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Lost my filler cap
blakep82 - 25/6/21 at 05:20 PM

I lost my fuel filler cap... Stupidly left it sitting on the top of the fuel tank as I rushed to get out to a track day...

It's an old SM Engineering tank. I contacted SM Engineering, the cap and filler neck came from a supplier who is no longer in business, and of an unknown thread, but he knows the current ones aren't the same

I've measured, the major diameter of the neck is 50.8mm (2”) and the thread pitch is 2mm, or 12.7tpi. it appears to be a mix of imperial and metric.

I can't find a matching thread spec. Can anyone think what it might be? Or where I can find (or if anyone here can make me) a new cap?

Thanks!

[Edited on 25/6/21 by blakep82]


SteveWalker - 25/6/21 at 11:47 PM

How accurate is the measurement? There are 12 and 13 TPI imperial threads.


BenB - 26/6/21 at 08:09 AM

True. An imperial pitch thread gauge set might be helpful- fairly cheap. Or just get a 13tpi bolt and see if the threads accurately interlock?


PAULD - 26/6/21 at 01:41 PM

I take it the filler neck is an integral part of the tank. Making a cap from your information would be a bit hit or miss. Can you post a sketch of what you want and I will see what i can do.


adithorp - 26/6/21 at 02:38 PM

When you get one it's probably worth considering fitting a tether. Having one has saved mine from going missing a few times.


rf900rush - 26/6/21 at 02:55 PM

Just googled 2" aluminium petrol cap
and found a few

like
https://www.premiermotorsportdevelopments.co. uk/aluminium-fuel-filler-neck-and-cap---2-id-820-p.asp


Benzine - 26/6/21 at 04:00 PM

Cling film + elastic band


gremlin1234 - 26/6/21 at 04:58 PM

quote:
Originally posted by adithorp
When you get one it's probably worth considering fitting a tether. Having one has saved mine from going missing a few times.
yea, and is now required for the IVA test


blakep82 - 26/6/21 at 07:18 PM

Thanks for the replies, so to respond in order

Yes there are 12 and 13 tpi threads. It's neither. It's 2mm, which is 12.7

I've got metric and imperial pitch gauges, it matches the 2mm pitch, and doesn't fit 12 or 13 tpi,

Yeah, the filler is welded straight on to the tank, so a friend of mine has informed me of an engineering shop he's used a few times. Bit of a drive from me. But hoping I can take the tank to him and he might be able to make a few up for me

I always meant to find a way to tether it, but couldn't think of a good way, I guess a hole through the top with a bolt and some copper or fibre washers would have done the job. Definitely happening for its replacement!

Believe me, I've googled. Problem is, imperial diameters tend to have imperial pitches, this is a 2mm pitch, not 12 or 13tpi, as confirmed with pitch gauges. That one is unlikely to be 2mm pitch

I had to do a track day with a rag and cable ties, once I'd realised it was missing as I checked fuel levels later in the day

It's not iva'd as just a track day car for now, so hadn't have it a huge amount of thought. Enough to know it needed done, but not enough to do it. I would like to iva it, so definitely getting tethered when I get a replacement or new neck fitted, if it needs to go that way.


Hopefully my mates suggestion can make one. Will try and see him at the end of the week

[Edited on 26/6/21 by blakep82]


adithorp - 26/6/21 at 07:47 PM

If you're having one machined, you could have a boss for a fixing chain to incorporated either inside or on top.


SteveWalker - 26/6/21 at 11:41 PM

quote:
Originally posted by gremlin1234
quote:
Originally posted by adithorp
When you get one it's probably worth considering fitting a tether. Having one has saved mine from going missing a few times.
yea, and is now required for the IVA test


Only for non-lockable caps or lockable ones where the key can be removed without the cap being in place.