Laverda 500 cylinder head

If anyone else has a secret stash of 500 heads please let us know. I’ve got several spare 350/668 heads but none for the 500 and I have a bike waiting for one. Alpino Head is fine.
 
Ok… now I start to understand when some people warned me about buying a Laverda 500… is being a nightmare to find spare parts.
No chance to find a cylinder head. I think I will buy an old engine just to have some spares. I already have one but only lower part.
I would like to rebuild the cylinder head, but I cannot risk my only working one, specially when I have to let it done by the local engineering workshop, as laverda specialists are not very happy about working this heads.
 
andre g said:

Found this but can‘t your head be repaired?
Click to expand...
Yes, it can be rebuild, will only need new valves, guides and maybe seats.
But, a few good Laverdist have warned me that it is relatively easy that the engineering shop screw up the head, if they are not used to work on those. In addition my head has been already repaired, with a new seat and some welding.
For that reason I would like to do a rebuild on a different head, if it works, great, if not, I can still use mine.
The issue with mine is that the shims are already 2mm, that means that I don’t have much room left before a total rebuild.
EE291D41-5E3A-45B4-8DC4-2247C8348854.jpeg
 
michipons said:
Yes, it can be rebuild, will only need new valves, guides and maybe seats.
But, a few good Laverdist have warned me that it is relatively easy that the engineering shop screw up the head, if they are not used to work on those. In addition my head has been already repaired, with a new seat and some welding.
For that reason I would like to do a rebuild on a different head, if it works, great, if not, I can still use mine.
The issue with mine is that the shims are already 2mm, that means that I don’t have much room left before a total rebuild.
View attachment 60872
Click to expand...
I'm no good with arithmetic but surely some swapping around of the shims will sort that problem?
For me, the main problem with your head lies with the cam bearings.
I should think that the combustion chamber can be tidied up.

Paul
 
Paul,

As with all 500 heads, and Laverda heads in general for that matter, the problem compounds itself from recessed valve seats and wear on the valves themselves. Especially the 500s are fickle in regard to well-sealing valves, one crappy seat and you'll be hard put to achieve any kind of steady idle due to the extreme lack of flywheel effect. To achieve a good seal, the old valves will need to be ground and the seat inserts re-cut, with the valves being lapped-in afterwards. When you're through with that, the necessary shim will have shrunk from 2.10mm to around 1.80mm, with luck. If the guides require replacing, even more metal will need to be removed from the seat inserts. Apart from the thin shims, which aren't really a concern regarding reliability or spring pressure, the whole valve seat geometry is out the window. The 500s aren't blessed with extreme torque and power to begin with, recessed valves will further limit power output and driveability.

Miguels head will require new seats and perhaps new valves and guides. Repairing the cam bearings will close up clearances even further, possibly the "correct" shims will end up even thinner! With new seats protruding slightly into the combustion chamber, shim size can be restored and flow is greatly enhanced (see modern car 4-valve combustion chambers), releasing quite a bit of additional power to boot, making the riding experience all the more pleasurable. The needle race can be reclaimed by laser welding and regrinding, the bushes are a simple alloy or bronze item that any machine shop can knock up after the cam journals have been tidied up. All in all, a quite straightforward but lengthy repair that won't be cheap.

Motorcycle maintenance is (should be) something normally measured in hours, not weeks and months searching for indescript shims or even resorting to having to make new ones. Keeping an old dog running by the skin of its teeth isn't my idea of fun motorcycling. Do it once, do it right.

piet
 
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Wow Piet!
Thank you very much for such explanation!

I should receive within the next weeks: valve guides, seats and valves. I already have cam end bushes NOS.

As my head is actually working, my plan would be to find an old/new head and do all that work there, to avoid the risk of destroying my only working head.

I think the same as you Piet, my bike would work as it is, but I like them in perfect condition, so I try to do all the job properly done.

Let me ask you a couple of questions:

- regarding the valve seats, if Wolfang sends me standard seats, they will not protrude, right? That means that I should look for other seats and adapt them. How much should they protrude? If new standard valves and seats are installed, why would that mean thinner shims? Wouldn’t it recover the factory shim size?

- why laser welding? Could it be done with TIG? I think there aren’t any laser welders in my area…
Best regards,
Miguel
 
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