Dominator breathing

When Norton put the 6 start gears on the Dominator in the mid-60s they made the oil lines and galleries larger, which helped the engine use the extra pump speed. I ran the fast gears on an early dominator for quite a few miles and the only time it blew oil out the breather pipe was if I let it sit for more than a few days and it had wet-sumped and gave the engine something to blow out.

You could check the condition of your pump and scavenge lines and system and see if it is not scavenging well. I recently found a bad soldering job on the oil manifold which bolts to the back of the timing side crankcase where one of it's passages was largely blocked by excess solder that was sitting as a blob inside one of the pipes passing oil between the tank and engine.

You may be able to bolt in a later oil tank from a post 62' Norton that has a froth tower incorporated. The timing disc fits in the end of the cam with tabs so it is probably not part of your problem.

The bottom line is, the engine can not blow oil out of the breather if the sump is kept scavenged. The sump should stay fairly empty when the bike is running, and it should stay fairly empty even after the bike has sat for most of a week as long as the oil passages are clear and the pump is in good shape and it's clearances are tight.

Running the oil breather to the chain on these bikes usually makes a mess, I ran my breather out to dump behind the rear tire and just manually hit the chain with made-for-the-purpose chain lube now and then.

If you get everything checked and fixed and the bike has sat for a week or two since it's last ride, then keep a clean pan handy with a nice wrench so you can quickly empty the sump and dump it back in the oil tank before you start it up and go for a ride, then it will not have to scavenge it out. Good luck...........

When Norton put the 6 start gears on the Dominator in the mid-60s they made the oil lines and galleries larger, which helped the engine use the extra pump speed. I ran the fast gears on an early dominator for quite a few miles and the only time it blew oil out the breather pipe was if I let it sit for more than a few days and it had wet-sumped and gave the engine something to blow out.

You could check the condition of your pump and scavenge lines and system and see if it is not scavenging well. I recently found a bad soldering job on the oil manifold which bolts to the back of the timing side crankcase where one of it's passages was largely blocked by excess solder that was sitting as a blob inside one of the pipes passing oil between the tank and engine.

You may be able to bolt in a later oil tank from a post 62' Norton that has a froth tower incorporated. The timing disc fits in the end of the cam with tabs so it is probably not part of your problem.

The bottom line is, the engine can not blow oil out of the breather if the sump is kept scavenged. The sump should stay fairly empty when the bike is running, and it should stay fairly empty even after the bike has sat for most of a week as long as the oil passages are clear and the pump is in good shape and it's clearances are tight.

Running the oil breather to the chain on these bikes usually makes a mess, I ran my breather out to dump behind the rear tire and just manually hit the chain with made-for-the-purpose chain lube now and then.

If you get everything checked and fixed and the bike has sat for a week or two since it's last ride, then keep a clean pan handy with a nice wrench so you can quickly empty the sump and dump it back in the oil tank before you start it up and go for a ride, then it will not have to scavenge it out. Good luck...........

I have a similar set up on a 60 99 and it works . I did open up the tank breather size. I don't think the 6 start gears help and you may be better off back to standard .The valve gear is poorly served as standard and you may wish to try the old dodge with the Jubilee tank fittings.My motor is pretty loose and that seems to offset the excess pressure the 6 start gears make.When i rebuild the motor i'll probably go back to standard.I did suffer a couple of siezures which is why i tried to increase the oiling, I suspect my problems were caused by overheating .

If the breather, from the oil tank, is not blocked it should not be possible for the tank to pressurise. First check the pipe is clear. I run a '54 Dominator, with the original set-up, breathing onto the rear chain (just over the gearbox sprocket).

There is no excessive oil blown over the back wheel, although after a run there a few drips from the chain-guard. Are you sure there is not too much oil in the tank?, it should not be more than 2 thirds full. If you top up before running the engine, after much more than a week, any oil in the sump will be pumped back, overfilling the tank. John.

Hi.

My Dommi used to blow oil out of the oil tank breather to the extent that it could only be filled to halfway! The engine breather was not connected to the tank and this too blew a fair amount of oil. What I eventually found was that the edge of thebrass plate on the oil pump was slightly proud of the pump/crankcase mounting surface stopping the pump from fitting properly. Take the pump off and place a steel rule across the mating surface, hold it up to the light and look for a gap. I filed the edge of the plate so it was cut slightly back and I could notbelieve the difference it made. The most marked difference was that the oil tank breather no longer chucked out anywhere near as much oil and I could now safely fill it to the right 'maximum'level. Scavenging wasimproved and could be felt in the way the bike 'picked up' on opening the throttle. There was alsoless oil from the crankcase breather although there's still a bit when used hard.

Cheers.

Ian.

It does sound as if your scavenging is suspect.Is the sump plug filter clean?. I went through all the fittings and opened them up with drill bits where suspect.I use 40 monograde.