Carb overflowing with fuel

[ZodiacG66]

Hello, can someone please help :( this has been a major pain over the last few weeks.

One of the carbs is overflowing with fuel, looking at the carb from the front (float bowls) it's the right side card.
It's over flowing when off and when running.
1st thing I have done, put a jet kit on the crabs . . . . still overflowing on right carb
2nd Set float to 14mm on both floats . . . . still overflowing on right carb
3rd changed carb seals and the carb float needle and made sure float needle had a clean seating when closed . . . . still overflowing on right carb
4th swapped the whole float assembly from right to left and left to right to see if float assembly was faulty . . . . . still overflowing on right carb
5th swapped the diaphragm and needle from the rear of the carb incase some sort of problem there . . . . still overflowing on right carb
6th got rid of the petcock and used a fuel tap . . . . still overflowing on right carb (only when tap is open, when closed stops leaking)

Please any thing else it can be? any other way fuel can get into the carb that's not through the float valve?

very sad ducati owner as the weather has been bright and sunny for days here :(

[ZodiacG66]

**UPDATE**
7th only open fuel tap HALF way . . . STOPED overflowing on right carb ? ? ? ? ?

[Gilps]

Try reducing the float height. I think I set mine at 12mm as I had the same problem

[Kato]

There is only one thing that will cause this issue.....

The Float Needle is not sealing I'd bet money there is a piece of grit however small stopping the seal

[ZodiacG66]

I swapped the whole float assembly and it still overflows, it dose not follow the float it stays with the carb chamber

[DrD]

I swapped the whole float assembly and it still overflows, it dose not follow the float it stays with the carb chamber
If kato is right, the grit is in that chamber
- you need to blow the jets through with air

[Kato]

If you don't have access to a compressor these can's work quite well, can be directed into all the little holes along with carb cleaner, I've been in your position it can be so frustrating as you are so sure things are 100% clean, as a last resort you could get the carb's sonically cleaned

http://www.clp.co.uk/Product.asp?Prd=471613&utm_source=googlebase&utm_medium=directory&gclid=CN-FpMvP48MCFebKtAodalkA3Q


Carb Cleaning
http://www.projex-uk.co.uk/ultrasonic.html

Or for not a huge amount of money you can do it yourself, its possible to pick up a sonic jewellery cleaner for about £30, I'd recommend this one

http://www.amazon.co.uk/Colour-Direct-Digital-Professional-Ultrasonic/dp/B00E8K13WM/ref=sr_1_7?ie=UTF8&qid=1423992908&sr=8-7&keywords=ultrasonic+cleaner

[utopia]

So your original fuel tap was leaking too.
Which does perhaps increase the likelihood of there being muck in the system, which has taken out both the tap and the float valve ?
How clean is your fuel filter ?
The only other thing that springs to mind is that some float bowls (namely the ones on my old 1968 350 Yamaha) have an internal tube which connects to a drain hole in the bottom of the bowl and rises vertically above the normal fuel level. This seems to serve as some sort of drain in case the float valve sticks open.
In my case the tube became dislodged, allowing fuel to drain straight through the carb and out....onto the rear tyre !!!!!
Fortunately I noticed the squirming before closely inspecting the tarmac.
Tbh, I doubt if you have a similar problem, but hey-ho, its a mildly interesting story anyway.

I assume its possible to replace the float valve seat, if your cleaning attempts bear no fruit ?

Or, thinking back to old school carb problems, could the float be punctured and therefore not rising with the fuel level ?
Or binding on its pivot shaft perhaps ?

[Mr Gazza]

I was thinking along the lines of muck in the fuel lines too.

Grit could lie in a swag in just one line and feed cac into the needle seat, but it would have to be very consisent in doing so everytime the system was disturbed to swap bowls and so on.

Logic tells me that the only thing staying in the same place during the swaps are the fuel lines.

Having not played with a carburetor for many years I don't know if the connection to Monster carbs are via a push on spigot or a banjo. I feel that the individual lines and connections are the place to look.
Could be a dodgy seal on a banjo or a split in the line some way from the carb'.

Just done a bit of plumbing at home and was teased by a little weep on one of the joints. It was suprisingly difficult to find which of many joints was actually leaking....Petrol is far worse to trace as it's so searching and can drip a long way from the source of the leak.

It follows that if you turn the tap down a little, the leak stops, as the pressure in the line will be a bit less whilst still running easily into the carbs.

A groove in the hose where it pushes on a spigot will feed petrol down the outside quite nicely, as will a split banjo washer, or a scratch or score on any of the mating surfaces.

.....And Kato...Brilliant tip with the ultra sound cleaner..:thumbsup:

[gary tompkins]

I'm not sure if the offending carburettor feeds front or rear cylinder, but if it's the front one that may cause bigger problems. Severe flooding can allow petrol to run past the jets into the combustion chamber. This can result in a hydraulic lock if engine's turned over, or allow fuel to fill the sump destroying the bottom end. Hope you manage to sort the problem - not fixing it properly could wreck your engine. The NC30 Honda has four downdraught carbs very similar to the monster, which are very prone to this issue due to faulty fuel taps. Several owners engines have been completely trashed due to fuel flooding in the past

[ZodiacG66]

Hi guys, thanks for all the advice.
When I 1st bought the bike there was no fuel pump or petcock on the bike it just feed straight from the tank to the carb (via fuel filter and 3rd party cheap tap) the guy did say if you open the tap all the way you got some overflow and to just keep it at half open. I did think this was because of there not being a petcock and pump on it but it still dose it. the float bowl covers have a 2 inch (ish) long brass pipe with a hole at the top as an overflow so maybe loose, will have to check.
Will strip it down again next weekend and blow out the valves but they are brand new, I only put them in 2 weeks ago to see if it was them causing it. there is only one fuel line going to the carb and that feeds both (it splits on the carb like a T junction). only thing that's missing as far as I can see is there should be a small filter that goes into the carb connection before you put the 8mm fuel line on it, maybe that's the problem but then I would have thought it would fill up both bowls not just the right side one (it feeds the top cylinder not the front one)

[crust]

Been there, had this on FCR carbs on my monster.

On mine there was no overflow it just filled the engine, first I knew was when it wouldn't turn over.

Firstly, according to my 600 parts diagram your bike should have a fuel pump and between the pump and the carbs there is listed a filter.

I'd look at re-instating a pump to save the half on/half off fuel tap you have going on, what happens on a fast motorway blat, do you have to open it more?

Secondly, the needle should seal against the seat, stopping the fuel. You've replaced the needle, however in my case it was the seat. Ideally you should replace needles and seats as a pair. I'm not sure if the original seats are replaceable, Allens Performance will be able to tell you. If you can replace the seat then great. If not have a good look at the seat with a magnifying glass to see if you can see whats amiss.

I've reground seats when I was desperate using solvol on the end of a piece of dowel with a cloth over the end.

[bluestoesonnose]

Sounds to me (and as been already said) the needle isn't seating. Try a new needle and if you can seat. Or if you have the patience lapping one into the other (unless the needle is Niton tipped).

[Sirc]

have to go slowly on this one or I will confuse myself : - Apart from post #2 (sorry Kato) there is another scenario* that fits other than a needle jet that is being stubborn and briefly on this note - have experienced several where there is a crust on the seat that WILL NOT be removed with ether, acetone or carb cleaner and have needed to lap with T-cut or similar v. fine abrasive (used toothpaste once) and a suitably fashioned tool (I modified a plastic biro)) before the viton tipped needle will seat again properly. Question to O.P. - are you certain that cock half open completely stops the leak? If so, possibly no need to read on.

* you can rule this second scenario out as being a possibility by looking at the float bowl to see if there are ONE or TWO short drain tube stubs cast into the body. If it is two then read no further. Generally (but not exclusively) later floatbowls had one drain tube stub as Mikuni designers cleverly combined the two requirements for draining into one - i.e. too much fuel in the bowl and (in theory) the fuel will exit through this tube but additionally if you undo the drain screw the whole contents of the bowl will exit via this same tube, but here's the bit that can mystify :- because the drain screw seals with such a fine taper (in the wrong hands) it's very easy to overtighten this screw which will lead to cracking the seat that the taper bears on. This in turn will result in fuel leaking out of the single tube although the screw is done up tight (and despite the cracked seat there are no other symptoms - i.e. fuel will not leak via the visible thread where the drain screw enters) making the owner think that the carb is flooding. I hope this explanation makes sense despite being long-winded. I have typed this up on here before but thought I would struggle to find the thread.

[ZodiacG66]

Hi Sirc,
Float bowl is older type, pipe for overflow another for bleed screw, not both into one.
Have swapped the float needle seat from the right hand carb to the left and it will still overflow on the right hand side carb so the float is working because the overflow stays with the right side chamber and not follow the float.
Going to try and swap the float bowl covers next to see if there is some sort of fault with the overflow pipe being loose and leaking lower down around the base but am thinking more that the 1cm round hole where the float assembly fits has some sort of "crust" that is letting fuel pass around the side even when float needle is fully closed. . . will update :)

[Sirc]

I think above posts have detailed how to set float height (else I will post). You could crudely compare both tabs (st/steel needle valve actuator) to see if the bad one looks bent more in the direction that would mean more fuel but the adjustment is so subtle that the difference can't be seen unless it's been really overdone.


EDIT If this has been happening a while then check your engine oil - has level appeared to have risen recently/does it smell of petrol when you remove filler plug. Despite the carb overflow facility fuel often finds it's way to the crankcase via inlet ports/valves.

[ZodiacG66]

HALLELUJAH!
Overflow has been stopped :)
Was the hole in the carb the float assembly fits into, had some hard crusty stuff on the lower edge so the O ring seal was not making full contact :)

Have already dropped the oil and put new in and replaced filter, ready to ride :) met office says only 10% chance of rain tomorrow . . . . good enough for me :) RIDE TO WORK :)

Thanks for all the advice helped lots, best forum ever!

[Sirc]

Well done for persevering : )