VFR400 NC30 Running Problem

[BenBray]

So a while ago I had some running problems where when I got to anywhere from 5.5k revs to 8k revs, it would splutter and not fire properly and not rev much higher. I got some new plugs and this stopped.

Now I'm having the same problem and it's not plugs.

The weird thing is, it's not all of the time, and it can happen for 20 seconds, then I'll rev up again, and it'll be perfectly normal.

My exhaust is blowing but I cant see that making any problems like that surely? Air filter is a bit dirty but isnt anywhere near bad. Didnt have a chance to get any further cause I had work, and it was okay on the way to work today up until the last set of lights.

Any ideas?
____________________
Current Bike: nc30

[Danzio]

is the breather hose connected to your tank properly?

ie: is it connected to the top breather outlet (on top of the tank)

and to the bottom connector (bottom middle of the tank?)

check these first.

[Blue_SV650S]

Have you tried to take the speed restrictor out?

Does it rev up cleanly in neutral?
____________________
The purpose of life is to fight maturity.

[Danzio]

also, im assuming your not stupid but check the other fuel and vacuum pipes leading to and from the tank for kinks/perishing etc. if the vacuum pipe gets really worn and perishes it can collapse when its sucking hard (excuse the inuendo) in its attempt to release more fuel from the tank. and in such fails. causing the bike to splutter??

might only be in the early stages for yourself?

[BenBray]

Breather hose is fine.

Will try revving up in neutral when it's playing up.

Cheers for replies

EDIT: Bike has seen 140MPH on its clocks off public roads of course, sure the restrictor isnt in.
____________________
Current Bike: nc30