Fuel problem

[rdteeler]

Im new to the Airhead /carberator bike.I recently bought my bike,they had to line the tank and put new petcocks on,cleaned the carbs,replaced the main jet to a 150,the pilot jet 45.I installed a new fuel filter.Got it running pretty good yesterday on the freeway it acted like its was running out of gas
then just flat died,in the middle of the freeway I yanked it over to the shoulder.I finally got it running after choking it,.What could have been the problem. :-?

[donbmw]

Float level not set right, carbs not really cleaned right. When you stopped did you pull the fuel line off the peacock. Did fuel flow when in on position and in reserve  position.

Don

[montmil]

There's an old saying regarding our Airheads and their occasional problems:
   When you think it's carburetors, it's probably electrical.
   When you think it's electrical, it's the carbs.
Although this old wives tale may not apply in your situation, it's often true.

You said the engine stumbled a bit and then, "flat died". I believe that both carbs would have to fail in tandem. The Airheads will run on one carb -not too well, mind you- but they will limp you home. Case in point, I had a diaphragm fail on one carb and that side quit. The still functional other carb got me home.

You did not mention the model and year of your BMW. As there are some ignition differences twix model years, that info would be very helpful for a diagnosis.

Pull the float bowls and check for debris. Also, gently lift the floats, turn on the fuel and confirm flow by lowering the floats. Confirm fuel stops when you lift the floats.

If it was an ignition anomaly, start checking ground wires. Brown wires are 'earth'. Confirm battery terminals are clean and secure at both ends.

Also check to see what ignition coil you have. If it's the black and gray Bosch "Crack-O-Matic", that's one of the usual suspects. Check the simple stuff first. It's usually the simple stuff.

BTW, what shop did your work?

[Barry]

Got it running pretty good yesterday on the freeway it acted like its was running out of gas
then just flat died,in the middle of the freeway I yanked it over to the shoulder.I finally got it running after choking it,.What could have been the problem. Huh
Back to top  

The first thing I would have done is quickly shut off the fuel tap and remove the fuel bowls to see what the fuel level was like. It takes literally a few seconds and is easier than pulling off a fuel pipe.  In that situation your only looking for a rough estimate of the fuel level and it should be about 1/2" from the top of the bowl. If substantially less then you have fuel starvation of one sort or another. Maybe something blocking the fuel filter or fuel tap that reduced the flow to the point the level gradually fell until the engine cut out.  

Not a bad idea to do this deliberately as a learning exercise  i.e. go for a run then shut off the fuel tap and continue on until the engine dies. Whip the bowls off and you'll then know what low fuel level looks like.

[skippyc]

sounds like a fuel blockage. the engine uses the fuel quicker than it can fill, but once you stop it slowly fills back up and starts again.

[Justin B.]

Try this, but ya gotta be quick.  When/if this happens again cut off the fuel-tap, pull in clutch, and shut off.  Coast over to the side and examine fuel level as suggested by Barry.

You can also try adding in choke (up to max) to see if it picks back up and starts running better.

A couple other things to check would be the ICU for fresh heatsink grease (maybe module is getting hot) and coil for cracks...

I got the Junkyard Dawg out for a rie yesterday and found that I had to use partial choke to get past about 45 mph.  I guess I have a date with the ultrasonic...

[rdteeler]

Finally found the problem,I took it back to the shop again!! had a different mechanic look at it.I told them to keep it until they found the problem that it was intermittent.Well it happened to the mechanic when the bike stutters he shuts fuel cock off,checked the bowls they were dry.What they discovered was the vent cap was not venting and it was drawing vacuum on the carbs ,emptying them.they drilled a hole in the bottom of the cap to help vent.Also he said it had the wrong jets and he replaced them with the ones that was supposed to be in it.I finally got the bike home yesterday,It is not even the same bike .it made that much difference.I hope this helps someone.