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Hi all,
My first post and thanks for my membership, and the knowledge base members provide, very very nice.
Wondering if any one has had a repair done to a head where the tunnel fits to the head ?
It is the hole that carries part number 37 in the below link, the only picture of it I could find.

https://www.ducaticlassics.com/parts/25 ... inder-head

(thanks to Ducati Classics), due to bad shimming mine has worn the hole in the head oval (not the bush,it measures fine)
- the hole in the casting of the head is oval - and so the bevel & gear shaft flop about.
I expect a fix to build up by welding and re-boring (where re-centering may be a hell of a task) and from other posts I have read
re-tempering may be a necessity also, the wear is greater than what the available oversize bushes would remedy.
I have approached a head work shops who have little interest, has any one had a successful outcome in this type of repair ?
Thanks

Insane Lozza

Oh, the eccentricity is pronounced, almost 1 mm side to side, almost 2 mm fore and aft, mostly aft. this is a video of it

https://www.youtube.com/shorts/URHyj6T9 ... ture=share

sad - I shall continue the hunt for a reputable machine shop/engineering works,
Appreciate the replies and time spent - thanks, Cheers

Hi Lozza
You do not give any figures as too the amount of ovality in the head bore. The last resort IMHO would be welding, as you will lose any reference apart from the bolt holes for re-machining, plus maybe distortion of the head.
As I recall the head has a counter bore to accept the outer flange on the sleeve, which is about 2mm larger than the flange. If this is not damaged, it could be used as a reference point too bore the head oversize, then make a new bearing sleeve as required.
I would have thought a good machine shop could deal with it.
Brian

Lozza

Just get the bore machined back round and central and have an over size housing made to suit. There is usually an unworn witness beyond where the housing sits, that can be used for setting up to machine out the oval worn bore. I would not advise welding the housing as it would probably distort, loosing the flat face as well, keep it simple. Regarding heat treatment of the alloy after welding, I've not noticed too much difference to these heads after welding....unlike more modern castings. Maybe give your location to get recommendations for machine shops, it is a relatively easy repair for a good machinist.

Regards Nigel

Thanks Nigel Lacey,
Bored round and custom bearing cup made.
Continues with the oil seal post. next comes reassembly and shimming ! yay.
I like steps closer as it is approaching summer here

Hi Lozza,

Can I pass on a suggestion from Nigel Lacey that I have found to be fool-proof? When you have finished shimming the bevels and are ready for the final assembly, instead of using a gasket between the upper bevel tower flange and the head joint, leave the gasket out and use silicone type sealer instead. This removes any possibility of the steel sleeve working loose in the head, because it is clamped tightly by the tower flange. I have found that the grey type gasket sealer works best.

Good Luck,

Colin

Hi Colin.
Thanks, good idea, I got ahead of myself, I haven't got new bearings for the shaft and cam yet. Shops open tomorrow though!
Cheers
Lozza W

Duccout wrote:Hi Lozza,

Can I pass on a suggestion from Nigel Lacey that I have found to be fool-proof? When you have finished shimming the bevels and are ready for the final assembly, instead of using a gasket between the upper bevel tower flange and the head joint, leave the gasket out and use silicone type sealer instead. This removes any possibility of the steel sleeve working loose in the head, because it is clamped tightly by the tower flange. I have found that the grey type gasket sealer works best.

Good Luck,

Colin

Hi Colin - did you do this without machining off the lip on the upper side of the bevel tower flange?

Regards,
MIke

Hi Mike,

I am sure that Nigel leaves the lip in place, and I have done it that way, but now I have machined the lip down on my two engines, leaving enough to allow for the sealant and to really clamp the bearing sleeve. I know that the correct gasket thickness can be cut to for the gap (Eldert's preferred method) but by using grey sealant I am confident that the bearing sleeve is really clamped and unable to move.

Cheers,

Colin

I can appreciate that the lip on the tunnel needs to be pressing on the bearing to keep the assembly snug in the head. On mine this would leave a gap of 0.7mm between the tunnel and head, tightening the screws could put the tunnel casting under stress.
I have ordered a pack of plastic shim stock so I can cut shims to fill the gap. https://docs.rs-online.com/6d7a/0900766b8150ad71.pdf
An easier solution would be to have "peelable gaskets" like those used on BSA Gold Star heads, maybe one of the suppliers could run with this?

Shim stock a nifty idea,
Reading mesh using blue is being a hard task, yellow gear paste on order.