Tapping then loud rattling sound.

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When out for a run to run in my 1960 Dominator 99 I heard a bit of a tapping sound, I thought a valve tappet needed adjusting. After a while there was a very loud rattling sound, I thought something had come adrift in the primary chain case and was catching the chain. The engine was still running ok so I managed to get a relatively short distance home. On having a good look around I found that a washer/spacer was missing on the left side exhaust rocker spindle. I am worried that the washer may have dropped down to the camshaft, as I couldn't see it in the cylinder head. I would welcome anyone's advice on a course of action. I thinking head and barrels off?

Is it physically possible…

Is it physically possible for a washer to be in place on the shaft and then fall off?

I agree it does sound…

I agree it does sound unlikely, but the other rockers have washers and no side play. This one has notable side play. I must admit I have adjusted the tappets but didn't notice if this one had a washer before.

Probably best to whip off…

Probably best to whip off the barrels, but it might be worth draining the oil,taking the sump plug out for a look-see first.
Can't say I've ever heard of a rocker spacer disintegrating in situ.

Drained what oil was in the…

Drained what oil was in the sump and it appeared clean with no bits.

Could be piston has picked…

Could be piston has picked up from overheating ( commonly on the drive side ) and there is extra clearance or a ring stuck in it's groove. A tight rocker ( slightly seized ?) may not follow the cam and clatter. Use a big screwdriver as a stethoscope to pinpoint the noise.

The left cylinder is oily…

The left cylinder is oily compared to the right. I feel the head and barrels need to be removed and examined as I'm not confident the left rings are ok. I am toying with starting the bike again to try and locate the noise before I strip it to know where to look?

If you can pinpoint the…

If you can pinpoint the area of the noise before stripping it can be helpfull . Nothing worse than not finding anything obvious , put it back together ? replace everything ?.

The rockers have a solid…

The rockers have a solid washer on one side and the Thakery (?) coiled spring washer on the other, to provide a cheap and simple factory means of controlling rocker end float. Has the coil washer broken? (Does that ever happen - and why?... it shouldn't be under any load)

SInce you've looked inside - have you turned it over with the plugs out? Rattling /tapping can be caused by one of the pushrods coming out of place either at top or even the bottom?

The oil drain paths from head to crankcase are not very large, but broken bits could go down there. Does the sump filter have any small bits of metal in it?

The coiled spring is ok. The…

The coiled spring is ok. The oil is fresh and had just been changed and looks clean with no bits.Turned it over and all rockers move as normal with no excessive gaps. I thought at one point the noise was coming from the front bottom of the barrels. I suppose any loose bits could end up down there quite easily and get trapped at the bottom of the pushrods? The engine was running well on the way home but was very ratty increasing and decreasing in volume.

I'd be dubious about…

I'd be dubious about starting the engine again, anything floating about inside would make matters worse.

I agree...

... you could cause a lot of damage. Getting the head off should be enough to identify the problem. Like others I fail to see how a washer on the rocker shaft can actually come off unless it split in two.

Maybe...

A significant amount of noise from the bottom of the barrels can be a Stellite tip coming off of the cam follower. But turning the engine over slowly with the rocker covers off will show a huge gap on the rocker which has lost its tip. (I would also expect the pushrod to jump out if not dealt with soon)

Thanks to everyone. I'm not…

Thanks to everyone. I'm not going to run it again, I'm going to strip it down and not cause any further damage. I am thinking something has dropped down or broken at the bottom of the barrel by the pushrods. I'll check piston rings too .

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