450 mark 3 with screw rocker adjusters

[machten]

Hi all,

I have my 450 back from Europe in January and am now preparing it for a little local moto giro in the wine country of the south west of western Australian in march. I hadn't reset the valve clearances for quite a few years as the 450 was In Europe and I have only used it for the rare riding over there. Now it's back it was time to check out the clearances. I'd forgotten four years ago when I was exploring a problem that turned out to be a bottom end failure that this 450 mark 3 had screw type rockers. The bike is a very late mark 3 (i'm yet to see later engine number) and wasn't registered in the uk untile 1975. It has the 32mm crank pin and radealli wheels.



Some questions....

Has anyone else seen a 450 springer with screw type rockers?
Are the valve clearances used the same as shim rockers?

Regards,

Kev

[Ventodue]

Has anyone else seen a 450 springer with screw type rockers?

Know they exist*, Kev, never seen one in the flesh**.

* 1. Massimo Clarke has a photo of one on page 75 of Scrambler, Desmo e Mark 3, with this comment:

"Solo un ridottissimo numero de motori (tutti cone distribuzione convenzionale) è stata dotato di bilancieri con registro filettato".

2. And there's also a (different) photo in the Moto Ciclismo restoration and maintenance guide for the Scrambler. The comment there is:

"Verso la fine della produzione, furono prodotti alucuni esemplari equipaggiati con registri a vite."

Maybe the factory had run out of the shim type for the 'soon-to-be-terminated' singles and decided to use 860 rockers instead ...?

** That said, my 350 Vento uses screw adjusters. Which leads me on to ...

Are the valve clearances used the same as shim rockers?

Can't see why they'd be different - it's only the way the gap is adjusted that is different. The specs I have are:
Vento: 0.05/0.07
SCR: 0.05/0.10

Ciao

Craig

[Jordan]

Screw rocker adjusters were normal fittings on Monza 250 and Sebring 350.
Being heavier than shim type, in theory would tend to valve bounce lower in the rev range. But I never noticed that disadvantage, so it seems to work fine in normal operation. The good thing is quick and easy adjustment, with no need for shims which aren't always to hand.

Jordan

[graeme]

Hello Kev,

I have a 450 head with the same adjusters

Graeme

[machten]

Thanks fellas.

"Verso la fine della produzione, furono prodotti alucuni esemplari equipaggiati con registri a vite."

Hi Craig,

What does "alucini" mean? Closest I can find is "allucini" which translates as hallucinate! I'm sure they are real. At least, I think they are real...

Being heavier than shim type, in theory would tend to valve bounce lower in the rev range. But I never noticed that disadvantage, so it seems to work fine in normal operation. The good thing is quick and easy adjustment, with no need for shims which aren't always to hand.

Hi Jordan,

Yes, I too think they have that disadvantage but also don't think it is of much consequence, particularly for a 450 which doesn't do the rpm of the smaller capacity engines anyway. A friend of mine has had a 750 GT for 30 years with the spring adjusters and has considered changing them many times over the years and then promptly dismisses it every time he does his valve clearances. I've got more than a complete set of shims but I'm happy to have one easy one in the garage too!

I have a 450 head with the same adjusters

Thanks Graeme. That's good to know. My engine number is 462965. Is yours around the same vicinity? Also, what do you set your clearances to and do you use anything other than tension to lock the lock nuts in place?

Regards,

Kev

[graeme]

Sorry Kev, it's just a 450 head (unfortunalely)

I do have a 450 Scrambler 462321 that has shims. Close numbers but I am pretty sure the factory used whatever was on the shelf towards the end of the singles in '74

Graeme

(I have an english bike that has screw adjusters, I've only ever tightened them and never had one come loose.)

[graeme]

That brings up another thing I've been meaning to ask,, what does all the faint number and letter stamps mean on head and case castings mean?

Graeme

[Ventodue]

What does "alucini" mean?

Don't mean nothjiong ...

Typo. Should have been alcuni = some, several.

Mi scuso. Or, La prego di accettare le mie più sincere scuse ....

[machten]

Sorry Kev, it's just a 450 head (unfortunalely)

Ah. Thanks Graeme.

Mi scuso. Or, La prego di accettare le mie più sincere scuse

Craig, after an incident with a certain backpack in Saint-Michel-de-Maurienne, you will never hear criticisms from me!



regards,

Kev

[graeme]

Kev,
Does your Mk3 have a B and F stamped on top of the left case above the clutch or just B ?
Weird question, but my '74 has B and my earlier # Desmo has both. Both 46---numbers.
And another pair of Desmo cases also has B and F