Well there’s been plenty of fuel getting through when the bike is ridden, so I wouldn’t imagine it’s an issue. That said, it remains a mystery so who knows?
The only reason I mentioned it is because on mine the lines are never full of fuel all the way down and you can clearly see the air (bubble) in them. This is more pronounced on the rear as the line is level but is still apparent on the front even though it is downhill all the way. And they stay like that during idle although I haven't leant over and looked at what they're like at speed mind... As I say I'm not sure if this would be worse if the lines went upwards for some of their route or how that could effect things.
That seems a bit odd to me. Have you tried opening the tank cap and flooding the carbs? Might be an air lock….
It may well be odd but there is no problem with it idling.... or fuelling at any speed. Tank cap open makes no difference.
I've just checked, because I wasn't entirely sure, but flooding the carb just moves the bubble of air down the tube and when you release the tickler it moves back. And from what I recall it has always done this in the 40 or so years I've owned the bike. I'm thinking (but not entirely sure it's correct) the air comes from the carb bowl itself when it's fuel level drops after it has been sitting. When next switching the fuel tap on & operating the tickler it will 'burp' back air into the fuel line as the bowl fills. But back to my original point, if the fuel line goes up & over summat in it's routing, this bubble may get caught in the loop.
I can't understand why the air doesn't just bleed back through the petcock.....is there a non-return valve in it?
Just in case anyone comes across this thread in a hundred years and wants to know the fix, it was faulty spark plugs causing the issues. Surprising but true, new plugs and the bike was fine. Nothing worse than a thread left hanging - all that reading and going off at tangents and still none the wiser....
