Does Anyone Know How to Adjust the Carb on a Small 2-Stroke?

"FTTOHG Has Moved to https://opposite-lock.com" (alphaass)
04/23/2016 at 13:30 • Filed to: STIHL, HOME OWERSHIP, TWO STOKE, HALP

So I tried using my Stihl FS45 for the first time in a few months and it’s running like shit. It keeps cutting out at idle even when fully warmed up, sometimes stalls when I hold it at an angle, and is really slow to spin up the throttle. When it is at full throttle, though, it still feels strong and cuts well. Running carb cleaner in a can seems to get it going for a few minutes, but then it’s back to how it was. So I’m thinking something is up with the carb. Possibly the needle valve sticking? Or maybe it just needs adjustment to the mixture at idle? I haven’t pulled it off yet... Is there anything I should look out for? Carbs for these are only like $15... Does it make more sense to just slap a new one on? Help, I’m starting to lose the battle with these stupid dandelions.

Thanks and here’s a Honda CR-V with an Infiniti G37 for your time.

DISCUSSION (25)

1111111111111111111111 > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 13:36

All I know is that if I’ve ever touched those two screws it stops working.

My X-type is too a real Jaguar > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 13:37

Check the spark plug if you haven't the carbs on these are generally injection molded plastic and not adjustable

Lumpy44, Proprietor Of Fine Gif > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 13:40

Can you get to these?

Kinja'd!!!

FTTOHG Has Moved to https://opposite-lock.com > My X-type is too a real Jaguar
04/23/2016 at 13:53

Thanks. It has a few screws that looked like maybe they were. Plug is easy enough to pull out!

FTTOHG Has Moved to https://opposite-lock.com > Lumpy44, Proprietor Of Fine Gif
04/23/2016 at 13:54

Yes, they are pretty accessible.

FTTOHG Has Moved to https://opposite-lock.com > 1111111111111111111111
04/23/2016 at 13:55

That's what I'm afraid of!

Brickman > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 13:55

Other than the idle mixture screw, there is a fuel and air screw. You need a special set of screw drivers for those, but 90% of the time thats not what needs to be fixed. I rebuilt my Huqvarna (cant spell) trimmer carb recently and acted up like yours. Good cleaning, new diaphragm, gaskets, pintle, etc.

Yours needs a rebuild, but if its cheap for a whole new carb then do it. Replace your spark plug, fuel lines, and fuel filter too.

jminer > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 13:57

If the gas is a few months old that’s probably your problem. It starts to turn after about 2 months. The first time I run my weedeater every year it runs like shit until I burn through the old gas and put a fresh tank in there.

coelacanthist > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 13:58

Save the headache and just slap a new carb on it. Most modern two strokes are either not adjustable or require a tool that the manufacturers literally only sell to servicing dealers. A dealer can be fined for selling one of these tools to the general public. Use the pre mixed fuel available at most auto parts stores, it is devoid of ethanol and will say fresh longer without destroying the membranes in the carb.

My X-type is too a real Jaguar > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 13:59

My experience with these things is the plug get gummed up over winter and has a weak spark causing them to flood

traitor joe > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 14:00

Your problem most likely has something to do with varnish in the carb. I would take it apart as far as you can, and soak it in carb cleaner for a few hours. Might be easier to just replace it.

Before storing your small engines, you should empty out the gas and then run them dry until they stop.

FTTOHG Has Moved to https://opposite-lock.com > Brickman
04/23/2016 at 14:00

I may try rebuilding just for the learning experience. If it doesn’t work I’ll just slap on a new one. I have a parts cleaner tub at work, should I use that? Also, the fuel filter is in the tank. The one time I did one of those on a chainsaw I never got the old one out... Do you just drain the gas and dump it out of the tank?

FTTOHG Has Moved to https://opposite-lock.com > jminer
04/23/2016 at 14:07

Yeah I already got some new stuff running through and it seemed a little better, but not much. I'm guessing letting it sit with the old gas got the works too gummed up.

FTTOHG Has Moved to https://opposite-lock.com > coelacanthist
04/23/2016 at 14:08

Thanks. I've been mixing my own, because when I bought it Stihl was running a deal where you got an extra year of warranty if you bought a case of their oil that I'm still working through. I've been running 93 octane with fuel stabilizer added in, but that's probably still not good enough.

Brickman > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 14:09

You will be replacing the gaskets so yes, parts cleaner will work. Have the carb apart so it soaks through.

Also good to replace any gasket that goes on the engine and doesn’t hurt to soak the muffler too. Too much carbon build up will slow down the engine.

After dumping the gas, I use a long hook to grab the fuel line and pull

A tip for putting new line in the tank is cut the line at and angle, push and twist the line into the tank and with long nose pliers pull the line out the gas cap hole. Make a clean cut and add the filter. Then pull the amount of fuel line to the carb you need.

FTTOHG Has Moved to https://opposite-lock.com > Brickman
04/23/2016 at 14:13

Cutting at an angle and using needlenose pliers is one of the few tips I have actually learned. I had to replace the fuel lines in my chainsaw because they dry rotted so I had to do the filter in the tank too. Amazingly, that crappy old 2.0cc McCoullough chainsaw just keeps running and running with stale fuel and no carb adjustment. I'll try going in there with a hook and fishing the old filter out.

coelacanthist > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 14:15

I remembered that they do that promo as soon as I sent that :) Go online and see if you can find a gas station near you that sells ethanol free fuel, they are still out there but hard to find.

E92M3 > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 14:15

Bingo. Just get a new carb. I bought a gasket set to rebuild one once, and it wouldn’t even crank afterwards. Bought a new carb for $20, and it fired up first pull.

Brickman > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 14:18

It should just fall right out if theres no line attaching it to the top of the tank.

FTTOHG Has Moved to https://opposite-lock.com > coelacanthist
04/23/2016 at 14:20

Wait those still exist?! There is one listed not too far from me as having ethanol free 89. I’ll have to see if that is true.

Funktheduck > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 14:23

You need fuel, spark, and air.

Spark and air are simplest: check plug and filter.

Fuel is the most “complicated”

First: try new, fresh from the pump gas. My mower (4 stroke) runs like crap with gas more than a few months old. Either dump the old stuff or freshen it up but if you want to eliminate bad gas as a possibility you’ll want all fresh stuff.

Check the lines and filter. It’s not unheard of for crap to get in there

A lot of law equipment have non adjustable carbs due to emissions regulations. If it’s the carb it’s either gummed up or eaten up by the fuel. Ethanol destroys the rubber and plastic bits of the carb.

If you wanna go easy, but a new carb. If you wanna save a couple bucks, rebuild. Be mindful that there are some really tiny pieces in the carb. Watched a friend rebuild some last summer and to save his eyes he used one of those shop light/magnifying glass things

gogmorgo - rowing gears in a Grand Cherokee > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 15:03

We have a bunch of those at work. Whenever one comes in with carb-ish issues, we just put a new carb on. For us it comes down to it being cheaper just to slap the new carb on than to pay our tech his hourly wage to spend a couple hours dicking around with it.

they-will-know-my-velocity > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 16:56

Kinja'd!!!

;)

sn4cktimes > FTTOHG Has Moved to https://opposite-lock.com
04/23/2016 at 23:11

I used to use Stihls when I was younger. Try just taking the air filter out and running it on on idle once it warms up. If it works, clean or replace the filter. That was usually the culprit on the ones we used. Also, you can tweak an idle screw somewhere... but you have to kind of adjust them for idle once they’re at running temp otherwise they can over idle / over heat. Give em a half trigger pull for about 30-60 seconds once you get it running then set the idle. If it ran “when parked” my guess is the air filter isn’t helping the situation. The carb cleaner might be juicing it enough to overcome the air shortage.

And like everyone else thinks, if it’s been a while it may need a rebuild. I used to do it off the back of a pickup so it’s not that hard to swap out the parts. Do the rebuild over the weed, maybe the gas will kill it.

FTTOHG Has Moved to https://opposite-lock.com > sn4cktimes
04/24/2016 at 10:13

Thanks. It does seem to run better without the filter in, but the filter seems pretty clean. It's easy enough to just replace that anyway. I've done zero maintenance on this thing since I bought it 4 years ago, so I'm ok with replacing several things now.