[Ducati] Help (NDC)

[Bob Marren]

My son races a 600 GSXR and float problems cause fuel in the airbox. 
Just one sticky carb can do it.
 Bob M

Stephen Abramson wrote:

>It's not for the 900, but I have to ask to pick the collective brain of the
>list for help. As an coach for Team ProMotion at Shenandoah/Summit Point
>this past Saturday, I left the pit on my '98 Gixxer 600 (extremely
>dependable-has never let me down until now..) to lead the Intermediate group
>on the first session of the day. Halfway through the first lap, as if you
>flipped a switch, the motor began to run as if you shut down a couple of
>cylinders. Felt like a cross between en electrical issue and like you had
>put the motor on full choke. Applying more throttle resulted in no gain in
>speed, just a burbling type of running. Made it back to pit, motor would now
>not start at all. Start poking around, the usual suspects given the type of
>malady at hand. Pulled the airbox, and found a bunch of fuel sloshing around
>in there. Checked electrical connections. (This bike is fuel pump in
>tank/carbureted). Normal startup pump process is as follows-flip toggle
>switch mounted by tach and hear fuel pump run-runs for approx. 4-5 seconds
>and then shuts off, just like the Ducati. I assume this means it has reached
>its normal operating pressure, shuts off, and is an on demand pump that goes
>on and off while you are riding based on the needs of the float bowls. So
>the pump cycles off properly. I pull the hose from the fuel pump, flip the
>toggle-fuel pumps out the hose at what appears to be more or less normal
>pressure. So the pump works. At this point the bike still won't start. So
>I'm thinking maybe a stuck float or something. In any case, I think there is
>way too much fuel in there right now for the bike to run, so I disconnect
>power to the pump, and start cranking the motor. After many seconds of
>cranking, it starts to fire- a little more and more, until the bike actually
>starts and runs. Blip throttle a few times, the motor cleans out, and
>actually runs cleanly-big blips, nice clean revs. I think, well I don't know
>what happened, but it seems to be fixed. (How cruel life can be to tease me
>this way). Airbox back on, tank down, seat in place. Try and start
>it-nothing. F*ck. Take it all apart again. Pull wire from fuel pump again.
>Crank, crank, crank, motor starts slowly, cleans out, revs clean. This time
>while it is revving clean, I plug the fuel pump back in, and lo and behold,
>after about 2 seconds, the motor loads up again, and basically starts the
>bog process and then shuts down. Won't start again. Hmm, let's try that
>again. Pull fuel pump wire, crank, crank, starts firing, cleans out, revs
>clean. Plug in fuel pump, 2 seconds later it starts to bog and then shuts
>down. (Dead battery now....f*uck again..)Get battery charger/jumpstarter.
>Try the whole thing one more time, same thing. OK. So there are these two
>little black mystery modules located behind the carbs under the tank. Each
>one has two wires going to them. One of them has a hose that comes out of it
>and splits to two of the carbs as well as a hose that goes to the airbox.
>The other has the same stuff, one hose that comes out of it, splits, and
>goes to the other two carbs as well as a hose that goes to the airbox. So
>I'm thinking that these mystery modules are pressure regulating devices to
>somehow control the pressure or amount of fuel to the float bowls. If one of
>them has failed, maybe there is an over-pressurization to two of the carbs,
>creating a super rich situation, which goes along with the symptoms the
>motor exhibited as it started to bog and shut down. When we disconnect the
>fuel pump, it allows only the fuel that is sitting static in the bowl to be
>delivered to the carbs, and as soon as you introduce fuel via the pump, we
>have an instant over-rich situation. I think this electrically based fuel
>delivery problem could be the case based on how quickly the problem came
>on-it was instantaneous, as if a physical component failed, as opposed to a
>quick onset problem that was purely fuel based. I suppose there could simply
>be a stuck needle, but I'm leaning toward  the mystery module. I flogged the
>bike for two days at Calabogie two weeks ago, riding one, sometimes two
>classes as a coach, and battling on my own within the expert class while not
>coaching. Bike was put away and not touched since that time. Gentlemen of
>the jury, have you reached a verdict? Thanks for your consideration.
>
> 
>
>Steve
>
>*****
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