Poulan 306A Idling at Full Throttle

[Jack Torrance]

I bought a Poulan 306A this past August, which had just had a carburetor rebuild and ran great. I've started it once or twice since then just for a few seconds, but never got around to cleaning it up and using it. Tonight I replaced the spark plug and tried starting it, but it wouldn't start, even with the choke pulled out and the throttle locked, so I sprayed a very small squirt of starting fluid into the carburetor, which I know is advised against by some. It fired right up, but ran at full throttle, even without the throttle locked. I'm guessing the carburetor needs to be adjusted, but like I said, it just had a carburetor rebuild and ran fine when I bought it, and it hasn't been used since. What would cause it to run at full throttle like that? Also, how do I go about priming it with gas? Do I just pour a bit into the throttle plate? Thanks very much for any help.

 

[Conquistador3]

Your engine is starved for fuel at present settings: that's why it only runs at full throttle and with starter fluid. And it has so little fuel it runs awfully lean, hence explaining why it runs at full speed even at idle.

What happened? It's surely a fuel delivery issue, especially if the saw was stored by either you or the previous owner for any length of time with fuel in it. Or perhaps the "carb rebuild" wasn't so through as the previous owner said.
Check fuel lines and fuel filter first. If they have never been replaced it's about time: use some decent fuel tubing (genuine Tygon is fine) and a Walbro or Zama fuel filter. If the saw isn't behaving yet, it's time for more carburetor surgery. Not exactly hard nor expensive but if you have never done it before take your time, pick a flat clean surface with good light and have a magnet at the ready.

 

[pioneerguy600]

If its running full throttle then its getting air from some where, start by checking to see if the throttle butterfly is completely closing in the carb, it may just be sticking open or the linkage may be stuck or jammed.

 

[Chainsaw Jim]

It sounds like this thing is due for a set of crank seals. When they leak the saw cannot pull fuel to the carb.. even when choked.

 

[Sam R]

I'm with the above I'd almost certainly blame that on a secondary air leak. Leanest possible carb settings don't mimic WOT, you might get it to 5k but not 10-12k of full throttle.

 

[a. palmer jr.]

A pressure/vacuum test is important for those older saws, gaskets and seals are over 40 years old I would imagine..it's kinda easy to rig one up and not expensive..I'm doing one right now on my old Poulan 25 deluxe and it failed the pressure test.

 

[Analyst Man]

You say that it starts and idles at full throttle, but only after a shot of starting fluid. Does it keep running or did it die after a few seconds of high rpm?

 

[Analyst Man]

FYI I found this information about your saw's fuel requirements:
"Fuel Needs
The saw’s manual called for a gas-oil mix of 16:1, or 8 ounces of two-cycle oil per gallon of regular-grade gasoline. But users could run it on a 32:1 mix, or 4 ounces of oil per gallon of gas, when using Poulan-brand two-cycle engine oil. The gas-oil mix lubricated the crankshaft’s caged-needle-roller and ball bearings and the chrome-plated cylinder walls."

What fuel/oil ratio are you using?

Here's your starting instructions for when you resolve the fast idle issue, don't "just pour a bit (of fuel) into the throttle plate".

 

[Sam R]

I think ratios on 35 year old saws are debatable. The oil today is much higher quality than it was back then, especially if you're using something like Stihl HP Ultra, (or whatever Husqvarna's equivalent is if you want to keep it in the family). 40:1 I doubt very much would have any long term negative effects on the saw. That said, I'd definitely not run it even to start it on straight gas or ether.

 

[pioneerguy600]

40:1 is fine for a 306A, I have two of them and that`s all I run in them, they cut hardwood firewood amazingly well for 37 year old saws.

 

[Sam R]

I did always wonder if the construction of the thing has any bearing on this. I have no idea how old stuff was built but, for example do old 306A's have closed transfer ports, are they 2 or 4 port designs? I suspect the way the engine is engineered has some bearing on heat transfer efficiency and cooling ability. Oil is better now than ever, doesn't break down like it used to I suspect, burns cleaner, etc etc - They show a couple backpack blowers that were ran WOT for 500 hours one on HP Ultra and one just regular HP oil, the difference is astonishing. Still I'm betting even with higher quality oil does that totally make up for less efficient designs?
Stihl classes touch on this somewhat, their newest and highest end designs have 4 port closed designs among myriad other improvements that allow an newer generations (eg, 029 vs 291) saw to have a higher BHP, lower emissions and lower fuel consumption.
Also I'm not sure the 291 has 4 port closed design, I'm just throwing out generational examples.

 

[Modifiedmark]

40:1 is fine for a 306A, I have two of them and that`s all I run in them, they cut hardwood firewood amazingly well for 37 year old saws.

The 306A was introduced in 1970. So its probably closer to 48 years old. Just sayin.

 

[Modifiedmark]

The 306 saws were never really bad for seals leaking, the PTO side seal is covered under the oiler.. Never seen seals on one leak bad enough to cause the saw to run as described. That said I always change them on saws that old.

The most common place for a air leak I have found is the reed valve adapter. Seems mostly after the carb has been removed. The surfaces of some of the adapter's seem to not be machined flat, I use a flat file to "mill" them down to flat and that with new gaskets usually takes care of that problem.

As said already, this may not be the problem but check the throttle linkage rod to make sure it was not bent when the carb was reinstalled. If bent it could be binding the throttle shaft and holding it open. If they got bent then can bind where the rod comes through the boot against the carb box.

Since these saws are this old, the top handle and tank assembly should be removed so the foam gasket can replaced between it and the crankcase. Most all of the original foam seals have deteriorated to dust by now and will let junk come up and under the air filter. The foam seal can be fabricated as originals are NLA and are probably junk by now anyway.

 

[Crackerbuilt]

It may be pulling air through the air filter cover screw hole. These saws can’t be tuned with the cover off the air filter. I ran myself crazy. Tuned with cover off. Put the cover back on and it wouldn’t crank. Then I discovered the screw hole was open all the way to the carb. 1.5 turns out on both needles is where I started tuning at ( with the air filter cover on)


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[hotshot]

It may be pulling air through the air filter cover screw hole. These saws can’t be tuned with the cover off the air filter. I ran myself crazy. Tuned with cover off. Put the cover back on and it wouldn’t crank. Then I discovered the screw hole was open all the way to the carb. 1.5 turns out on both needles is where I started tuning at ( with the air filter cover on)

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You’re really confused, maybe you’re thinking of a little Poulan S25DA or the micro series saw.

Or maybe you just replied in the wrong thread, I dunno.

 

[a. palmer jr.]

Yep, that's true about the 25. I never did get mine right, I think I may have a bad carb. It runs okay, not like an air leak but it is inconsistent in the idle especially coming down from high speed to idle.. I always started at one turn on my 306s and that didn't require much further tuning..

 

[Crackerbuilt]

You’re really confused, maybe you’re thinking of a little Poulan S25DA or the micro series saw.

Or maybe you just replied in the wrong thread, I dunno.

Video coming up,shortly.


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[Crackerbuilt]

You’re really confused, maybe you’re thinking of a little Poulan S25DA or the micro series saw.

Or maybe you just replied in the wrong thread, I dunno.

WTF May only be my S25DA but here is the issue I had with tuning my saw.




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[Analyst Man]

Interesting video.
I wish Jack Torrance would answer this question.

You say that it starts and idles at full throttle, but only after a shot of starting fluid. Does it keep running or did it die after a few seconds of high rpm?

 

[hotshot]

There’s a stud that is permanently Loctited into that bolt hole, so yes he created an air leak by pulling the whole thing out.

That’s something he created, and not by design.