It seems you have it sorted out, but thought I'd toss this in just for fun.

The carb was never designed for much pressure on the float valve. If you put too much pressure on it it'll blow it open and flood the carb. Those inline regulators do work, but only when there's flow, in my experience. When the bike is stopped and there's pressure on the high side, it can trickle fuel through and still flood the carb if it doesn't seat properly, like a bit of the crud you're trying to filter out getting in the valve. You're also dependent on, lets face it, a cheaply made aftermarket will-fit accessory.

You just need to increase the flow rate at gravity pressure for that height. I would have suggested a larger filter or multiple small ones in parallel, but you've done that. You also could use a screen rather than a filter- so long as it's equal to the filtration of the carburetor's screen you're set.

Good to know that for future reference Donald. Cheers :thumbup1:

You're right ! I did sort the problem.

I bought a much larger capacity transparent filter and looped the fuel pipe so there as little frictional resistance as possible (no kinks, sharp bends, vertical rises etc).

It immediately sorted out the problem. I can leave the bike for weeks now and it still fires up with no issue. I'm so glad it wasnt the carb and just something as simple as a restrictive filter and a poor angle.

What through me is that the bike would run fine once it was going and 95% of the time time it would run at full throttle with no issue.

Gremlins eh !! :D