Hi all, I’m looking for a little advice regarding unburned oil in the left had exhaust pipe and using 1L of oil per 650Km. This only seems to have started since I replaced the cylinder head gasket and the 6 oil seals a few weeks ago. Wisdom on the web suggests oil scraper ring and/or exhaust valve guide. I’m just wondering if I messed up fitting the oil seals and if I did could this result in unburned oil getting into the exhaust ? Otherwise the old thing runs like a train and there’s no sign of burning oil (eg blue smoke). Any advice would be welcome.
Many thanks
Andy
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That’s a lot of oil to burn, surely you would see blue smoke if you were burning that much.
Did you take the barrels off when you had the head off?
Did you just do the one side?
What was the oil consumption like before you did the work on the bike?
What are the plug colours like?
It started after having done something to it, so I would make up my mind to have it apart again for a coating of looking at, rather than keep guessing.
One thing that just occurred to me is, was the head gasket put on the right way round?
Both head and cyl. base gaskets have holes for the drain tunnel in the barrel, and it’s too easy while thinking about everything else to get one back to front, aka upside-down, then the drain hole is blocked. This will fill up the rocker box so that oil gushes out of the valve guides.
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… or it could come out of the rocker cover breather. If you have the standard airbox some of that oil could make it out of the drain rather than recycle into the sump.
Another thought is - did you remove the top hat from the crancase breather?
Hi all, thanks for the replys. I made sure that the cylinder head gasket was the right way around and the drain hole was lined up correctly. I have K&N filters fitted and the le mans type flapper valve box fitted. The plugs are fine and there is no blue smoke from the exhaust when running. The beast doesn’t appear to be burning the oil. I’ve had the bike 5 years and it’s not used any oil between oil changes (3000km) I just wonder if I’ve messed up with the oil seals though I can’t see how they wold let oil into the exhaust. As I said the old boy is running like a train but using oil. I’m now at the point of giving it to Nige at NBS to sort out but it really bugs me that I can’t figure out what’s causing it…
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If it is not coming from the head it must be coming past the pistons.
If you did not take the barrels off, then this is unlikely unless you have over-filled or started using a lower grade oil.
Latest recommendations are to use 10w60 in all big block bikes. However, if you swap to synth from non-synth then it can upset the seals and may start oil consumption. Most vulnerable are the main bearing seals behind the clutch. Have you checked underneath?
Finally, is the oil actually inside the silncer can, or is it on the outside as it would be if the breather was blowing a bit more?
Like yours, my 1997 Cali does not (noticeably) use oil betwen changes since I replaced the clutch and the main bearing seal at the same time. I swapped from 20w50 to 10w60 for some years i.e. when my stocks of 20w50 ran out.
PS. Just occurred to me. Have you checked the cylinder base? If weeping; retorque the cylinder heads and re-set the valve clearances.
If the plug colour is fine, that would suggest it’s not being burnt so it can’t be coming up past the rings. That leaves the exhaust valve guides or some miscalculation regarding the quantity of oil that has been used.
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Take the rocker cover off and poke a long slim rod of some sort down the drain hole to check that it isn’t blocked by the head gasket being the wrong way round. How do I know that this can happen…guess!
Ah! I see you have already checked.
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Surely that would cause smoking.
Good point.
If oil is being drawn down the exhaust vale guide, it would go straight into the exhaust port and be blown into the exhaust pipe.
Yes, but usually that results in blue smoke on the overrun and when reopening the throttle. Oil down the inlet guides gets burnt during combustion (well, mostly) and sooty, oily residue in the cooler parts of the exhaust.
All that being said; the solution is to be found in removing the offending head, inspecting the guides for play (springs off, I’m afraid), new guides and seat profiling plus valves as necessary and carefully replacing the seals.
It may be that the seal was damaged during reassembly. Easy to do, particularly if the valve stem is slightly burred where the rocker arm makes contact.
Hi all, thanks for the replies. I’m taking the head off this weeknd to see if there is anything obviously wrong. If nothing is apparent then I’m afraid it’s a trip to Nigel at NBS. I would like to solve this myself but as this is my go to bike I need it to be rideable for the winter. If I find a solution I’ll update this post. The bike has only done 63000 Km (genuine) so I would be surprised if it was a wear issue.
Thanks again for your help
Andy
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