1971 Norton headache

20M3S/143398
Motor was rebuilt some 10 years ago.
We put it in the frame and have done lots of other work on it.
Started it up and it really shakes. It begins to settle down as the RPMs increase but a long way from being right.
Oil on top of the pistons. Shining a light down the plug holes I can see the cylinder walls glistening with wet oil. The valve pockets begin to collect oil.
I put in fresh rings and honed by a very reputable shop that I have worked with many times. Their work is good. No change.
I had the head gone through by the same shop to search for any possible headaches. Valves lapped and new seals. No change.
I found a damaged oil pump and replaced it. Good oil return.
I have a Comstock sump breather. I have used several of them with very good results. However it is a variable in this situation so I have to suspect it and hopefully rule it out. Is there any reason I should be having a problem with this combo? It's pumping plenty of oil when the motor is running so I know it's passing oil. The breather is breathing.

Also, the bike has a good amount of vibration. So much so that I am beginning to wonder if it has an Atlas crankshaft in it. Originally it had dual Amals and with plenty of fiddling I got nowhere. I replaced it with a single Mikuni from my own bike so I know it is carburetting correctly. That should have smoothed the motor out immediately. No change.

I am going to install the original sump filter and see what happens but I am open to suggestions before I go any deeper.

Points or electronic ignition? Are you sure it is running correctly on both cylinders? I seem to remember that an Atlas crankshaft is different at the primary side as it only has to drive a duplex chain whereas the Commando drives a triplex. Are the plugs getting oiled up on one or both cylinders when you run it for a while?

Pazon
both sides but more on the left

Easiest way is to spray the 4 isolastics places with Silicone spray after checking the gaps with a feeler gauge. It's a starting point. Check headsteady rubbers too.

I already checked the isolastics, they've been replaced with aftermarket adjustable isos and appear to be in good shape. Difficult to adjust and be accurate with these but perhaps .010 up front and .007 in rear.

Are your front iso's from RGM? If they are, the rubber in them is very hard and takes a while to bed in.

The front end is like a jackhammer up to 3000 RPM until they bed in.

You could try putting a wooden lever (to save marking the paintwork) in between the bottom of the front engine mount and the frame tube, lever it across to one side and while there, measure your iso clearances and adjust. Then repeat on the rear. You need to take the slack out of the system.

Yes the whole motor-Transmission needs to be pushed or levered to one side. The side without the Vernier adjuster. Then your measurement will be taken on the slack side (adjuster side),. Then adjust with that threaded adjuster to specs. :?

Originally, the two prototypes had NO vibration transmitted into the frame above about 800 rpm. Unfortunately, they were rather weak in the basic job of holding the mechanical bits in place. Immediately after the 1967 Earl's Court show, the Commando program was declared a production program and no longer experimental. The whole thing went from the Wolverhampton Development Group to the Plumstead manufacturing facility. A lot of the people working on it at Wolverhampton were relocated also.

I got switched over to the development team on the AJS Stormer, which was an interesting bike to work on. It's the only bike I ever ran in reverse. It stalled as I was approaching a red light and I just popped the clutch out and in, using its motion to turn the engine over. It restarted, but sounded a bit odd. A double-decker bus stopped behind me while the light was red. When I let the clutch out, as the light turned to green, the bike tried to climb the bus radiator grille! We had a lot of trouble with cylinder damage, caused by the rings welding themselves to the cylinder momentarily as they passed the exhaust port. Castrol "R" solved the issue, but repeatedly having to shake the bike after it had stood for a couple of hours (to re-mix the oil and gas) was a PITA.

After a few months on the Stormer program, I could see N-V was headed for the toilet. I applied to Boeing, was accepted and we moved to Seattle in July of 1968. I retired in 1998 (at only 57 years old) after getting tired of all my trips to the Arab world. That last year, I was away from home for 28 weeks and none of the trips was more than 10 days.

.....why do I want to suggest that the motor timing is off upon rebuild assembly inside the timing cover....

The motor timing is correct. While I did not build the motor, I put in the very substantial Jwis timing chain and lined up everything correctly.
Today I went after the only other variable which is the sump breather. I have used it several times before with good results and I would buy another one. However, there is something strange going on with this motor. I put the traditional cam-end rotary breather back in and the heavy vibration went away, about 85%. I put a clear hose on the breather to see how much oil was going through and the rotary breather seems to pass a fair amount of oil. There is something peculiar happening and I am wondering if I am running into the problem of the odd cases that need some metal removed to drain properly. The original oil pump was damaged...crud chewing up the gears...and I put in a used one which seems to pump well.
There is no small drain plug, only the large sump plug.

Just a thought on the oil issue. Rocker shafts can deliver excess oil to the head if they are installed the wrong way around.

I put them in myself. I know they are in correctly.