Leaking 450 SCR head

[Wolf]

Hi everyone!

After assembling my 450 motor and motorcycle I drove it for say 300 km. Everything fine but the oil leak problem still exists: between head and cylinder is an oil leak. I assumed (falsely) that this oil leak might have come from the stud bolts bringing up oil. During the rebuild of the motor I have used a thread sealant - this should have prevented any more oil from coming from the motor casing.

Fact is, there is still oil coming, it starts on the top fin of the cylinder.

Sadly, I have not checked the head for breeches of the spindle holes to the bolt holes. If there are any, what is the remedy?

Many thank and regards

Wolf

[Duccout]

Hi Wolf,

That is a pain after all the work that you have put in. I can suggest two places where the oil could be coming from. Firstly the cam end cap, either past the gasket or through the screw holes. The screw holes go all the way through to the cam box and can let oil through. Secondly, the top of the bevel tunnel where the flange meets the head joint. There is also the screws holding the rocker covers on, some of which should have tiny aluminium sealing washers, and to finish, the oil drain bolts often weep. Any of these leaks can find their way around the fins and make it hard to find where the oil is coming from (and don't I know it!).

Good luck, keep us informed.


Cheers,

Colin

[blethermaskite]

Wolf, Its likely to be the cylinder head oil feed dowel rubber O ring seal leaking, this is not uncommon, unfortunately it means the head off again to inspect, however I would firstly check all the areas Colin has suggested none of which need the head off to address. You need to be sure you are using the correct spec. O ring otherwise if too 'thick it will squeeze out and not seal....and if too thin it won't seal either .......and make sure there is no damage where the O ring seats. To be sure of the correct O ring Nigel Lacy will have them.
Cheers,
George

[graeme]

Wash the engine with petrol or similar and dry it thoroughly.
Cover the suspect areas with talcum powder.
Start it for a short time to get it to leak and you should see where the leak is by the wet powder.

Good luck

Graeme

[Jordan]

You can remove and replace the cylinder head of a Ducati single within an hour.
It's one of the best things about our bikes.
Don't mess up the cam timing!

The O-ring at the cyl/head dowel can be replaced.
Current advice is to use one made of Viton material.

Inside diameter 7.65mm
Outside diameter 11.22mm
Cross section diameter 1.78mm
Size code OR2031

[LaceyDucati]

Wolf

Aside to the usual head 'O' ring issues 450's can spring leaks from the rocker spindle holes like Desmos do, due to the proximity of the holes to the head bolt holes. Check in the rocker spindle holes that they do not breach into the head bolt holes, I've found this several times. Curiously there is often a counterbore on the inside of the casting at the spindle hole that accepts a head 'O' ring....perhaps the factory was aware of the potential machining errors and leaks. If there is a breech, sleeving the head bolt hole or fitting an 'O' ring can fix the issue. Often this issue is very marginal and changing the spindle, damage due to other component failure or general wear can just start a leak. Test the hole with solvent and see if it leaches through the bolt hole.

Regards Nigel

[LaceyDucati]

Wolf
Having reread your original post, I see you are aware of possible leeks from the spindles. The solutions are fit an 'O' ring in the counterbore if there is one, or to sleeve the head bolt hole. The head bolt hole is much larger than 10mm (usually 11mm plus). Bore/ream the first part of the bolt hole 12mm past the spindle hole. Then make a brass or bronze sleeve 12mm O/D, 10.5mm I/D and press/ glue it in the hole. Then carefully scrape/ ream out the spindle hole to remove any incursion of the brass sleeve into the spindle hole, being careful not to enlarge/damage the bore. I've fixed quite a few heads in this way. you could sleeve the spindle hole, but doing it the way I describe is far less critical for accuracy and can be achieved quite crudely on a pillar drill and lathe. If you are using a press fit, I would put some sealant in the hole etc just for extra paranoia. All the fixes I carried out never returned.

This all assumes you have a leak from the spindle hole, which you would need to confirm.

Regards Nigel.

[Jordan]

Nigel, could you please sketch your counterbore fix for the cylinder to head joint?
I could not work out a solution for improving on the standard countersink that the factory provided, for lack of space to do it.
Jordan

[LaceyDucati]

Jordan

I was referring to the rocker spindle holes, some 450 heads have a counterbore on the inside face next to where the rocker shims sit. This counterbore seems to match the same size as a head 'O' ring. Rather odd as I've not noticed on smaller engines, and maybe ties up with some 450's leaking down the bolt holes due to breaches. I've never deviated from the standard chamfer for the head 'O' ring and have never had a leak from a head 'O' ring even though I use standard Nitrile 'O' rings....maybe lady luck has been shining on me for 35 years!

Regards Nigel

[Wolf]

Hi Nigel,

thanks a lot for your valuable input! I'm very sorry for the late reply - I was a little distracted by other things going on, like riding the TT on a small racetrack.

Very interesting, the possibility of an inbuilt sealing system- I will have a look whether I have these O-ring counterbores, maybe it is so because my model is a rather late 450. This would be a nice solution!

The idea of inserting sleeves to the head bolt hole would be the next thing, but this will happen if necessary earliest in the autumn of the year.

Because I have no bolts but studs it is not that easy to remove the head to do the check with a solvent to see if there is a connection of the spindle holes and the stud holes.

I will back to this thread

Kind regards


Wolf