the ninja saps power and should be used on the highest power engines only. try a gator blade instead

I agree 100% with lawnmowerdan. The Ninja requires a _lot_ of power to run through any kind of serious grass at all. All that recutting of the same clippings that makes it such a great mulching blade also requires that much more power. And your engine was a powerhouse to begin with, and with a lot of hours on it now (I assume) it is less powerful than when new. It's not that you're asking too much from the mower, but you are from that engine. The Gator blade will recut a lot less and still leave you with perfectly acceptable mulching performance. It's not expensive - maybe $15 at the most, I think - and would vastly improve your experience.

Thanks to both lawnmowerman and mattv21. I think I'll go wrastle me a gator.

I would replace the Ninja with an original equipment blade. If you want a mower to work like it's supposed to, make it original.

gators work better than oem blades on every mower. there is no down side to using a gator -truly one of the best products ever made for a lawnmower but saxman is to stubborn to try one. i have gators on EVERY mower in my fleet

I've just recently starting mowing my lawn with an older Snapper P21407T. Based on some good advise from this forum I replaced the Ninja blade with a Gator. As described, the Gator blade does seem to do a good cutting job, but I still feel that I'm just not getting the kind of performance I expect. Other than cleaning the carb and replacing the spark plug, where could I look next to see what may be sucking power out of my machine. I don't suspect a compression problem, since I do not see any signs of smoke in the exhaust (bad rings) and the mower starts easily. Any suggestions would be appreciated.

lawnboy dan -1 saxman-0

"I would replace the Ninja with an original equipment blade." My Snapper came "stock" with the Ninja blade. I think a lot of Snappers do.

Found some information about tuning the caruretor on the Tecumseh 4 h.p. engine that is on my mower. I tried to follow the adjustment procecedure to see if my "power" issue is carb related. Although I was able to increase the rpms, and the engine seems to run fast, even, and strong, as soon as I get about half way through a row of grass the engine either bogs down to a stop or the engine rpms start to cycle high then low. This is the same results I had before tinkering with the carb. Anyone have any suggestions?

The cycling between high and low speeds sounds somewhat like a lean condition under the increasing load as you mulch through a row of grass. I have no idea on your engine how to adjust the mixture, or if instead maybe it needs a bigger jet or has an air leak at the carb gasket (just some ideas). But as you mow a row, the grass getting recut by the mulching setup continues to build up to an extent, which increases the load. The Gator blade is better at not continuing the buildup forever than the Ninja (which seems capable of not releasing clippings until even the strongest motor bogs). But if something isn't right with the mixture (again, just a guess) then evne the Gator could cause problems.

Thank you for your response, mattv21. I have come to the same conclusions and have started looking for information to help diagnose the power issues. I have found a Tecumseh sevice manual online that has a plethora of information. However, anyone out there that may have some first hand experience with tuning carburators and/or trouble shooting engines with a surging problem(the Tecumseh manual calls it "hunting"), please chime in. I could alway run my mower down to my nearby Snapper repair shop, but where's the fun in that!