E: Engine Comet Sumping and Really Smokey

[tom wilson]

Hi all I have a 'Series C' Comet that is a real 'Smokey Joe' I have found that if I drain the crankcase then start up the bike at first the smoke clears .... but returns after 1 minute's running. Then when I stop the engine and drain the crankcase, I remove around 1/4 pint of oil. I have removed the return oil pipe from the crankcase and blown through it .... it is clear all the way to the oil tank. I suspect the oil pump before I start to strip does anyone have other ideas or suggestions as to why? many thanks in advance. Also is it easy-ish to strip/gain access to the oil pump as I have not done a pump removal/assemble before?
I have removed the pump all seems well, the only thing I have found is that the slotted screw peg is worn it has 2 flats on it .... I have ordered a new one lets hope that sorts it ..... fingers crossed.

 

[chankly bore]

The oil pump and sleeve removal is covered in "Richardson". You can make up a slide hammer using one of the longer crankcase studs as they should be the right 5/16" B.S.F. thread.

 

[lee_812d]

If it's smoking like a steam train it might be worth checking the exhaust valve guide is still firm by looking up the exhaust port - mine was loose and it went from hardly any smoke to loads when the guide became loose. Hopefully it is not that.
In the first few runs of mine back in the spring I was amazed at the lack of smoke from the bike - someone pointed out that maybe it was because there was no oil flow - hopefully a bit of a joke but made me stop and think, oil has always returned to the oil tank well on mine (as viewed from the oil tank). But maybe your smoke clearing is because the crankcase has been drained and there is not so much there? A quarter pint doesn't sound excessive, but I don't know what the expected amount is - if the return flow to the oil tank is not great despite the oil in the crankcase then the pump could be suspect.

 

[Bill Cannon]

Hi all I have a 'Series C' Comet that is a real 'Smokey Joe' I have found that if I drain the crankcase then start up the bike at first the smoke clears .... but returns after 1 minute's running. Then when I stop the engine and drain the crankcase, I remove around 1/4 pint of oil. I have removed the return oil pipe from the crankcase and blown through it .... it is clear all the way to the oil tank. I suspect the oil pump before I start to strip does anyone have other ideas or suggestions as to why? many thanks in advance. Also is it easy-ish to strip/gain access to the oil pump as I have not done a pump removal/assemble before?
I have removed the pump all seems well, the only thing I have found is that the slotted screw peg is worn it has 2 flats on it .... I have ordered a new one lets hope that sorts it ..... fingers crossed.

Quarter pint sounds normal to me. No oil will return until there is a pool in the crankcase for the return pipe to pick up. This can take several minutes from a dry start up.

The smoking is probably unrelated. As said valve guides or stuck rings possibly.

 

[ClassicBiker]

I had a similar experience with my C Shadow. I narrowed down the cause by first doing a leak down test. Which surprisingly wasn't to bad. So my next step was to run the engine and warm it up and make sure the oil was circulating. I shut the engine off by passed the oil feed to the valve gear, sending the oil straight back to the tank. When I restarted the engine the smoking had stopped. I only ran the engine 5 minutes at most. But this lead me to believe that the problem lay with the valve gear. It is easy enough to pull the push rods and rocker assemblies from the engine and this is what I did. Looking into each tunnel to see what I could see. Sure enough the front cylinder lower exhaust valve guide had gone. I retrieved what remained of it from the muffler when I removed the exhaust. The upper valve guides are sufficient to keep the valve in line with the seat and allow the engine to run. The damage was contained to the threads of the lower valve guide lock ring being destroyed, but that was easily overcome by the use of a Walker Widget, now available through the VOC Spares Co.
So before focusing in on the oil pump, I would see if there are simpler explanations to the cause. Particularly if the bike didn't smoke before and has only just started doing this. I should think replacing a worn guide or freeing a stuck ring is an easier proposition than replacing the oil pump.
Good luck and let us know what you find.
Steven

 

[erik]

I would recommend to close the oil feed line to the clinder wall.If this oil line is not 100% oiltight between the cases and the liner you will have more oil in the crankcase and much less on the camshft where you need it most.I have closed this on all three of my Vincents without any problems sinc thousends of miles. The easiest way to block it is a small disc of gasket paper or from the metal of a beer can in the timing cover.Erik

 

[Albervin]

A Comet that smokes so soon is a problem. The sump is supposed to have some oil in it so the pump works. Think about it. It takes quite a while to pump oil into the sump, move to the top end and back to the tank. Whatever you may think, a minute's running should not cause smoke. What is happening with the breather??

 

[tom wilson]

A Comet that smokes so soon is a problem. The sump is supposed to have some oil in it so the pump works. Think about it. It takes quite a while to pump oil into the sump, move to the top end and back to the tank. Whatever you may think, a minute's running should not cause smoke. What is happening with the breather??

Hi Al thanks for the reply. I have fitted a very large breather to the inlet rocker cap (no difference). I have disconnected the return oil feed from the rocker gear and the smoking stops and returns when re-connected. I shall fit some metering wire to to the rocker bolts. The guides etc seemed serviceable, I have found a very worn oil pump slotted screw which I shall replace ...... fingers crossed.

 

[ClassicBiker]

If the large breather you have fitted doesn't have a one way valve in it and your timed breather is still connected, air is simply being pumped in and out of your crankcase. There are several threads here on the forum, explaining how the timed breather is supposed to create a slight vacuum in the crankcase so that oil isn't forced out through joints and seals. The valve guides may appear serviceable, but heavily smoking the with the oil return connected to the valve gear tells another story. Hopefully the metering wires will help as well as the new pump screw. Let us know.
Steven

 

[stumpy lord]

I had a similar experience with my C Shadow. I narrowed down the cause by first doing a leak down test. Which surprisingly wasn't to bad. So my next step was to run the engine and warm it up and make sure the oil was circulating. I shut the engine off by passed the oil feed to the valve gear, sending the oil straight back to the tank. When I restarted the engine the smoking had stopped. I only ran the engine 5 minutes at most. But this lead me to believe that the problem lay with the valve gear. It is easy enough to pull the push rods and rocker assemblies from the engine and this is what I did. Looking into each tunnel to see what I could see. Sure enough the front cylinder lower exhaust valve guide had gone. I retrieved what remained of it from the muffler when I removed the exhaust. The upper valve guides are sufficient to keep the valve in line with the seat and allow the engine to run. The damage was contained to the threads of the lower valve guide lock ring being destroyed, but that was easily overcome by the use of a Walker Widget, now available through the VOC Spares Co.
So before focusing in on the oil pump, I would see if there are simpler explanations to the cause. Particularly if the bike didn't smoke before and has only just started doing this. I should think replacing a worn guide or freeing a stuck ring is an easier proposition than replacing the oil pump.
Good luck and let us know what you find.
Steven

I have heard of at least three lower valve guides having broken up completely, and the engines continuing to run, with no lower valve at all, granted very oily, but run they did. the fact that when you disconnected the oil return pipe, and it stopped smoking, to my mind that points to a problem with the lower valve guide, a quick check is to pull the exhaust pipe , and have a look up the hole, or pull the rocker out.
stumpy lord