Dripping petrol

[Bic_Bicknell]

I recently fitted new jets and needles to my H2c. it's run well for the last few hundred miles, no issues at all.

Now suddenly it is leaking petrol and pooling under the carbs. Only noticed it this morning when I stopped riding and seems to be dripping from the left hand carb bowl. I had just turned the tap onto reserve a few miles earlier. It stops if I turn the tap into off position. Can't quite tell yet but it seems to be OK when running, just dripping when the engine is stopped.

My question is whether the problem is more likely to be in the carb like a stuck float valve or something or could the problem be at petrol tap?

Thanks

[Wolfie]

a stuck float valve or something

[Malcolm]

It is as Wolfie says most likely a sticky or failing float, give the float bowl a tap with the handle of a screwdriver and it often releases.
An H2 doesn't have an off position on the fuel tap as it is vacuum operated. Up is Prime, horizontal is reserve and down is on. Unless you have some sort of aftermarket tap.

[Barrie]

As stated the tap should be a vacuum tap as standard,
It is probably one of two things , ether a brass pipe in the bottom of the bowl has split, or more commonly the float needle assembly has a bit of dirt in it,, or has worn out,
in any case remove the offending bowl, check the tube,
remove, clean and reassemble the float needle,check the float height,
put the bowl back on and test,
if you still have a leak replace the float needle and seat

[Doctorpayday]

All of the above and is it left on the side stand?

Doc

[Barrie]

All of the above and is it left on the side stand?

Doc

both my machines are fuel tight on their side stands , and my h1 does not have a standard fuel tap!

[Hal]

As it is dripping with the motor not running it also sounds like the vacuum petrol tap isn't shutting off properly as well as a secondary problem - assuming you are not leaving it in the "Prime" position that is. There is no "Off" position on the standard tap as it relies on the vacuum to do this. It has just "Normal" and "Reserve" plus "Prime" which makes it on all the time by bypassing the vacuum operated part.

Tap recon kits are available from Z Power but not particularly cheap. I think it is normally only the little O-ring that needs to be replaced to cure it rather than the large pentagonal diaphram as well. This big diaphram is not shared with other makes or models as far as I am aware, but the little O-ring should be robbable from other kits that are cheaper and easier to find.

[Triple Parts]

Give the float a shake to see if there is any fuel in it.

[Olde Coney]

As it is dripping with the motor not running it also sounds like the vacuum petrol tap isn't shutting off properly as well as a secondary problem - assuming you are not leaving it in the "Prime" position that is. There is no "Off" position on the standard tap as it relies on the vacuum to do this. It has just "Normal" and "Reserve" plus "Prime" which makes it on all the time by bypassing the vacuum operated part.

Tap recon kits are available from Z Power but not particularly cheap. I think it is normally only the little O-ring that needs to be replaced to cure it rather than the large pentagonal diaphram as well. This big diaphram is not shared with other makes or models as far as I am aware, but the little O-ring should be robbable from other kits that are cheaper and easier to find.

+1

[Bic_Bicknell]

Well, thanks everyone.

I'm not at home for the last few days but reading the comments on holiday I already know what the problem is then. I didn't realise that the tap positions were as stated. I thought down was on and reserve was up so on the few times I've run onto reserve I have obviously been actually running in the prime position.

Funny, because I only just got hold of an owners manual at Stafford and haven't got time to read through it yet. Whether I'd have noticed this detail I'll never know. I'm sure all my old '70s Japanese bike taps were all down for on and up for reserve so it's an old habit that I wouldn't have thought about questioning.

Another classic newbie error I guess.

Thanks again.

[stevie747]

They shouldn't leak even if you leave it on prime - the float valves should cut off the feed. If float height/valves are good - check for wear/cack on the pointy bit - you could have a split overflow pipe as Barrie mentioned - the brass tube that sits in the carb bowl. This happened to me and I didn't discover it until I'd tried everything else. The tube had a microscopic split running down it - hard to see with the naked eye - which allowed fuel to bascially leak into it and out of the bottom.

To test just take the bowl off and pour some petrol in it and leave for a while to see if the level drops. I fixed mine (happened to two carbs now) by buying some thin brass tube from a model supplier and araldited it in - they are a push fit it you can get the exact original tube size, if it is that make sure you get the length the same as stock or you'll be giving yourself all sorts of new problems

Presumably you've checked that the float still floats

[Barrie]

to get the pipes out of the bowl just heat the bowl gently with a gas flame as they are a tight interference fit,
When I refit the pipes I use a smear of bearing fit
Note put a piece of leather around the pipe when using pliers on the pipe , to help them grip the tube

[El Presidente]

All good info (with Hal leading the advice line) - If fuel is coming from the side overflow then you have a punctured float, if it is coming via the base of the float bowl then the issue is with the float height or more likely dirt in the valve, and as Hal correctly points out, neither should leak if the tap is working correctly and the motor is not running.

[gsxrtriple]

I to have been having carbs dripping but cured now tried most ideas but what I have found that set your vernier to within spec 24mm to 25mm I then gently push down on float till needle seats adjust float to suit measurements no more leaking my float levels are just out of spec at 5 mm from gasket face

[SERPICO]

Got the same problem on my H1D fitted with an aftermarket tap with an off position. If you leave the tap on and the bike on the sidestand it leaks from the left hand carb. Tap on and on the centre stand no problem. Runs fine.

[mraxl]

Here is something to consider....
Float valves should stop fuel flow in carbs even if no petcock exists.
If carbs leak, most likely either float valve is not seating properly or floats are leaking. Either way, it also means float/fuel level is not correct. Stopping fuel flow at petcock may stop leaking carbs but float/fuel level in bowl will still not be right.

[Tilly H2C]

I agree but I guess you are really into how badly the float valves are leaking, If they were only leaking say a teaspoon of fuel per day it would hardly affect the running fuel level height, but over the winter would empty the fuel tank into the engine.

Even with a brand new genuine set of float valves mine has 'over flowed' a carb a couple of times on different carbs over last seasons use.

I have two fuel taps, one that the 'O' ring seat/fuel cut off was beyond servicing and another that is perfect,

I modded the u/s one to give off/on/reserve (dead simple mod) and I just cant come to trusting the 'perfect' vacuum version, maybe if I was 18 again and this was a daily user and it didn't sit for 5 months doing nothing I would think differently.

The end result of either the fuel tap plus carbs and the oil system one way valves passing doesnt bear thinking about.