Smoking

Before you next start the bike, remove the sump plug and drain whatever oil has collected in the crankcases. There should only be a small amount. If there is a lot, then the engine is 'wet-sumping' - a misnomer really, but it means that oil is draining into the sump via the oill pump when the bike is left standing.

On starting, this excess can find its way into the combustion chamber, until the scavenge pump has cleared it.

If this is the case, your oil pump needs servicing.

Aren't there drain passages from the exhaust valve pockets on a Commando? Is it possible that one of the passages are plugged letting oil pool in the pocket?

Probably the RHS inlet valve seal has come off, seems to be a (recent) recurring problem. If it smokes after ticking over for a while (eg at traffic lights) when pulling away I'd suspect that first, head off job I'm afraid!

Buy "genuine" seals

There is a drain in the RHS near the valve which allows the oil in the rear of the head fall back into the crankcase, if you've inadvertantly blocked it with silicon or similar then thatpotentially couldcause the problem.

As Gino says but to confirm you can pull the carbs and intake manifold first. If there is a puddle around the back of the valve then it is the seal that has failed/become dislodged or damaged by overcompressedretainer. Of course if you are unlucky that valve will be open when you pull the carbs and the oil will have disappeared! There should be some evidence though.

Buy "genuine" seals

Yes but make sure they are a tight fit on the valve. I had 'Genuine' seals from a Midlands 'Stealer' with bores big enough for a 9mm stem dia. When I visited and complained (yes they did leak) he told me I'd damaged them but did replace them grudgingly.

I do not think that this is a problem at the top end of your engine. Both the valve guides & sealswould have to be totally knackered for so much smoke. Plus.....you say that it is clears after a short while. Problems at the top end would most likely cause the smoking to continue.

I am going to put my money on one of the following:-

1) The pressure release valve spring is dying and allowing too much oil to flood the timing cover. From here it is passing straight into the right hand bore where your new rings, (which still need to bed in to do a proper job), are letting lots of this black gold up to the head. Once the oil warms up a bit, then the pressure in the system is dropping enough for the release valve to cope and stop the excess heading straight for the sump. The cure is a new spring and/or some shims to up the pressure release point.

2) Possibly your oil pump is not in the best of condition and is taking too long to clear the sump. However, if this was the case then I would expect to see smoke from both exhausts!!! DIY servicing of these oil pumps is very easy and can be done in just a couple of hours and is well worth doing on a Commando that has more than 50,000 miles under its belt.

3) Is there a problem with the right side oil control ring and it is failing to cope with oil leftthat gathers inthe sump. Perhaps the glaze busting has left a patch that is going to need more running-in mileage.

I would suggest that you put up with the smoke and oil consumption until 200 more miles have passed and then re-evaluate. It the smoking is still bad on just the one side then check out the list above again.

I'm with Gino on this one - classic Valve Stem oil seal worn / dislodged. From the engineering point of view, if it was related to the re-bore and new rings it would happen whilst under way. When mine had gave up the ghost, I spat a pint of oil out the back on a run up to Birmingham, the Honda VFR and rider where totally waterproof for the rest of the day!!

Another way to check, is to look at the valves, can't remember exactly whether it was inlet or exhaust, but I saw oil dripping from them after the bike had been left a day or so, which was the big give-away.

Previously wrote:

Probably the RHS inlet valve seal has come off, seems to be a (recent) recurring problem. If it smokes after ticking over for a while (eg at traffic lights) when pulling away I'd suspect that first, head off job I'm afraid!

Buy "genuine" seals

No need to remove the head, see Roadholder No 291, Jan 2012.

Previously phil_hannam wrote:

I do not think that this is a problem at the top end of your engine. Both the valve guides & sealswould have to be totally knackered for so much smoke. Plus.....you say that it is clears after a short while. Problems at the top end would most likely cause the smoking to continue.

I am going to put my money on one of the following:-

1) The pressure release valve spring is dying and allowing too much oil to flood the timing cover. From here it is passing straight into the right hand bore where your new rings, (which still need to bed in to do a proper job), are letting lots of this black gold up to the head. Once the oil warms up a bit, then the pressure in the system is dropping enough for the release valve to cope and stop the excess heading straight for the sump. The cure is a new spring and/or some shims to up the pressure release point.

2) Possibly your oil pump is not in the best of condition and is taking too long to clear the sump. However, if this was the case then I would expect to see smoke from both exhausts!!! DIY servicing of these oil pumps is very easy and can be done in just a couple of hours and is well worth doing on a Commando that has more than 50,000 miles under its belt.

3) Is there a problem with the right side oil control ring and it is failing to cope with oil leftthat gathers inthe sump. Perhaps the glaze busting has left a patch that is going to need more running-in mileage.

I would suggest that you put up with the smoke and oil consumption until 200 more miles have passed and then re-evaluate. It the smoking is still bad on just the one side then check out the list above again.

Something most over looked is the timing cover oil seals damaged or gone hard the timing case oil Seals there is two of hem one is behind a circlip fits to crank shaft end for the oil feed to the crankshaft and if damaged can leak in side the timing cover and over fill it, thus giving to much oil being sucked up the cylinder walls for the oil ring to cope with ,Next the small rubber O ring for oil pump end can produce the same effect and like wise if both have been damage or are needing replacement,

now you can fit this into your memory bank yours anna j