Atlas valve timing

A small dollop of grease sometimes help to temporarily fix things in place. Either sticking the washer to the inner case or to the back of the pinion/sprocket. This also works when trying to get the two front cylinder head nuts and washers onto their respective studs. The grease holding the nuts inside the socket or box spanner thus preventing them from going on the studs crooked or worse still dropping alongside the stud and being impossible to retrieve..

Use lots of heat on the pinion. One way to lock the crankshaft is to feed about a foot of thickish (8 mm) rope in through a plug hole, with engine at BDC and then turn the motor forwards until it all locks up. You need to check that this is going to happen on a firing stroke and hang onto the end of the rope.

? Mod 50 is 38 degrees or 15/32" (11.88mm)

? ES2 is 38 degrees or 17/32" (13.5mm)

? Mod 88 is 30 degrees or 1/4" (6.35mm)

? Mod 99 is 32 degrees or .307" (7.8mm)

Mod 650 is 32 degrees or .343" (8.69mm)

The Atlas / Commando has the same stroke as the 650 so within reason 28* ought to be 12% less. So close to the 99 measurement at around 0.303" or 7.65mm.

One of the old Roadholders of 3 or 4 years ago has the numbers in it.

Generally, the idler shaft is a tight fit in its housing. As long as it does not wobble too much, when setting the chain tensions, the timing cover will hold it in position. You could try loctite but the seal will probably break as soon as the timing cover is fitted.

The oil feed hole in the spindle must face downwards. The pinion gets its lubrication from an oil mist passing through this spindle and dripping onto it. This happens when the pistons descend and set up a bellows effect that helps to lubricate all the moving parts.

Previously Phil Hannam wrote:

Generally, the idler shaft is a tight fit in its housing. As long as it does not wobble too much, when setting the chain tensions, the timing cover will hold it in position. You could try loctite but the seal will probably break as soon as the timing cover is fitted.

The oil feed hole in the spindle must face downwards. The pinion gets its lubrication from an oil mist passing through this spindle and dripping onto it. This happens when the pistons descend and set up a bellows effect that helps to lubricate all the moving parts.

Ladies & Gentlemen,

I have a 1965 650SS and I am having terrible problems with not being able to get anything other than a weak mixture and I'm coming round to the belief that I have the valve timing out by one tooth. Should the crankshaft pinion have a centre pop mark on the tip of its tooth and the intermediate gear have its centre pop mark in the valley of its tooth? My intermediate gear has a centre pop mark that seems to be on the tip of the tooth so I could go either way whne setting up the valve timing.

If I was one tooth out would that cause the inlet valve to be open for a shorter time and therefore give me less petrol/air mixture per revolution and cause my permanently weak mixture? The carbs are totally standard and jets etc meet all the correct specifications. I have renewed the petrol tap, float and float needle. The main jet needle is currently at position No 4 i.e. the needle should be giving me a rich mixture.

The machine ticks over beautifully but when pulling it hesitates awfully.I am almost demented by my inability to cure the weak mixture - that's why I'm turning to the duration that the inlet valve is open.

Any suggestions would be gratefully received.

Regards,

Peter Bolton

Incorrect Timing can result in a serious loss of pulling power despite the engine roaring away. Attached photos show timing marks. On the intermediate pinion someone has added some extra dents because the chain tends to cover the originals marks when all the bits are pushed home. I prefer to use a blob of white paint or Typex.

Is your camshaft chain correct with 10 rollers between the sprockert marks?

Previously Phil Hannam wrote:

Incorrect Timing can result in a serious loss of pulling power despite the engine roaring away. Attached photos show timing marks. On the intermediate pinion someone has added some extra dents because the chain tends to cover the originals marks when all the bits are pushed home. I prefer to use a blob of white paint or Typex.

Is your camshaft chain correct with 10 rollers between the sprockert marks?

Dear Phil,

Thanks for all that information. Please find below a photograph of the crankshaft pinion which has a pop mark clearly visible on the tooth - no problems there. However on the other photo of the intermediate pinion the pop mark does not appear in the valley of the tooth. It is further confused by two scribe marks going from the pop mark to the valleys of the teeth either side.

What really irritates me is that I restored the bike 37 years ago and got it right then but cannot get it right now.

The only reason I had the timing cover off was to have the mag re-wound. I noticed however that the auto advance springs seemed a bit weak. Would that make a difference?

If I was one tooth out that would make a difference of 7.5 degrees on the valve timing - sufficient to reduce my inlet charge of petrol/air to make a big difference I guess.

I'll put a dab of tippex on the relevant teeth and see what happens when I re-assemble. Oh I timed the ignition to 28 degrees instead of 32 BTDC to take account of petrol changes. Perhaps I should go back to 32 degrees?

Regards,

Peter Bolton

Previously anthony_bolton wrote:

Previously Phil Hannam wrote:

Incorrect Timing can result in a serious loss of pulling power despite the engine roaring away. Attached photos show timing marks. On the intermediate pinion someone has added some extra dents because the chain tends to cover the originals marks when all the bits are pushed home. I prefer to use a blob of white paint or Typex.

Is your camshaft chain correct with 10 rollers between the sprockert marks?

Dear Phil,

Thanks for all that information. Please find below a photograph of the crankshaft pinion which has a pop mark clearly visible on the tooth - no problems there. However on the other photo of the intermediate pinion the pop mark does not appear in the valley of the tooth. It is further confused by two scribe marks going from the pop mark to the valleys of the teeth either side.

What really irritates me is that I restored the bike 37 years ago and got it right then but cannot get it right now.

The only reason I had the timing cover off was to have the mag re-wound. I noticed however that the auto advance springs seemed a bit weak. Would that make a difference?

If I was one tooth out that would make a difference of 7.5 degrees on the valve timing - sufficient to reduce my inlet charge of petrol/air to make a big difference I guess.

I'll put a dab of tippex on the relevant teeth and see what happens when I re-assemble. Oh I timed the ignition to 28 degrees instead of 32 BTDC to take account of petrol changes. Perhaps I should go back to 32 degrees?

Regards,

Peter Bolton

Forgot to attach the intermediate photo.