Posted on the VFR facebook page the other day asking for help with an issue regarding my bike dropping cylinders on ride outs but when I pull over and let it idle on 1,2 or 3 cylinders it picks up to all 4 again. It starts and runs on all 4 but once I get up to speed it drops them one by one as if I'm running out of fuel. I was told it could be an air lock in the tank, I rerouted the breather, unscrewed it a bit as I was told too, bought a new vacuum pipe and clamps for either end and it still does this issue. It makes the bike hideous to ride because of this!

Im really losing it with this bike because I've done everything I can to it...serviced everything, carbs are spanking clean, jetted correctly, balanced perfectly, new plugs, new leads, new coils, oil change, oil filter, air filter the list goes on and on but it still refuses to play ball.

Any help?

Cheers

Plenty of fuel in the tank?

benny wrote:Plenty of fuel in the tank?

When I tried it today, there was more than enough, but I had the tap on res as from the looks I would have called it a reserve amount...but even the other NC's Ive owned never did this on res!

If you think its fuel starvation have you tried running it on a surrogate fuel supply which would eliminate a tap or rusty tank problem also worth checking the charging system is healthy as that can cause running issues with the ECU and give the symptoms you describe ?

Tank tap diaphragm fucked?

Something is restricting fuel flow enough at speed to make this happen, but not enough at idle, which is why the cylinders come back. I second the notion of the diaphragm or the tap. Also check the vacuum line to the tap.

viewtopic.php?f=22&t=26174

as the others have pointed out. Try fuel tap repair.

There is a one way valve in the tank vent cap. With the fuel tank filler cap open can you blow through the vent hose. Should not be able to suck.

Fuel tap on, suck on tap vacuum hose, fuel should flow easily.

Issue resolved. I forgot I even made this thread and some fellas on the VFR facebook paged helped me out. After overhauling literally everything on the bike, it turned out to be a bodged, clogged fuel line restricting fuel, starving the engine of fuel at high speed, then once ive gone back to idle the other cylinders fired up again to make all 4. So the bike is now 100%. Cheers for your comments anyway!

I'm glad we managed to help you on the facebook page