That looks like a 6-pint 500 oil tank as well but both very practical even on a 350...

I've just pulled out a rather grubby 52-55 type, I wouldn't like to guarantee the spigot height(partly because it's still got the copper gasket well stuck on) but the diameter is about 3.156 - maybe 3 5/32 ? However, I've got a feeling that the later ones also have an extra fin - this one's got 10 f...

From 1952, bigger finning on head and barrel, head gasket and smaller spigot on top of barrel (smaller diameter and slightly lower as well). The 350 kept an iron head until 1956, and in 1955 (I think for the one year only)there was much more pronounced finning in the area above the push rod tubes. (...

Not sure.....but that's an interesting use for a plunger frame

Uncaged bearings don't like revs (the rollers twist and bind against each other). I never got a 350 big-end to last longer than 7000 miles - although that was using motorway speeds. The 500 is overgeared so it might be kinder to uncaged bearings...but I can claim to haver broken a duralumin cage (ve...

It's a 7.5:1. If the GPM really is 7:1 (according to google) then I wouldn't think it would be any quicker, but it might be smoother if it's lighter. Having said that getting the bottom end set up really well seemed to have a big effect on mine. (How odd, there was a 5045 just like that on ebay not ...

According to the Avon web site the 100/90 AM26 (Roadrider) has a min rim width of 2.15 and thats a WM3 (the WM2 is 1.85)
I think I might do some more measuring - I'm about due for a new pair of rims, maybe I'll go fro a WM3 on the back!

Interesting! Way back when, the rear tyres were always 3.25 or 3.50 on the WM2 rim. Judging from the swing arm in my '56 frame there's plenty of room (the tyre is wider than the rim so the tyre width would be the limiting factor - looks like a WM3 rim might give the option of a better tyre - 4.10? -...