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Hello, I have lost one of the exhaust emission plugs (CO plugs) from the rear header. Does anyone know what thread they are?? Dont really want to disturb the front one to measure it. I have temp plugged the hole with part of old spark plug, but its not the right thread so does not screw in correctly.

Thanks

10mm I believe, course pitch.

Can't help much, but I got replacements from an old fasteners place in Surrey. The bloke was pretty impressive at identifying stuff, but was a bit confused at first as he reckoned it was a thread that was normally used in plumbing applications.

He gave me some very slightly tapered grub screws that he suggested I didn't overtighten so they wouldn't split the boss and use thread lock. That was about 6 years ago and they're still good.

Take the other one out and try to get a match at a proper plumbers merchants. Then buy a bunch as they'll probably cost 30p each

They're not a plumbing fitting, they're a metric thread. 99.9% sure they're M10.

Nooj wrote:They're not a plumbing fitting, they're a metric thread. 99.9% sure they're M10.

I'm with the boy with the hairy legs, M10 taper thread

Aren't plumbing fittings taper thread?


and european and american taper threads aren't compatible in some sizes.

I found a plug at work its 1/8 BSP thread

1/8BSP is 9.5mm thereabouts, so chances are it is M10

Kwackerz wrote:1/8BSP is 9.5mm thereabouts, so chances are it is M10

Close, but no cigar. They're a different pitch.. Meaning you chance either stripping the screw or cracking the insert. Not heard of a taper thread on metric sizes.

Pitch of M10 is 1.5mm, Pitch of 1/8 BSP is 0.90mm. 0.6mm is a massive distance in engineering terms.. Might not sound a lot, but it's huge when it comes to screw threads..

Also, the TPI of 1/8 BSP is 28, and i think M10 is 24 TPI..

Oh indeedy, however with the 1/8 being a smaller diameter, it would fit in the hole quite well, regardless of tpi and pitch.

How many modern bikes, especially european, use a British Standard Pipe thread on their components? I'll have a quid on it being a metric thread..

One's on the VFR were BSP.. had to replace a few before it went.

It's fallen out.. So chances are it is metric..lol..

Right - just checked the parts catalogue and its a 10mm taper standard pitch

Interesting, well the 1.8BSP plug is installed. I thought all metric thread were parallel, and the plug seals on a washer too. If anyone has a spare standard plug I will happily put it on the shadowgraph at work and work out what it is exactly. BSP thread is the standard used across europe the the pneumatic fittings industry and the states use NPT.

a Shadowgraph.. wow.. cool.. I thought I was the only one who still had one..

Fantastic - a thread thread. When I were a lad - all we had to bother about were Whitworth and BSF