It's not clear what you are doing to your engine during the restoration. When I did mine, I had valve seals fitted to the inlet valves. The engine needed a complete overhaul. I use the original D breather which I piped to an aluminium bicycle bottle tucked away behind the battery carrier and is barely noticeable. I do a few thousand miles a year and whilst you can feel air pulsing from the vent I put on the bottle, very little oil collects in there over a season ( about 1/4 ins). I put a dip tube from the breather pipe into the top of the bottle and a vent in the top at the opposite side with some SS pan scrub in it. The tubes are 1/4 diam. The dip tube is about 1/4 ins above the bottom of the bottle and I put 1 ins of oil in there to help create a slight vacuum. The only oil leak I have, is from the filter nut because this year I forgot to put some sealant on the threads at oil change time. I haven't needed an anti sumping valve and even before the rebuild a very tired engine didn't sump so I wouldn't fit an anti sumping valve unless absolutely necessary.
I got a replacement seat and exhaust down pipes from Bob Culver. There were a couple of issues with the seat. It came with a "garden gate" hinge and the front of the seat was too high because of too much padding. The seat that came with the bike was home made but had the original hinge. Even swapping the hinges did not allow the seat to lift to its full extent because it fouled the tank. I took the seat to a local trimmer who re profiled it to match the old seat and that solved the problem. The new seat has fibreglass base and was correctly fitted with captive nuts so that the original series D hinge fitted. The down pipes fitted ok but I have since changed them so that I could fit fully machined exhaust nuts. I still have them complete with cast brass nuts so if you re interested in them drop me an email. The front pipe will require re flanging. Mine is an open D.
Regards Mac
