smokin Joe

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Sep 19, 2007
I bought my 850 Commando this summer after it was sitting for a few years. (even a mouse nest in my inlet filterbox).
I got it to run but it was smoking quiet a bit out of the right exhaust. When I lfted the head and removed the valves I found indeed that the right inlet valve guide was badly worn, so I've got a head job done by a Norton expert with new guides and valves, new rubber inlet washers. etc. While I were at it I also installed new rings. The pistons were still standard (11K) and they didn't measure much wear. Finally I 've got everything together again and guess what? It smokes even more as before!! Both exhausts now, but the right hand side more then the left.
I hardly can believe that the slight wear of the pistons would cause so much oil to burn! Anybody have any ideas how I can eliminate this smoking problem? I don't smoke and my Norton shouldn't either....
I'd give the new rings a wee while to bed in and things will likely improve.
Did you glaze bust or hone the bores, and you did put the rings the right way up with the gaps staggered didn't you?
Fingers crossed,
Check the inlet valve guide seals. They could have poped off or have been crushed during the rebuild. You'll need a good light and a small mirror to see passed the springs.

Need to know under what conditions it smokes. On startup, hot or cold, acceleration or deceleration, blipping throttle?

Ring sealing will be most noticeable under power. Valve guides or seals will show up during high intake vacuum conditions (idle, blipping throttle, and deceleration).
still smoking

The smoking is pretty heavy when I first start it up, especially the right exhaust/cylinder. But it also smokes when it is warmed up. After decelarating (not too much smoke) it will give a complete cloud of smoke when I then accelerate. Unfortunately the sparkplugs foul up in a hurry so there is not much riding I can do before it starts to run on 1 cylinder.
the new rings were put in with the gaps randomly located. I'll give it a few more tries before I will get the whole thing apart to see of I can find any obvious problem. Thanks for all the advice!
oops - got a bit worried when i saw the posting (still smoking after some work on the head).

I have a smoking issue too, and will pull the head off this weekend.

My symptoms: smoking on left side only. No smoking till good and warmed up, then it's enough that i think some tree-hugging Prius driver is going to attack me at a stop light. Have a single Mikuni carb.

History: bought the bike 3 months ago with 14k miles. Put 500 or so since then, on mostly short rides. Prev owner blew up a cam lobe at 12K miles (1992) and replaced the cam, resleeved the right cylinder, replaced piston and rings. He also replaced valves, guides, etc at the same time.

My diagnosis: quick and dirty test points to valve train as culprit instead of rings. I got the bike warm and smoking, then disconnected the rocker oil feed at the banjo bolt on the timing case. Started it back up, and after 4 to 5 min, the smoking diminished and then disappeared. Stopped it, reconnected oil feed line, restarted and presto - the smoking returned. So it's top end, and i suspect the intake oil seal on the left side. Anybody with other suggestions>
I think that the oil seal is the favourite but check also for guide to head fit and that oil drillings in the rocker spindles are correctly fitted (flat on the spindle facing outwards).
Sorry got my two cents in and you already found the problem. Wow how does that get to the combustion chamber? Doxford
79x100 could have the answer here, I was thinking the same coming home in the car (sad bu**er or what).
All you have to do is get a bit of wire and bend it like a long backed staple at least as long as a spindle. Remove the spindle cover/lock plates and cut one leg short enough to fit inside the spindle. Poke it around until you find the oil way. The long leg will point to the spindle flat. You'll soon find out if any are wrong.

Best of luck,

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