Fuelling fixed - "This time I know its for real"

So I took the float bowls off to check the float heights. The first thing I noticed was the amount of sludge in there. This was despite having completely cleaned them out 18 months ago and running the bike with two additional filters!

A good dose of carb cleaner soon shifted the goo but still ... I'm hoping that it was just a very fine rust from the tank and that my efforts to seal the tank will mean the end of it.

The floats were about 1mm too low, at 13.5mm compared with the spec in the Haynes manual. That might explain why the bike was hesitating just off idle and the amount of fuel evident when I pulled the carbs out. The floats are measured with the carbs inverted so they are bearing down on the valve that admits fuel to the float bowls. Low floats mean high fuel - can be confusing. So I set them all to 14.5mm.

I remember having trouble setting them when I rebuilt the carbs last. I had removed the plastic cages that hold the floats and remember that it was difficult to re-seat them afterwards. They push into an O-ring, which was springing back. No such trouble this time.

I did two other things to lean off the mixture as well. This is silly from a scientific perspective: any change could be due to any one or a combination of any two changes. But I thought, "while I'm in there, I might as well", as you do ;-). These were:

• to reset the pilot jet screws which control slow running. Haynes says they should be two turns out from fully seated. As it was, they were between 2.5 and 2.75 turns out. So I set them all to 2 turns out.
• to lower the jet needles. They were on the standard setting, which is position three of five. I set them all to position two. This really wasn't necessary but I wanted to see what effect it would have on the middle rev range and progression off idle.

I was pleased to see that the carb diaphragms were all in great condition - clean and supple.

I put new fuel pipes in (again!) with new t-pieces but no filters this time. I also fitted a new thick-walled vacuum pipe between carb 3 and the fuel tap. The routing of these pipes to the carbs is now clean, with no horrible bends - and a shorter journey!

She started up when the float bowls were full - and idled really rough. Not what I wanted to hear. The carb balance was way out after these changes. I suspect resetting the pilot screws was the main reason. After balancing them up with my old Morgan vacuum gauges, nice and even. I managed to get a tick over at an indicated 500rpm. Sweet.

I've done about 100 miles since and there is no sign of fuel starvation. I'm guessing the big change was the new vacuum pipe for the fuel tap. Better still, that hesitation off idle is no longer there. Result. I think the mixture is probably a bit lean in the midrange but nothing drastic. I'll run the bike like this for a few hundred miles than may put the jet needles back to position 3 again. That's easy to do with the carbs in place.

The sun is out. It's time to ride.