Amal Concentric 26mm, good choice for NC 250?

[narrow_monza]

I've just measured the inner diameter if the intake manifold and the 2 spacers and they all have an ID of 26mm which matches the Amal 626 I just bought. The carb does have a rubber o-ring sitting in a grove in its flange. Hmm, perhaps I don't need a spacer at all. I also remember seeing asbestos spacers in the past.

-Adrian

[DewCatTea-Bob]

[quote= narrow_monza ...
" I've just measured the inner diameter if the intake manifold "

____ The stock 250Scrambler-manifold (which came with the 27mm-SSI), should have a 27mm-ID !



" and the 2 spacers and they all have an ID of 26mm "

____ That's nicely fortunate but, what-about your Scrambler-cyl.head's 'intake-port' diameter ? ...
If it's also the same dia.size,, then it's NOT of a Scrambler-head, but rather a Monza-head, (of which it's mounting-flange mouth-diameter ought actually measure (a rather narrow) 26.5mm [+/- .15mm] !).
(So that's rather more suited to a member-name of 'narrow_monza', don't you agree ? )



" which matches the Amal 626 I just bought. "

____ What bike-engine did it come from ?



" perhaps I don't need a spacer at all. "

____ That would allow the carb to absorb more engine-heat, which in-turn would warm-up the contained fuel,, and while warm fuel should atomize better, it also ought-to then be less dense. _ So those two effects tend to cancel each other, to varying degrees on engine-performance.
__ As I recall from old mag.articles on the subject,, gas-mileage is increased with the improved vaporization due-to warned-up fuel, while fuel that's rather kept cool as possible increases engine-performance.
So there's not a real final-consensus as to which is best overall, (cool or warmed-up fuel).
But I-myself tend to believe the cold-gasoline is best theory. - (I wonder what Eldert or Harvey think !?)

-
Curious-Cheers,
-Bob

[DewCatTea-Bob]

[quote= ducwiz ...
" but why does the Ducati factory add a n/c Monza spacer into a w/c 250 set ? "

____ I must assume that your newer-type gasket-set has been previously opened & robbed, cuz I believe the w-c.set came with at-least two different rubber-spacers with varied IDs for correct fitment on whichever Duke-model.
Besides that, the smaller-ID unit fits both n-c AND w-c 250Monza-models, anyhow !


Dukaddy-DUKEs,
-Bob

[narrow_monza]

[quote= narrow_monza ...
" I've just measured the inner diameter if the intake manifold "

____ The stock 250Scrambler-manifold (which came with the 27mm-SSI), should have a 27mm-ID !

+++ Then my cylinder head is probably NOT a scrambler. hmm...

" and the 2 spacers and they all have an ID of 26mm "

____ That's nicely fortunate but, what-about your Scrambler-cyl.head's 'intake-port' diameter ? ...
If it's also the same dia.size,, then it's NOT of a Scrambler-head, but rather a Monza-head, (of which it's mounting-flange mouth-diameter ought actually measure (a rather narrow) 26.5mm [+/- .15mm] !).
(So that's rather more suited to a member-name of 'narrow_monza', don't you agree ? )

+++ yes originally I thought it was a monza but then I saw the hole where the chain guard mounts, which is a scrambler feature, I think.

" which matches the Amal 626 I just bought. "

____ What bike-engine did it come from ?

+++ Actually it's brand-new out of a box.

" perhaps I don't need a spacer at all. "

____ That would allow the carb to absorb more engine-heat, which in-turn would warm-up the contained fuel,, and while warm fuel should atomize better, it also ought-to then be less dense. _ So those two effects tend to cancel each other, to varying degrees on engine-performance.
__ As I recall from old mag.articles on the subject,, gas-mileage is increased with the improved vaporization due-to warned-up fuel, while fuel that's rather kept cool as possible increases engine-performance.
So there's not a real final-consensus as to which is best overall, (cool or warmed-up fuel).
But I-myself tend to believe the cold-gasoline is best theory.

+++ I'll probably stick with one of the 2 spacers I have.
-

[DewCatTea-Bob]

[quote= narrow_monza ...
" +++ Then my cylinder head is probably NOT a scrambler. "

____ Another differing-detail between the two head-models, is that Monza-heads have screw-adjuster type rockers.



" +++ yes originally I thought it was a monza but then I saw the hole where the chain guard mounts, which is a scrambler feature, I think. "

____ Yes, those 6mm-holes are-not found on (stock) Monza-motors ! _ (And also, we already realize that your motor has a non-Monza type alternator.)



" +++ Actually it's brand-new out of a box. "

____ That's a nice-find for your Duke-project !
__ So then what motorcycle-engine was it jetted for ?



" +++ I'll probably stick with one of the 2 spacers I have. "
-
____ Either one will help isolate the carb (& fuel) from cyl.head-heat.


Dukaddy-DUKEs,
-Bob