Mowing ..

[DFB FGXR6]

Originally Posted by Citroënbender

Still yet to achieve this outcome, had to divert for prior scheduled jobs in Sydney.

Crash Bunny has an FS38 bent shaft Stihl trimmer with carby issues (plug looks almost new). Hard to start then won’t rev. Likely to come good with a carb adjustment or just chuck another complete unit on?

That's an easy one, remove the spark arrestor from the muffler outlet, it will be blocked solid with carbon. You can use a wire brush, but its easier to burn it off with a flame of some sort. Reinstall and it should start and rev like new. Because this happens gradually, it sort of loses performance very slowly over time, so might not notice the problem until it won't rev or start properly. If the user isn't running the machine at full tilt, then it tends to increase the likely hood of the carbon not burning off fully.

[Citroënbender]

Indeed, the spark arrestor was solidly caked with carbon. Presently got the whole muffler in chemicals to try and remove much as possible.

Hoping there is no further issue, but I notice the primer bulb never gets a really “firm” feel to it so there could be supply side investigations later.

Originally Posted by DFB FGXR6

That's an easy one, remove the spark arrestor from the muffler outlet, it will be blocked solid with carbon. You can use a wire brush, but its easier to burn it off with a flame of some sort. Reinstall and it should start and rev like new. Because this happens gradually, it sort of loses performance very slowly over time, so might not notice the problem until it won't rev or start properly. If the user isn't running the machine at full tilt, then it tends to increase the likely hood of the carbon not burning off fully.

[DFB FGXR6]

Originally Posted by Citroënbender

Indeed, the spark arrestor was solidly caked with carbon. Presently got the whole muffler in chemicals to try and remove much as possible.

Hoping there is no further issue, but I notice the primer bulb never gets a really “firm” feel to it so there could be supply side investigations later.

Easiest way to remove the carbon is to set fire to it.................probably let the chemicals dry first though. I actually did two of my BG86's yesterday with a gas torch flame.

Same topic, but deeper, the two BG86's at work had been losing power and not revving properly. They were sent in for "service" at the Stihl dealer, only to return exactly the same. I guess they thought a sale would be forthcoming.

I pulled the exhaust screen out, but it wasn't too bad. I then removed the muffler to find the exhaust port on the head almost completely blocked. I chipped away the carbon, reinstalled the muffler and they both ran like champs again. Sometimes, you have to do things yourself to get the result.

[Citroënbender]

Yes, as you suggested - wash out the degreaser after gentle agitation with a fine brass brush, then blowtorch. Exhaust port nice and clean.

It still stumbles a bit like a spark or over-rich mixture issue (sounds “fat” if you know carbureted cars and the exhaust note changing with richness/leanness), but will actually rev hard now.

Your advice has got it going so much better though - thank you!

[DFB FGXR6]

Originally Posted by Citroënbender

image

Yes, as you suggested - wash out the degreaser after gentle agitation with a fine brass brush, then blowtorch. Exhaust port nice and clean.

It still stumbles a bit like a spark or over-rich mixture issue (sounds “fat” if you know carbureted cars and the exhaust note changing with richness/leanness), but will actually rev hard now.

Your advice has got it going so much better though - thank you!

Adjusting Idle (LA), Low speed (L) and high speed (H) -