What's the most recent reed valve saw that was made?

[spacemule]

Was it any good?

 

[Cliff R]

Echo still has a couple of reed valve engine saws in production, CS-346 and CS-306? (Can't remember the exact model numbers this early in the morning). They are variants of the 300-301's-3400-3450's, etc.

They are decent little saws, but WAY down on power compared to thier piston ported counterparts. Rugged and reliable little saws otherwise, but not comparable anyplace to the CS-330/CS-360T, CS-370/CS-400 models that replaced them......Cliff

 

[spacemule]

Are there any advantages to reed valves?

 

[stinkbait]

Are there any advantages to reed valves?

You can use them to pick the steak from in between your teeth.

 

[JasonBmac]

Reed valves usually help with mid-range power and smooth idling with less carb spit-back... They limit high revs. They make the intake timing asymmetric, which is a good thing until they reach their maximum cycling rate... Then it's like valve float in a 4 cycle... Just won't go faster.

J

 

[thomas72]

Reed valves have many advantages. One of which is achieving higher crankcase pressure. Their are a couple of disadvantages and cost being the biggest one. The only other disadvantage would be a reed breaking and going through the engine. Reed valve engines can rev just a high as a piston ported engine in most cases. A cr250 does not have any problem getting 11-12500 rpm.

 

[tdi-rick]

Reed valves usually help with mid-range power and smooth idling with less carb spit-back... They limit high revs. They make the intake timing asymmetric, which is a good thing until they reach their maximum cycling rate... Then it's like valve float in a 4 cycle... Just won't go faster.

J

Reed valves have many advantages. One of which is achieving higher crankcase pressure. Their are a couple of disadvantages and cost being the biggest one. The only other disadvantage would be a reed breaking and going through the engine. Reed valve engines can rev just a high as a piston ported engine in most cases. A cr250 does not have any problem getting 11-12500 rpm.

The old air cooled reed 100cc kart engines from the late eighties (Junior International and Senior Reed) spun to over 18,000RPM under load and made much more power than any equivalent sized piston port engine. Carbon fibre reeds really helped reliability and revs.
The rotary valved engines spun even harder.

 

[JayC]

Reed valves have many advantages. One of which is achieving higher crankcase pressure. Their are a couple of disadvantages and cost being the biggest one. The only other disadvantage would be a reed breaking and going through the engine. Reed valve engines can rev just a high as a piston ported engine in most cases. A cr250 does not have any problem getting 11-12500 rpm.

AND a small displacement reed engine (dirt bike) makes on the order of 0.25 HP/cc, as compared to the highest strung modern saw motor, which makes roughly 0.075HP/cc, ~30% the HP as a reed motor. The single advantage is simplicity.

JayC

 

[Cantdog]

Reed valves have many advantages. One of which is achieving higher crankcase pressure. Their are a couple of disadvantages and cost being the biggest one. The only other disadvantage would be a reed breaking and going through the engine. Reed valve engines can rev just a high as a piston ported engine in most cases. A cr250 does not have any problem getting 11-12500 rpm.

Yep but Boyesen composite two stage reeds solves the second problem.

 

[Farley9n]

Back To Chainsaws

The Homelite 410 is a good running 68cc, 4.15hp and 9500rpm saw from the mid 80's. A bit heavy by todays standards but a solid low end and a not bad top end too. You can really lean on one of these........Bob

 

[MS460WOODCHUCK]

The Poulan 5200,5400 and 8500 at 85cc were all reed valve engines that would run with Stihls 660. You could lean on them as hard as you wanted with a 28'' bar and they would just laugh at you and say why don't you run a 36''.

 

[JoshRountree]

Can anyone explain what a reed valve is and how it works? Just curious.

 

[thomas72]

As for the last reed valve engines to be produced. My vote would be to the Poulan 8500 and Poulan pro 655. I am sure there may be more, but those are the only professional saws I know of.

 

[leeave96]

Some of the little top handle Echo saws I think are reed valve engines.

I bought a rear handle Echo, a model CS-306 a couple years ago and it is a reed valve engine. It is decent little saw for brush clearing and light firewood duty.

Funny thing about that saw is it sounds just about the same as my Dad's old Homelite Super XL.

Bill

 

[Mastermind]

Good topic Space. Thanks for bringing it up.

 

[hoss]

I agree, this is an interesting thread.

 

[joe912]

The piston port design is a rather old one, but it's simple and works. The reed valve design is more advanced, but more complex. IMHO, I believe that piston port design is utilized because it is simpler and more compact than the reed valve. As for sucking a petal, done it on my Ski-doo. It's sucks. Boysens are good, but I'm more of a V-Force guy. And yes, it was an early version that broke and sucked into the cylinder.


As emissions continue to get tighter, i would not be surprised to see reed valve saws with fuel injection (like rotax and inject fuel into transfer port) in the next several years.


Rotary valve 2-strokes......those things ripped!!! too bad they were heavy. A finely tuned, triple piped Mach Z is a sight to see and hear.

 

[spacemule]

Can anyone explain what a reed valve is and how it works? Just curious.

I've not had a reed valve saw apart, so I'll just explain my understanding. In the common modern 2 stroke, the intake opening is controlled by the piston--when the piston is near the top of the stroke, it passes the window behind the carburetor, and the resulting suction from the rising piston draws fuel through the carburetor throat and beneath the piston. When the piston goes down, the intake opening closes and the transfers open, which are merely channels around the side of the piston. The closed intake along with the descending piston forces the air/fuel mixture around the piston sides into the combustion chamber.

A reed valve 2 stroke engine controls the intake opening and closing with the separate reed valve. Essentially, it is merely a one way valve/diaphragm that allows fuel to come into the crankcase but does not allow it to leave. When the piston rises, fuel is pulled through the valve. When the piston descends, fuel is once again forced through the transfers, against the closed reed valve, and into the combustion chamber.

 

[BIGBORE577]

I've not had a reed valve saw apart, so I'll just explain my understanding. In the common modern 2 stroke, the intake opening is controlled by the piston--when the piston is near the top of the stroke, it passes the window behind the carburetor, and the resulting suction from the rising piston draws fuel through the carburetor throat and beneath the piston. When the piston goes down, the intake opening closes and the transfers open, which are merely channels around the side of the piston. The closed intake along with the descending piston forces the air/fuel mixture around the piston sides into the combustion chamber.

A reed valve 2 stroke engine controls the intake opening and closing with the separate reed valve. Essentially, it is merely a one way valve/diaphragm that allows fuel to come into the crankcase but does not allow it to leave. When the piston rises, fuel is pulled through the valve. When the piston descends, fuel is once again forced through the transfers, against the closed reed valve, and into the combustion chamber.

In essence yes. However, dealing with a lawyer in training, I'm reluctant to say anything in fear of being sued.

 

[spacemule]

In essence yes. However, dealing with a lawyer in training, I'm reluctant to say anything in fear of being sued.

Feel free to correct me.