Reed Valves-the modern ticket to 2-stroke power

[bwalker]

The first GP set up from Yamaha as I remember was a 250 CC with 120 Ponies. I worked for a Yamaha dealer in the sixties. We had a works bike on display for awhile. It definitely was a rotary valve. I think it red lined at 24 K. I can not not imagine what it could have lacked except a super man rider. Very light plenty of aluminum with duel disks in the front and a gigantic disk in the back. I was not allowed to tinker with it but tried anyway. Thanks

The motors I spoke of where from the mid 90's.

 

[Ted Jenkins]

Then there is case reed induction and cylinder induction. I still have both would any of it help a chain saw though. I love my MX bikes but really hate to work on them every time there is a race. Thanks

 

[weimedog]

I grew up racing dirt bikes, first "piston port" Bultaco's thru the case reed / exhaust valved Honda's. Then into the four strokes. So much development and subsequent innovative designs came out of that horse power race, especially in the 125 class. KTM had a hot rod around year 2000. I think physics and cost brought the development to a point of diminishing returns. Some may remember the differences between the on paper 2000 Honda 125 and the competition where the reed block and housing simply got too big...too much volume. Fast but peaky , they had found the boundary went a little past. ( of course the same company tried oval piston v8's to get valve area to compete with two strokes earlier in their history ) Also have been a out board mechanic/enthusiast since 1978 on and off. Also watched a similar evolution. Outboards designs relied on reeds before the single cylinder dirt bikes for obvious reasons. The old 1950 era mercury's had that goofy reed block surrounding the crank. That design persisted into the "classic" 50 four cylinders.....decades. All the OMC/Johnson/Evinrude depended on reeds. And when the "loopers" were releaseed, it was like an outboard revolution! Some really cool designs happened in the 70's into the 80's. One of my favorites were the v6 mercs. They went thru displacement increases and reed block changes to get to the HP the market was looking for. And the saws....they also relied on reeds in the early days. I think the Husqvarna L65/L77 were among the first truly modern piston port designs. Always loved how the service requirements drove the designs.....saws being light and cheap to manufacture pushed from reeds to piston port designs and were getting "enough" power along with the light weight and smaller over all package sizes while out boards went all out with big carbs/fuel injection with reeds to fix the resultant issues. Motorcycles ..... went all out with expansion chambers, exhaust valves, water cooling, BIG intake ( for displacement ) and reeds as the out boards.....then epa to 4 stroke . Also Evinude "E-techs" might be the last two strokes as now OMC is gone and four strokes rule for out boards. But the point relevant to the thread is those reed valves allow so much and in my most humble opinion allowed the two stroke to stay in the market longer vs. the typical piston port designs. Who knows how that concept could be applied in different parts to drive to a different set of design objectives.. I have a hunch we won't see as the battery is going to eclipse our favorite way to produce power.

 

[weimedog]

To the OP's point.... this dude used reed valves in a unique was AND a rotary valve for the exhaust vs intake

 

[Huskybill]

I had a chance to measure a ported 2100 cylinder from Husqvarna. The exhaust port was raised, the intake port was lowered. Both ported were widened. The piston skirt was shortened thus changing the port timing more. The timing was advanced. The governor in the carb was plugged.

Instead of a turbo or blower how about pressurizing the air box. I think little reed type windows on the inside and outside on the top cover over the air box can balance the air flow equaling the pressure. Or a small muffin fan operated by the g option generator for the heated handles.
A pot can be installed to adjust the fan speed.

I’m in the process of building a clone to the saw above. I have a few other changes I tried on the Husqvarna dirtbikes that worked out well.

 

[Ted Jenkins]

Those of us who rode raced dirt bikes during the last sixty years know what kind of development they have undergone. When I was working for Yamaha back in the sixties we had a works road racer on display for awhile. It was the V 4 rotary valve 250 CC with 120 HP. It was untouchable by the competition at that time but was very complicated. Chain saws are lite weight and very uncomplicated. I lug around my 076 and 070 happily. They make enough power to do the job. I cut twenty feet of a 30 to 40'' log today that took almost three pickup loads to haul away. I did not touch a thing on the saw but fill the tanks and was ready. Any body could keep working on development to get more HP for what reason. Twenty years ago when I was racing at a international Yamaha brought three Pro guys that I knew a little bit about to introduce their new line of MX bikes. They were battery powered open class bikes. They all turned in respectful times and were so quiet. Here in California all gas powered saws are supposed to be illegal in the next couple of years. One thing for certain which nobody understands is that there is no power to charge said pieces of equipment. For the time being I am not worried that some one is going to take away my saws but those after me may need to learn to operate electric saws. So to develop high performance two strokes is fun but am reserving that for my race class machines. Thanks

 

[Huskybill]

Piston ported or add reeds?

I took a 71 suzuki ts 125 and cut the bottom of the piston. No reeds it’s piston ported. No other porting. Down the straights this antique bike was beating newer kx80”s. We had a ‘72 suzuki ts 185 stock piston ported, a 76 ts 185 reeds. The engine with the reeds was smoother running. Both bikes were street legal so I had seat time.

 

[Ted Jenkins]

Piston ported or add reeds?

I took a 71 suzuki ts 125 and cut the bottom of the piston. No reeds it’s piston ported. No other porting. Down the straights this antique bike was beating newer kx80”s. We had a ‘72 suzuki ts 185 stock piston ported, a 76 ts 185 reeds. The engine with the reeds was smoother running. Both bikes were street legal so I had seat time.

In the middle sixties I had some one weld a reed cage onto my 135 CC cylinder but a bigger problem was at that time was 32 MM carburetors were unheard of. Try porting a 32 MM Amal form the sixties. When every thing was just right there was no competition. Thanks

 

[weimedog]

 

[weimedog]

20hp? And just getting started with his crazy reed valve, rotary exhaust valve, super charged 50cc two stroke,

 

[weimedog]

 

[weimedog]

Reed valves and a supercharger on a 50cc two stroke?

 

[weimedog]

An interesting series for sure but spot on relative the the OP. AND he's also doing what so called experts see as impossible. Supercharging a one cylinder two stroke So far a possible 30hp out of the 50cc kluge

 

[weimedog]

AND we now see some results

 

[weimedog]

And NOW it runs. Interesting enough it was a unique reed valve arrangement that did the trick. AND isn't that what this tread was about?

 

[NSEric]

The 50-65cc dirt bikes can make close to 15 hp.
The trouble is the motor is twice the size of a chainsaw and it needs a huge pipe.
To get more power out of a two stroke you need big cases, big reeds, big carb and big pipe which isnt going to work on a work saw.
The current piston port motors fit nicely into a saw you can carry.

 

[weimedog]

AND He has figured this thing, expect some really good numbers now...

 

[weimedog]

Two video's, the "anti-reed valve" type concept. We have seen a concept like this from Faibanks Morse in their submarine motors. But instead of two "wavy things" they had two crank shafts.

 

[weimedog]