Amal on my 450

[Teckhardt]

That is very interesting. The VHB carb slides onto the manifold. Could be a custom manifold or maybe someone welded a flange onto the end to bolt to.

Not to hijack, but I have wondered about putting a bigger carb on because the choke point would still be the intake manifold and the intake on the head. There must be an optimum size carb for the stock 450 intake.

This is all greek to me...

http://hondanighthawks.net/carb14.htm

[DewCatTea-Bob]

____ Thanks for the close close-ups Mike ! _ Now, it's very clear just what all you have on there.


" Because of the extra bracing on the 450 frame, I had to crush the filter to make it fit, "

____ I'm now wondering exactly what that extension-manifold is from !?
__ The handy thing about installing AMALs is that their mounting-holes are already spaced the right amount for bolting directly-on to DUKE-heads, without the need for any adapter-manifold.
So it seems that you may have more than one reason to try it with that extension-manifold taken out of the intake-tract.
In any case, the alignment-matching of all the intake-tract's port-mouths, ought to be checked-out anyhow, (to see if that unstock set-up was done by someone who actually cared about doing it well).


Happy-Cheers,
-Bob

[DewCatTea-Bob]

" Not to hijack, but I have wondered about putting a bigger carb on because the choke point would still be the intake manifold and the intake on the head. "

____ Just a quick side-note (which will later be removed from here), about possible 'hi-jacking' of the main topic-matter of any newly started threads...
I think that our Leader -(Jim, of this w.site) is like-minded with myself in that I feel we all should at least try to keep each individual thread fairly limited to it's main-topic of the thread-title and that of any of it's DIRECTLY-related tangents. _ Cuz otherwise, established threads can (& do!) end-up concerning anything-&-everything, which certainly can become disconcerting after such diversion has begun to occur, within any thread.
Even though I'm so-concerned, (& also somewhat guilty), concerning this diversion-issue, I think that it was perfectly A-OK for anyone else to bring-up anything to do with any carbs & intake-tracts for 450s ! _ (And diversion off to 250 & 350 heads would not be too far off, either.)
Anyhow, since we all seem to have the sense to realize the special uniqueness of Ducati's OHC-singles -('DUKEs'!), then I'm sure that we all also have the sense to be able to realize when we may actually be stretching a thread-topic too far off, and thus just knowing that it's an issue to keep in mind, should be all it takes to keep the diversion-issue in check.

____ Concerning the "choke point", it's no worse than at the point where the valve-guide enters the port's air-tract... And good or bad (depending on the cam's valve-timing), that choking point tends to do for the air-flow what a water-hose hand-sprayer does for the hose's water-flow/stream.
So it seems that the stock-manifold's most restrictive ID would not be the sole limiting factor restricting air-flow through the intake-tract.


" There must be an optimum size carb for the stock 450 intake. "

____ Since the stock 450/large-valve head's intake-port starts out at 29.5mm, then at least a 30mm carb would make sense to keep the carb itself from being like a 'bottle-neck' in the air-flow tract. _ But it's not really certain to say what the "optimum size" could be for the unmodified/stock intake-port,, however if the port's mouth/opening is not modified, then certainly nothing bigger than a 32mm could be an optimum-size.
And also, it shouldn't be overlooked on how the cam's valve-timing must certainly figure into how the chosen carb-size effects performance at various RPMs.
__ Whatever the cam & carb combo may be, a 450's power can certainly benefit by increasing the diameter-size of the head's intake-port !
It could be increased to a (round) 33mm dia. through to the valve-guide, (or even a 33 by 36mm wide oval-shape), if one's willing to attempt to do such a port-job. _ But even then, a 36mm carb would be the limit to go with that size port. _ You'd thus need an adapter-manifold to properly match carbs up to 40mm to the cyl.head's intake-port, and that size of intake track would probably not be very useful for 450s which still employ the SCR/White-cam. _ Sure would help the max-power of 450s with wilder-cams (like the DESMO) though !


DUKE-Cheers,
-Bob

[MotoMike]

____ ...The handy thing about installing AMALs is that their mounting-holes are already spaced the right amount for bolting directly-on to DUKE-heads, without the need for any adapter-manifold.
So it seems that you may have more than one reason to try it with that extension-manifold taken out of the intake-tract.

Happy-Cheers,
-Bob

Bob

If I mounted the carb right on the head, wouldn't it be canted forward too much for good performance. Seems to me that since the float pivot is aft, the float would be caused to rise prematurely and create a lean condition. Amal's set up tips are quite particular about the fuel level in the bowl and that it should be mostly level. the old floats are not adjustable.
Mike

[DewCatTea-Bob]

" wouldn't it be canted forward too much for good performance. "

____ One would think so but, I recall reading cycle/bike mags back in the 60s when the (then) new Amal 'concentric' carbs started coming on Brit-bikes, and the great-news about them then, was their big advantage over previous carb-models, in that they could much better tolerate changes in their angle from vertical and also any normal centripetal-effects on their stored fuel-level.
__ And besides, have you not seen the same type Amal-carb mounted DIRECTLY to the heads on the Spanish-DUKEs?


" Seems to me that since the float pivot is aft, the float would be caused to rise prematurely and create a lean condition. "

____ You are a good-thinker, and I can understand what you're thinking on that (and I might have assumed the same), but because I recall much of the hype from back when the new 'Concentric' -(as it came to be called) came out on the market, a little deeper thinking about the rounded/bowl design of the underside of the float itself, should also have you yourself realizing that as the fuel-level towards the front of the float increases, (due to the cyl.head's forward-slanted cant), don't overlook that also the level against the backside of it decreases by the same, as well,, thus keeping the float at the same position/level anyhow. _ And also, the metering-valve is kept very near to the float's fulcrum-point, thus much reducing any difference in the actual fuel-level with respect to the float's level - (in other words, the float-level can vary a lot relatively compared to the controlled fuel-level.)
(Am I making very good sense for ya?)

____ If you decide to try it with the extension-manifold removed, it would be nice to first run your 450 against another well-matched motorcycle, to then later be able to do so again afterwords, so as to learn of any possible changes in performance.
And also, it would be nice to see a picture or two of that special manifold you have there, while it's unbolted to anything !


Hopeful-Cheers,
-Bob

[Eldert]

the manifold on Mike bike is a original one with a flange welded on to it .

Bob asked a couple of times how other people fabricated their manifold . here is a pic i had on my computer



its a build up manifold it tapers from 40 to about 33 mm . i use tapered allenhead bolts to secure it ( no room for the M8 nuts ) and it is for a rubber mounted carb

the valve in the picture has a 7 mm stem . retainer is chrome/moly from R/D and was intended for a Honda
this retainer has the split keepers ( i use Kawasaki items ) way down so no need for removing aluminum at the base
of the coil spring . the coil is just a weak assist coil to set the valve timing correct

head is from a 450 and the valves are reangled and the combustion chamber reshaped .
i posted a pic of that combustion chamber in the any restos going this winter thread on page 6 here

Eldert

[Teckhardt]

head is from a 450 and the valves are reangled and the combustion chamber reshaped .
i posted a pic of that combustion chamber in the any restos going this winter thread on page 6 here

link for those who want a peak

viewtopic.php?f=3&t=20&start=20#p223

[DewCatTea-Bob]

By: Eldert...
" the manifold on Mike bike is a original one with a flange welded on to it . "

____ I myself would have to see it in hand before I could be so sure.

. . . . .

" its a build up manifold it tapers from 40 to about 33 mm "

____ That then must have quite a steep port-reduction between carb & head, but there's not much else that could be done, in order to use such a fair-sized carb for a 450's displacement.
__ For better throttle-response, a 34mm carb ought be preferred (over a 40mm).


" this retainer has the split keepers way down so no need for removing aluminum at the base of the coil spring . "

____ It seems that Eldert was fortunate enough to find such a valve-keeper/spring-retainer collar set-up, so that he could then use a high-lift cam without also needing to modify the "base" -(near where the valve-guide fits into), to avoid otherwise possible coil-binding in any (even thicker) non-stock coil-type valve-spring, during full valve-lift.

____ Eldert's work is that of very-few-others who's work I would accept done on any of my DUKEs !


Dukaddy-DUKEs,
-Bob

[MotoMike]

Eldert
that looks great, and extensive. Is the applicaton for racing only? how does it change the character of the motorcycle?
I'd love to see it all together
Mike

[Pete]

I had the tank off my Spanish built 350, so I thought I would take a picture of the Amal 930 bolted directly to the head. It's not the best picture, but should work.


Pete