Gordy
Well-Known Member
I decided to share my personal opinion on reed valves.
The short and skinny:
Do not reed valve an engine without a pipe upgrade!!!
You will have to add a windowed piston or window your own piston.
Reed valves add power, however it will not on otherwise stock engines.
And a little more in depth...
The reed valve allows more positive pressure in the crank case as well as more air and fuel. With a good pipe a reed valve will add a basic CG alot of power, however the pipe is key. A genuine MZ65 and a reed valve would be a very good power adder to any engine. Paired with some simple porting, you'll have a powerhouse of an engine. As far as porting goes, the intake won't need any work other than general something out
Reed valves do add to overall case volume, which decreases the intake charge velocity. This can be countered with case stuffing for max performance.
This is a very good read with amazing information. So what if it was written 53 years ago. Information is information.
magazine.cycleworld.com
Now for the actual modification of the engine.
Reed valves themselves bolt on. The piston however will need either swapped to a windowed piston, or windowed.
Adding a window to your piston may be intimidating, however it is quite simple. You can either rotate your engine to BDC and mark the port shape onto your piston, disassemble, drill some holes to start, and use a Dremel to bring the window to match the shape... Or if you don't feel comfortable with it or don't have the tools, the Christmas tree shaped stepped drill bit can do just fine. Just mark where the center of the port is when the engine is at BDC, drill a pilot hole, and drill it out to the height of the port. This method isn't as good, but is still functional.
CHAMFER THE WINDOW ON THE PISTON AND BE SURE ALL YOUR PORTS HAVE A CHAMFER ON THEM!!!
Which reed should you get?
That's a great question. There's tons of options out there that bolt on.
The main reeds available are:
G2
Dio
OZ
People tend to think the bigger the valve the more air and fuel it will move. That is false. The larger reed valves were not designed for these engines. In order to not have low pressure portions and create odd turbulence larger reeds need to be stuffed (filling excess space). This can be done with JB weld (alot of finish work) or 3D printed stuffers.
I personally do not recommend the larger valves.
The dio is a decent valve, however it is very unnecessarily large IMO.
The G2 isn't a bad choice stuffed, however they have major issues with sealing. The bolts need to be drilled and tapped to M6 and they do need alot of care assembling without over tightening the bolts using Dirko HT red or Permetex Motoseal. However they still have a tendency to leak, especially with an unsupported carburetor.
My pick is the OZ. Small package, doesn't require stuffing, and comes with some of the higher power engines. The only issue is the spigot is only available in a 23mm diameter max. That is too small for booted carburetors.
But they will fit a Mikuni VM18 carb which will make very good power.
A stock BoFeng can be used on very high output engines and still perform. Members have even developed modifications to make them even more powerful.
BoFeng mod thread...
motoredbikes.com
Also a good read...
motoredbikes.com
I will soon be building a manifold to bolt to the OZ and a Nibbi PZ20 for my case reed Phantom 85 chop top. I will update this thread or post another when I do so. That will definitely make for a perfect set-up IMO.
The short and skinny:
Do not reed valve an engine without a pipe upgrade!!!
You will have to add a windowed piston or window your own piston.
Reed valves add power, however it will not on otherwise stock engines.
And a little more in depth...
The reed valve allows more positive pressure in the crank case as well as more air and fuel. With a good pipe a reed valve will add a basic CG alot of power, however the pipe is key. A genuine MZ65 and a reed valve would be a very good power adder to any engine. Paired with some simple porting, you'll have a powerhouse of an engine. As far as porting goes, the intake won't need any work other than general something out
Reed valves do add to overall case volume, which decreases the intake charge velocity. This can be countered with case stuffing for max performance.
This is a very good read with amazing information. So what if it was written 53 years ago. Information is information.
The Reed Valve | Cycle World | JAN 1972
magazine.cycleworld.com
Now for the actual modification of the engine.
Reed valves themselves bolt on. The piston however will need either swapped to a windowed piston, or windowed.
Adding a window to your piston may be intimidating, however it is quite simple. You can either rotate your engine to BDC and mark the port shape onto your piston, disassemble, drill some holes to start, and use a Dremel to bring the window to match the shape... Or if you don't feel comfortable with it or don't have the tools, the Christmas tree shaped stepped drill bit can do just fine. Just mark where the center of the port is when the engine is at BDC, drill a pilot hole, and drill it out to the height of the port. This method isn't as good, but is still functional.
CHAMFER THE WINDOW ON THE PISTON AND BE SURE ALL YOUR PORTS HAVE A CHAMFER ON THEM!!!
Which reed should you get?
That's a great question. There's tons of options out there that bolt on.
The main reeds available are:
G2
Dio
OZ
People tend to think the bigger the valve the more air and fuel it will move. That is false. The larger reed valves were not designed for these engines. In order to not have low pressure portions and create odd turbulence larger reeds need to be stuffed (filling excess space). This can be done with JB weld (alot of finish work) or 3D printed stuffers.
I personally do not recommend the larger valves.
The dio is a decent valve, however it is very unnecessarily large IMO.
The G2 isn't a bad choice stuffed, however they have major issues with sealing. The bolts need to be drilled and tapped to M6 and they do need alot of care assembling without over tightening the bolts using Dirko HT red or Permetex Motoseal. However they still have a tendency to leak, especially with an unsupported carburetor.
My pick is the OZ. Small package, doesn't require stuffing, and comes with some of the higher power engines. The only issue is the spigot is only available in a 23mm diameter max. That is too small for booted carburetors.
But they will fit a Mikuni VM18 carb which will make very good power.
A stock BoFeng can be used on very high output engines and still perform. Members have even developed modifications to make them even more powerful.
BoFeng mod thread...
Free mod for huge power gain!
Took a bofeng carb and bored the roof right off it! Gains across the board. Starts better idle better,alittle more torque and ALOT more top end! Let me be clear I not great with a dremel at all nor did I measure anything but this mod cost nothing and greatly improved my bike! Avenger,g2...
motoredbikes.com
Also a good read...
What carb should i get?
I’m new to the hobby but have experience with engines and wanting to upgrade my carburetor shortly so i was thinking something along the lines of a dellorto 19 or a VM18 or the Nibbi equivalent of it,has anyone with these carbs ever had much problems apart from the jetting?
motoredbikes.com
I will soon be building a manifold to bolt to the OZ and a Nibbi PZ20 for my case reed Phantom 85 chop top. I will update this thread or post another when I do so. That will definitely make for a perfect set-up IMO.
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