Has anyone ever tried blocking off the oil feed to the back of the barrel?

Looking with interest. A recent magazine article I've just read describes doing that on a Velo and in that case it started tightening up. The Inter has an adjustment screw...another thing to worry about. My Inter oiled plugs badly, but I removed the barrel and deglazed it (with fashionable helical marks) and that seems to have given a big improvement. But of course it's hardly been tested.   My bore looked a bit like a mirror finish. My guess is that it had been run in too gently?  Where it is adjustable (on Inter), the instructions are to open it until there is a bit of blue smoke, but if oil is passing the rings you get that anyway. Actually, perhaps the rear feed is only needed when the bores are new and the rings are sound?

Goff Clatworthy, and Aussie ES2 racer, told me that it is not necessary, so I have blocked it off on a road bike I am building. He thinks it may be a hangover from racing days when a cold start to a race needed it to reduce seizing in first few miles.

Is this type of feed used on many other makes? Don mentions Vincents. The Dommie design doesn't have it.  I've not encountered a car with it.

Rudge Ulster has one.  Rudges are well known to seize if built with "normal " piston /bore clearances ,and many swear by starting with 8 thou ! . I would think that with a combination of decent oil, enough clearance  and slightly on the rich side carburation then the cylinder feed is not really needed.  Another factor could be that as roller bearing motors need hardly any oil supply to survive ,thats all that  some get, these would be the ones that may  benefit from an additional cylinder feed . Motors with a  well arranged crank supply  ie gear pump in good nick  throwing oil everywhere can do without.   Too many variables  in the mix  to be  conclusive.

I think I'll bow to Edgar Franks and leave well alone. Anything that reduces risk gets my vote. I've watched it pumping (with head and barrel removed) but can't remember or never noticed..does it inject oil above the rings on the way up? If so, it must have quite a big effect on oil consumption. If not, it's hard to see how the oil gets spread about...although the piston wall would smear it around.

Not above rings unless you like a smoke screen ! . You could always replace with a little modern 2 stroke in the fuel  which would protect the tank against rust , lube the carb needle , inlet guide and  give a bit of cold start protection from the bore wash we get from  too much tickling .

...its skirt lube.  I don't run my ally barrel Inter with any feed as it rarely sees high enough temperatures to warrant it. 

Keeping octane levels high is hard enough without sweeping oil into the mix. 

As an aside to your earlier post in this thread David; the (nominally 45 degrees) crosshatching formed during the honing process is there to retain such oil on the surface finish of the bore. Your comment on glazed to glaze busted proves the function. 

 Cheers

Jon

Hi Don/all,

   The main factor with piston lubrication is the type of aluminium alloy which the piston is made from. Older pistons require more clerance and lubrication than more modern lo-ex materials. Cast alloy generally has better resistance to damage than forged alloy, which can lead to extreme seizures with-out sufficient lubrication and can be a problem with alcohol fuel. My personal view for normal riding is to restrict the flow. I use an old or broken drill shank of the full hole diameter with a small flat ground on one side so only around 25% area is open for oil flow. This is then inserted into the timing side crankcase from the outer cover joint face.

When redoing the top end of my 1961 ES2 I found that the rear of the barrel oil feed was not drilled thru the cylinder liner. I drilled it open it to the full diameter of the passage so there would be oil to rear of the piston. I rode approx 1000 miles last summer without a problem and the plugs did not foul at all.

Greg

...this topic with interest!

I'm in the process of building up a garden gate Inter and my mate who I bought it from said to shut off the oil feed to the cylinder.  He used to race his Manx with it shut off also.  Claims it is not needed.

Interesting, if a bit sad...

As the flywheels spin forwards, they are probably flinging oil towards the front of the cylinder but not so much at they back?

I didn't mention, but I probably should have. I was doing the rebuild on the top end because I having minor seizing. The ES2 was new to me and had not been ridden for about 25 years. I bought it from a friend of the owner who had passed away. He said that his friend had just rebuilt the top end before parking it When I open it up the rear of the piston had scuff marks on it. I replaced the piston, honed the cylinder and opened up the rear oil feed hole which was not drilled through the cylinder wall. I rode it all last summer without any further problems. My feeling is that you cannot have too much oil lubing the piston with all the heat and friction that it suffers.