one carb per cyl - various falcon motors

chad

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Starting to step on some 1s thread pretty heavily.
Sorry,
(no excuse) I just get into it & forget, not the 1st time. Gotta keep a lill more centered & not get so excited ~
Here's the entry, reposted here as a redirect offa the guy's back:

I guess for the "1 per cyl" a cardboard template (after the logectomy & mill pass)
and a total redesign of the carb linkage/spacing is in order.

The experts here R suggesting the Keihins? because they flow more appropriately for the combustion chamber & cyl sz? No rejeting or other internal adaptation?
The intake would B a one-design.
I'd think these would not B 'progressive' but 'unitized' (operate together) .
Would a rod linkage be suggested (w/may B Lokar cable to the skinny peddle)?
May B I better take this to a new thread - getting away from the SU/CI,
Sorry.
 
chad":2ca1vwxa said:
Starting to step on some 1s thread pretty heavily.
Sorry,
(no excuse) I just get into it & forget, not the 1st time. Gotta keep a lill more centered & not get so excited ~
Here's the entry, reposted here as a redirect offa the guy's back:

I guess for the "1 per cyl" a cardboard template (after the logectomy & mill pass)
and a total redesign of the carb linkage/spacing is in order.

The experts here R suggesting the Keihins? because they flow more appropriately for the combustion chamber & cyl sz? No rejeting or other internal adaptation?
The intake would B a one-design.
I'd think these would not B 'progressive' but 'unitized' (operate together) .
Would a rod linkage be suggested (w/may B Lokar cable to the skinny peddle)?
May B I better take this to a new thread - getting away from the SU/CI,
Sorry.

I would expect they would need jetting, not sure why the preference for Keihins, but whatever... In general, bike carbs are setup for a cable...
 
'S all helpful, thanks, RichC.

any more visitors? comments? ideas? interest?
8)
 
You would need a carburetor with an accelerator pump.
There are at least 3 choices in the motorcycle world.
Mikuni RS or HSR
Heihin FCR
S & S Super

Mikuni no longer makes the PHH series which was their automotive carb.
There are some available on Ebay

The price tag will be the limiting factor.
 
I seems like it would be a tuning nightmare. Seems like you'd really want to know that all the carbs are in excellent and very similar condition.
 
"...must have an accelerator pump…"
OK, thanks. Wasn't aware.
(Also didn't know Mikuni made automotive - vs m.cycle, & up till 1990).
The "VM" I'm familiar with may NOT have that feature.
My original idea was because it was one of the few I knew of that were side draft, reliable, simple, right sized.
I'll f/u on the Heihin, S&S (I think they were on HDs), and the Keihins mentioned in the other literature cited.
 
There are two types of carbs generally used on bikes- Slide needle and Constant Depression Not familiar with the Mikuni or S & S, but I believe the FCR is a slide needle. Traditionally, slide needle carbs run on bikes were jetted rich,to mitigate the need for an accelerator pump.Dellorto was one of the few bike carb manufacturers that used an accelerator pump on slide needle carbs used on production bikes; in the early 80's other manufacturers started adding accelerator pumps to their aftermarket slide needle racing carbs so they could lean the running mixture for more power,

Slide needle carbs in general started being replaced in the 70's with constant depression carbs.These have a slide and needle like the side needle carbs, but also a throttle butterfly which a slide needle does not have. The throttle linkage on a slide need carb works on the slide, while on a constant depression carb the throttle operates the butterfly. The slide and needle are controlled by a vacuum signal based on throttle position and airflow. constant depression carbs do not require a separate accelerator pump function, as the slide and needle form a virtual accelerator pump.

Whack open the throttle on a constant depression carb, and the grater vacuum signal drags additional fuel from the jet until the vacuum signal starts to lift the slide & needle.

I had my rack of Keihins built because they are the most common carb on large displacement 4 cylinder Japanese bikes. Mine are 40mm. Sizing for an IR manifold is way different than needed on a system with a plenum. In a log manifold (or any manifold with a shared plenum between the carb and valve), the manifold is drawing mixture 100% of the time, so has a more or less steady flow through the carb bores. On an IR system,the stub manifold goes from no flow for 600 or so degrees of crank rotation to drawing for 120 degrees or so.so to support a high rpm engine the runner needs a relatively huge throttle bore.

Sorry for rambling, but thought it may be helpful
 
agreed Econo.
Tuning (syncronising) them is no big deal with a hose, but there is a gadget called the Unisyn that takes all the guesswork out of the job.
But now I hear there's a Carter YH side draft (an early '60s thru '66 I've heard) that's reliable (just so many sizes it's hard to assure/ID the right one) used on early vetts too.


"...thought it may be helpful…"
Not ramblin. Like I said, it ALL helps !!!
 
Hot 6t Falcon":1a3a3l9w said:
Matt Cox at Vintage Inlines sent me a picture a while back of some Falcon boat engines the had multiple sidedraft carbs.
Check with him. https://www.vintageinlines.com
Thanks for the post:
All I saw was (under "Photos") some shots of his own vehicle…
R these pic on the VI site or did they come 2 U personally?
Were they "1 per cyl"?
What make carbs?
Thnx Dennis~
 
I'm still working on my set up. Have yet to post anything on my project and have been working on it on and off for about 3 years. Had it idle for the first time this weekend. Around 550rpm with a 260H cam.

I took 2 ZX9R carb banks and modified the linkage spacing to work with the port spacing on the 250-2V head. Clearance is extremely tight between the towers and the headers. I had to dimple the the six exhaust tube on my pacemaker headers for carb clearance and may need to move that header tube completely.

Hopefully this weekend will finished the throttle cable and pedal set up (using a 1970 mustang pedal). Tied both banks together using a cable splitter off a triumph motorcycle.



 
"...tight between the towers and the headers…"
my goodness, yes! But U fit it in,no!?!

The 'plenum' between the carbs & head look no thicker than an inch or so. Just a thick plate.
U manufactured that plate urself, no?

It's not the "ZX9R" intake is it? Nother fella made a much wider intake between the carbs and head. Not sure how it would fit unless angled up like the Lynx or another (forget which one) Oz major automotive after market company's design.

And those R the Keihins you're using?
 
Yes it all fits! But one of the carb bowls is a little closer to the number one exhaust tube than I like.

I built the intake on my hobby cnc. 1/2 6061 plate with aluminum tubing brazed to fit the carbs to. Most swaps I have seen with the ZX9R racks preserve the spacing between the carbs and have the intake make up the difference between the port spacing. I did the opposite where I modified the carb spacing to match the port spacing. Was a little more time consuming as I had to modify the linkage between the carbs.

Yes the carbs are keihin cvk's. The constant depression style carbs similar to SU's.

I kept the intake straight off the head for mounting simplicity but I feel an angled intake would definitely be better for overall header and tower clearance.
 
thats a good looking set up -

any more photos of your manifold?

and this is an Australian 250 2V head ?
 
Thanks WDoug!
I'm still not sure due to not having the operational definitions or ignorance on what the parts terminology actually means (in terms of the objects seen in an assembly). But I LOVE pic and thank you profusely for them.
I'll wait and hope I can understand by observing the discussion (isn't that the OP's role in initiating threads anyway?).
BTW: do U have any pic of the same set up but disassembled (like an exploded diagram)?
Thanks much - U guys R helpin me 'get there'!
 
Yes, its a 250-2V. These carbs like very low pressure. I actually swapped the spring in my low pressure regulator to get it down to 1lb of pressure.

Here are some more pictures.



 
Thanks! I'm hoping I'll have a video this weekend of her running. Just in time for the nice weather 8)
 
Do you have any shots of how you modified the head and the intake throats w/out the carbs? That is the most amazing setup we have seen in a long while.
 
Have you figured out how to jet these yet?

Real similar to the deal I have, except I used the rubber carb spigits screwed to a flat plate for the intake.

I'm tying to figure out how to best use the rubber velocity stacks inside an air cleaner.

What filters are you running?
 
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