After my first ever day out trail riding I was coming back along the main road and the bike all of a sudden lost power like it does when you run out of fuel. It then picked up and then did it again, so I switched the bike to reserve thinking I was running out of fuel. However this continued until I stopped at traffic lights and the bike completely cut out.
The bike would then start and run on tick over with no problems at all, but as soon as you open the throttle any amount the bike cuts out. I did get the bike home the last mile by pulling out the choke and keeping the revs up as it will run with the choke open.
Any help for an incompetent mechanic would be very helpful. The bike is a 1998 Open Enduro.
Nige, it sounds like there's a vacuum being created in the tank, possibly a cap vent blockage.
Usually, as the petrol level goes down air is usually admitted in compensation through a one-way valve in the filler cap.
If this valve gets clogged/blocked then no air can enter the tank to take up the space left by the diminishing petrol - thereby creating a vacuum.
To test this, take the bike for a little run and if it stops then release the petrol cap to let air in. If you hear a hiss then eureka - that's the problem.
If that doesn't work then it may be a case of a carburettor strip and clean or maybe fuel line inspection time.
Just a quick update for you. The problem turned out to be a broken needle, yep broken, and a tank which was full of rust and gunk. The tank has now been cleaned out and the needle is on order, so hopefully it will be back up and running soon!
could be wrong but start there and see
