96 m900 fcr41 carb leaking issue

[ducriderinct]

A little backstory on my current issues. It may or may not help with diagnosis...

So I have a set of FCR's that were on my last 96 m900 that was involved in a crash last November. The bike has sat for almost a year now. It's been started a couple times but that's it. Fuel in the bike and the carbs is from a year ago or so at this point.

Yesterday I pulled the FCR's off that bike and installed then on the same model and year new bike.
When I pulled the carbs, I noticed some varnished fuel on the outside bottom of the forward most section of the left carb bowl. I didn't think anything of it
As the bike started and ran fine after the install. I wasn't able to ride it due to weather but I had it running for quite a while with no leaks or smell of fuel.

Today I had a chance to ride the bike.  Rode great initially, after about 7-8 mins it started having low to midrange power issues and I smelled fuel when stopped at a light.

I now have fuel dripping from in between the two carbs which looks to be coming from the left side carb above the bowl area. When I pulled he air filter off there was a large amount of vaporized fuel in the throat of the left side carb.

I've done some reading and it seems that the most likely explanation is that the float is stuck.  In my research I found some posts about dropping the bowl down without removing the carbs but no real description of what to actually expect once I get in there. I'd rather not pull everything apart again.

Is this the most likely problem, or could it be something else?

Does anyone know of I can simply pull the bowl and everything inside there will stay put, and I can spray everything down safely with carb cleaner or are all the inside contents of the floats, valves, etc going to end up in my hands?

If it is safe to spray down, is there a particular brand of cleaner than best to use with FCR's?

Sorry for the long winded post but I wanted to give as much info as possible.

[Speeddog]

Yep, most likely a stuck float due to debris or sticky muck.

FCR's are a bit finicky that way.

A bit aggravating to get a bowl off in situ, but doable.

I'd try removing the big plug on the bottom of the bowl and turn the fuel on and see if it'll wash the debris out.

[ducriderinct]

Thanks. Will I need any sort of replacement gasket or something if I do that? Do you know if I can just remove the bowl itself and the internals will stay mounted?

[koko64]

Try Speeddog's suggestion first as the drain nut has an o-ring. Catch the fuel with a cup under the carb when you turn on the fuel tap. Hopefully the float needle is washed clean. The float bowl will also have an o-ring and they are quite sturdy but try the fuel flush first. When replacing the nut/cap/plug, dont over torque it but make it snug.
Then when you turn the fuel back on give the float bowl a tap with the back of a screw driver to seat the float valve. Its toilet cistern tech in there. Do a search here on carb flooding, there is a wealth of info.
Make sure you are using fresh fuel.

[greenmonster]

+1 on koko`s advice, been there, done that.

[koko64]

I just remembered, the overflow tube exits between the carbs and needs a hose safely routed away from the motor. Does it have a drain hose?

[ducriderinct]

Hmm...no hose in there. I was wondering about that. Kinda expected there to be an overflow tube to be honest. I'll try draining the bowl in the morning. It's entirely possible that there's some crap that was in the lines which made its way into the carb. Will check tomorrow and report back. Thanks guys!

[Speeddog]

In addition, check the oil level on the engine.

If you've not installed a manual fuel valve, and the vacuum operated valve is eliminated or stuck open, the FCRs will gladly dump a gallon of gasoline into the sump.
Causing all sorts of mayhem...

[ducriderinct]

Oil level seems normal. Vacuum fuel valve seems good. I drained the carb bowl by removing the bolt and some dirty fuel came out. Put it back to gather and started it up.

No leaks while idling ( but then it didn't leak before when I started it and idled it) so I went for a ride for 15 minutes. Got back and it seemed ok during the ride, but when I stopped and pulled up the air filter there was a haze of fuel vapor inside that carb throat and I felt a little fuel on outside of the left carb between both carbs. I have a feeling. If I'd ridden longer it would've started dripping again

[koko64]

Get that hose on the overflow tube. Its most likely leaving fuel on the lhs carb due to the angle on the sidestand. You wont be able flush it unless you disconnect a line and supply fuel to it because of the vacuum tap.
Have a good read of the carb flooding threads via search function and at least give the bowls a rap with the back of a screwdriver at idle as a shadetree method of seating the float needles. Its just like smacking the toilet cistern to shut it up. A manual tap gives you more options on dealing with this issue. With a bike sitting that long, you may need to service the carbs properly. You could drain the carbs and spray up into the bowls with carb cleaner but some carb cleaners are harsh as hell and could damage paint and rubber.
With modern fuels containing additives helpful to EFI but unhelpful to carbs you cant get away with leaving untreated fuel for long periods without expecting to service your carbs.

[ducriderinct]

So it would seem that your initial expectation was correct. The vacuum switching valve for the fuel on off, is not working correctly. I checked on the bike this afternoon and the left carburetor was filled halfway up the carburetor throat. I'm wondering if this is the result of the impact of the bike being hit last year, or if it's the result of it just sitting with fuel in the bowls of the carburetors for almost a year

My crank case is now full of fuel and oil I promply drained the oil after disconnecting the fuel supply from the tank.  I'm assuming at this point that the heads of the engine are now full of fuel as is everything else apparently.  

I thought about the carb cleaner option, but I was very hesitant to try that due to its harshness and the expectation that it would likely destroy the rubber O-rings and seals and gaskets in the carburetor.

Unfortunately, I am leaving tomorrow for five days to for a trip. I've drained the oil out of the engine, do I have to worry about any damage occurring due to the fact that there might be residual fuel in the crankcase? I don't have time to properly drain,fill and flush the crankcase with fresh oil before I leave.

How complicated is it to clean out this carb? I was thinking id try to remove the bowl with the carb on the bike as there is plenty of room, but I'm in very unfamiliar territory at this point. I work with my hands on a daily basis and routinely take apart porsche ferrari, mercedes bmw, etc to install built in radar detection systems, so Im familiar with finesse, I just don't know much of anything about carburetors...

[Speeddog]

The vacuum petcocks seem to just eventually fail.
I've not seen any particular cause.

Your vertical cylinder is filled with some amount of fuel, so don't crank the motor.
Both horizontal and vertical heads will likely have some gasoline-contaminated fuel in the rocker/cam area.
The gasoline in those areas needs to be removed as well.

I don't think there will be any issues with it sitting until you get back.

[koko64]

Take the oil filter off too and let the case drain, take the plugs out and turn the motor over manually with a crank turning tool or putting it in gear and turning the wheel by hand. Put rags over the plug holes and under/around the bike. I once saw the fuel hit the wall hard when cranked with the starter. It's good to let it dry out if your shed is clean and warm. If you have compressed air blow it out. The front exhaust valve cover should be removed to free the oil there too.
If you are paranoid like me you can run a cheap oil and filter for a few minutes idle and replace it with the good stuff.

Replacing the tap instructions will come up via the search function,  but basically you fit an in line tap and blank off the manifold vacuum port. After all that I would run it with an over flow hose and see if the carbs were actually flooding, but they were probably ok. If they occasionally do flood (modern fuels can cause occasional flooding), it is so much easier to deal with when there is a manual tap. The overflow hose is an important safety feature and if your bike runs rough a quick glance down will show the fuel escaping harmlessly to the ground snd not your hot motor. Vacuum fuel  taps were meant to be a safety feature in themselves, but when they fail they bypass your carb overflow drainage system and pour raw fuel straight into the motor!

[ducriderinct]

So you think the carbs could be fine after all and the vacuum fuel thingy was just flooding the motor when off? If this is the case, what would cause the issues with excess fuel while running?

How do I remove the fuel from the front cylinder? Would running some cheap oil through the motor with a cheap filter for 3-5 mins then draining it out and replacing with good oil and a new filter?

It may be important or may not be, but I swapped over the carbs and the upgraded fuel pump from the doner bike as well as the fuel vacuum thingy. The doner bike has zero issues prior to being hit.

Both bikes have aftermarket exhaust but I have not swapped the forza cans from the doner bike. Could this be a possible cause of the issues?

[koko64]

Any future flooding after the tap swap will be carb floats not seating. Either from dirt in the fuel or from fuel additives designed to clean injectors congealing or waxing up the float valve! What helps injectors, clags carbs. Often, just turning the manual tap off for 10 seconds then back on can reseat the float valves.

The stock oem style pump is plenty strong. What pump you using? It needs to be a high flow but low pressure pump or you will get flooding from too strong a pump. It would be difficult to tell the cause of flooding without an overflow hose to separate the causes of flooding; one from unseated floats leaking out the hose overflow and the other from fuel poured straight down the manifold bypassing the carb from a faulty vacuum tap.

Just turn the motor over by hand sans plugs and leave the valve cover off to drain. You could take the valve covers off and blow with compressed air down any oil galleries. An oil flush with cheap oil wouldn't hurt but it depends how much things have evaporated off. It's best to do whatever gives you the most peace of mind so your head doesn't mess with you.

Pipes are fine.