Hard Starting String Trimmer

[bill18163]

I have a Stihl FS130 string trimmer. Last year toward the end of the season it got hard to start. Even after you did get it started and had it running for a while if you stopped for a bit it was still hard to start even when it was warmed up. Well it's doing the same thing this year too. Very hard to start even when warm. When you press on the primer button it doesn't seem to build up any pressure and there is not very much gas in the bulb. Once you get it started it runs just fine. No problem at all. Only starting when hot or cold is a problem. What might be the cause of this?

[KE4AVB]

Start with the basics.

May need the valves adjusted. Also check spark arrester screen.

For valve adjust you will need kit PN 4180 007 1005 as it takes a special feeler gauge tool.

[bill18163]

Well I did have to adjust the valves. The intake was way off. It still will not start. It's not getting any fuel. I can pull on the start cord many times and then go check the plug and it's dry as a bone. Compression seems Ok. My readings are a little iffy because I have to use an old press in style gage. I don't have a screw in gage. Looks to be in the 80's and the spec for this engine is 100/87. It's getting spark for what that's worth. I took the carb apart and except for a small adjustment needed on the needle valve lever everything else looks OK. Very clean inside. One thing that bothers me and I can't make sense of is why would the fuel tank have pressure in it? When I was taking a carb hose off the other day fuel came squirting out full force from the hose port on top of the tank. I had to grab the fill cap and open it to balance out the pressure to stop the fuel from squirting out. What would cause the fuel tank to build up pressure? Now that I think of it as I write this post wouldn't the tank vent valve balance the pressure in the tank to agree with atmospheric pressure outside the tank? Isn't that what it's supposed to do? Is my problem as simple as a bad vent valve? Any comments or suggestions would be appreciated.

[bgsengine]

Well I did have to adjust the valves. The intake was way off. It still will not start. It's not getting any fuel. I can pull on the start cord many times and then go check the plug and it's dry as a bone. Compression seems Ok. My readings are a little iffy because I have to use an old press in style gage. I don't have a screw in gage. Looks to be in the 80's and the spec for this engine is 100/87. It's getting spark for what that's worth. I took the carb apart and except for a small adjustment needed on the needle valve lever everything else looks OK. Very clean inside. One thing that bothers me and I can't make sense of is why would the fuel tank have pressure in it? When I was taking a carb hose off the other day fuel came squirting out full force from the hose port on top of the tank. I had to grab the fill cap and open it to balance out the pressure to stop the fuel from squirting out. What would cause the fuel tank to build up pressure? Now that I think of it as I write this post wouldn't the tank vent valve balance the pressure in the tank to agree with atmospheric pressure outside the tank? Isn't that what it's supposed to do? Is my problem as simple as a bad vent valve? Any comments or suggestions would be appreciated.

Nah tank should hold a few PSI (3-4) of pressure - tank vent will hold a wee bit of pressure its to prevent fuel from getting out, and main purpose is to allow air in and prevent vapor lock. I'd suggest pour about a teaspoon of gas into the spark plug hole and put plug back in, see if it will fire on that gas, if it does then likely a fuel supply problem - if not, could be a valve hanging open (which might explain why the excess clearance if it was)

[bill18163]

I'll do an update. The trimmer is not getting fuel. You can pull on the starter cord all day and keep checking the plug and there is not a drop of fuel on the plug. As BGS suggested I poured some fuel down the spark plug hole. The trimmer will start and it runs like a bear. Once it is warm you can shut it off and it will start right up again as many times as you want to keep doing it. Let it sit over night and try to start it and it will not start because it's not getting any fuel. Spark plug has no fuel on it. I bought a rebuild kit and rebuilt the carb. Ran the stripped down carb through my ultrasonic cleaner three times and put the carb back together paying close attention to the carb breakdown drawing. Metering lever is set to specs right on. Tried to start the cold engine and it will not throw any fuel. Plug is dry. I poured fuel in the plug hole and it will run. Starts right up and idles. Idle needed a small adjustment to keep the string head from turning. The trimmer was bogging a little from the initial screw settings so I adjusted the high speed screw some and the machine will scream with no hesitation. Idles well and accelerates with no problem. It will run as long as you want at idle. If you shut it down it will start right back up again. I took the limiter caps off the adjustment screws when I rebuilt the carb and I actually think the machine is running too fast by the sound of it. If I ever get this problem solved I'll put my tachometer on it and make sure it's within specs but for the little amount of time I test run it I don't think I can hurt it. Further suggestions??

[KE4AVB]

Make sure the choke is latching the throttle slightly open when you set the choke as it sounds like the choke is not working correctly. Also it should have only hole in the Choke butterfly vane open the other is should be blocked by the choke shaft and the vane fully closing.

[bgsengine]

I took the limiter caps off the adjustment screws when I rebuilt the carb and I actually think the machine is running too fast by the sound of it. If I ever get this problem solved I'll put my tachometer on it and make sure it's within specs but for the little amount of time I test run it I don't think I can hurt it. Further suggestions??

I would do the tach thing right now, and get your idle and high speed settings dialed in to factory spec - Idle setting is very important and if it is maybe a bit lean (and masked by a bit rich on the high speed side) it can be hard to start. So, I'd find out the factory specs for both idle and high speed , and follow procedure (with proper load applied - this may involve removing guard to allow a longer string, or shortening the string to a specific length) to set the idle mixture first to get it dialed in (basically turn in/out the idle stop to get specific RPM while adjusting idle mix, then do the "rich down") and then do your high speed mix adjustment, THEN see if it starts properly after a cool-down - those mixture adjustments can have a huge affect on startability.

[KE4AVB]

FS130, Series 4180 Powerhead

Engine must warm for at least one minute.

The basic setting is carried out with the high speed screw H and the low speed screw L as follows:

Lightly seat both mixture screws.

Initial mixture settings.
Open the high speed screw H 4 turns counterclockwise.
Open the low speed screw L 2 3/8 turns counterclockwise.

The idle maximum engine speed should be between 3,100 and 3,300 rpm.
Use the idle speed screw (LA) to set the engine idle speed to 3,200 rpm.
With the engine idling, turn the low speed screw (L) counterclockwise and set the engine speed to
2,800 rpm.

Max rpms 10,500 ± 500 rpm if too high the coil's speed limiter will kick in so it might be necessary enrich the H fuel mixture to get down to 10,500 rpm so the limiter doesn't kick. Also this is with the trimmer line at designed max length for proper loading.

Install new limiter caps when done.

[bill18163]

I started working on my FS130 because it was hard to start. I looked at the valve settings and the intake was way off. Exhaust wasn't bad. It took about a full turn or more to adjust the intake. Anyway I got the valves adjusted. I still had trouble starting it. I rebuilt the carb. Still hard to start. I found out that these Stihl 4mix machines are prone to getting carboned up. I decarbonized it using the Stihl fluid. It must have taken out a lot of carbon because the valve adjustment was way off after I did it. I reset the valve adjustment to specs. Fired it up and did some carb adjusting and this machine runs like a bear. No hesitation at all. Set RPM's using my tach. Shut it off and you can start it right back up again and it runs fine. But if you let it sit for 20-30 min and try to start it again it is very hard to start if you can get it started at all. Next morning with cold engine it will crank right up. Get it hot and let it sit awhile and it's hard to start. It takes 10-15 pulls to start or maybe it will not start at all. I checked compression and found it at 60lbs. Specs call for 101/87. Squirted a little oil into the cylinder and got 130lbs. I'm thinking rings but could there be something else I'm missing before I go for replacing the rings?

[KE4AVB]

It maybe just a sticky ring since you apparently had a lot of carbon. I never had a Stihl in the shop that carbon up, spark arresters clogged with carbon. Now have had rings stuck before with carbon on regular 2 cycles.