[RED-85-Z51]

Use Echo Power Blend, or Stihl Ultra, mixed with 89octane gas, @ 50:1 ratio, these are ashless, smokeless oils...so you wont get smoke at all.

When tuning, get your low end set so it idles smoothly, it doesnt try to race off, and it doesnt load up and flood.

Once the low end is set, take your high needle and blip the throttle from idle to wide open for just a second. If it stumbles, hesitates, at all...turn the idle needle out 1/8 turn, and turn the High needle out 1/4 turn. Now try it again..if it does not hesistate at all, you should not have to touch the LOW needle anymore.

Now, once it is accelerating off idle with no hesitation, take the H needle and turn it out 3/4 turn. Now hold the throttle wide open. it will probably rev up some and start to sputter, run rough. Slowly turn IN the H needle until the exhaust no longer has that rough "4 stroke" sound to it, and it gets that sharp 2 stroke whine. Now back it down 1/8 turn.

Go down to idle...now pull it wide open, it should rapidly come up to a smooth wide open speed, not too fast, but not "4 stroking".

To fine tune it, make a couple cuts, in the middle of the 2nd cut, shut it off, pull the plug out..it should be a medium cocoa color. If the ceramic is white, light ash colored, go 1/8 turn out on the H needle and make 2-3 more cuts, cutting the engine off during the last cut..and reading the plug again.

You are looking for The medium Cocoa color on the ceramic.

 

[RED-85-Z51]

The best way to tune a 2 stroke is plug reading...and with a tachometer.

With a tach, you turn the H needle until you hit the target rpms. On like, Husky saws, I turn the newer ones in the 14000 range wide open, I turn the Echo stuff in the 12,000 range. I Tune trimmers to a max no load speed of 10,000rpms. Blowers are more complicated...the load is always the same, I like to plug read blowers...

I run stihl saws, like the newer ones, MS362, 261, whatever they call em now..in the 12,500 range, up to 13,000.

 

[RED-85-Z51]

I have a tach, but it only goes up to 9999 RPM, and my saw is supposed to be tuned higher than that, so it didn't help me all that much.

I did some reading about carb tuning for saws after I bought my Stihl 032AV. One suggestion/approach for tuning the high-end mixture was that the saw should be 4-stroking at full-throttle with no load. But that it should clear itself up and be 2-stroking under a load, when making a cut. And that it should still 4-stroke at full-throttle immediately after the cut.

If people will excuse the link to another forum, this is one thread discussing saw tuning, and includes a video showing the above process. You can hear the saw run differently in and out of the cut as he tunes it.

http://www.arboristsite.com/chainsaw/113538.htm

I never tried pulling the plug during testing, that is an interesting approach. And it may be better than what's described above. I just mention this method because I found it helpful.

If a 2 stroke is 4 stroking, its too rich, maybe not by alot, but too rich. YOu want it so it doesnt overrev under no load (too lean) and doesnt 4 stroke ( too rich).

 

[RED-85-Z51]

Keep in mind that a fuel supply problem is not always carburetor related. Either of the crankshaft seals, intake boot, crankcase gasket..can leak air in, which will make them run lean.

Most often, an idle problem that is either too rich or too lean, is an air leak somewhere.

2 stroke carburetors are super simple..but at the same time they are a fickle mistress...

 

[RED-85-Z51]

Tygon is not bad line, its whats popular now and the only line to choose from in most places. There are like at least 5-6 sizes.

Tygon line life is only about 3 years in most cases though, Ethanol and heat are not kind to it. Ive put Tygon on saws and had it cracking and breaking the following season.

The way the purge system works on like, poulan, and homelite, Ryobi equipment is basically a priming draw-through system.

You have a line that goes into the gas tank, its usually small in diameter, it goes to the inlet on the carburetor, so the carb draws fuel direct from the tank. Then the primer has an inlet and an outlet with check valves. The inlet side of the primer hooks to the outlet side of the carburetor (usually a smaller line). And the outlet side of the primer dumps into the gas tank (larger line).

Push the primer in and it blows air/fuel into the tank through the return line (large). When you release the primer, it draws fuel up into the carb, through the inlet line and filter...into and through the carb, then into the primer. It basically makes it so when you flip the choke, fuel is in the carb, ready...and the carb doesnt have to draw fuel up into itself from the tank.

The only fuel line that will effect how it runs is the line from the tank to the carb, other lines being off or cracked, loose...will only effect how it primes up.

Alot of equipment is setup like this, to prevent flooding from a primer bulb forcing fuel into the carb. some primers are integrated into the carb body, same basic design but does away with the line between the carb and primer.

Having said this, which line can you not draw a vacuum on?

 

[RED-85-Z51]

Thanks for the confirmation on the primer circuit. I was initially troubled when I didn't see the primer line going into the tank, I at first thought it to had disseminated. My last followup post tells how after reattaching the fuel in line to the carburetor that the saw again ran, and rather well (the two cycling verses 4 cycling sound is beyond my skill and hearing - so if the rpm is steady I feel it is idling well). I put the vacuum pump on this carburetor more for reference and as noted the very small nipple left me without a hose/adapter that could seal on the nipple. However I have one cone shaped adapter that fits well enough, I estimate, to establish some vacuum if the line was closed. In the case of this Craftsman/Poulan saw I couldn't see any vacuum build..again not a great seal at the nipple.

But, on another troubles saw, a Homelite, which has a larger nipple I found that a vacuum measurement there showed a complete block...thus I am prepared to guess the problem with this saw is the carburetor is dirty/plugged. The two saws have very similar carburetors physically, but different manufacture: Zama on the Craftsman and Walbro on the Homelite.

Are you trying to pull a vacuum on the inlet fitting or the outlet fitting? The inlet fitting should build a vacuum, if it doesnt, the needle inside isnt seating.