Forum

[Beezabryan]

Does the engine run, has it been ridden?
If so how does it run?

[mart]

did you reset the float level when you fitted the new needle? it might be slightly different to the old one.
have you checked the float bowl gasket?
to test the float valve: hold the carb upside down with the float bowl removed. gently blow through the fuel pipe and see if the valve lets any air through. if it does apply gentle pressure to the float with your finger and see if you can stop the airflow. alternatively: carb detatched from the bike, with the float bowl removed and petrol hose connected to the tap. hold the carb upright and hold the float up with your finger. turn the petrol on and see if your finger pressure prevents fuel flow. you'll need a bucket of course and a full risk assessment!
drain some fuel into a clear jar and see if there is any crap in the fuel.

[Mark B]

At the risk of stating the obvious, are all the gaskets/seals in good condition and seated properly?

[daveh]

PROBLEM SOLVED
The brass floats had a leak inside, so fuel was getting inside, meaning they no longer floated properly.

I had previously checked this by dipping it in warm water and looking for bubbles. There were no bubbles.

This time I checked shaking it, and I thought I heard a subtle sloshing sound. So I sawed the offending float in half, and lots of fuel came out.

Moral of the story: dipping brass floats in water is not a got method to check for leaks.

Thanks to all those who suggested solutions.

[Wheaters]

Dave, The usual method of checking for leaks in a brass float is to put it in a saucepan of very hot water, just off the boil. This causes the fuel inside to evaporate and bubble out. The float can often be salvaged by boiling all the fuel out (obviously not over a gas burner!) and then soldering over the leak. Done this a few times over the years on various bikes. Anyway, good to hear you've fixed the problem. I presently have a similar issue with one or two of the four carbs on my Honda CB750 Nighthawk - the floats aren't leaking - but they are made of plastic anyway so replacement is the only way to fix a leaking one of those.

[John L]

daveh - Good to hear you have it sorted. These things usually have a very simple cause - but that doesn't necessarily make it obvious at the time.......

[daveh]

AHH! Problem not sorted. I having left the bike parked overnight with the fuel tap on, it is now dripping fuel again.


Just to recap - I've already replaced the fuel hose, fuel bowl gasket, float valve assembly, floats, and checked float height. I've checked the float valve with the bowl removed and fuel hose connected - it seems to work very well with light finger pressure on the float enough to stop the flow of fuel. The bike itself is running very well.


I'm now going to check that the fuel is clean. After that I don't know what else to do. Your ideas are welcome.

[Aethelric]

I saw this post on another (BMW) forum about a dripping Bing carb. It seems appropriate.



I once sent a fairly intemperate letter to Bing on this very topic (yes it was that long ago in the time before emails). They replied "We do not make petcocks, we make carburettors. When you leave your bike, turn the petcocks off."

[Beezabryan]

I'm with Aethelric
Leave now well alone, go for a ride, clear the head and as you approach home reach down to the petrol tap and turn it OFF.
Happiness

[John L]

daveh - Oh dear....sorry to hear the problem persists. I didn't mention it at the time, but I had a similar problem on my 500ES Bullet (sold 4 years ago). The Mikcarb began to leak when the bike was left standing for a few days - but this only manifested itself when the fuel was turned OFF - made NO sense whatsoever. After checking out the cause of the leak I eventually replaced the float needle and seat and checked float level, etc. after which the leak ceased. I then experimented with the the fuel tap (which itself must have been leaking - how else could the carb. leak with the tap turned off?) and tried leaving the fuel pipe disconnected from the carb. (but pointing into a container for safety) after parking the bike up. I was unable to get the tap to leak. My bike also started and ran perfectly OK. Only observation I would make re your problem is that it is generally considered bad practice to leave this type of machine parked up for anything more than a few minutes without turning the fuel OFF. You could give this a try, as well as turning the fuel OFF before you park up, leaving the engine to run until it stopped with an empty float chamber. If it's dirt in the fuel it'll probably drive you nuts.........DAMHIK