after about 20mins (warmed up) of riding bike seems starved of fuel only wants to idle or should i say slow tickover twisting the throtle does nothing, letting the throtle go cutting out totaly, but leave for 1/2hr bike fires up perfectly to get me home. answers on a postcard to 400greybike cheers ian ps the new loom works a treat solved me charging problem

i'd go for knackered plug/lead first i think, if it was the coil the you'd lose two cylinders and not sure it would idle then. But may well be wrong! It has def. been known!

Have you checked the filler cap vent as if this is blocked it will slowly starve the carbs of fuel, also check if you have a blocked fuel filter as it will restrict flow to the carbs then refill them slowly when you have stopped I've had this before due to a rusty tank.

the fuel filter was changed not so many miles back clean as a whistle will check breather hole in the morning keep them coming while i was waiting for the magic 30 mins to pass i did take the petrol pipe off the tap and i was getting plenty of fuel through it so am thinking maybe not the breather

The brether is in the bottom of the tank.

It could be the fuel filter in the tank on top of the fuel tap and there's another one where the fuel pipe joins the carbs.

Blocked idle jets ????
Do the revs rise before it stalls - that would be fuel starvation.

It might be the coils, but they do get warm under use.

no theres was no increase in revs it was a instant loss of power from 50mph to brrrrrrrrrrr then me pushing it to some farm driveway realising i'd only gone and forgot my phone might be the coils is good enough for me seen a set 35 bullets

You wouldn't have noticed a rise in revs if you were riding the bike, but if it was on the stand then the revs would rise.
I can't say it's the coils, they'd need to have the resistance measured to gat an idea or not.

will take the coils off tomorrow and test them, what should i be reading on the meter for good or bad coils ? if they are bad a guys selling a new set for a 87 1wg he never fitted will they fit the 88 3en1?

I'm pretty sure they will fit.