Left side smoking

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Look at the intake valves, they have light brown spots, thats from the oil. The same would happen to the piston if they rings pump the oil. I bet the valve is oiled, if you look from the manifold side ! Is the valve seal still on its place ? Or is it hard like stone ? Anyway, you have torn your engine, check all, bore, pistons, valve guides and replace the things that are close to worn, for a long ride :D

Marco
 
Good job, we need another photo or two though. A well lighted close up of the sides of the rings. It looks to me from the little I can see that you have fallen victim to the all too common modern hone job syndrome. Some shots of the bores would be good. All the new bikes and cars get fine grit hone jobs Our bikes need a finish made from 150-200 grit stones. 9 out of ten shops don't even have these in the shop.
 
The pistons look unused as do the rings I can only surmise that the hone was too fine. The rings never seated. You have a near new machine no valve recession and all but the rings and the wrist pin retainers can be reused. This assumes the bore is within spec though. Looks like you need a good 200 grit hone. I would check the valve guides for the fit of the valve stem no more than .001 slop. Than leak check the guide to the head with liquid, make sure the intake seals are live. A crack test at the intake guide is still a good idea.
 
Thanks Norbsa. Just to check....You don't think I need new rings but the hone may be too fine. As I have the head off I'll check the valve stems and if I find anything I'll let you know.

What's the solution to the honing problem if I can't find anything wrong.
 
No, you need new rings and a coarse 200 grit hone job. Also some fresh wrist pin retainers. The bore has to be very carefully washed before assembly.
 
Everybody runs this oldstyle lead shoes and rings, i would do my next overhaul with ultralightweight www.rosspistons.com, they make custom fit pistons with small low tension piston rings ( These rings are good for a long life of the cylinder bore). With a 10+ compression and a good cam it revs better than any combat. I run this pistons in my car without any trouble (street and strip).
But anyway check your valve guides !

Marco
 
From the photos it looks like there's very little wear with next to no blow by, 'cept on the first there's marks on the rings and piston. Have you got a thrust problem? Has the crank end play been set up correctly?
Just a long shot.
Cash
 
4onthefloor -

Have you talked to Ross Pistons about making custom pistons for a Norton? I see from their site that the minimum # they will make for one order is 4 (makes sense - I expected it would be even higher).

Anyway, i am not in the market for new pistons right now, but will be in the future. (I have a Mark 3, stock piston size currently). And Ross is located a couple of hours away from where I live.

Do you think the quality of their pistons would be that much better than others available? Rings too?

Do you know of anyone who has used their product in a Commando?

Keith kelly
 
Hello Keith Kelly

they will custom fit the piston to your specifications, maybe you have to bushing your rods. Be prepared to balance your crank with such light weight pistons! There are a lot of other good piston brands, but i know 4 good friends who use these pistons in a strocker combo. Until now we have never had a piston failure. The most negative point is the noise during warm up, they have a lot of end play, in case of the forged design ! Sounds like a much of valve lash :lol: . Oil consumption is ok, it takes a little bit during a race weekend. Ross give also clearances for nitro, marine and blower applications ! Call the guys and ask.

Marco
 
Cash says, "The seal can be replaced without removing the head. "

Could anyone please give me some place to find details on replacing the seals without pulling the head? Thanks
 
It involves rope and a special tool to remove and replace the valve keepers. Are you scared yet?
 
My situation is that I have a '73 Mk I 850 that is smoking (oil smoke) out of the right pipe (it has a cross over tube). I blocked off the oil to the head and it stopped smoking. I suspect valve guide seals and was just trying to decide if a method for changing the seals without removing the head was worthwhile. I have never been into the motor on this bike so I would learn a lot with the head off but would also sure enjoy a quicker fix so as to be riding again.
 
Well one parts straight forward enough. Pull the tank,pop out the plugs, pull the valve covers put it in forth gear. One cylinder at a time,bump the rear wheel till the intake valve has just closed. Now start stuffing a thinnish cotton cord in through the spark plug hole, pack it right tight it's going to be holding up your valve. Once you have that done you have the tricky bit.
You have to build a tool that can lever down on the valve retainer and still give you room to remove the keepers. ( I use a magnet on a stick) Now on a Norton there is not a lot off room for this on the intake side you might swear a bit. A good start for the tool could be found at a Auto parts store , it's the tool used for doing the same job to a Chevy V-8. You would need to cut it to fit into the tight space but it's near the right shape. You would have to add a lengh of rod on a hinge to the tip of this tool so as to provide a pry point up against the frame in some handy spot.. You might try it because you still need some special tools to do the job when the heads off.
So you now have removed the collar and the keepers just slip off the springs there's the seal remove and replace oh another special tool to tap on the seal but it's just a bit of pipe the right size. Oh did I mention the rocker will be in the way? Well now you do need to buy that service tool to remove the rocker shaft (don't drop any washers into the motor) and you will have to get the push rods installed just right on the way back on. And are you scared yet. Are you broke yet ain't it fun.
 
Yellow_Cad,

Personally I suggest you remove the head and do the job the normal way, as it should be fairly straightforward, but you really should have a workshop manual handy, or the information given in the online manual for 70-72 models in the Sticky Commando Information post would be OK for 850 cylinder head removal.
 
If you have the facility to make the crude tools I'll photo my kit. However, if not, I would recommend LAB's suggestion.

I'm not so sure of the string method hold the valve up, others do swear by it, but a steel hook will and so to compresed air.

Cash
 
I do have the ability to make the tools you mention and would sure like to see what you describe. My email is jimhearn1@comcast.net. Cash, have you done a valve seal job this way? Is the reassembly a little worse than the disassembly. Do you need a special tool to remove or reinstall the rocker arms? Thanks
 
Yellow_Cad said:
Do you need a special tool to remove or reinstall the rocker arms?

Yes: http://www.nortonmotors.de/ANIL/SI%20Se ... 0Tools.htm = Item "06-4298
Slide Hammer for Rocker Spindles and Auto Advance Unit"

But you could make one easily enough using a 5/16" - 26 tpi threaded rod, nuts and a weight?

Or there is an alternative tool that draws the spindles out like my own one shown below:


Left side smoking
 
If you want to hold up the valves with air, then rip out a spark plug and weld a airhose adapter to it. Maybe you'll find a shop that sell such stuff. The right tools makes it an easy job !
 
It's a 360 motor your going to use compressed air to hold the valves against their the seats. All the while working away on the intake valve. This is not a V-8 I live in the town were they were made at one time trust me on this. So you put the air to it and the piston is forced to BDC so unless you have loosened the valve adjuster they will reopen when the piston moves. Now even 50lbs of air will put about a 150lbs of force against the piston. Now do you see why I gave a beginner the rope trick. And also tried to explain the job and the tools evolved so that he may understand that it might be a good time to pull the head. He did directly ask how is it done. If you are one to suggest the use of air and than not include directions on it's safe use shame on you, this is a man who has never pulled a Norton head. A written list of the special wrenches to pull the head and how to deal with the push rods would scare me off as a novice. I say, pay an expert and pay them extra to watch and ask questions. Silly looks are still free.
 
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