I have been through it all with my used exmark lazer 44". Well I when I brought the mower used it had a kawasaki FH500v engine. It had a huge oil leak, it would burn plugs every weekend before I start cutting and it also smoked. The power was not optimal enough to power the blades and hydros. Quickly I start to get frustrated because some days I will off schedule getting to my accounts and we all know in the lawn care TIME is MONEY. So I stumbled upon a local guy selling a Kawasaki 22hp (FH661v). I paid 200 bucks for it, it ran beautifully and had zero leaks. I brought another hydro drive spindle and went on with the engine swap. BOY did this new engine make a difference. It was more reliable and very strong. Never knew my mowers true potential until then. I do all residential accounts, but have 2 huge lots I cut and my new engine tends to kill after about 35 minutes of cutting time. I usually have to wait 20 minutes before I can get back to cutting. My question is what's causing this problem? The way it kills is like a sputter. sort of like it has starving for fuel. instead of a instant kill if the plugs would stop firing. what do you think the problem may be?