75 Norton Mk III Excessive White Smoke-Left Side

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Have been slowly assembling this unfinished project that someone else started (purchased from estate). We finally got to the point of starting it and got a lot of white smoke, mostly from the left side. Unfortunate because it appears to run and start really well? I removed the valve covers and found the intakes with oil residue on them, stuck a Q-tip down in between the valve springs and came up with a black oily glob.
We checked the head bolts that were easily accessible and they were all pretty close to spec so at this point we are assuming they were all torqued correctly and hopefully in sequence.
I am looking for a 5/16-26 bolt to pull rocker shafts out and check for proper direction.

I'm thinking there should not be any sign of oil in the intake valve pocket, or in exhaust valve pockets either but the oil should be contained inside the rocker assembly, not sure?
We also tried the test of removing the rocker feed lines and running it around the block a couple times, but very nervous about running it to much like that for fear of seizing something up. Smoke never stopped and was missing pretty bad?

Very disappointing, that bike really really wanted to go...

Any ideas or if we're heading in the right/wrong direction would be very much appreciated.
 
I am looking for a 5/16-26 bolt to pull rocker shafts out and check for proper direction.

You should be able to find the hole positions using a thin piece of wire with a short 90-degree bend at the end without having to extract the rocker spindles.

Any ideas or if we're heading in the right/wrong direction would be very much appreciated.

Inlet valve seals probably need changing. Check the oil drain from the inlet valve side to the timing chest isn't blocked.
 
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Thank you, I'll start looking at these. I'll have to find a good diagram of the head to understand these locations.
 
By inlet valve seals do you mean valve guides? If so can these be replaced without pulling the engine?
I'm not finding any diagrams indicating where or how the rocker oil feeds are returning or draining?
Thank you again for your help.
 
By inlet valve seals do you mean valve guides?

The valve stem seals on the inlet guides.
Item 8 (x2)
https://andover-norton.co.uk/en/shop-drawing/214/engine-valve-gear

If so can these be replaced without pulling the engine?




I'm not finding any diagrams indicating where or how the rocker oil feeds are returning or draining?
 
Hello, It's been a while. With hunting, holidays and a family emergency we are finally back to the Mk III.

Using a small wire we checked the direction of the rocker shaft installations, all 4 were correct.
A cold compression test gave us 110 psi on the left and 120 psi on the right.
Removed the timing cover and blew compressed air into the timing drain hole, a lot of air came up though the intake valve drain hole, there may have been a very minute amount of air coming up to the exhaust valve drains but so minimal it was almost undetectable.

I did try to remove one of the rocker shafts on a cold engine. Stripped 2 of the 5/16 bolts trying to pry it out (cheep bolts). Do the springs need to be released prior to pulling the shafts? Maybe the tight spring is causing to much pressure against the shaft? Any secret remedies would be appreciated!

I believe this leaves us with the valve stem seals?

Will the tool you show above fit between the frame and valve springs to enable me to compress?
I need to get the rocker shafts out too in order to get to the seals, correct?

As always your help is greatly appreciated!!!
 
I did try to remove one of the rocker shafts on a cold engine.

Heat the head as it says in the manual and I suggest you don't attempt to pull them out (or fit them) cold.

Stripped 2 of the 5/16 bolts trying to pry it out (cheep bolts).

I suggest you buy or make the correct rocker spindle extraction tool (then use it after heating the cylinder head). The spindle thread is 5/16" - 26 (BSC).

Do the springs need to be released prior to pulling the shafts? Maybe the tight spring is causing to much pressure against the shaft? Any secret remedies would be appreciated!

I'm not sure what you mean by released but the valve should be completely closed therefore the rocker arm needs to be slack. The valve needs to be held in position when the spring collar is released.

Will the tool you show above fit between the frame and valve springs to enable me to compress?

I haven't used that tool so I can't say that it absolutely will.

I need to get the rocker shafts out too in order to get to the seals, correct?

Yes, the rocker spindle has to be removed to release the rocker arm.
 
Thank you! Any suggestions on heating the head? Of course the fuel tank is removed, carbs are still in place.
 
Bad valve stem seals would not cause it to smoke that much.

Are you sure it wasn't just wetsumped??
That will easiliy produce the smoke you are describing.
 
Thank you, I'll start looking at these. I'll have to find a good diagram of the head to understand these locations.
You must be a brave man, relying on the current state of the engine. If it was rebuilt in the past, how do you know the workmanship was good? On the other hand, if the engine hasn't been cared for since new,
how do you know the piston rings aren't frozen, and the oilways not gummed up? Your q-tip test didn't inspire confidence, me thinks.
At the very least you should tear down the engine and do a proper inspection, preferably by an expert. Before re-assembly of cleaned parts, make sure all oilways are free of oily residues and debris.
This OP is quickly done and may save you big money.

- Knut
 
I bought a new 1974 Commando many yearsago. After about 400 miles it started putting out smoke from one side. It was under warranty and the valve had ridden up fron the guide and onto the valve stem and so was burning oil. New seal solved the problem
 
Hi Rondo:

While I am not a Norton expert, I am currently suffering a similar issue. Recently bought myself a 1974 Norton Commando MkII 850 that supposedly has a rebuilt engine, but the bike had been sitting unused for at least a decade. Runs well, but lays out a white smoke screen, (on acceleration) worthy of a destroyer trying to hide itself, or the fleet, from an enemy warship!

The advice I have received suggests a problem with oil seeping past the valve guides, maybe valve seals dried out or slipped etc. I recently went through the head on my 1962 Norton 650SS because of lack of oil to the head. What I have learned - that relates to my Commando issue, is that it is important to check the orientation and type of rocker spindles being used. For the "high pressure" Commando oil system the spindles should not be "scrolled" and the "flats" in the center of the spindle should be facing outwards. Failure to do so can apparently easily cause excessive oil delivery to the head. I'm planning to pull the head, hoping my problem is valve seals, but while I am in there I intend to also check the spindles and oil feed return galleries.

Of course the problem may well be the rings / bore etc, but the head seems like a good place to start!

Good luck.

Cheers,

James
 
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