I have had a couple of good runs on my ES2 - 1600km and 1200km mostly at 60 to 65 mph - and it has gone very well except i have been finding the exhaust valve clearance disappears every 400 - 500 km. Loss of power while running and lost of compression once the engine cools down. Redo the setting and all is good again until another 400 or 500km.
Alfin barrel and alloy head, new push rods, new (but came in unmarked packaging) exhaust valve and new guide.
I have been doing the head sleeve nuts to 35 ft lb but the two exhaust ones have become tight in the head so may reduce that to 30 ft lb (there are hard washers below the nuts).
Is it a feature of these bikes to need such frequent adjustment?
Do you have to tighten the lock not on the push rod adjuster to gorilla tight rather than just ordinary tight?
I've ordered a valve from Norvil in case the previous one wasn't up to scratch.
Any other thoughts or suggestions appreciated.
My 1960 ES2 (alloy head with the original iron barrel) hardly ever needs its tappets adjusting - noticeably less than when I had an all iron top end for some reason.
Norton list the Inlet and Exhaust valve under the same part No. from 1948 on and may have done so before then.
However - somewhere in the depths of time I've seen (pattern) ES2 valves listed specifically as 'Inlet' or 'Exhaust'. I'm guessing that these Inlet valves were made from a different steel than the Exhaust - maybe you've got one of these fitted in the exhaust (as they're otherwise identical) and the edge of thevalve's burning away? Otherwise, when you fit the new valve check for aloose guide, worn guide/valve stem resulting in carbon build up. Abnormal valve seat wear and/or burning of the valve as above. Look for signs of oil starvation in the top-end. Clutching at straws here but check the ends of the push-rods and make sure they're secure so oil can't get under/between the steel caps and the alloy rods.
Valve seat recession due to use of unleaded fuel perhaps.
A number of possible areas to check out.
Valve seat recession...........or possibly valve head seatwear. Unlikely after such little riding. Unless the valve material is incorrect.
Valve stem ends not hardened and starting to pit or mushroom. Not unknown.
Camshaft lobes beginning to die.......likewise for followers. A favourite with Commando owners in the 70s & 80s.
Duff pushrods............possibly they had loose ends to start with which gave false gap/clearance readings. AMC pushrods had adjustable ends but the lock nuts for these were often coming loose.
Rockers seizing on the rocker spindles. Quite a common problem if the oil feed to the headis poor.
Valve seat recession only starts above 3,000 rpm, so unlikely to be the problem in this case. I would suspect the valve first, pushrod second.
If you check out all the mechanical bits and do not see anything wearing in the valve train, try dumping a shot glass of synthetic two-stroke oil in each top-up of your fuel tank for a while and see if the problem goes away. Running a bit lean with modern fuels sometimes uses up the valve seat and face faster than was common back in the day.
Thanks for all the feedback, have been thinking of having he crank rebalanced next time things were apart so this looks like the time if i'm going to lift the head and open the timing side.
Will update when i have had a look.
Update 1 - head off, valve seat looks good but the valve is lunched and definitely wasn't up to the task - stem worn, head is deformed around the edge. It was running lean which won't have helped.
Hopefully the Norvil replacement will arrive soon and be made of better stuff than its no name predecessor.
Had this happen to my ES2 caused by radial cracking of the exhaust valve
Test ride yesterday with new exhaust valve installed and so far all goes well, fingers crossed.