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Thread Like Summary
Allan G
Total Likes: 4
Original Post (Thread Starter)
by Allan G
Allan G
So. I have a set of cases which has had the wrong oil pressure switch fitted. Despite ordering the correct switch I didn’t check the thread, and it was indeed a taper thread switch. I have since fitted the correct switch but the taper switch did damage the thread somewhat. The NPS switch screws in tightly but only if the crushable copper washer is omitted. I fear that this won’t be enough.

Annoyingly, you can get BSP and NPT timesert kits but there is nothing for NPS (not even a wire thread insert and I know a wire insert isn’t the right way to to seal a pressurised thread).

So I’m stuck for what to do.

The NPT timesert kits look to have an NPS outer thread, but it will still be a taper internal thread. But I could fit a taper switch with no worries of the thread being damaged further.

I could go the BSP timesert kit, but then I’m looking to what switch would fit.

Or I could get the 1/8 NPTF tap and see if I can clean up the thread so the taper switch fits best. (That would be the cheapest option)

I could suck-it-and-see. There’s a chance that there’s enough thread to hold it, I did apply some loctite 542 to the thread when fitting. It might never blow... or it could act like a 50psi cannon when it does.

Has anyone else had this?
Liked Replies
by DavidP
Originally Posted by Allan G
Would the NPTF switch want to seat all the way flush with the case like the NPS switch does or just until the switch is tight in the thread? Being NPTF it should be self sealing as I understand it (although I’d still feel more comfortable using a liquid thread sealing compound).

Still happy to hear other opinions on the matter.
For some reason straight pipe threads are rare in this country. For most applications it is quicker and easier to simply tighten the fittings without the need for sealant or tape.
Problems arise if one tries to screw the fitting too tight, it only needs to be tight enough to deform the threads enough to seal. I can't say why the new switches come with a washer, it is not needed. Seems to me that the washer only tempts people to overtighten the fitting to get the washer flush.
1 member likes this
by NickL
The switch should seal without any help if it's a taper fitting.
My opinion on this is that they should always have used a taper fitting
across the group. That way there wouldn't be so many damaged triumph
timing covers around and one switch could have served all the bikes.
(when you screw a taper switch into a triumph cover it breaks the casting.)
1 member likes this
by Stuart
Hi Allan,
Originally Posted by Allan G
1971 A65 which should use the NPSF thread.

the F stands for fuel(s) and the thread seals completely when tightened. Zccordi g to the service sheets the NPS type threads at least should be of the fuels type (aka dry seal) link showing comparison
Hmmm ... I would've said Triumph and BSA used just NPS thread? I understand the mechanics of "Dryseal" but, steel switch screwing into ally, "Dryseal" theory was never going to work in practice for any length of time.

Originally Posted by Allan G
noticed FEKED list the same switch against both Smith's part numbers for the NPSF and the NPTF
Ye-ea-ah ... Feked is scary-bad:-

. '74-on 60-3719 - Veglia? They were made by Smiths before '79, Veglia only made 'em after Smiths stopped. 24 tpi or 26 tpi? Originals were 27 tpi NPS ... shocked

. Apart from that, the Triumph 60-2133 number is just the standard trade confusion. The original Triumph equivalent of BSA 19-6504 was D1943 (60-1943). Used first on the triple engines, first built in June 1968. That is a taper-thread switch.

. Meriden then caused the monumental part numbers confusion by printing D2133 in the '69 twins' parts books but fitting some of their early '69 ones with taper-thread switches. When the Triumph triples changed to straight-thread switches is recorded as January 1969; Meriden issued a new parts book around the same time, with D2133 for the switch ... Meriden failed to record when they changed the twins from taper- to straight-thread but afaict before they started using the date-code-5-figure-number VIN format in October 1968.

. Educated guess says Rocket 3's changed from taper- to straight-thread switch (19-6504 to 19-6508) around the same time as the Tridents; however, is there any record of when the '69 BSA twins did?

Originally Posted by Allan G
Draganfly (where I got mine from) don't distinguish either way.
Draganfly is just confused (reflecting they're fairly recent Triumph and BSA dealers) - if you look at their entry for Triumph 60-2133, it's the same switch as BSA 19-6508 but the 60-2133 entry says it's taper-thread, that - as I say - is just the general trade confusion over the part numbers. facepalm If you want an NPS switch for your '71 A65, order 60-3719 from the confused trade ...

Originally Posted by Allan G
would imagine there is just as much meat on an A65 as there is surrounding the threads on a triumph casing.
Mmmm ... I'm only familiar with the switch position on a '70-on single; if the A65's similar, much more "meat" than a Triumph timing cover.

[Linked Image from]

... gives an idea of how little "meat" there is around a Triumph twin's OP switch hole ...


1 member likes this
by Stuart
Hi David,

Originally Posted by DavidP
I recently ordered a new switch from The Bonneville Shop. They listed both the early and late parts. I ordered 60-2133.
What I got was LF Harris, and has a straight thread and an O ring in place of the usual copper washer.
Intriguing ... 60-2133 is the earlier of the two numbers the trade's used (60-3719's the other); the later number must be NPS; if 60-2133's also being supplied as NPS, what's being used for NPT? confused

1 member likes this
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