So today I fixed my carby, so happy to cure my long term running issues. To cut a very long story short it was the float needle all garnished up on the tip. Cleaned and its not pi$$ing fuel into the cylinders causing fouling of the plugs. Rear cylinder was the worst and its been puzzling me for ages, chasing jets, ignition and clearances. So there you go. Now to insure it again and enjoy the troublesome Biaaatch!!! I did clean the carbs but never thought to clean this needle. It was manky!
Ha! Well, I fitted new float assemblies as I didn't like the look of my float needles - and even one of the new ones caught me out. There was a tiny nick or imperfection in the assembly needle seat which the soft tipped needle had deformed into since storage by supplier or since manufacture - as soon as fuel went into the carbs, the needle turned a bit and didn't seat properly. Another new float assembly cured it.
Are you aware that by brimming the tank and putting it on a rear paddock stand, you could end up with a siphon as the fuel finally finds its way past the breather valve? It will also do it if you put the bike away with a hot engine and the tank brimmed on a hot day - as the pressure in the tank rises, it can pressurise the fuel system and start a siphon down the overflow tubes.
