FCRs flooding - BAD!

[ducfun]

All,

I've searched and can only find threads with fuel starving issues. I've had a recent carb flood problem.

'96 M900
Stock metal gas tank
FCR 41 (kit from CA Cycleworks)
Cut airbox with K&N filter
CA Cycleworks exact fit coils
     With new wires and plugs
Manual petcock
Stock mechanical/vacuum fuel pump
Arrow exhaust

After a test ride that included a 5 mile highway run at ~ 60 MPH, my M900 died at an exit ramp stop light. Battery and oil indicators came on. I pushed it to a safe parking spot and sat for 15 or so minutes. During that time I surveyed the bike - do I have gas (yes, nearly full). At this point I notice that the socket head cap screws that retain the gas cap allow the cap assembly to wobble around with some gap between the metal tank and cap ring, WTF?!? I was close to a family members house, so I blip the throttle to prime the carbs (no choke on FCRs - probably didn't have to do that, D'oh!) and start it again. I rode no more than a mile through a residential area and it died again. Battery and oil indicator on again. This time when I get off I hear a kind of bubbling sound and smell gas. Pop the tank, pull the filter and I literally see gas nearly flowing into my airbox. Both carbs flooded, but maybe one slightly higher.

Everything I've searched suggests one of or a combination of fuel pump (although most seem to fail closed), tank pressure, and/or carb float.

The carbs are about a month old, tuned by Chris and delivered fedex from CA to MD. The bike has been started regularly although not ridden normally (as I've been fighting all summer to get it road worthy). It starts with relative ease.

This may have been the first ride with a mostly full tank since starting the project.

Starting cold with the FCRs sometimes includes a pop/bang from the carbs. I've also noticed sudden opening kind of bogs down (as if fuel starved).

I know there are plenty of folks that have or at least used to have FCRs...heard of anything like this?

I plan on tearing into the pump to examine the diaphragm, doing a gravity feed (bypass pump), checking tank vacuum lines and tank cap this weekend. Other thoughts? Priority?

This place has been a tremendous help...any thoughts are much appreciated...

[ducfun]

*clarification - carbs were set by Chris at CA Cycleworks as he does with all FCRs before shipping. This was a baseline, not full on tuning for my bike. I have not noodled with this baseline....

[Howie]

Flooding is usually caused by a float needle/seat assembly failing to close.  Two reasons could be dirt in the assembly or excessive fuel pump pressure 9not an issue with the OEM pump.

[ducfun]

Flooding is usually caused by a float needle/seat assembly failing to close.  Two reasons could be dirt in the assembly or excessive fuel pump pressure 9not an issue with the OEM pump.

Howie, on reason two: to clarify, are you saying excessive pressure could be a cause, but an OEM pump wouldn't contribute to excessive pressure? Gravity alone with a damaged diaphragm probably couldn't create this excessive pressure situation, right? So, that is either some other pressure source (maybe tank not venting) or float not closing due to crud?

[Howie]

Howie, on reason two: to clarify, are you saying excessive pressure could be a cause, but an OEM pump wouldn't contribute to excessive pressure? Gravity alone with a damaged diaphragm probably couldn't create this excessive pressure situation, right? So, that is either some other pressure source (maybe tank not venting) or float not closing due to crud?

The other pressure source would be an aftermarket pump that puts out higher pressure.  Gravity won't do it.  Tank not venting causes fuel starvation.  I think crud is your problem.  You can try lightly tapping on the carb inlets and see if that helps.

[ducfun]

Awesome! Thanks!!!!

[koko64]

+1.  Another method is this. While riding, and being careful to keep your eyes on the road, your manual tap can be shut while the bike is running and the flooding will subside. Then as the float bowls get low open the tap again to slam the floats shut.

[motoxmann]

do you have a fuel filter installed on the bottom of the tank? if so, how old is it?
did you install a fuel screen on the fuel inlet to the carbs? if no, you should.

it also sounds to me like you have something in the fuel line that got caught up in the float needles causing them to not be able to close all the way

[ducfun]

+1.  Another method is this. While riding, and being careful to keep your eyes on the road, your manual tap can be shut while the bike is running and the flooding will subside. Then as the float bowls get low open the tap again to slam the floats shut.

Brilliant! I was so frustrated that I didn't think of that. I probably could have done this stopped too.

[ducfun]

do you have a fuel filter installed on the bottom of the tank? if so, how old is it?
did you install a fuel screen on the fuel inlet to the carbs? if no, you should.

it also sounds to me like you have something in the fuel line that got caught up in the float needles causing them to not be able to close all the way

I do have a fuel filter. It is about a year old. I don't like it either. I ordered it from NAPA and it doesn't have the right angle outlet (although the part number appeared correct). Since it would fit under the tank, I relocated it to where the vacuum petcock used to be. I should replace it with the stock configuration...

I don't have the inlet screen. Sounds like another worth addition. Thanks!

[motoxmann]

I get my fuel filters at napa too, probably a different one than you though. Part#: 3087 is what I get, it's completely identical to oem Ducati filters.

http://napaonline.com/Catalog/CatalogItemDetail.aspx?R=FIL3087_0289048352