Petrol Tank Filler Cap

I desparately want to change the petrol tank filler cap from the ugly plastic thing to a nice shiny screw on, or something similar. Is the diameter of the petrol filler hole unusual in any way, or the way it’s constructed? I have a filler neck/funnel arrangement that fits the filler cap yet unless the rim of the filler hole is widened this neck won’t fit. As it is I expect to have to cut the excess metal away that is in a triangular shape away but it looks like even more will have to come off. Am i missing something? This is what i want to fit…only have the neck at the moment… Thanks.

I have a v50 tank without the filler cap assembly on. The opening is 47mm if that helps.

Thanks Grahame…is that off a Mk3? I shall take a photo of mine, which looks considerably different to yours…has yours already been modified?

I’m not sure what model it is from though it does have clearance for a MkII brake reservoir. I bought it as it is many years ago to put on a MkII I was building, it was going to be fitted with a twist off cap. I found a cheap ratty Monza to use as a runaround instead and work on the MkII stopped.

flip cap fitted to your type of tank (i think), fitted here

Yes that is what mine is like…took a couple of photos a few moments ago… I have seen that build on DTT…forgot about that. Not entirely sure how he reduced the width of the existing metal and still keep the holes for the hinge…any ideas?

Yes I can see how he did it, but hard to explain in words. They’re new holes - he’s cut along the straight edge closest to the filler on the right and the left leaving material in the middle roughly the same size as the new filler cap’s locating hinge, folded the resulting flaps, trimmed the ‘height’ of these flaps, and drilled new holes. You’re basically replicating what is already there further in each side. Its a good solution and it’s a classic Guzzi filler cap too. If I’ve got a spare moment this evening I will try and Photoshop some arrows onto your pic to try and explain…italianmotor2013-10-27 17:27:46

That would be really useful, thank you. I am new to bike rebuilding and any kind of fabricating work, so a dummies guide is appreciated.

Well I’ve just spent a half hour trying to P’shop a sort of diagram for you but I just can’t do anything that makes sense I’m afraid - but you need to look at this picture below that he posted and them compare it with yours, keep looking, and it WILL be come clear - all he has done is cut away some material from the middle of the existing ‘tang’ and then folded some of the metal that was already there over, trimmed to size and drilled new holes. You will need to have the filler cap with you first to measure it all out.

Can anyone else explain better? Otherwise if you find yourself not far from Thame/Aylesbury, bring your tank and I’ll show you!

italianmotor2013-10-28 10:10:37

I think I have got an idea of what he has done now along with your explanation. I guess if I get it wrong I shall just have to cut it all away and pop a filler neck in there with matching cap.

Thanks for taking the time and effort to clarify this for me.

Like I said it’s a good solution but one of those jobs that needs some careful measuring up, and removal of material little by little. Sure you can do it! Get a Dremel and some decent small needle files.

I have both! I am going to give it a go…what’s the worst that can happen :wink: