Mastermind
Work Saw Specialist
Wise Man, watch and learn boys...lol.
What's the most recent reed valve saw that was made?
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Wise Man, watch and learn boys...lol.
igpoe
Addicted to ArboristSite
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.
As to age, my Mall two-mans are piston ported.....1940s.
Homelite XL 925 is my favorite reed valve saw
Igpoe
timberwolf
Addicted to ArboristSite
A little upgrade done on a read valve Stihl, actually it was a bit of a PITA to do.
I think the 009 was in production until 2005 in USA and maybe 2006 in Canada.
I think the 009 was in production until 2005 in USA and maybe 2006 in Canada.
BIGBORE577
Addicted to ArboristSite
Correction on what? I'm agreeing with you but, reluctant because of your nature. Is this so odd that you couldn't notice? Don't be so paranoid.
Old thread, I know. I have a Poulan 1800 chainsaw that was given to me. It's an oldie, about 1996, I think. It starts and wants to run after a thorough carb cleaning (and new gaskets & diaphragms) but can't quite get going. I also replaced the gas line and checked the exhaust port/spark arrestor - both clear. Piston has no scoring. I note from the parts diagram that there is a reed valve on this unit which is merely a flat piece of metal that resides in an opening under the carb. This is my first encounter with a reed valve which, as I understand, is a one way valve letting gas & air into the cylinder. Today's saws accomplish this through their porting configuration. I suspect that this reed valve could be my problem but I have no idea how to test it or otherwise examine it to see if it is functioning properly. Anyone know? It is #23 in the diagram.
Attachments
Out of an Intertec service manual. Check your inbox.
A single petal reed valve is located under the
carburetor and attached to the underside of the handle assembly. Maximum
gap between tip of reed petal and seating surface is 0.010 inch (0.25 mm).
Renew reed if bent, broken or otherwise damaged. Inspect reed petal seat and renew
carburetor housing handle assembly if seat is damaged or warped. Washer
under reed retaining screw serves as a reed stop and should be installed
with sharp side against reed petal. Tighten reed petal screw to 8-10 in.- lbs. (0.9-1.1 N·m).
A single petal reed valve is located under the
carburetor and attached to the underside of the handle assembly. Maximum
gap between tip of reed petal and seating surface is 0.010 inch (0.25 mm).
Renew reed if bent, broken or otherwise damaged. Inspect reed petal seat and renew
carburetor housing handle assembly if seat is damaged or warped. Washer
under reed retaining screw serves as a reed stop and should be installed
with sharp side against reed petal. Tighten reed petal screw to 8-10 in.- lbs. (0.9-1.1 N·m).
To bad Bigbore577 no longer posts here..
it's not unusual to find debris, that made it past the crude foam filter, stuck between the reed and the valve seat. i've seen this numerous times in the echos. the reed valve in the poulan is dodgey. it's like a bumblebee, no way it can fly but somehow it does. if you remove the air filter and run it, you will see a cloud of mix above the air intake. that's gotta be why the air filters in those things are usually soaked with mix.
Mark71GTX
ArboristSite Operative
Echo CS-306 has all of that.
chris-
i think the echos meet your requirements. my memory is the model numbers ar 302 and 346. i gave a 346 to my groundperson, angela, several years ago. it's the only saw she will use.
that beiing said, both the echos and the poulans (in the many incarnations) have only one reed, directly behind the carb. the high performance saws tend to have multiple reeds in a prism shaped cage. i suspect the single reed limits the performance.
Chris-PA
Where the Wild Things Are
Thanks, I will look into those. I've never messed with a reed valve, primarily as rear handle, chain brake and A/V are the minimum requirements for me to actually use the saw. I forgot about those Echos though.
Also, I can see the single large reed might have slow response.
Also, I can see the single large reed might have slow response.
Mark71GTX
ArboristSite Operative
I only know about them because I recently repaired one. It is sitting on the shelf in the shed. I need to get a bar, chain, and at nuts for it. Or get rid of it, whichever happens first!
bikemike
loud pipes save lives
Yeah ppl that say reeds are slow my ass and better torque too. The echo 340 was slow turd but they had a really small port that did not match the carb bore. Run a hone through the reed Plate and that helps the saw big time with rpm. Kinda wish I still had the saw, but I don't miss it
bikemike
loud pipes save lives
You can also get some really thin carbon fiber and make a reed. Older moto x bikes had boisen reed upgrade they were stiff thin and light if they snap they didn't chew up a engine like a steel reed does
Up to now, the Echo 346 has been my favorite grab and go saw--never fails to start (have a spare in waiting)! Just acquired an Echo 330t, putting a new short block in it. In my thread about the 330, I get the idea it may become my new favorite saw--but it'll have to be good to pass the old reed valve 346!
dannyupsolate
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MTD has a reed weedeater and blower lately allows them to mount carburetor on plastic crankcase cover.
Meanwhile, back to the Poulan 1800 ...
Ray, wow, an old service manual!! Thanks so much. Based on the instructions therein, I don't think my issue is the reed valve. It says that there should be no more than a maximum gap of .010" between the tip of the petal and its seating surface. Mine actually looks flush on the surface but it is definitely not more than .010. It also is not bent or damaged. My concern was that the valve was not opening to allow fuel from carb to cylinder. But I can push it open with light pressure. So, should I presume that it is, in fact, opening via the pulse action of the piston and cylinder and thus not preventing gas/air from entering?
Ray, wow, an old service manual!! Thanks so much. Based on the instructions therein, I don't think my issue is the reed valve. It says that there should be no more than a maximum gap of .010" between the tip of the petal and its seating surface. Mine actually looks flush on the surface but it is definitely not more than .010. It also is not bent or damaged. My concern was that the valve was not opening to allow fuel from carb to cylinder. But I can push it open with light pressure. So, should I presume that it is, in fact, opening via the pulse action of the piston and cylinder and thus not preventing gas/air from entering?
