I don't know that they can be fixed, might be easiest to get hold of a good used one.

It is a one way valve, air into tank but stop fuel from coming out. So blowing into tank with cap off should be real easy and sucking back difficult.

Cammo wrote:I don't know that they can be fixed, might be easiest to get hold of a good used one.

Would this one from a NC24 fit?

http://www.ebay.co.uk/itm/HONDA-VFR400- ... 500wt_1287

Just took the breather off the tank and blew through it.

I'm guessing it should be like breathing normally? Because I had to blow quite hard through it.

This would probably also explain how it struggles to idle at lights after 10 mins of riding and why the temp shoots up about that time too (that is if I'm right in thinking engines run hotter when they're running lean?).

Yeah, there should be very little resistance. After running for a while, if you open the fuel cap, does it hiss as the pressure equalises? Might be worth taking the breather cap off, and blowing straight into the tank too, just to check that's nice and free flowing.

That cap looks about right, but there'll be someone else who can confirm. I'm sure Geoff33 had hundreds of nc30 ones, try giving him a shout.

Okay so I got myself a new tank breather, checked the air flow into the tank without the breather, all okay, fitted the breather, went for a ride to see if it's fixed, and no.

It's still fecking doing it. As soon as I get near 60mph it bogs down and behaves like a rocking horse.

Now I have a theory (correct it probably isn't), but the set of geoffs rads that I just fitted to the bike, the top one is straight not curved like the original, and I think is slightly taller when installed.

What I think is that this is interrupting the airflow into the airbox (especially seeing as I have no rubber flap fitted). To back this theory up, when I went over to my mums on a windy day (more turbulent obviously) it started doing it at 50mph not 60mph.

I have a rubber flap somewhere in the garage I bought a while ago and never got round to fitting it. Worth a try right?

Any other ideas would definitely be welcomed, as this has me stumped if the rubber flap doesn't work.

bikemonkey wrote:Okay so I got myself a new tank breather, checked the air flow into the tank without the breather, all okay, fitted the breather, went for a ride to see if it's fixed, and no.

It's still fecking doing it. As soon as I get near 60mph it bogs down and behaves like a rocking horse.

Now I have a theory (correct it probably isn't), but the set of geoffs rads that I just fitted to the bike, the top one is straight not curved like the original, and I think is slightly taller when installed.

What I think is that this is interrupting the airflow into the airbox (especially seeing as I have no rubber flap fitted). To back this theory up, when I went over to my mums on a windy day (more turbulent obviously) it started doing it at 50mph not 60mph.

I have a rubber flap somewhere in the garage I bought a while ago and never got round to fitting it. Worth a try right?

Any other ideas would definitely be welcomed, as this has me stumped if the rubber flap doesn't work.

Looking at your airbox setup is interesting. Sorry if it's been already covered but how is your vaccum hose?

Vacuum hose is fine, all in good condition, no kinks splits and it feels pretty solid.

One quick question though, the clutch switch, I have literally five minutes ago as I was putting the bike back in the garage, noticed that somethings wrong. I haven't taken it apart yet, but would this cause limp home mode too?

Your thoughts on the missing flap and new radiators are interesting. I can see two problems, hot radiator air and reduced entry area into the carbies. I suggest you first fit the flap or something similar that directs the air over your new higher radiator, this will stop the hot radiator air from reaching the carbies. See how it goes, hopefully some improvement. You will still have a smaller entry area because of the higher radiator profile and that will be more difficult to overcome.

Any thoughts on the clutch wiring I mentioned above though magg?