I am sure there are more complicated issues that can cause this, so you might want to wait for one of the more advanced users on here to give more detail but: I had a leaf blower that was doing this. The rewind cable was stiff and slow taking back up. It turned out that the rewind mechanism was just dirty. I cleaned it out following an exploded parts diagram to take it apart and put it back together, using a all-components-safe engine degreaser (avoiding applying it to anything with bearings) to do most of the cleaning, then spraying it off and drying it out. Lubricated a bit and put it back together and it works great now. But again, there may be a more serious issue going on. That was just my experience.

Steve, you should push it to the corner of your driveway, so I can have it, then you can go out and buy a brand new mower! JUST KIDDIN'! Congrats on your mower! Is it your first LB? There are several LB fans here that wouldn't trade them or sell them off for anything, especially now since they're no longer made. It's amazing how well a 30 year old mower can still run and handle,almost like it's 3 years old! Like Walt said, those years had an aluminum tag riveted to the deck usually between the rear wheels. Later on, they used an aluminum backed sticker tags sometimes towards the right rear wheel, and some on the left side back at the rear wheel. Unless the deck had been reconditioned, those tags generally will still be visible. I'm actually getting ready to totally recondition one of mine with all new engine parts and powder coating the deck, new wheels etc. All my other LB's ran forever and well enough never for me really get the desire to do this, just something to do! This mower will no doubt be around long enough for me to end my mowing chores as an old man.

A mower shop that refused to change the oil for you? Are you serious? Anyway, if you don't happen to have jack stands(I use them for convenience), use 2 milk crates or something similar in height so the mower stays level but off the ground, so you can lay down next to and under it to change the oil. As Bill said, that engine requires a straight 30 weight oil. Anybrand will be fine and you'll have extra to top it off. Start the engine and let it warm up for about 5 minutes. Then prop the mower up both front and back. Look under the engine towards the center of the blade for the drain plug. It should be either a recessed 3/8" drive plug or an actual square 3/8" plug. Using a 3/8 drive ratchet and extension, remove the plug counterclockwise and let the warm oil flow into a coffee can or old container of somekind. When done dripping, replace the plug and snug it down. Don't get excessive with the retorquing. You can then add 20oz. of new oil through the fill plug or dipstick tube depending on the year the engine was made. The airfilter needs to be removed from the housing by taking out the screw that runs through it. Remove the major chunks by hand, then wash the filter completely with dish soap and warm water until it's as clean as can be. If the filter is really dirty/oily or caked with dirt, take it to a small engine shop for replacement. Once the filter is clean, put about 1 teaspoon of engine oil(you can use the same you filled the engine with) on both sides of the filter, and squeeze it thouroughly throughout the filter. You wanted to squeeze out any oil that drips from your hand-don't over saturate it, or the engine won't breathe or run. Replace the filter in the housing and snug down the screw. You should also replace the spark plug at this time also if you haven't done so already. Champion's RJ19LM is a standard plug used in many 4 cycle small engines from 2 through 12 horsepower. This is a basic small engine tuneup minus a carbureator rebuild which should be left up to a qualified tech. Hope it runs well for you! Good luck!

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!!