As i understand it, the fuel sender sends a signal to the rev counter when the fuel goes below a certain level to let you know your getting low and you can then hit the reserve switch, which apparently messes with the ignition and cuts the spark to a couple of pots (get me to a garage mode)

If this is correct then mine aint working properly, i over did it yesturday before filling up, ended up farting and poping about 7km from the nearest garage, i made it just, and after filling up it ran much better but only on 3 cylinders, until the revs picked up then it was fine, so slow running jet in no3 carb was blocked, cleaned the carbs this morning and it's all good, but that doesn't help me next time

so does anyone know how to test the fuel sender, I've gone cross-eyed looking at pdf's, i know i've seen it but can't find it now, anyone know where to find it or just how to test it

cheers steve

Isn't it the fuel level sensor in the tank ??

It sounds like it's working but just detects the low fuel a bit ... well low. You should be able to take it (and the fuel pump) out of the tank and clean it up. While you at it take the fuel tap out and clean the filter on it. There's another filter where the fuel hose joins the carbs (iit's in the brown bit on the carbs). Clean the tank and change the fuel filter.

yeah it is (that's what i meant by fuel sender) but i hadn't switched the reserve on at that point, so it shouldn't have been missing, i think that was just due to crap being sucked into the carbs, i did try the reserve switch later as i nursed it up the road, but it made no difference, which is why i think the fuel sender/fuel level sensor is knackered, but i can't find the info on how to test it

as i said i've cleaned the carbs and fuel filter but i didn't know there was a filter in the fuel pipe (brown bit ) so i'll give that a clean as well, but i need to test the fuel sender/fuel level sensor to figure out what's not happening that should or this is going to happen again

I'd start by checking the reserve switch - it sounds like that's what went wrong.

I've tested the reserve switch and that seems to be ok,

so i've had a think about (and a look at) the fuel sender, as far as i can tell, it's just a switch which is operated by the amount of fuel in the tank,
ie the small cylinder at the top of the fuel sender is hollow and fills with fuel, as the fuel is used up the cylinder empties out tripping the switch,

so by testing the terminals in the fuel sender terminal block (where it connects to the loom) with a continuity tester i should have no continuity with the sender immersed in fuel, and continuity when the fuel sender is empty (assuming it's a normally open circuit, normally closed would be the other way round)

as i have continuity whether full or empty i reckon the fuel sender is unwell

any bright sparks feel free to pour scorn on my reasoning, if it's way off