Weird running 1979 R65

[Barry]

If I'd had a spare bowl I would have done it by now.  

Wirespokes did it I think by driving the overflow tube out the bottom of the bowl a short distance so he could attach a thin flexible tube..

In the absence of a spare bowl I've thought about drilling and tapping the bottom of the bowls to fit a short nipple but the metal is not very thick so I'm not sure how well it would work.

[nhmaf]

I don't know - I think those bowls are made out of some largely Zinc alloy - easy enough to drill but prone to thread stripping unless you've got a thick section to tap

[Barry]

- I think those bowls are made out of some largely Zinc alloy - easy enough to drill but prone to thread stripping unless you've got a thick section to tap  

That's the reason I haven't done it yet, that and not wishing to modify original bowls.  I need to find a spare bowl.

[georgesgiralt]

I've played with my extra bowl.
It was decommissioned because a drop of water had seized hard the choke jet and on removing it the threads where destroyed.
I first planned to extract the overflow tube and put a plastic tube on it. Bad idea. The tube broke and I was obliged to smash it hard in order to plug the leak it has caused.
As I had found a very small nipple I though I could use it and I only had to drill, thread and voila !
But this is not so easy. The bowl walls are thin and in the center the hole for the main jet make this worse.
Fortunately, there are a couple of leftover from pouring the hot metal which are more suitable for threading.
Done. The nipple is on. Now, remove the plug on the "wrong" hole (opposite the choke jet) in order to put the bowl on left or right carb..
Last but not least, and I'm stuck here, how would I hold the plastic tubing in order to compare properly the  level on the carb bowl ?
Any idea ?

[Barry]

Last but not least, and I'm stuck here, how would I hold the plastic tubing in order to compare properly thelevel on the carb bowl ?
Any idea ?  

Given the carbs are inclined forward the level check needs to be made in the same place for both carbs.   I would position the tube at the side of the bowl in the centre aligned with the main jet.  I expect the fuel level will be only a few mm below the top of the bowl.

[georgesgiralt]

So I've to devise two ways of fixing the tube as the bolw has to be reversed for each carb....
Maybe this night will bring an idea ?

[skippyc]

Weak idle mixture and leaky exhaust flange did it for my B50.

[georgesgiralt]

Hello !
I had an idea ! I made a spring with some iron chicken wire, on a 5 mm mandrel (an M5 screw...) which I "threaded" onto the plastic tube. The end of this spring serves to attach the tube to the bowl retaining clip on the carb.
The measuring is that the level stops at the carbs jointing end between the bowl and the body. On both sides.
I bet this is the reason the mixture tube protrudes from the body in the gas passage chamber otherwise the gas will flow into it...
Measuring the level on the bowl after removing it gives me 21 mm measured from the bottom of the center dip  (but not from the bottom of it, my measuring device s too large to go that dip).

[Barry]

The measuring is that the level stops at the carbs jointing end between the bowl and the body. On both sides.  

So due to the floats and a substantial part of the casting causing displacement the operational fuel level is right at the top of the bowl.

To be honest I thought the level would be up to the top of the bowl at the front edge due to the downwards inclination of the carbs.  If it's up to the top of the bowl in the middle then it would overflow at the front and might be flooding the pilot circuit.  My test has been that if the idle mixture screw is removed and fuel drips out the pilot circuit is flooded and the level is too high.

Not quite sure what to make of your 21mm measurement.  How about measuring the fuel level down from the top of the bowl and subtracting that from the overall bowl depth which I make to be 33.65mm.

[georgesgiralt]

I never said my fuel level was perfect  
I gave you the measure I've got this afternoon. As the bike runs very well but has a not so good mileage I suspect there is something to tweak on the carbs...