tdi-rick
Addicted to ArboristSite
A good article on diaphragm carbies here (Walbro WB-3A in this case, but applicable to anything we use) http://nkn.com/nationalkartnews/articles/AnatomyOfWalbro0708.pdf
I keep telling you to get the bloody thing.....if that 084 is still available to you at a good price you sould pull the trigger....one of stihls better saws, and better from what ive read than the 088/880...............
that sucks......
ill keep my ear to the ground.......I know where there is a few 2100's :hmm3grin2orange:
Forgive me for being an obsessive tuner, but the carb issue on work saws is still bugging me - and after reading all the tricks on EC Birts forum, I feel there has to be more in it for a work saw.
The analogy I make is that a race saw is set up for the sweet spot in porting - kind of like setting up a dragster. Whereas a work saw is more like setting up the jetting on an enduro bike.
When you are cookie cutting, you try and keep the saw in the sweet spot - it seems that almost any carb can be set up to work within that narrow range. I've seen some bored out carbs for racers that I know would never meter well on a work saw.
However, the varying conditions of a work saw demand a broader range of good metering (like the enduro bike). I noticed the last time I was cutting that if I opened up the high speed needle another 1/8 turn that it seemed like I could pull the saw down below peak torque and not have as great a problem with bogging. I also noticed that it knocked some power off my peak horsepower.
All this is largely a subjective feel. If I had a tach installed on the saw I would be able to monitor and document the rpm levels to confirm the spread of power and where it bogged.
I just may have to get a tach to mount on the saw and a pop off guage (and a bunch of springs and shims). I could start out with one high speed setting on a log and document where the power was, then tweak it a bit and see how that changed the spread of power. Then, try a different pop off pressure and re-test.
My gut feeling is that a slight drop in pop off pressure along with a slight leaning of the high speed needle would give me broader and more forgiving powerband - just what I want for a work saw.
Matt, do you have any more of those tachs?
And this is for Trav and Andrew.
Unfortunately it won't work on Randy, he's already seen it and guessed what I had in mind
It's courtesy of our current Australian Open Chainsaw Champion (overall pointscore)
Cheers lumberjackau !
I thought that was settled when mcBob got envolved and basically admitted that it isn't the saw so much as the driver. chainsaw races mean JACK snot in the real world anyway!
Had my 660 singing today, could hear the couple of huskies in the distance struggling their butts off, bogging in logs half the size of what I was cutting!
Rick, I read the article. I did find some interesting information, especially on the relationship of the area of the diaphragm to the diameter of the metering needle orifice. I did agree with what he said about the high and low speed screws being the most important adjustments, but that's a, like Duh, I don't think anyone would disagree with that statement.
I kept waiting to get to the good stuff, then he wrote "I will have more to say about the hype and misunderstandings surrounding pop-off pressure and metering lever adjustments shortly." - You beauty, getting to the guts of the inquiry.
I then arrived at the end of the article without one further word about pop-off pressure or metering lever adjustments. - Bummer, I felt ripped off.
I have been through numerous threads on EC Birt's forum where certain recommendations were made about changing their pop-off pressure and changing the metering lever adjustment - and the replies were like "thanks, that fixed it!" yada, yada.
I'll get a link in just a sec.
Sounds like stihls may have improved. What I remember is that they were overweight, overpriced and underpowered.
Lighter cheaper and higher powered, and more reliable don't you mean? I can buy a big stihl cheaper than a husky that even comes near the same performance levels! oh and much lighter than the no longer available macs in the size range!
sorry randy but you did leave yourself open to that one!
Rick, I read the article. I did find some interesting information, especially on the relationship of the area of the diaphragm to the diameter of the metering needle orifice. I did agree with what he said about the high and low speed screws being the most important adjustments, but that's a, like Duh, I don't think anyone would disagree with that statement.
[snip]
I'm getting the impression if I want to get to the bottom of this, I'm going to have to do my own testing.
some pics of todays efforts! my new/old 034 and the 660 versus some big mahogany! more to come!
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