That's right, and the special sealant is required. When a Duraforce spits black crud out, it has been running too rich or has water in the fuel. Yours is because the raw fuel leaking in after shut-down collects in the transfer pipe and is blown through the muffler collecting carbon on the way out. Definitely get the carb fixed and the in-line fuel valve is an excellent idea on any mower. Chances are with the lean-running Duraforce and today's improved oils you will never have to clean the ports.

Well, I had a few minutes to check a few things over last night. Gotta love these things, engine shroud off, removed carb, float bowl....tools used, 1 screwdriver.. :-) So..float bowl was clean and crud-free, so signs of gunk in the needle valve, moves freely, etc. Cork float is all in one piece, and once the surface gas dried upp it doesn't seem saturated. The air vane moves freely, spring not broken. Throttle is held wide open, vane will close throttle, spring back to wide open, seems fine. I blew through the ports I could with the carb off....did NOT touch mixture screw (I assume it's the brass one sticking straight up behind the throttle through-shaft?) The mixture screw has not been touched at all (as long as I've had the mower, and it worked well since I've had it). Exhaust port is clear. Pulled the plug out, cleaned it up, a fair amount of wet sludge (from running so rich)..cleaned it up like new, reinstalled. So, that all checks out.....put everything back together, same issue. It's running rich to the point that you can tell it's sputtering when you move the air vane...it should rev up but it sputters instead, like it's way too rich. It ran a few minutes while I tried each direction on the click wheel (it changes the idle speed but it remains rich and doesn't want to rev up...sputters instead), and it left a big oily spot on the lawn under the exhaust port....so..yeah, rich... Also, it's spitting gas out the intake. Not a huge amount, but enough that it gets the air filter wet, and will fire drops into your eyes if you stick your head down there with the air filter off. LOL I didn't fiddle with the mixture screw. (Any time I fiddled with carb mixtures in the past ended with a trip to the small engine shop to have them fix what I screwed up.) If someone can confirm how many turns from bottom it should be, I'll pull it out in case there's a piece of dirt or something in it... As for the adjustment..it 'should' be good..it was never changed... So...recapping::: rich, will idle not too bad, but as soon as you cut any grass it just slows right down and stalls. Will not rev up any significant amount when moving the air vane..it wants to but just loads up with fuel and sputters instead. The issue came on slowly over 2-3 mowing sessions..it wasn't there all of a sudden...it came on slowly and got worse and worse over time. Feel free to toss the hints at me....thanks in advance!!

Darn I'm Good! Fixed it.It was an 8240. Downloaded service manual Set Float level to 7/16, adjusted air vane Another Quality LAWNBOY mower in my collection. Just in time to pick up the Pin Oak leaves.Only took 3 days to fix it, Let's see that out to be worth about 10 cents an hour. Pretty good for Retirement Pay, No Job, No Boss, No Money No Stress. Even have time to answer my own post.WHAT A LIFE.

'Can a compression check tell you if the reeds are bad?' No, not at the spark plug hole. What you have to do is check compression in the crankcase, which is necessary for the 2-cycle to run. You can remove the spark plug to make it easier to pull through, then remove the air filter to see if it's blowing air out of the crankcase. Since we already know this one is, now he has to find out what's wrong with the reed valve. Also, they all blow some air out as there is some leakage before pressure builds up enough to close the spring steel reeds, but you should be able to tell if they're leaking bad. The faster you pull it through, the less leakage you will see with good reeds.