I think the hole at the front in the recess is for allowing water out after washing/rain or maybe spilled fuel as I think it connects to the front of the tank where the rubber hoses connect near the key. Question is, what's the hole in my racing cap for???
Sorry - I was referring to the holes in the tank mount - you're referring to the hole in the new filler eh? I really don't know and would only be guessing I'm afraid, I originally assumed that hole faced forward.
Yeah sorry. I dunno. If the breather hole is free then block the little bastard hole up and see if the tank builds loads of pressure from the fuel, if it doesn't then I'd say you fixed it! Black the bastard up and test it. Ah ok thanks for the info re the front hole!
999 Facebook group says "It's a racetrack part. It has to vent air (like the stock one) but unlike the stock one it isn't emission compliant. So it vents liquid as well." So 1/2 full tank is required.
Hmmm a race part that is designed to leak fuel sounds like bollox to me mate, emissions compliant or not. What happens when you drop the bike, you get a fire risk. I dunno mate but it sounds like tosh.
I have the DP version on my 749, I will be home tomorrow and will take a few pics if you like. Looks similar to yours, but, never had fuel leaking from it, even when the tank is full.
FB update. "The hole is there for air/vent and designed for racing tanks with no vents built in so it can be blocked off" How does this sound? I trust you guys over FB.
Fair enough and it's easy for you to test it. Just do regular checks at first for any pressure by taking the cap off occasionally.
pressure will build in the tank, so if pressure IS building in the tank then you know the fuel is unable to vent. If, when you take the filler cap off, you hear the sound of escaping gas then there has been a pressure build up.
You'll create a vacuum in the tank which will restrict the fuel pump's ability to pump fuel and the engine will splutter and die. So nothing major . Andy
I don't know whether it's expansion (I always thought it was) or a vacuum - but either way you do hear a 'hiss' when the breather is blocked and you open the filler cap. Whether it's going in or coming out I dunno. On hot days if you open the filler cap you can visibly see the fumes venting out of the filler cap hole.
When stood on a hot day petrol fumes will expand causing a pressure build up, when the bike is running as fuel is used up it will create a vacuum. Steve
Right, i've had a delve. To me it looks like that hole needs to be there to stop the expanding pressure or vacuum. You can see the OEM is built way more complex and links up to a breather tube that runs through the inside of the tank to the left outlet at the front. So i'm not blocking the hole. So I either live with 70ml fuel range and 3/4 full tanks or go back to OEM.
