My Super Z has very recently developed a problem with what seems to be the choke on the Kawi engine. When the engine is cold, it starts normally with a little bit of choke. It warms up quickly and runs fine. (329 hours as of today) After about 20 minutes of mowing, it starts stumbling and the only way to keep it running is by pulling out the choke. With the choke all the way out, it runs. It doesn't run very well but it will cut grass. If I park the mower and let it cool down, (half an hour or so) it'll give me about 20 minutes of mowing again before this problem comes up. Also, the blade engagement switch has started causing problems as well and just like the choke problem, the switch will engage fine when the mower has just been started up in the morning but once the machine warms up, the switch will NOT re-engage the blades. For example, if I start the blades and mow for a little while, then I have to get off of the machine to open a gate or something, when I get back on and pull the switch to re-engage, nothing happens. I'm wondering if the 2 problems are related. Any ideas?