My 850 Mk.1 has taps that screw into the tank up to a flange. All the other taps I see for sale etc. have a locknut on them, yet they are sold as original type taps. Also, mine have a nylon insert, all others have brass. Never seen the type I have for sale, are they rare? I can't get on with these locknut types, seem to leak on me.
There was never a Mk.1, until there was a MK.2

Good luck finding originals. I had to go with the aftermarket, locknut types. Many of the originals had a plastic core that hardens and breaks over time. My plan is to wrap the threads in teflon pipe thread tape before assembly and use the rubber-lined sealing washers on the nut.

If you don't use the thin flat washer with the sealing washer when you tighten the jam nut the rubber will skip out. Good dealers who sell the sealing washers are assuming you have kept your flat washers for re-use. The sealing washers are a one use affair.

Anyone know of any aftermarket petcocks that are longer and have a disconnect coupler built in?

Be careful with teflon tape...it is really intended more to lube the threads than to seal, and gas will wick along the tape if it is not tight enough. To get it tight enough means you gotta really torque on your tank fitting. Kinda scares me. I would lean toward one of the available liquid thread sealers if I were to put something on those threads.

norbsa48503 wrote:If you don't use the thin flat washer with the sealing washer when you tighten the jam nut the rubber will skip out. Good dealers who sell the sealing washers are assuming you have kept your flat washers for re-use. The sealing washers are a one use affair.

Very good point.

Norvil sell these Dowty style washers and they work well. Mine have been in use 12 years with BAP taps and the locknut. I should use a washer next to the nut as suggested but they've been OK. I'm sure lots of other places have them.
http://www.norvilmotorcycle.co.uk/065329.jpg