Since it ran well for so long, the first thing I would check is the fuel bowl on the bottom of the carb for water. You'll need a 1/2" socket. With the engine cold, pinch the fuel line from the tank or, better yet, remove all the fuel from the tank. Loosen the bolt from the bottom of the carb and let the fuel drain into a shallow container and look for water in the fuel. It will be under the gas. If you find water, empty the entire tank and remove the fuel bowl. Use compressed air to dry the tank or just let it sit in the sun. If this is too much to do, drain the fuel tank and loosen the bolt on the bottom of the carb. Get as much fuel out as you can. Leave the bolt loose and put some fresh gas into the tank. Allow a teaspoon or two to drain out of the carb. Tighten the bolt; don't overtighten. Try to start. If that doesn't work, then you probably have dirt in the main jet. Look at this post for pictures of the various jets. Scroll to the bottom. http://forums2.gardenweb.com/forums/load/lmower/msg061811009450.html?10

Tecumseh with plastic bowl - if it is flooding, at the bottom of the bowl on the side is a screw. Remove that and inside is a plastic piece, this meters the flow of fuel and if missing can explain flooding. Also carb is extruded aluminum and there is a small hole drilled in it for the bowl to breath, that could be the other cause. Lastly dirt is holding the carb needle open- hold the carb bowl in your hand off the carb and let the gas flow in and see if the bowl overflows while outside the carb. If it only runs for a sec, upon removing the screw from the bowl the plastic piece inside - get a drill and drill it just a hair larger - so far this personaly worked for me 3 for 3 of these. Do this after trying cleaning it out the same piece with a paperclip. Sorry all if parts of my post are a repeat. ihwall50- black smoke, too much gas from dirty air filter, try banging the filter on the street curb knocking dirt loose and try again. if it improves, get a new filter.

I have used and tuned lots of two cycles over the years. I get no lag when i accelerate from idle. Idle is slow enough to prevent chain rotation and still purr. problem is that even with new gas and vent lines I'm not getting consistent fuel flow apparently. I have ordered new check valves. That is the only part that I Have not checked. I even went so far as to remove the vent plug (porous metal filter on end of return air line) and that didn't change the problem. I suspect it is the check valve because when I open the fuel tank I find that the system doesn't cut off. In case anyone is going to say something about the exhaust, I have run this saw pretty cleanly so there is absolutely no carbon buildup on the muffler (BTW, it would take one heck of a lot of rich fuel operation to foul a significant percentage of the muffler screen - speaking of this as a likely problem is a real red herring).

I also installed this heater about a month ago and had all the same problems and was just about ready to get rid of it when a gas man that knew his stuff came along. It took him only a few minutes to fix. All he did was increase the gas pressure. My heater now stays on and no longer cycles. It ignites much quicker and I no longer get the gas smell. The only thing that bothers me is that several people seem to be having the same problem so the setting must not have been done properly at Hayward factory and they won't pay the gas guy so the customer gets stuck with the bill($200+ in my case) as they say "not under warranty". Thanks a lot Hayward. I know that I won't forget this experience next time I need a new piece of pool equipment.