Hello all,
Odd problem happened on Saturday. Drove to the supermarket about 3miles from home, just after leaving the carpark on the way back I had got into 4th and was buzzing along at 40 when it started to die. No hesitation or coughing, just felt like an anchor had been attached. It wouldn't rev, and I changed to third and then second while it got slower and slower and then the revs picked up cleanly and accelerated away (luckily no other traffic around). Fuel should have been ok, but stopped and filled up (18litres) on the way home.

It's been fine since, which doesn't really help the fault finding. Any ideas please?

PS. It had a new fuel pump before salbris, new fuel pipe and filter (still looks clear), battery is charging ok. It's got a yellow coil and lumenition.

Possibly a sticking valve?

Did 18 litres fill it to the brim?

Well you could see the petrol in the filler neck

I think it may have been a blocked jet, but since it's been ok since am reluctant to go looking for trouble!

It had new valve stem seals etc earlier in the year when the heads were done.

Ambient temperature at the time?
High humidity and temperature slightly above freezing are ideal conditions for carburettor icing to occur, even more probable if the engine is on a light throttle.
The symptoms would include needing to open the throttle wider, but with less and less effect.

Other symptoms are; stop engine, open bonnet and have a look around, scratch head when all looks fine, shut bonnet, start engine and drive normally...

ken.

Could be Ken - didn't have the muff on. Had driven about 3miles at a constant 50mph, stopped it for 5mins then got back in to drive home. Temp was about 2ºC.

Mines been doing something similar even when the engine bay nice and toasty. Cleaned the jets with a good spray of carb cleaner and it goes away for 200miles or so.

ethanol i tells thee ,get some esso or bp super unleaded in tightwads its only a few pee more

Someone here is selling a good bike.....

and French.....

maybe try that ?

Mine has done the same, always been fuel related. trouble is, it's been a right pain and I've had to change a head, gone back to a standard carb, I've gone from 123 to points, changed plugs blah blah blah just because I've had no end of problems this last week. The muff will deffinatly help, maybe a couple caps of redex just to clear it out a bit?