The generalization fails, as does the imputation of Ludditry.

Gas mileage was excellent for a 1000 cc - especially if pottering along, though - normally you wouldn't be doing that. Maybe excellent at the ton too, but can't say I made effort to measure that specifically. Somewhere there may be numbers I writ..

(Another example of ~ good but not Groovy-New design, was my Cit. DS-M with staid 4: which got 22.x mpg on one run at near constant 90 mph. 30+ years ago. What do new comparable-sized cars get at 90? If you can still find a place to do that.) Hmmm. You can! less-Puritan Deutschland.

In Vincents, the cams were located high in the cases, using short sculpted (for lightness, strength) pushrods and a clever bevelled (donut-like) 'ledge' pressed-on near the middle of the valve stem -- on which the short forked-rocker applied lift. 54 HP @ <5600 rpm IIRC in ~51 when first Series C appeared. (Dunno about B's vs mileage) Don't need better valve control at those rpm.

Net result: minimal mass, good er 'radius of gyration'; something in-between the DOHC approach and [virtual opposite] say, Harley - with its cam buried deep in sump, humongously loong pushrods, ergo mass + lots of rod-'flutter' too.

Point being - it is fucking formatory too! to imagine that, "all engines which can turn fastest" via all the expensive alloys [energy of mfg. cost, materials yada] MUST be the best for all purposes.

A modern v-twin (as the Vincent was - only earlier!) benefits from the torque available at normal speeds and normal usage: yer 10K screamer is running on the torque of a V- a quarter its size! under those conditions. Conditions most often used (most riders).

(And I see this phenom when driving a friend's Acura Integra - it's a Screamer. One Hell of a lot of thrashing where on a Vincent say - to zip around something - a mere slight twist on throttle = a big bump in the ass, at lo rpm. QED?)

You may not extrapolate the above to the generalization you made. I didn't.


:-\ufffd

Er umm - well, one 'lifts' the valve off its seat where the spring has (better - has) held it.

Desmo is about No spring (er maybe weak one for taking up clearances) - no? It 'places' the valve up + down exactamente. And its essence would be / nay is: to permit even higher RPM without fear of float. So it is the very essence of a modern major ge - er Screamer, no?

Maybe my description didn't convey..

Imagine a swaged-on donut about midway along the valve stem. From the side, a (hardened) fork abuts this collar (the donut has a flat face on that side). There's a step in the valve stem dia. upon which the collar sits, in addition to being a tight fit on assembly.

Consequence too, less valve mass overall. Larger valve-guide dia. at bottom, where seat is - smaller at top = just to prevent side wobble. Two guides better than one -- when ya gots such room! 'Austenitic iron' valve seat inserts, to complete the aim for longevity. Many made it over 100K fast miles.

A bearing in middle of rocker of course; the other side of rocker has a spherical socket - to match the ball-end of a double-tapered pushrod. Light alloy rocker with hardened 'business' inserts. *Modern* design - as any Screamer, I assert: Every gram was contemplated, and while "no expense" is alwys an exaggeration - Irving fought against any serious compromises. (An early bronze timing gear was.. finally replaced with lightened, steel one with fancy hardening process).

It is a short pushrod because of the high placement of the cam, in crankcase ~ near the lower visible part of juncture of the cylinder fins. This-all, instead of pushing on the Top of the valve stem, as normally.

Saves height of cyl head too - rocker need not be Above valve. Saves valve guide wear; on Phil Irving's design: these two guides unique. Add-in superior finishing of such sliding surfaces as are unavoidable in any cam/valve assembly.

Or were you just being a smart-ass, odd as that thought is?

OTOH - IIRC the VOC (Owners..) kicked around the natural exploitation of the valve collar approach. One problem re returning valve to seat desmodromically: collar is er 'swaged' onto something which runs as hot as anything (inside) an engine.

You can only pay so much attention to How-tight that collar must remain at all temps, via friction VS simply cracking it from too Much interference fit. 'Close' motion wants to lift up that collar!

Pinning it.. is out for all obvious reasons.. Maybe special forged valve with lumpy stem + split-bearings for the lower guide? Never heard more. Why bother? Well folks in US and UK were pushing it - also in Oz. Alcohol, 11:1 pistons one-piece cranks, etc. to where more rpm could have been useful. Nothing exceeds like excess...


A.

PS there's a Shadow running ~ these parts I hear. So far no spot.