fault codes. Click here and go to page 71 to find out how to read the fault codes from your Motronic.

[dirtrider]

Hi again Peb

 

Well if you see no leak and smell no raw gasoline it could be a misfiring cylinder or maybe even from another automobile.

 

Maybe do a quick engine start then see if both side exhaust pipes get hot. If one side is cold after a few seconds of operation you know that side is not working correctly. Careful those pipes heat up quickly.

 

[Steve W.]

Maybe a throttle body popped off the head. It has happened.

Cheers

Steve

[4wheeldog]

Maybe a throttle body popped off the head. It has happened.

Cheers

Steve

 

This. Or a spark plug failed, ceramic loose in the metal part. Or you had a valve fail. Listed in decending order of likelyhood. Good Luck.

[peb]

Well I have lost a cylinder. Started the bike, felt the pipes, one hot one cold. I will take it to my buddies garage tomorrow and we will dig into it. I will let you know what wrong with it when we find it.

 

Thanks to everyone for your help.

[dirtrider]

Well I have lost a cylinder. Started the bike, felt the pipes, one hot one cold. I will take it to my buddies garage tomorrow and we will dig into it. I will let you know what wrong with it when we find it.

 

Thanks to everyone for your help.

 

Afternoon Peb

 

Before changing or moving too much take a look at the right hand spark plug wire where it comes close to the right hand TB cam. I have seen a few where the wire has contacted the TB cam and worn a spot through the plug wire.

If that is the case a simple spark plug replacement will usually correct the problem but only for a short time as the root problem is still there.

If you start by replacing spark plugs or moving things you might miss that as the problem could be easily overlooked.

 

 

 

 

[4wheeldog]

Well I have lost a cylinder. Started the bike, felt the pipes, one hot one cold. I will take it to my buddies garage tomorrow and we will dig into it. I will let you know what wrong with it when we find it.

 

Thanks to everyone for your help.

 

Those are the symptoms of a TB popping out of its boot.

[peb]

Good news, the TB popped off of the rubber boot. Put a new band on it and the bike runs great. Thanks again for everyone's help.