I noticed something odd after I last filled up.
Some miles and a few days later, I started smelling a strong petrol odour when approaching my bike, but there was no obvious signs of any leak onto the ground. Then I noticed a strange residue around the petrol cap, which also turned out to smell strongly of petrol. Took the cap off and there was a whoosh of vacuum being released. At no point did the engine stop running.
This happened again a couple more times having ridden some miles. Engine running fine but a vacuum building up in the tank and strong smell of petrol when near the bike.
So I then put the cap back on turned through 180 degrees when fitting it - and the problem seems to be solved!
The cap does seem to have a right and wrong way round…?!
Just spotted this Jim. I don’t know if you’ve resolved the issue but here’s the answer. If you remove the cap and look carefully around the edge of the chrome bit you’ll see a very small hole. Insert a small drill bit whilst rotating it and it will come to a stop when it hits the centre gubbins of the cap. Withdraw the bit whilst still rotating it and then check that you can blow through the hole. It is the tank breather. Another tip is that the hole for draining water from around the filler is under the metal surround that the cap fits into. Do0 not push anything down this to clear it as it’s only an internal pipe to the bottom of the tank where there is an aluminium nipple. It’s this nipple that gets blocked. I suggest the you unscrew the nipple from the bottom of the tank and drill it out to a slightly larger hole. If this drain is blocked water can get into your tank and people blame the alcohol in modern fuels for this fault.