Well, TWO of them actually. One is a Craftsman self propelled push mower made around 2000ish, and the other is a John Deere self propelled push mower from 2010. Both have had recent tune-ups, and both have nearly identical Briggs & Stratton 6.75hp engines. Both are having the exact same symptoms: they won't freakin start. The John Deere always ran well, but I noticed it's been getting harder to start the last few times I've used it. It took several hard pulls last time to get it to eventually fire up, but it ran perfect (like always) once it came to life, and didn't skip a beat. Well I tried to mow the grass on Monday and it wouldn't start at all. It seems to come close, then falls on it's face. The Craftsman is new to me; it started right up today and ran great at first, but quit on me 5 minutes into the mow. It just sputtered and died and wouldn't start back up. I let it sit for a while and tried again with no luck, and now it's in the same boat as the other one, it tries to start but won't fire up. I've checked them both thoroughly. Clean air filters, clean carbs, primers seem to work fine, the brackets on the start cables seem to be engaging properly, the pull cables feel normal. Both have good looking spark plugs. Bowls had fuel in them, filters/floats looked good. I drained the tanks and tried fresh fuel from a new container, and it made no difference. There doesn't appear to be any gaskets or O-rings missing anywhere. When I was taking apart the JD earlier this week, I noticed the air filter housing had TWO gaskets on it for some reason, and one of them was really crusty. So I ordered two new gaskets thinking that might be the problem. While I was waiting on those to come in, I figured I would buy another cheap mower (the Craftsman...just got it today from craigslist) and use it for a while, then sell one of them once I fixed the John Deere. HA, so much for that. I cleaned the carb thoroughly on the Craftsman and replaced the spark plug, just for the hell of it. Didn't help. I didn't have starting fluid but I dumped fuel into the carb, still wouldn't start. I'm at a loss for words here. In summary, I should have just bought a new mower instead of dicking around with old craigslist junk. Lesson learned. But what's done is done, and at this point I just need to get one of these piles running. I suppose should pull the plug and check spark while I try and fire it up, but other than that, I'm dumbfounded. Any ideas?