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Hans
I would agree that Viton is essential for the Desmo guide O ring (same size). However the originals were Nitrile as they went rock hard after years of use. Anyone who's ever tried to remove a guide O ring after years of use will know what I mean, not easy! There are certainly no disadvantage in using Viton O rings of the same hardness, only cost...which is nothing in real terms. Regarding the colour of Viton seals, many are supplied as black, so it is not a hard and fast, green or brown identification with all makes. Mentasti used to supply Ducati with green guide seals, which are in there catalogue as green.....but now come supplied black. The Viton O rings we supply for the Desmo guides are also black.

Geordie,

Sorry if I missed the "clean oil" bit, I would then suspect a bango or top bevel gasket. Is the banjo face distorted and does it have unflanged bolts? If all is flat, alloy washers should seal it well. However if the faces are less than perfect, you may need a little sealant, or some other parts.

Regards Nigel

From experience with dismantling newish engines, I think the O-rings first used on Ducati singles were not Viton type, because they had become hard in use.
When Viton O-rings and valve guide seals became available they became the desirable upgrade.
I think that was after the last Italian Ducati singles were made, after 1973.

Evening All,

Never had a problem with either Nitrile or Viton 'O' rings on the cam feed spigot to cylinder head joint. Have had black of both rubber types and the green and latte colours. Clean oil for assembly and pump some down the feed for priming. This is with both the standard and Lacey high capacity pump.

Occasionally get a wee weep from the around the left-hand cam cover and a wee drop of 'Captain Tolley's' sorts it out.

As for the alloy washers on the banjo bolts as mentioned by Nigel, I have used both annealed copper washers and Dowty washers, as I didn't have any aluminium washers to hand. I have had no problems using either of these alternatives and at present have Dowty washers in place that have now been run for over 4,000 miles, with no problems.

I know that an engine shouldn't leak oil, but having been originally assmbled by "indolente" Italian or Spanish fitters, kicked around for at least 40 years, non original parts, or parts of unknown vintage, pattern gaskets, butchered by bodgers, fixers and racers is it any wonder that the fitting and assembly process can be nightmarish? And then the engine has a wee weep from a seal or gasket. I also know that with meticulous attention to detail and countless hours of patience, the wee beastie will do 3 laps of the TT course at a gnats under an average of 100mph for all three laps and still be immaculate, with not a drop of lubricant in sight!

Whilst I enjoying the fitting and assembly it can drive me loco and I'd much prefer to get some miles under the wheels.

Good health and get the miles in while you can. Bill

LaceyDucati wrote:Geordie,

Sorry if I missed the "clean oil" bit, I would then suspect a bango or top bevel gasket. Is the banjo face distorted and does it have unflanged bolts? If all is flat, alloy washers should seal it well. However if the faces are less than perfect, you may need a little sealant, or some other parts.

Regards Nigel

Thanks for your time Nigel. I added Dirko HT to the top bevel gasket and bought Dowty washers for the flanged banjos. The o-ring is from Jesus Guzman, not the local hydraulic shop as before. All spotless before assembly and countersink polished with imperfections removed.

To no avail - same leak. I add the pic for amusement! Drip from above I hope

OH! that doesn't look so good Geordie. Is that a bubble of oil that I can see on the lower face of the nut? I would suspect that there must be some pressure forcing that oil out, rather than it dripping from the top end of the engine. Or am I talking ballcocks?

I haven't seen an engine blowing bubbles like that since the external oil lines of a '53 AJS 18S I once owned had a wee leak. Have you removed that engine mount plate to see if there is oil between it and the crankcase, or along the length of the mounting bolt. You know where I am heading, with a weep from between the two crankcase halves due to either the gasket moving during torquing up; or more likely, crankcase pressure build up finding a path of least resistance.

I hope that I am wrong.

Good health, Bill

Yes, pressure there somewhere....... That looks to be a clue as to what is happening!


Colin

Has any one mentioned the crankcase breather? the only time I have ever encountered an oil leak on one of my rebuilt engines was due to me forgetting to remove the rag plug I had pushed into the breather pipe stub to keep dirt out during assembly , another issue I have encountered was a kinked black plastic breather pipe on a friends 250 desmo.......result oil leaks, just a thought.
Cheers,
George

Hi George,

That was my thought on seeing the oil bubble on the engine bolt. There must be high crankcase pressure.

Colin

themoudie wrote:OH! that doesn't look so good Geordie. Is that a bubble of oil that I can see on the lower face of the nut?
I hope that I am wrong.
Good health, Bill

Yes, I think it was. I cleaned everything up then nipped the mounting bolts up. 650km since rebuild. Added another 25km and it hasn't reappeared. The centre gasket was greased only.

blethermaskite wrote:Has any one mentioned the crankcase breather?
Cheers,
George

I've done two runs, one with the crankcase breather as supplied new (Mototrans type) and the other with it removed. It made no difference to the oil leak at the head.
The pic shows wads that I had in place for the run with the breather fitted.



The long wad was behind the chimney and rules that out as source Bottom left is adjacent to oil way, top left is down slope from that. I'm ruling out head bolts. It's the o-ring.

I'll fit number 5 at 1,000km. Gives me some time to think up a foolproof plan.