Fuel pump fitting thread

[MTBiker_Boy]

Anybody know what the thread is on the mechanical fuel pumps? I thought it was 1/8 NPT, and it is very close, but not quite. The black fitting in the pictures is a 1/8 NPT fitting i bought, thinking it would work.

[banzai510(hainz)]

Im sure its metric. I dont know off hand 8mm x1.25?

[MTBiker_Boy]

Yeah it’s probably metric, but it was so close to a 1/8 npt that i was really hoping it was. It is a tapered thread, so not any standard metric stuff though.

[MTBiker_Boy]

Alright i might have the answer, from the 620 facebook group. BSPT, british pipe taper, also known as JIS, japanese industrial standard, is a supposedly identical diameter and only one tpi off from npt. They still use inches for the sizing though. Fucking hell

[datzenmike]

Everything is metric since the 520/521. With the exception of the oil pressure sender 1/8 BSPT. Anything that has to seal liquid or vacuum will be a taper pipe thread. If it leaks you just keep tightening till it stops. Don't know about the fuel system fittings if they are also British.

[Crashtd420]

4 hours ago, MTBiker_Boy said:

Anybody know what the thread is on the mechanical fuel pumps? I thought it was 1/8 NPT, and it is very close, but not quite. The black fitting in the pictures is a 1/8 NPT fitting i bought, thinking it would work.

Its probably bspt as Mike mentioned or that jis.... 

 

You could always pull your oil sender out and compare the threads to be sure.

 

Are you trying to change the fitting to a AN line?

 

If so you can retap a 1/8 bspt to 1/8 npt without issue, should work for the jis since they say it's the same as the bspt....

 

Just use your fitting as a gauge... do a little at a time you dont wanna go to far...

Put a little grease on the tap to catch the metal chips....

Edited November 13, 2022 by Crashtd420

[Stoffregen Motorsports]

1/8-27 is NPT, which this is not.

1/8-28 is BSPT, which this is.

 

But yes, you can re-tap it to 1/8 NPT and call it done.