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I have a 1981 Lawnboy, model 8671. Kind of a unique situation where I bought the unit in 2008 and it was still new in the box. It ran great for the first few years and I really enjoy using it. You just cannot buy this type of quality now, and I think that is a real shame. However, I am having a problem with it. When I start it up it runs great until warmed up. Then, it begins to loose power and starts to smoke badly. I have done all the obvious to it like the spark plug, rebuilding the carb, and even replaced the coil. As it is about to run out of gas it roars to life for a second and then dies. Any advice is greatly appreciated.

Thanks, John

It seems to be running too rich (too much fuel relative to air.)

The first thing I'd look at is the float valve: be sure that it's shutting off the fuel flow, not allowing fuel to overflow into the engine.

This is obvious... but check the air filter for clogging.

It's neat that you got a 27-year-old Lawn-Boy new in the box. :thumbsup:

Let us know how this comes out.

Not to play doomsday but if the fuel flow remedy mentioned above doesn't fix it, ( and I hope it does!!), I'd at least run a compression check of the engine. Not really familiar with the unit but wouldn't hurt to check. Not a bad idea to do it anyway if there has been too much fuel flowing through into the cylinder(s).? Hope it works out and have a great day! :smile:

Yes, I do seem to have it fixed! I took a carburetor off of a parts machine I pulled out of the garbage a while back. I cleaned it up, but did not even adjust it. It's pretty wet out today, so I did not cut much. But it did seem to smooth out and run correctly.

A mechanic did mention the seals might be leaking or worn somehow, even if it did only sit in the box for so long. We'll see how it goes once I really us it this summer. I will post more when I use it.

One interesting thing about it was a tag indicating that starting in 1982 all mowers will have a "dead man" switch. Not worded that way though.

Now I just need to fix the original carb some how. I have attempted to adjust what I see as the only adjustment screw on it without success, in the past.

Thanks for all your help.

The main seals (on both sides of the crankshaft) are important -- if they're not sealing tightly, that's a problem. However, the symptoms that you described suggest that it was running rich and bad seals won't do that.

If you get a chance, post a photo of your mower.

I might add that replacing the main seals is a big job -- I wouldn't take it on unless I had a pretty good idea that it needed to be done.

I just cut the entire lawn with it. Seems to be running a lot better. I'll try to post a picture by tomorrow.