74 Mk II 850. Blue Smoke Rh Side. Any Guesses?

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Saber

Saber

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I acquired the bike in Oct 2018. It sat for 30+ years prior. 8,400 miles on it. My son and I did the basics (no engine work) and got it started in Dec. 2018. So we went ahead and fixed it up over the next several months and put it on the road in April. We had a fun time with it this past summer. Still no engine or gearbox work as it checked out ok with some local norton expertise. At the end of the fall, it started blowing blue smoke from the rh side. Abruptly. It still ran ok but i decided to park it. So we took the top end apart and found the problem. Any guesses?
 
Intake valve seal embrittled with 45 yrs of aging. My 850, similar miles did this after first year of riding after resurrection. I swapped in new KibbleWhite viton seals and new springs for good measure without pulling head. Blue puffs at throttle blips cured.
 
Top apart, could be just a removal of head, or head and barrells. It's not clear.
I go with the above, stem seal...
 
We took head and cylinders off. Not the valve seal. We are replacing those regardless.
 
Winner! Although leak is an under statement. (Correction it was LH side)
 

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I would have thought that with a major head gasket failure like that one there would be a great deal of fuming and crankcase pressure symptoms, rather than just smoke out the exhaust?
 
I've seen it a few times. Smoke from the exhaust was the only obvious symptom.
 
Yep. Cylinder hone, new piston rings, new valve seals, in process. Along with taking the opportunity to paint cylinders, clean up head and carbs, etc.
Lifters and cam look good. Will wait on the major head rebuild for now.
Also, am adding the "torque head bolts" to my reminders.
 
1 heat cycle than re torque 100 miles re torque than 500 and repeat. Also recheck valve lash each time
 
bill said:
1 heat cycle than re torque 100 miles re torque than 500 and repeat. Also recheck valve lash each time
Click to expand...

At least.
And then check it yearly after that. Or more if you put on miles like I do....
 
bill said:
1 heat cycle than re torque 100 miles re torque than 500 and repeat. Also recheck valve lash each time
Click to expand...

I did it more frequently than that when using composite gaskets, and was amazed how much the fasteners turned each time. First time I thought something was wrong, stretched bolts or stripped threads etc, but no.

I was told by an old Norton guy to over torque them a little upon assembly. Kinda risky I know, but I tried it and it did work, it definitely reduced the issue.

I assume when these were new that bikes were collected, and head bolts not touched until the 500 mile first service, is that correct? Or did the owners handbook detail the re-torqueing procedure we use now?

If the former, I reckon they must have over torqued them on the assembly line to last out until 500 miles.

Does anyone know what they actually did?
 
I tend to overtorque a bit the first time, but after that I torque to specs.

With my motor that runs no head gasket, I torque to 5 lbs under specs. I find the head stays flatter that way.
 
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