Screw fit fuel union for 750mc 2011 regs
Hi,
I thought I would share my experience modifying the fuel line connection to my carb. The 2011 regs call for the factory press fit union to be replaced
with a screw fit union.
Section 5.7 5. Induction Systems : " Press-fit fuel unions on the
carburettor body must be replaced with screw-in unions"
I bought a 1/8 x 8mm NPT union from Burton Power (part number FACFPA903A) and a second tap 1/8 NPT x 27 (8mm)
here
I chose a second tap as a compromise, I didn't want a taper tap because that would have left me with two few usable threads and given nowhere to
practice a 'bottom' tap on its own a bit optimistic  (I've learnt that even with a tapered tap i.e. NPT (National Pipe Taper
thread) you can buy a taper taper tap.....)
We put a bolt inside the old press fit union and used mole grips to clamp it. I held the carb body and my mate held the mole grips - I can tell you it
was in BUT GOOD! Shame to be replacing it really....
Anyway, the next challenge was getting it clamped in the drill vice so the inlet was vertical so we could deepen the hole slightly. The existing
diameter of the recess was about the 8.6mm diameter that the 1/8 NPT tap called for. I had an 8.6mm drill, but from what I've read you could
also use an 8.5mm.
We basically deepened the recess to the point where it was close to reaching the fuel filter chamber. Next we cut the thread, plenty of oil and very
gently, but ultimately successful. We cut as far as possible, the tap bottomed out. This gave me enough thread to insert the fuel union to within 2
threads of the top. I tried using PTFE tape but I couldn't get this to seal. A trip to Screwfix later, and a bottle of Loctite 572 and I'm
pleased to say that its well sealed and not a hint of fuel leakage.
I hope this is useful to someone!
cheers, Keith
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