Camchain adjustment and oil

I need to adjust my camchain and am not certain if it is necessary to drain the oil from the bike or not. I have done the chain before but always with the oil tank drained.

I just changed the oil about 6 weeks ago and would prefer to leave it in if possible rather than drain it and refill.

I've looked through the Norton and Haynes Service manuals but can't see any tips on this one. Does the oil stay behind the pump ot not when the engine is not running?

mike916sp said:

I need to adjust my camchain and am not certain if it is necessary to drain the oil from the bike or not. I have done the chain before but always with the oil tank drained.

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If the engine has been run recently then the oil should (theoretically) be in the tank, and not in the sump, so there shouldn't be any significant amount laying in the timing case, although if you remove the timing cover, oil will slowly begin to drip from the pressure relief return drilling, so it is necessary to temporarily insert a timing cover screw into the return drilling (which is threaded for this purpose) but there should be hardly anything at all coming out of the pump.

Thanks very much. It was run last Sunday and has been left on compression since so there shouldn't be to much oil in the wrong places.
Thats the cover off tomorrow morning then Cheers

Sorted out the timing chain no probs and the tip of using a screw worked a treat

L.A.B. said:

if you remove the timing cover, oil will slowly begin to drip from the pressure relief return drilling, so it is necessary to temporarily insert a timing cover screw into the return drilling (which is threaded for this purpose).

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I also found a useful tip as well. When you are replacing the cover you need to remove the screw, clean up the gasket faces, put the silicone seal on a dry face before fitting the cover. You can't do this with oil dripping from the return drilling. The solution - use a mole grip to lightly clamp the return oil line and you can the fit the gasket and tighten up the case screws.

I know that plenty of people probably do it this way but just though it worth tagging on the end of this thread for anyone refering to it in the future

Can't say that I've ever used silicone sealant on the timing cover joint faces, only a gasket, and that has always resulted in a 100% oil tight joint.

Its just something that Les Emery at Norvil recommended. I only live two miles from him and am always popping in for bits and tips

Be careful about eliminating gaskets. For instance, eliminating the gasket from the timing cover will decrease the clearance between the timing gear and the cover.

Can't say that I've ever used silicone sealant on the timing cover joint faces, only a gasket, and that has always resulted in a 100% oil tight joint.

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And as I have said before, if you insist on using silicone on cirulating oil systems, be very careful. Use it sparingly and don't allow it to be squeezed from the joint on the oil side. If you have a spin-on filter it may be caught in the filter, but if not it will be caught on your rod bearings.

L.A.B. wrote;

if you remove the timing cover, oil will slowly begin to drip from the pressure relief return drilling, so it is necessary to temporarily insert a timing cover screw into the return drilling (which is threaded for this purpose) but there should be hardly anything at all coming out of the pump.

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When I had the timing cover off a couple of months ago, I wondered where the oil was coming from and why the hole was threaded. At the time, I didn't have the inclination to work it all out as I was in a hurry to replace the camshaft oilseal, which as it turned out was not the source of my leak. In fact the leak was coming from a loose timing cover inspection cap, and the oil was blowing around the points cover housing! Another puzzle solved.

Thanks.

On the 850 MkIII the return drilling in the crankcase serves no real purpose, as the MkIII timing cover has a different venting arrangement for the pressure release valve.
Unlike the earlier models that direct the excess oil from the release valve through the drilling back to the inlet side of the oil pump, the MkIII release valve vents its excess oil directly into the timing case.
The MkIII timing cover effectively blanks off the crankcase drilling when it is fitted, as there is no drilling in the timing cover.

Jason Curtiss said:

Be careful about eliminating gaskets. For instance, eliminating the gasket from the timing cover will decrease the clearance between the timing gear and the cover.

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I use a gasket as well as the silicone seal - which I use sparingly - so clearances are not affected

L.A.B. wrote;

The MkIII timing cover effectively blanks off the crankcase drilling when it is fitted, as there is no drilling in the timing cover.

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Yes, that's what was really puzzling. The drilling sat directly on top of a flat faced casting (the timing cover), so the oil was going nowhere, so what was the purpose of it? Thanks for explaining why it was there.

Reggie said:

Yes, that's what was really puzzling. The drilling sat directly on top of a flat faced casting (the timing cover), so the oil was going nowhere,

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Not really a case of the oil going nowhere, as I said, the pressure release valve vents into the timing case on an 850 MkIII, the drilling is a return passage for the release valve on all non-MkIII models as the oil has to pass through the pump and into the timing cover gallery to get to the release valve, where it recirculates back to the pump inlet through the drilling, the MkIII timing cover just blows the excess oil into the timing case so does not recirculate the excess oil back to the pump inlet.

Reggie said:

so what was the purpose of it?

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If the return drilling had not been kept then anyone fitting an earlier model timing cover to a MkIII (or MkIII crankcases) would effectively have blanked off the pressure release valve.
So I guess they retained the drilling in the MkIII cases so that there was certain amount of interchangeability between various crankcases and timing covers.

L.A.B. You never cease to impress me with your level of knowledge on Norton Commandos.

I nearly feel inadequate. :shock: