Hi Paul,
You where right the Revmaster is an Edelbrock carb. I can get these
for $221.00 US each. I am waiting to get a price for the postage of
these units. Its very simple to modify the float bowl. in the
modification I will make the base hold both carbs. By making the left
and right you get a great installation and only have one leaning
valve.
Regards Don
http://www.edelbrock.com/motorcycle/carbs/carb_internals.pdf


It would be too small for the rotary but maybe all right for the
six cylinder 110 HP Jabiru if you used two.
Max rating on these is about 50 HP each.

The cross sectional area is what counts. They are about 40 mm which is
1250 square mm.

A Le Mans engine runner would be about 1.875" or 48 mm in diameter.
The area would be 1800 square mm or about 50% more area and HP each carb.


Paul Lamar


Hi Paul,
I was running one of these on my Jabiru 120hp engine. The original Bing
carbi would only rev to to 3250 rpm. straight and level. With the
Revmaster 40 mm I was getting 3500 rpm with the same propeller. The last
30 % of throttle did nothing as it would get full power without having
it wide open.
Don

Just one? Wow something not adding up here.
Those Edelbrock carbs are designed for all those off road quads,
bikes and small motor cycles with about 50 HP. Did you monitor the
manifold pressure in both cases? How big was the Bing? Did the Bing
have a butterfly valve in addition to the slide? Could be the Bing piston
was not moving up as far as it should or the piston spring
was too stiff.

BTW here is the mixture monitor I was talking about.

http://www.siliconchip.com.au/cms/A_111003/article.html

Paul Lamar
Hi Paul,
All Jabiru 6 cyclinder 3300 cc engine have one Bing of 40mm throat.
They have been dyno many times and there is thousands of them all
producing 120hp. They have a piston that moves the fuel needle up
and they have a butterfly down stream for the ice to build up on.
Details & Application Notes:

Mikuni's new HSR48 is a special version of the proven HSR42 carburetor. Its purpose is to provide maximum airflow for the most demanding high performance engines.

The amount of power any engine can deliver is directly related to the volume of air it can use in a given time together with its efficiency in using that air. Everything else being equal, more air equals more power.

Leaving port and combustion chamber design aside, airflow through an engine can be enhanced or limited by anything it must pass through. A restrictive air cleaner assembly, a too small carburetor, restrictive intake manifold and a restrictive or poorly designed exhaust system can (each or all) limit power output. The HSR48 was developed to deliver additional airflow to highly developed engines.

Modified Harley or Harley-based engines tend to fall into one of three categories:

1)      Modified stock --- This engine typically has stock cylinder heads, a high flow air cleaner, high flow mufflers, perhaps a bolt-in cam and (Hopefully!) a Mikuni HSR42 carburetor.

2)      Highly modified --- A hotter cam, professional cylinder head port work, a more specialized exhaust system, high compression pistons and (Please!) a Mikuni HSR45 carburetor.

3)      All-out ground pounder --- Highly modified heads, a displacement increase, either by way of fitting larger pistons, a stroker kit or both. This engine is more likely to be a special engine, built from the ground up to be stronger and to process more air than even a highly modified Harley motor. This is the sort of motor that should have the HSR48.


There is little to be gained from installing the HSR48 on an engine with stock cylinder heads or one that is going to be fitted with an exhaust system more suited to looking good than passing gas. The number of bolt-on performance options becomes very narrow when one attempts to get their engine above 100 (or so) Horsepower. We advise that you carefully consider the suitability of other performance components when you consider installing the new HSR48.

Our HSR48 is slightly larger than either the HSR42 or the HSR45. It is taller and the spigot (engine side) is larger in diameter. This may result, with some installations, in interference problems with chassis parts. We do not make special manifolds for engines with non-standard cylinder head spacing or larger diameter intake ports. However, our HSR48 kit includes our rubber flange adapter that fits the S&S "G" series manifolds.

The large variation in "Ground Pounder" engine configurations together with the relatively small number of such engines limits Mikuni's ability to produce special manifolds. You may need to cut some metal.
Airflow:

The stock Harley CV40 carburetor flows about 185 CFM (cubic feet per minute) when flow is measured at a pressure difference of 12 inches of water. All the Mikuni HSR series flow considerably more:

Stock Harley: 185 CFM
Mikuni HSR42: 213 CFM
Mikuni HSR45: 237 CFM
Mikuni HSR48: 270 CFM

If carburetor airflow were the only factor, the HSR48 could deliver almost 50% more power than the stock carburetor. It isn't, of course, but a 50% gain could not be realized without a high flow carburetor.

In fact, one of our test "48's" was fitted to "Fireman" John Kownacki's 113" Evo-based motor with which he then recorded 156 Horsepower on a Dynojet 150 Dyno. This is a streetable engine and Mr. Kownacki prides himself on the fact that he rides it nearly every day.

If you think your motor is a candidate for an HSR48, contact your favorite dealer. The "48" is available from all the usual sources.
   Regards Don

Hello Don,
How are thing going?
Here is some of the info I have collated due to my carb research.
The Stock Harley is about 80 hp, so if the stock Harley is needing  185 CFM
my guess is that equals about 80 hp.

Advise to me ( Carb salesman) is that if you need in excess of 120hp you
need the Mikuni HSR 48 ( 42mm Venturi).

I would suggest that a HSR 42 ( 36mm Venturi) would get you to about 100hp
and a HSR 45 ( 39mm Venturi) would get you to 120HP.

Now we need between 140 CFM ( 6,000 rpm) to 175CFM ( 7,500 rpm)  each rotor
( 100 VE only), this equates to needing a 44mm dia carb ( no Venturi) each
rotor - my calculations. The Venturi does speed up inlet velocity but can
also act as a restrictor - so where the benefits start and stop is anyone's
guess.

My own guess is that I need a 44mm ( no Venturi) for my single development -
44mm will give me about 120mph inlet velocity. Advice to me is that between
200 and 300 mph is optimum for best VE. This seems to gel with the HSR48 (
42mm Venturi) for anything over 120 hp. I'm targeting a Max of 125 hp for
the single P-port. The max venturi I would look at is actually 42mm so the
HSR is indeed what I would look at.

So I don't see how you could be getting the stated 120 hp on a 40mm carb
with unknown venturi. My feeling is your not getting the advertised HP even
though your getting better than you did before. Given the velocity might be
higher (higher VE), 146 mph ( half as fast again to PL's 48mm dia) there is
also the skin wall friction drag Paul speaks of, to consider. I haven't
worked on that aspect of the calculations yet.

So I'm a little confused myself. I guess as long as it's doing the job is
the main argument. If your Revmaster 40mm has no Venturi (no restriction)
and the Velocity is right up there, getting max VE, you might just be on the
cusp of 120hp or a little below that. However your no where near the magical
200 to 300 mph for max VE, as suggested to me.

Please advise of any Venturi restriction and I will work out the inlet
speed.

George (down under)