Curious problem with a MKIII

I just purchased a 1975 MKIII with 29,000 miles on it. The bike hasn't run in ten years and was in the guy's living room with 15 cats. The smell... After douching the bike several times I started adjusting the valves and changing the oil.

Curiously the left intake valve and rocker had a lot of slop even when the adjuster was screwed in -1/8" or so. Asking around-cam or cam followers were suspect.

Pulled the engine apart today
-The cam looks beautiful, no scuffing at all on any lobes.
-The cam followers look perfect. I removed the left side and compared the two.
Smooth no regression, same length.
-Next were the pushrods. Same length, no wear.
-The rocker arm was removed and looked fine. The adjuster screw was compared to the other intake and was the same length.
-Tested for a bent valve with liquid in the rocker cavity, no leak.

I'm going to pull the valve and chek that next.

Other suggestions?
Thanks, Pete

Yeah, next time take a dog with you, should liven things up a bit.

Meow.

It’s a bit of a fallacy that a worn cam shows up as a loose tappet. It’s the cam lobe that wears out... but tappets are set with the valve closed, ie on the base circle.

If it’s been stood for that long unused, it’s possible that two of the valves may have stuck partially open, or at least not seated correctly.

Turning it over may have freed it up?

If it’s been sitting that long, you’ll almost certainly have two compressed valve springs, for their cost, I’d advise a new set as a matter of course.

Also, if you’re not familiar with the topic already, check out the gearbox layshaft bearing story on here... probably something that should be high on you TTD list before putting serious miles on the bike.

Fast Eddie said:

It’s a bit of a fallacy that a worn cam shows up as a loose tappet. It’s the cam lobe that wears out... but tappets are set with the valve closed, ie on the base circle.

If it’s been stood for that long unused, it’s possible that two of the valves may have stuck partially open, or at least not seated correctly.

Turning it over may have freed it up?

If it’s been sitting that long, you’ll almost certainly have two compressed valve springs, for their cost, I’d advise a new set as a matter of course.

Also, if you’re not familiar with the topic already, check out the gearbox layshaft bearing story on here... probably something that should be high on you TTD list before putting serious miles on the bike.

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Appreciate the tips Eddie. I put liquid (WD_40) into the rocker to see if it would leak past the affected valve. No leak. Pulling the valves out today.

Was the push rod sitting on the rocker arm, I have never had my Norton drop a push rod but had my old Triumph do it, valve stuck and dropped a push rod off the rocker arm.

Ashley

ashman said:

Was the push rod sitting on the rocker arm, I have never had my Norton drop a push rod but had my old Triumph do it, valve stuck and dropped a push rod off the rocker arm.

Ashley

Click to expand...

It's possible. If i can't find anything wrong I will put it back together and see if that works. Taking the valves out now.

Been helping a newbee club member sort out atlas/commando parts differences.
Very closely check that at some point that a shorter stem atlas valve has not been slipped in while no one was looking.
It would require the adjuster to be screwed in 2-3 turns extra.

We pulled the valves-there is ~.040" difference in the height when installed. Valves appear to be the same length. The seat is recessed more on one side. Still doesn't explain the slop. I have one exhaust valve guide that was very sloppy in it's bore. I will need an oversize valve guide. Replace the valve too. One rocker shaft -rt intake-was also loose, came out w/o heating it.