125 Sport valve collets

[LexH]

Hi all,

I'm rebuilding the top end of my 1963 125 Sport and I have a bit of a dilemma with the valves and retaining collets.

I have a new set of valves from recambiousado in Spain, which is all good, except that the new valves have a groove at the top instead of a tapered recess to accept the original tapered split collets. I can machine a tapered recess in the new valves to accept the original collets, no problem there, but there is another problem: my old collets are damaged and I don’t want to re-use them.

I found and bought a set of NOS collets on eBAy which were described as 125/160 bevel collets but on receipt, to my dismay, they turned out to have a straight internal bore, not a tapered internal bore as the originals do. They were sold as 125/160 bevel collets but it seems they aren’t. The straight internal bore is about 6.2mm dia so it seems they are intended for 7mm valves but not 125/160 valves.

So, to some questions:
1. Does anyone know what these NOS collets belong to?
2. Where can I get some new tapered split collets of the correct type for 125 Sport?
3. Has anyone successfully used these Spanish valves with retaining groove, and how were they retained, with a matching groove type split collet?

I guess if all else fails I can machine a straight recess in the new valves to accept the NOS collets, but I’m still interested to hear what others have to say..

[Duccout]

Strange....My first thought is that Recambiousado may have sent the wrong valves, or maybe the design was changed during production. The collets must be available from somewhere, these bikes were pretty common in their day. Apparently Lacey Ducati has some spares so may be worth a try.