4F Oil Feed Bath - Holey Moley

[camstevens]

Hi All
I imagine this could almost be described as "esoteric", given the small number of 4F bikes out there, let alone those who have dived into the internals, but here goes;

Pre-1957 (when the bike last ran) some chap decided cyl 3 needed much more oil than it was getting, and to drill out the oil delivery hole from the oil well. Clearly this is not correct as the size of the hole (now) is such that cyl 2 would be totally starved. We also forensically discover that the pump and oil system have major issues, so it seems this was somehow a remedy for that!

Does anyone know of a data source that could reveal what the design size of the holes were? It appears the other side may have the original diameter, so in a tight spot I guess I could use that. PDF of photo attached.

Regards
Campbell

[paul.jameson]

Its as original so don't worry about it. Photo taken just now:

[camstevens]

Thanks Paul
Does your hole on cyl 3 go all the way to the bottom of the internal bearing well? Our one does, and I struggle to see how cyl 2 gets any oil at all.

C

[paul.jameson]

Looking carefully at the oil feed bath, the holes for Nos 1 & 2 cylinders are 3/16" diameter, the one for No 3 is 3/8" diameter and the one for No 4 is 1/4" diameter. I am pretty sure that I remember correctly that the holes were different diameters on my previous ohc four.

As far as I can reasonably measure with my vernier, the bottom of both Nos 2 and 3 holes are around 0.145" above the trough base. Given that the oil pump is delivering a constant supply of oil into the trough via the long internal pipe from the oil filter, the oil is going to slop around in the trough as you lean left or right, accelerate or decelerate so some oil will get out of each of the holes into the dipper troughs. I can only say that, in my experience, the system works as I did over 16,000 miles on my previous ohc four.

Paul

[camstevens]

Thanks Paul