1951 Norton Big Four, cylinder lubrication?

Hi Karl,

I have two post 1948 Big 4 engines. One is in my bike and is a runner, the other is a spare. I seemed to recall being suprised by the same thing as you regarding the lack of oil hole. I've gone down to the shed and pulled out my spare engine and checked it for the lack of oil hole, on the contrary, there it is, oil hole in cylinder and oil hole in crankcase. This is on a 1948 motor.

The motor in my bike is from 1951. It's been a couple of years since I put the motor together, but I related to your puzzlement when I read your note. I'm sure the 1951 motor had no oil hole. Probably really need a third opinion here. I often take photos of my bike workshop exploits, but have no records of the Big 4 in bits. As I said, I've had my bike running for the past couple of years. I've done nothing but ride and ride the thing. I've been clocked at 76mph by someone else with a reliable speedo as my speedo is a bit hazy. My point being, I have had no trouble what so ever from the motor, it is one of the most fun and reliable Norton singles I've had.

It would be interesting to hear from another Big 4 owner.

Bob

Ive owned my 1951 Big4 for 38 years and I have been to St Tropez on it and Switzerland the lubrication of the bore and piston has never caused a problem so don,t worry about it.

Bruce

Karl,

While post 1948 the singles had the revised engine design and alloy head, meaning revised cams and cam box etc etc, there was still another change in case design around 1950 when the laydown gearbox replaced the upright box. For one thing, the oil feed and return connections on the earlier cases with the upright box were connected to the cases with seperate screw in fittings. When the laydown box came along the gearchange ratchet mechanism was now down low and nearly up against the engine cases, there was a lot less space between the engine and gearbox in this area, so required a different connection method for the oil lines. This is when the change was made to the manifold block with two metal pipes held to the cases by a single bolt. At the same time, the oil tank was also changed. Kept the earlier shape, but the oil ways exiting the tank now pointed downwards and forwards at around 45 degrees, so they were more or less looking straight at the engine connection. Previously the oil ways came out of the tank in a forward horizontal line, had a 90 degree fitting on the oil screen outlet and dropped straight down to the cases. This oil tank lasted only a year or two before going to the rounded bean shape.

So, this would have been the opportunity to make any other changes to the cases like deleting the oil passage to the rear of the cylinders. Puts it bang on your engine and my running engine both having laydown boxes.

Hi Bruce,

is yours the bike I've seen a few places on the nett pulling a trailer??

Bob

Previously wrote:

Karl,

While post 1948 the singles had the revised engine design and alloy head, meaning revised cams and cam box etc etc, there was still another change in case design around 1950 when the laydown gearbox replaced the upright box. For one thing, the oil feed and return connections on the earlier cases with the upright box were connected to the cases with seperate screw in fittings. When the laydown box came along the gearchange ratchet mechanism was now down low and nearly up against the engine cases, there was a lot less space between the engine and gearbox in this area, so required a different connection method for the oil lines. This is when the change was made to the manifold block with two metal pipes held to the cases by a single bolt. At the same time, the oil tank was also changed. Kept the earlier shape, but the oil ways exiting the tank now pointed downwards and forwards at around 45 degrees, so they were more or less looking straight at the engine connection. Previously the oil ways came out of the tank in a forward horizontal line, had a 90 degree fitting on the oil screen outlet and dropped straight down to the cases. This oil tank lasted only a year or two before going to the rounded bean shape.

So, this would have been the opportunity to make any other changes to the cases like deleting the oil passage to the rear of the cylinders. Puts it bang on your engine and my running engine both having laydown boxes.

Hi Bruce,

is yours the bike I've seen a few places on the nett pulling a trailer??

Bob

Yes

My Big4 has had a trailer linked to it for many years

Bruce

Previously wrote:

I am in the process of restoring a 1951 Big 4 (laydown gearbox model)

Whilststripping the engine down over the weekend, I was shocked to see that there was no oil wayhole in the paper base gasket, that was stuck to the cylinder base.

On removing the gasket from the base of the cylinder, I revealed no evidence of any oil way drilling in the base of the cylinder, which in the case of the 16h side valveis at the back of the cylinder drilled up at an angleto the cylinderback wall, therefore do Big 4'shave an oil drilling into the back of the cylinder ?ifnot, how are the cylinder and piston oiled.

Any info would be much appreciated.

Hi Karl, The 1948 Big 4 has an oilway in the barrel. My spare later enginebarrel has no oilway. I think they gave up asoil probablygets thrown up from the flywheel dipping into the sump. John

Hi Karl, I've got a 52 Big 4, and a spare 53 motor for parts. I've just taken it all apart this week as every bearing in the old girl had worn out, gearbox too ! I do use it a lot i should add.......but none of my barrells have an oil hole, not all brit bikes do, as they rely on oil being splashed up by the fly wheels, also post 49 gasket kits for 16h and big 4 fit, some come with alloy head gaskets, others [ payen type ] have a copper asbestos composite gasket, I always use the composite type.....any comments on the alloy ones gratefully receiced ....

Bob Mitchell