looking for a 'universal' reed valve
Greg
I have searched on the internet but so far I have not had any luck
finding a 'universal' mounting reed valve to put on a two stroke
piston port engine.
It would seem there would be a market for such a device that could be
installed in the intake manifold of a piston port 2 stroke between the
cylinder and carburetor. This in itself could conceivably provide a
modest performance gain, but if the piston skirt were also drilled or
ported appropriately, it would seem a substantial performance gain
might be realized. Can anyone suggest where I might find such a
device?
Greg (still riding a 70's moped)
ES
news:4fa30f44.0305...@posting.google.com:
You won't find one, cause there ain't no such thing. Engines are designed
to use reeds, or not. If you have an engine that uses reeds, boyeson reeds
will probably make a replacement.
If you have an engine that you want to install reeds on and it doesn't have
them, you will have to do a lot of machining. The opening between
crankcase and carb will have to be widened considerably for one thing, like
about four times as large, to hold the reed cage and to provide more space
for air flow. Putting a reed between a carb and crankcase on a non reed
engine without enlarging the air passage to the crankcase will restrict air
flow severely, you would probably lose about half your top end power or
more.
The advantages of reeds are as you say, but it only works if the engine is
designed and built for using reeds. You don't necesarily need to drill the
piston either, using reeds allows you to dispense with piston porting
altogether (for intake anyway), so you can relocate the carb away from the
cylinder and piston, so that it has access to the crankcase at all times.
Ray Curry
pailf...@yahoo.com (Greg) wrote:
In the 70's before power values, there was a company selling reed
conversion, might have been Boesen. Actually I'm not certain of the
exact name or speeling. Each kit was specific for a bike and consisted
of an aluminum extender cage with an insert that held the read. It moved
the carb back a bit and the cylinder had to be routed out to allow the
kit to be inserted into the cylinder. A friend of mine installed
several, one on a 400 Husky worked particularly well. Universal would
have been hard because of the differences in frames and where the carb
had to end up. They didn't make them for all bikes. The basic design was
similar to what Yamaha adopted on some motocrossers before they went
power valve. When properly fitted, the conversion did broaden power, cut
top end a bit and bottom end too, and became a point of failure because
the reeds broke. The carbon reeds helped, first ones were steel, but
both had to open which took a bit of air pressure and both reduced the
airflow a bit. Bit ports and carbs helped but the powervalve
revolutionized things. In any case, I haven't seen one advertised for
years and no one races even off road or desert races using older bikes
so the market would be really small. I would be very surprised if you
could find them.
--
Advice is free... and worth every penny.
Greg
> pailf...@yahoo.com (Greg) wrote in
> news:4fa30f44.0305...@posting.google.com:
>
> > Hi all,
> >
> > I have searched on the internet but so far I have not had any luck
> > finding a 'universal' mounting reed valve to put on a two stroke
> > piston port engine.
> >
> > It would seem there would be a market for such a device that could be
> > installed in the intake manifold of a piston port 2 stroke between the
> > cylinder and carburetor. This in itself could conceivably provide a
> > modest performance gain, but if the piston skirt were also drilled or
> > ported appropriately, it would seem a substantial performance gain
> > might be realized. Can anyone suggest where I might find such a
> > device?
> >
> > Greg (still riding a 70's moped)
>
> You won't find one, cause there ain't no such thing. Engines are designed
> to use reeds, or not. If you have an engine that uses reeds, boyeson reeds
> will probably make a replacement.
>
> If you have an engine that you want to install reeds on and it doesn't have
> them, you will have to do a lot of machining.
In some cases this is true I am sure, but in my case it is not.
>The opening between
> crankcase and carb will have to be widened considerably for one thing, like
> about four times as large, to hold the reed cage and to provide more space
> for air flow.
Your value of "four times as large" (above) implies that you have a
very specific design and shape in mind. I also have a specific design
in mind, but mine does not require so much as four times. It could use
a section of intake manifold approximately double in area, and with
long reeds (or petals if you prefer) the flow could be very
comparable. But in fact, I do have room for an intake manifold more
than your suggested "four times".
>Putting a reed between a carb and crankcase on a non reed
> engine without enlarging the air passage to the crankcase will restrict air
> flow severely, you would probably lose about half your top end power or
> more.
This is very true. I did not realize that I had implied otherwise!
>
> The advantages of reeds are as you say, but it only works if the engine is
> designed and built for using reeds.
You are obviously not familiar with the 125cc Hodaka reed valve kit,
or various other aftermarket reedvalve kits. Some of these kits
require that you buy and use a new cylinder which has the appropriate
mounting surface for the reedvalve kit (and directions on how to drill
your piston).
> You don't necesarily need to drill the
> piston either, using reeds allows you to dispense with piston porting
> altogether (for intake anyway), so you can relocate the carb away from the
> cylinder and piston, so that it has access to the crankcase at all times.
A reed valve can indeed be placed in between the carburetor and the
cylinder on a normal piston port 2-stroke engine. Kits are made for
this purpose for some bikes. But even without custom kits, many people
have done this. Often they use reed valve assemblies made for other
applications and adapt them to their piston port engine. This can take
some machining and/or aluminum casting. I just read an article,
complete with pictures, where a guy manufactured his own entire
reedvalve assembly including reeds (petals) from aluminum stock and a
piece of flat steels. In fact, some have suggested using the leaves
(if that's what you call them) of a standard mechanics feeler guage to
make the reeds from. A super idea in that you could easily experiment
with different thicknesses!
At any rate, if you do this with a simple piston port design, then you
can gain a lot by making holes in the skirt of the piston, right where
the skirt covers and closes the port (leading from the carburetor,
through the manifold, and to the cylinder).
If your engine will accomadate it, a case mounted reed valve would be
even better. But, it is not necesarily possible to do this with some
engines. It would be a very difficult task with the engine I am
working on. A reed valve, mounted in the manifold between the
carburetor and the cylinder would indeed be do-able in my case. It has
been done many times by many people.
My question was not "is this possible" because I already know that it
is indeed very possible. My question was "does anybody know of a
source of a somewhat universally adaptable reed valve (a kit
perhaps?).
I am still open to any suggestions anyone might have regarding a
source of some kind of universally adaptable reed valves, or perhaps
any reed valve assembly for a specific application that may be
relatively easily adaptable.
I am not really interested in hearing from the "it can't be done"
crowd, but rather I am interested in hearing from those who may be
more inclined to say "here is an idea that might work".
TIA