Laverdist exploring Ducati Bevel Single

[machten]

Re big end, These late model singles had a crank improvement that suposedly significantly improved things. I didn't build this engine, so I don't know what is in it, but I'll find out soon.

Re your head...I'm a relative singles "newbie", but it looks like there has been some welding done on that head around the exhaust thread. Maybe that's what prompted the radical "bolt" approach. The exhaust nut looks like it is sitting a fair way too far out to me too. I'd have a good look at the thread setup inside.

Also I think the front of the top cooling fin has been replaced. Note that it doesn't have the small vertical fins on top of it as can be seen on mine and I don't think that ever changed over the years.

What's the light for in the middle of your dash?

And I guess we should move this thread to the Singles forum? How does that happen?

Kev

[MarnixSFC]

The thread is in good condition, but think a thread bush was placed in there. I too noticed that the ring doesn't go in as far as it normally should, may be 2 reasons:
* I fitted a brass exhaust gasket ring from a Laverda
* I think the down pipe has a rather wide 'ring' at the end.

Everything is tight and sealed so no problem for the time being.

Red light: Don't have a clue really, but shouldn't be there I know.. Also miss the original light switch in the headlight, seems to be a hard to find item?

Moving the topic is something only moderators can do I suppose.

Marnix

[Craig in France]

Was wondering if the big-end is the engine's Achilles-heel just like the twins?

Generally, no. The big-end weakness essentially started with the 860 engine and lasted until the crank pin was enlarged in 1978.

I can't think of any real weak points with the wide-case engines. The narrow cases suffered from weak kick-start mechanisms, but Ign. T. sorted that with the w/cases.

Also note the bolt locking the exhaust ring. Not really a sound idea isn't it?

Nope, have seen better . Should be done something like this ...



... but as Kev has ponted out, you seem to be missing the upstand fins on the head

Ciao

Craig

[Craig in France]

Also miss the original light switch in the headlight, seems to be a hard to find item?

According to the parts list I have for the 450 Desmo, the part # is 0690.38.323.

Is this one?


If yes, go
http://www.guzzino.com/switcheskeys.html

Otherwise, perhaps Wolfgang? Or Phil at Road and Race.

Ciao

Craig

ADMIN EDIT - or perhaps you could support THIS place and suggest our shop unstead of pointing people everywhere else........... http://shop.bevelheaven.com/detail.aspx?ID=154

[MarnixSFC]

Craig,

What I need the the light switch that sits on the l/h side of the headlight, not the ignition switch.
It's a mostly metal affair that looks a little like a key in a lock but basically just a three position switch only. The Honda item that is in there now works fine but has to go as you can imagine..

Yes the ribs are indeed missing. Then it must be factory racer!

Marnix

[Craig in France]

Ah, my bad, Marnix. Chiedo scusa!

Part 3 below?



That is, like this ...?



If yes, part # is 0795.38.330. (The '0795' tells me it was first used on the 1972 750s, btw). It was made by Aprilia who of course went bust not long after (1974, I think ...?).

So no, not especially easy to find and tend to be expensive (I have one on my SCR which is how I know ).

Andy Nienhagen has reproductions for ... €125
http://www.desmo.net/pr_liste.htm

[MarnixSFC]

Yes that's the one. Maybe with heaps of luck I'll find one in Italy one day.. At least I know exactly what it looks like, thanks Craig.

Marnix

[bobnorton]

Smoke and oil is likely valve guide loose or seal, desmos not faster than v/spring as too vibratory to gain much at high revs and moderate cam profile used. only real benefit reduced seat wear and pose value. Check oil drainage working from head.

[MarnixSFC]

Removed head and barrel last night to find several reasons for heaps of blue smoke.

Valves have a little play in the guides but not excessive, the valves were not leaking. Exhaust seal very hard and clearly leaking oil into the exhaust port. There was a 1,83 mm shim on the exhaust valve so suppose the valve has sunk too deep in the seat?

Piston measured 85,75 mm, so standard size which is nice. Play between skirt and liner around 0,20 so too much I suppose. Piston looked healthy.

Checked the end gaps. 1st compression ring 1,5 mm, second one 2,9 mm and oil scraper 3,6 mm!!!!

All in all some work needed...

Haven't properly inspected big-end yet, but axial play seems a bit much..

Marnix



Marnix

[bobnorton]

If compression good and not burning oil or noisy then piston and ring clearances are irrelivant i think.But 3.6 !!. Shims often used in caps for setting clearances, usually as valves settle in and hammer the seats the clearances close up, so i dont try to set too closely and dont worry about a few thou extra clearance, it will sort itself out!. With the low milage many restored bikes do some never get run in enough to run as well as they did before the rebore.Sad but true.

[Jagbruno]

Hello all, I am also a Laverdista (1970 750SF) wandering into bevel singles world...I am the very happy owner of a Condor A350/Ducati, that I ride every day and I am currently looking at a nice 1970 450Mk3...I enjoyed this thread and would be happy to hear about the fate of Marnix' bike.
(Not his Laverda, I saw it at the Biker's Days in Francorchamps in June! )

Happy ridin', Bruno from Brussels[/img]