Old Stihl FS80 Trimmer-I'm Exasperated!!!

[Davy Crockett]

Thanks, Al.
I think the screen is clean.

When I put the new manifold and gasket on, I checked to be sure that was lined up (or at least I knew to do it)

What do you think about an air leak somewhere?

I do see a few air bubbles in the carb side of the primer while it's running.
Maybe the new hoses need heated so they shrink better around the fittings?
My 22 yo son is doing some of the work and he sometimes may want to cut a corner or two

[Seditious]

Thanks, Al.
I think the screen is clean.

When I put the new manifold and gasket on, I checked to be sure that was lined up (or at least I knew to do it)

What do you think about an air leak somewhere?

I do see a few air bubbles in the carb side of the primer while it's running.
Maybe the new hoses need heated so they shrink better around the fittings?
My 22 yo son is doing some of the work and he sometimes may want to cut a corner or two

Fine wire makes good clamps for small fuel lines. Have you looked at the reed valves? They can seat at idle and fail to seat at higher rpm.

[Al Swearengen]

New hoses shouldn't need shrinking of any sort. Wouldn't hurt to recheck for cracks and tight fittings though. These rascals can be finicky.

Just wondering if you unscrewed the top of the carb and checked to see if that needle valve (inside the slide) was still secure. You can check it when you get the top off by just pushing up lightly with your finger on the pointy end. It shouldn't move up or down.

[Davy Crockett]

I did not yet check for that needle valve.
This is a brand new (not rebuild) carb.

I'm out of daylight for today.

Which side is the top?

I get nervous around carbs.
When I was a kid, I tore enough carburetors apart and never successfully reassembled one

[Davy Crockett]

Seditious, you're explaining to a moron.
What is a reed valve, please?

[Seditious]

Seditious, you're explaining to a moron.
What is a reed valve, please?

Two stroke engines use reed valves to meter the air fuel mixture into the cylinder during the correct stroke. If they don't seal during the compression stroke, the engine misfires. Sometimes they seal at low engine speed but fail to seal at higher RPM.

Never mind. Your trimmer engine is piston ported and doesn't have a reed valve

[Davy Crockett]

Al, mine is a TK (?) carb

[Davy Crockett]

If anyone has any suggestions (please), here is where I'm at.

The machine starts really easily and will idle forever. I do have the idle set a little high.

I can start and let it idle for a bit to warm up.
When I squeeze the throttle slowly, it will accelerate to what sounds like a good operating speed.
If I keep it running wide open for 15-20 seconds, it starts to bog down.
If I let off the accelerator and slowly pull again, it won't fully rev.

The last time I had it running while doing this, I had a little fire shoot out by where the muffler bolts to the cylinder

[Al Swearengen]

I did not yet check for that needle valve.
This is a brand new (not rebuild) carb.

I'm out of daylight for today.

Which side is the top?

I get nervous around carbs.
When I was a kid, I tore enough carburetors apart and never successfully reassembled one

Well I guess you don't have a model with a slide/needle valve. Probably just a simple diaphragm model (Zama? Walbro?) Zamas are usually swapped out for Walbros if possible. Older Huskys had the slide carbs.

Hmmm.