Rebuilt carb on old Poulan Micro XXV running away

Sep 9, 2015
Howdy all,

I've been in "restoration" mode for awhile replacing carbs on older tools for myself and my dad as backup tools (leaf blower, weed trimmers). This time my dad had two old chainsaws that he would like to be work horses for smaller brush.

The two chainsaws are older Poulan Micro XXV Deluxe 14" chainsaw and the other one is the 16" variant. I'm starting with the 14" chai saw. I could not find any aftermarket carbs for this thing it's so old. I believe it's carb is a Walbro WA19. I purchased a rebuild kit and it seemed to have all correct gaskets etc.

So I tore apart the carb and tried to clean it the best I could. I replaced all gaskets, the needle thing and the lever thingy with the spring that attaches to the needle. Sorry, I don't know the terms. I ordered a new spark plug, replaced fuel line and fuel filter. The air filter is on the way shipping.

I figured I'd at least fire it up to see if it ran since I had everything on it except the air filter. Fired it up and it ran good.

My problem is that it seems to be running away on me, like a diesel does. I'd fire it up, it'd start running, I'd give it some throttle and then let it idle. But the idle would just keep getting faster and faster and faster. And then it would, I'm guessing, flood itself off.

I didn't mess with any settings regarding the idle screw, low or high screws. I made sure that lever thing attached to the needle was at the same level the old lever was. I made sure all parts and gaskets matched up before replacing, so at this point I'm quite confused.

I don't want to mess with the screws without the air filter installed, but even without the air filter, I feel like that's not the issue. It also calls for 50:1 gas ratio but I got some 40:1 89 octane mix in it.

Any help or guidance would be greatly appreciated! I'm new to this carb rebuilding thing, I'm used to replacing the entire carb, so I'm not familiar why this is happening.

Edit: also I'm noticing white smoke coming out of the exhaust. I'm guessing it's running lean?
Last edited:
Feb 25, 2015
Sask, Canada
Its possible the crank seals are leaking, causing a lean condition.

Tuning isn't to hard so I would richen both high and low a touch at a time and see what she likes.


Thread starter
Sep 9, 2015
Thanks for that! I was able to tune it pretty well! It's running pretty good now, still need to see how it does with the air filter in it, but was able to make a couple cuts.

Kameleon, I have the Deluxe Micro XXV.

I just got done with the 16" one. Replaced fuel line, fuel filter, rebuilt carb using carb kit, put new spark plug in it. This one won't even fire. Had the choke on, throttle engaged, and it wouldn't even fire :(. Gonna leave it sit for a night and try again tomorrow