help...leaking overflow...again

[whiteylfc]

has anyone got any tips to stop the flaming nuisance of the carb overflows leaking on my CB750 F2 Honda Britain...If I havnt used it for a while,one of the 4 carbs will start free flowing petrol out of it,usually necessitating a carbs off fiddle around and half a day wasted.The carbs had been professionally rebuilt with new seals,floats,etc,so shouldn't need anything new.Any tips for cleaning out the carbs without taking them off??   John

[steff750]

  I feel your pain been there done that wasted half my life tinkering with carbs they need to be used,I just ride mine with the fuel tap off and turn it on when I have rode a few hundred yards they settle down after a while. you can try leaving the bike on the main stand if you park it up for any length of time and leave the petrol on as long as possible before stopping engine at least the bowls will be full and the floats all be up ,I suspect you have a float bowl sticking down they have a tendency to stick if left on side stand for too long, when you start the bike hopefully you will still have enough fuel to start the bike and warm it up then turn on the petrol after about a minute if you are not to worried about petrol spilling on the road then ride the bike with the petrol tap turned off and when the big starts to die of fuel starvation turn on the tap and hope the floats do their job

[UK Pete]

I would make sure you have a good inline fuel filter in place , and check the float height it might just be that your carb guy set them a bit out, i have a proceedure where i shut off the petrol tap at the end of my road so i then use up some of the fuel in the bowls as i ride on this has stopped all sorts of garage smelling of fuel problems on some of my bikes
pete

[whiteylfc]

thanks for the tips guys.the bike had a new inline filter which hasn't cured the problem when I've left the bike for a few weeks.i have been leaving it on the sidestand in the garage and I can see how this could cause a problem.i'll give the other tips a go as well before I get the bloody spanners out again......john

[Bryanj]

You need an old wooden handled screwdriver to whack the float bowls with---wooden end that is

[whiteylfc]

i'd considered that......infact I've looked at using a lump hammer on a few occasions!!!!!

[Waggles]

I think, as has already been said, that regular useage is key. Modern fuels evaporate more quickly and leave sticky residues that you can't see. Regular 'washing' with fresh fuel ( ie regular use ) helps a lot. When I first got my F1 on the road being a 'Born again biker' of, er, mature status I took things carefully, used it only a little when it was dry (ish) and experienced similar problems and smells of petrol in the garage. Now I use her daily all seems cured.

Can't help wondering whether teflon coated needles / seats would help for those who can't use daily? no idea if such things are available or possible but maybe a different type of float needle would be an idea? I have seen some with metal tips and others with rubber like tips over the years, are there others?

[whiteylfc]

thanks mate...unfortunately its in showroom condition(or was!!!)so it doesn't get used as regularly as it should.i listened to some of the advice above and kept it on the mainstand and it didn't overflow when I next fixed it up....result!!!!

[K2-K6]

You seem to be on the right track with parking it on the centre stand as if you turn the fuel off before you get home it should then leave all of the four float valves in an open postion and also dry of fuel  so that they operate normally when you next use it.

If you don't turn the fuel off before journey's end, then leave it to stand at tickover with the fuel tap off before switching off to lower the fuel level in the carbs.

Critical for the F2 carbs (as they have an accelerator pump fitted) is not to blip the motor as you switch it off (some people habitually do this) as it pumps neat fuel into the inlets that won't get burnt off during higher engine speeds, it'll also promote internal exhaust corrosion as well if left in there.

For bikes like this that have expensive/rare exhausts, the hotter and drier they are when switch off for storage the longer they will last.

[whiteylfc]

thanks mate....all good advice....

[matthewmosse]

On my 500 I always seemed to get away with a stong dosage of redex petrol cleaner for carb engines, added neat to the carbs after running the bike for a few minutes with the tap off. I had to deal with sticky carbs a fair few times, even with the bike as my only transport. a tap with a screwdriver handle sometimes sorted it but I found the redex was more reliable.

[daveh]

Check that the overflow tube in the float bowel is not leaking. I found one of mine had a pin hole in it not visible to the eye which was causing the leak from the overflow. New piece of brass tube cut to the appropiate length sorted the problem. But it took numerous carb strip downs before finding the cause.
Dave.

[Bitsa (Ralph Wright - RIP)]

Hi,
If it acts like mine starts with  the odd dribble here and there, look for it see anything no, scratch head and forget.Bit later over a period of time steady flow.Remove bowl then with a good magnifier see a tiny split in the overflow tube mounted in the bowl.Replace bowl problem gone.If you take the bowl off empty it of fuel put finger over the top of the tube blow into the bottom if split you will hear your breath,air escaping.Hope this helps you.
Cheers
Bitsa

[BigAl (Alan)]

Hi,

I have the same problem when the bike has been on the side stand for a while. Put the bike on the main stand and run with the fuel tap in the OFF position at tick-over, as the engine starts to fade switch the fuel back ON.
The full movement of the float hinge & fuel inlet normally shifts sticky crap.

Alan

[sonsman]

Top tip, had the same issue after leaving my F2 on the sidestand. Put it on the centrestand, fired her up with the tap off and when it started to die switched the tap on and hey presto - no leak. Brilliant!