Mk3 Timing cover on a Mk2 engine, anything to pay attention to?

Jagbruno said:

Yes, as I wrote, this was when we first open the cases when I bought the engine 5 years ago, I have the right seal now going in with the new pump. Thank you.

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Well, what you said was: "I found this picture from a few years ago when we rebuilt the engine," but ok, as long as it's got the right one in there now.

If it were the wrong seal, what problems does this cause?

The orifice in the pre-mk3 cover is conical shape to fit the seal - the mk3 seal is flatter as it abuts the spring-loaded plunger

Jagbruno said:

Ok, thank you very much. Assuming it exist, wouldn't it be safer to plug the hole in the cover rather than in the crankcase?

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The hole in the Mk3 cover [assuming you got one of the weird early ones with a hole] is not threaded. Therefore it would be much harder to plug. Simply install a set screw into the threaded hole in the right side crankcase. Apply Loctite or Liquid Teflon Tape on the set screw's threads.

Jagbruno said:

Yes, as I wrote, this was when we first open the cases when I bought the engine 5 years ago, I have the right seal now going in with the new pump. Thank you.

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If the engine does not have the correct Mk3 style oil pump seal in it now, that may well be the cause of the wet sumping.
Please take a photo of the inside of your timing cover, when you remove it.

chaztuna said:

The hole in the Mk3 cover [assuming you got one of the weird early ones with a hole] is not threaded. Therefore it would be much harder to plug. Simply install a set screw into the threaded hole in the right side crankcase. Apply Loctite or Liquid Teflon Tape on the set screw's threads.



If the engine does not have the correct Mk3 style oil pump seal in it now, that may well be the cause of the wet sumping.
Please take a photo of the inside of your timing cover, when you remove it.

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Thank you for that, yes I will take pictures and post them in due time of course!
Concerning the seal, I am 99% sure that the seal presently in the engine is the right MkIII type.

Yves and I started working on the thing today (temperature in his shed about minus 6°Celsius), here is how the crankcase looks:



And a close-up view of the timing cover:



A wider view from the timing cover:



If I correctly understood all the comments above, everything seems to be as it should be, so it would seem that 600ml of oil COULD get through my oil pump overnight after all...
A new oil pump is already in place, but is there anything else we should be looking for before closing the engine?
Any remarks?
Thank you in advance!

Nothing out of the ordinary there by the look of it. I suggest you plug the oilway and the oil pump outlet and check the rate of drain with the cover off.

Ok, Yves and I have opened the thing today, here is a picture of the

L.A.B. said:

Nothing out of the ordinary there by the look of it. I suggest you plug the oilway and the oil pump outlet and check the rate of drain with the cover off.

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Well, we have already replaced the oil pump today, so it would be unconclusive

Jagbruno said:

Ok, Yves and I have opened the thing today, here is a picture of the


Well, we have already replaced the oil pump today, so it would be unconclusive

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Unless the Mk3 anti-drain plunger jammed open then I wouldn't expect 600ml to drain 'overnight' under normal circumstances even if the pump was worn.

L.A.B. said:

Unless the Mk3 anti-drain plunger jammed open then I wouldn't expect 600ml to drain 'overnight' under normal circumstances even if the pump was worn.

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The plunger is in place and seems to be operating very smoothly and normally.

A long shot perhaps... but you’re not using ridiculously thin oil are you?

Fast Eddie said:

A long shot perhaps... but you’re not using ridiculously thin oil are you?

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No, I am using Denicol SAE50 Mineral, same oil Yves has been using for years until his recent switch to Redline in the 920cc. So oil is not the problem.

Is the gasket in place between the pump and case?

comnoz said:

Is the gasket in place between the pump and case?

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Yes, Jim it is. Very thin gasket, identical to the one I received with the new pump. It was in excellent condition, I was even able to remove it without breaking it.

Well,
Do as Lab suggested and plug the two holes and watch to see if there is a leak.
I would suggest permanantly installing the 1/4-20 socket head setscrew into the hole in the case that leads to the oil inlet passage. This would prevent the possibility of leakage at the timing cover gasket. Use some epoxy on the screw and do not screw it in so far that you restrict the oil feed passage to the pump. Jim

Thank you Jim,
I did check when I opened the timing cover, there was no leak at the gasket, it was completely dry around the hole, but we'll probably plug the hole as you suggest.
I am still wondering how possibly 600ml of thick oil can drain overnight through the pump (albeit worn)...

Unless the shaft was a loose fit where it comes through the front cover of the pump, even a worn pump should not leak through the check valve -as long as it was not stuck.
I would fill the tank and look closely. I have run into a case where there were pores between the passage behind the pump and the crankcase. Oil that was poured into the tank would dribble right on though into the cases and out crankcase drain plug.
I also found one one time that had a pore between the scavenge side of the pump and the crankcase. The scavenge pump was pulling air through the pore and was not picking up the oil from the bottom of the case so the crankcase would wet sump when running.

One last thought. Are you using a stock oil tank? Would the scavenge return tube have a hole in it below the oil level? If it did that would allow oil to return to the cases through the scavenge side of the pump. Jim

Hi Jim, thank you very much for trying to solve this issue for me.
I haven't seen anything weird when taking the timing cover and pump apart, in fact it all looked very good.
The hole in the scavenge return tube is an intriguing idea, although I have an oil filter in the return line which should prevent that from happening. My bike is a Slimline Featherbed with a 850 'fast' (PW3, lightened rockers, balanced and lightened crank, flowed head..) engine.
Here is a 3 year old picture on which the oil'tank is quite visible:



When I bought the bike 5-6 years ago, it still had its original Dommie oil tank, and I know from the PO that the bike was very hard to start, ie. wetsumped constantly, which certainly was the case when I bought it.
I then installed a brand new central custom alloy oil tank bought from England, but it didn't halt the wet sumping. Unfortunately it is quite difficult to remove from the bike to be properly tested. But I think I can test it in place quite easily by simply removing the return line from the tank and then filling it up.

About the 'porous' hypothesis, the crank flange onto which the pump is affixed looked clean and polished, without any visible mark on it. I guess we could look at it again very closely althought we have already installed the new pump, but it is not too much work to remove it again.

Finally, the old pump was not stuck, has no 'hard points' while turning it and looking at the gears through the small holes, they appear clear and unmarked. It would be normal, as I replaced them 2 years ago.

So we will keep looking, thank you again to Jim and all the others who are participating to this Sherlockesque thread.

Jagbruno said:

The hole in the scavenge return tube is an intriguing idea, although I have an oil filter in the return line which should prevent that from happening.

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Not all spin-on oil filters have an anti-drain back valve.

Salut Bruno and All,

A few posts above, Jim mentioned the larger flange to use with a MK3 oil seal and you said it wasn't clear for you. You can see that larger flange protruding a little bit out of aand behind the seal in the first picture posted by Gortnipper. It shows what it is and how it must be located.

Hope this helps.

Laurent