I'm riding a VFR400 NC30 and over the past year it has developed a problem.

Whilst riding, the bike loses power and I have to keep the revs really high just to keep it going. Ultimately I have to stop and then the engine dies and it won't start again (the battery and starter motor work, but the engine doesn't fire). This has been 'fixed' by a local mechanic, but after about 3 months of riding the same problem happens again.

Does anyone know what could cause this?

its got to be one of two things..........

electrical or fueling.

when it dies is there any misfiring or is it just as if the bike is running out of fuel?????

any backfiring at all?how does the bike start first time in the morning with choke,without choke etc????

next time it happens put the choke on and see what happens.

you may need to check all electrical connections,at the coils,leads and plugs.see if there is a good spark at each one.also check condition of the plugs.

you may also need to strip the carbs down and inspect them,check float height as this may be needing adjusted.




wull

Thanks for the reply

There's no mis-firing, it's just as if it's running out of fuel.

Now it won't start, period. Prior to this, it starts fine and runs fine. This problem happens about every 3 or 4 months. Could it be a build up of rust/crap in the fuel tank?

Check the vacuum hose that runs from No3 cylinder to the fuel tap. It perishes over time and eventually collapses and the fuel tap shuts with the subsequent loss of vacuum to it.
Simple to check and fix. Get some 3mm vacuum tube from halfords and replace it as a matter of course.

Check ur idle screw. Increase(Turning clockwise) it and try starting it then.

Good Luck

i suggest to take a look on air filter.