Have a problem with my 64 SS80 as it smokes a lot. OK on initial start up but soon starts smoking as the oil gets round. Reving the engine indreases the smoke. Just been rebored and new old stock piston fitted as well as new valve guides. Valves measure up at 0.309 ex and 0.310 inlet which seems to be correct. Measured on the wear areas and the areas above and below the guide wear sections and all come out the same. I can actually see oil coming out of the exhaust when the engine is running. When the head was removed, there was a lot of oil on top of the piston and inside the head. There was also oil inside both inlet and exhaust ports. I have checked that all oil return holes are clear, so the oil should be returning to the sump ok. Running out of ideas. Experience/guidance greately appreciated
What rings did you fit eg cast iron or steel, who did the honing and what grit did they use and did you do a dry install or soak the rings in oil, what oil did you use for running in. When the bike was first started did you leave it ticking over or did you ride it immediately.
Hi Kommando and thanks for the reply. Bought a new old stock Hepolite piston with rings. Brought that to a local engineering company who do a lot of motorcycle engines. He insisted on having the piston prior to doing the job. Engine was only just reassembled with oil on the moving parts. I used Halfords Classic 20/50 oil. Yhr engine has only been started and run for about tem minutes, partly at tickover with some gentle reving to see how much smoke there was. The reason for the rebore/new guides was that it smoked just the same before and had the same symptoms
You need to find out the grit used, it needs to be course at say 120 or 150 to match the NOS old rings if it was a 180 or higher then it needs redoing. Oil is ok but leaving it idling and reving it with no load does not force the rings out into the bore, this is needed for the grit to start to wear the rings in to suit the bore. Also its best done with a dry bore with a dab of oil on the front and rear face of the piston, been doing this for 20 years and never had a problem with rings not bedding in.
Oil is in exhaust and inlet plus on piston, so it's either both guides or rings so more likely rings. Other possibility is the head gasket as there are for the B40/B44 at least too thin head gaskets but then the oil would also be coming out of the head/barrel joint.
Thanks again. Just crossing T's etc. Measured the recess in the head and the hight of the barrel stub. I have two thicknesses of head gasket and the thicker one was fitted. Dimensions seem pretty close and may have allowed oil to be sucked into the barrel, bus as You say, itb is more likely to come out than in. There was no oil leak from the head, Will call engineering shop on monday and ask re honing grit size.
You say that you have done this recent work and not cured the original fault, I would be looking at two things here, the first would be crankcase compression, the second would be the integrity of the seal across the head / cylinder, If you go for the second, clean both surfaces and use micrometer blue on the cylinder top and gently rub the head and cylinder in the general position where it would normally fit, this would show if the head has distorted around the bolt /stud holes, if this is the case, then have the head re surfaced, I am not too familiar with the C15 but I would use a good quality solid copper head gasket, see how you go!, I now realise that due to the register on the cylinder the two surfaces will not contact, so therefore smear a sheet of glass with micrometer blue and check this way, I would also sit the head on the cylinder and with feeler gauges check that the gap between the head and cylinder is smaller than the head gasket.
Thanks to you both for your thoughts. The engineer was not in today so I could not check the hone grit. I was told to bring the barrel and piston in if I thought there was a problem there. The c15 breaths through the cam into the outer cases and out to atmosphere. All looked OK when the motor was apart. Will remove the timing side and recheck that the cam holes are clear. Will also check the flatness of the head and the fit to the cylinder asap. Thanks again.
I recently had a similar issue with an A65, I fitted 3 piece oil control rings obtainable in any size from a company in York called Performance Unlimited ,give them the bore dia depth and width of the piston grove, they supply the total seal ring,
Thanks again guys, Will check breathing and oil pressure valve at the weekend. Also when I reassemble, if it smokes again I will cut off the oil feed to the head for a few seconds and see if the smoking stops. Should tell me if it is the guides.
Re reading from the top. Andy probably has got it right. The inlet sucks and on many engines had the only valve guide seal. The only place the inlet can get oil into it is through the head. Three options, Down between the guide & valve Between the guide & head Through a crack in the head.
Of thse 3, the first would happen all the time so you will be smokey at start up while the other two will get worse as the head heats up. Badly sealing rings will make this a lot worse as you get excessive pressure in the crankcases finding the easiest exit path, which is into the cylinder. Blow by into the cylinder from the bore will not deposit oil in the inlet tract as it has to go against the flow of the incomming charge.
Bad / blocked crankcase breather will make this worse.
Update to the smokey C15. Checked head is flat, all OK. Bought new old stock valves and fitted to new guides. Checked clearance at head/barrel. All OK here. Checked breathing system, all clear. Hone was fine 180 grit. Rings fitted correctly. Run motor and it smoked. Noticed that oil was returning to tank in a constant stream. I did expect there to be a lot of air in the flow as the scavenge side of the pump out performs the feed. Non return valve in the cases is good as the bike has stood for a couple of weeks and oil level in tank was only slightly lower. Pressure relief valve was checked and reseated. Spring is correct length. Going to take it out this afternoon, when all the relavent parts are refitted and see if it settles down. Only mod to the engine was the fitting of a timing side roller bearing in place of the bush.
The return oil constant stream should become bubbly if you rev the bike up once the sump excess has cleared, if not then your engine is wet sumping and the pump needs a freshen up and the return route checked for restrictions, eg old oil pipe can delaminate internally and slow or stop the flow.
Seamus, I have had problems with sets of original BSA "KitPac" rings (come in a red and white BSA ring box) not seating and smoking a lot that I sell from time to time. Just a poor quality issue. Put in different brand of rings and all is well. This doesn't really address the problem of oil actually blowing out of the exhaust pipe and oil everywhere that you describe in the first post though.
Thanks Gentlemen. I had also changed the feed and return pipework. I will check out the metal pipework from the engine to the pipes and the pipes to the oil tank. I guess the only work possible on the pump is on the faces of the plates and the end of the gears to minimise clearance. Need to look at the teeth of the gears to see what they are like aswell. Seem to be chasing my tail here as all this work has not yet cured the original problem. Assume that a bad pump would cause smoking due to excess oil under the piston.
I guess the only work possible on the pump is on the faces of the plates and the end of the gears to minimise clearance.
Yes, simple but laborious as you have to check to make sure you do not go to far, end plates first until they are smooth and then check to see if the gears still move if oiled, it should be stiffer but if stuck or tight then go for the gear end faces.
Need to look at the teeth of the gears to see what they are like as well.
Yep, the return side especially as they can get chewed up from rubbish entering the sump
Assume that a bad pump would cause smoking due to excess oil under the piston.
Yes, I have seen a return side work until a filter was added and then the engine smoked until the pump was refreshed, it had lots a clearance.
Check the amount of oil in the sump after a run, excessive amounts show its wet sumping. Also check the return pipe inlet to make sure its anti drain ball bearing is moving freely.
This problem is almost certainly caused by the rings not seating and is an issue I have previously experienced with unit singles following re-boreing and new piston and rings. Despite my best efforts I have sometimes been mystified to find black oil leaking from the exhaust port and blue smoke in the exhaust.
I don't think the oil pump is at fault since you have a good flow of back to the tank. Instead the problem is likely caused by the rings not seating against the cylinder following a rebore.
This problem is probably caused by one or more issues as follows:- - the cylinder hone finish wasn't coarse enough. 180 grade is OK but is towards the finer end of finishes, 150 would be better. - the standard cast iron rings weren't run in properly. This means that you need to run the bike hard in the first few miles to ensure sufficient pressure in the cylinders to get the rings to seat. Don't make the mistake of letting the engine idle in the garage after first start-up as there is only a small window of opportunity to get the rings seated against the still coarse cylinder barrel. - there may be a leak around the cylinder head gasket so check the surfaces and whether the copper head gasket is thick enough. Consider using a thin smear of high temp silicone to help seal around the oil drain holes and a thicker head gasket, pattern ones are sometimes thinner - hopefully you are using some kind of classic oil and not the latest synthetic which might not help with the rings bedding in - finally, I have found using three piece oil control rings to be helpful. Examples include Cords, Hastings and Total Seal rings. These type of rings have much better sealing and oil control properties than the original single piece cast iron rings e.g. Hepolite
Last edited by gunner; 07/19/165:51 pm.
1968 A65 Firebird 1967 B44 Shooting Star 1972 Norton Commando
Thank you again for the suggestions. All been to bits again (can do itin my sleep). Oil pump was ok. no wear patterns showing and gears were fine. Fitted a new set of rings and decided to run a honing tool up and down the bore as it was a bit polished. Guess it only got a very quick hone. Reassembled and took it out. Very little smoke and now its stopped. Really pleased. Thanks to all who offered advice. Really appreciated.