Stihl 031 help

[Klapka]

I'm working on a friends 031. We can't get it to start. It will start with gas down the carb. I blocked the exhaust and intake manifold and hooked a vac to the impulse and it held at least 15lbs for over 20 minutes. The impulse pulls just over 5lbs when I pull the recoil. It was points, but converted with the Kawasaki module. I rebuilt the carb and tried a new carb and a carb off a parts saw. He put everything together on the parts saw and it did the sam thing. any help is appreciated.

 

[grizz55chev]

I'm working on a friends 031. We can't get it to start. It will start with gas down the carb. I blocked the exhaust and intake manifold and hooked a vac to the impulse and it held at least 15lbs for over 20 minutes. The impulse pulls just over 5lbs when I pull the recoil. It was points, but converted with the Kawasaki module. I rebuilt the carb and tried a new carb and a carb off a parts saw. He put everything together on the parts saw and it did the sam thing. any help is appreciated.

Three things neede to fire, spark, fuel, compression. Fuel doesnt seem to be the problem, spark has been addressed(?), I'd pull the muffler and have a look at the piston and go from there.

 

[Klapka]

The piston looks good. The only thing I haven't done is a compression test. I don't have a compression tester, but it feels like it has decent compression from pull starting it. As long as we keep putting fuel down the carb it will stay running, but as soon as we stop the saw dies.

 

[HarleyT]

Have you looked at the fuel line/filter? The innards of that filter break apart after 30 years or so, and the fuel line gets gummy with the newer fuels.

 

[Klapka]

Checked the filter and it had a ball of foam in it. I checked and changed the one from the parts saw. It didn't have foam in it but it has a lead ball in it. I guess to keep it in the fuel. It will idle now, but it won't take throttle. I'll order a new line and filter for it.

 

[HarleyT]

Originally the foam was barrel shaped, and starts breaking apart. The residue collects in the carb's screen and clogs the passage under it, so you need to check that passage.

 

[Klapka]

Is the lead ball suppose to be inside the filter or did someone add that?

 

[HarleyT]

It should look more like a hollow point bullet.

 

[Klapka]

That's what it looks like. I ordered a new line and will replace it when it gets here to see if that works. The screen is new and the passage is clean. I'll let you know if the fuel line fixes the issue. Thank you for your help.

 

[Klapka]

The new fuel line fixed the problem. Tha k you for your help.