"...Remember, you're probably doing the same thing to both blades, so taking an eighth-inch off the ends of them gives you a quarter-inch gap in between where they used to overlap...." Your gemoetry is correct in principle, but who takes off an 1/8" when sharpening their blade?... maybe 0.010-0.015 at most. What is a big contributor to this problem in 3-blade designs is blade tip speed. The spindles etc are all designed for a certain max RPM, but that RPM in a 2-blade configuration results in higher blade tip speed than in a 3-blade configuration, because of the length of the blade. What I did to solve this same problem on my L120 was 3 things: 1. Increase the governor Engine speed form the standard 2900 to 3300-3400. I figured my spindles won't last and that I'll have to replace thm every 100 hours... but they did last.... I sold the mower with 400 hours on it - no problems... And the striping problem was gone. 2. To help with juicy spring-grass, I also stopped mulching, and started side discharging. With the cutting height set to 3.5" to 4", if I saw dried out grass clippings that didn't fall in between the growing grass a day or two after the cut, that meant that I needed to cut more often, so I'd shorten the time between cuts by a day. Spring & fall time (cool & wet) = every 5 days. Peak of summer (hot and dry) = every 7 days. 3. Used my high-lift blades (that came with the bagger kit) all season. I only used the bagger in the fall - for the leaves, but using the high lift blades all-year pumped so much air out the discharge chute, that the clippings would fly out 12-15 feet to the side, scattering nicely, and not leaving any thick clumps. Good luck

The top picture looks more dense than I would expect in a Marathon fescue lawn. Is the lawn grass thick and dense when it's growing well? And are the tips of the new growth blunt instead of pointed. Does the grass send out runners over top of the ground? Here's a picture of St Augustine with the blunt tips. Or is it fine bladed with pointed tips? Runners or no runners?

Pix did not come through. Did you use the forum tools for the pictures? Generally you fix stripes by fertilizing crossways to the direction you went the first time. If you are worried about over fertilizing, use an organic fertilizer this time. Something like Milorganite would work fine. You cannot over fertilize with Milorganite no matter how many passes you need to make.

I live in Canada, AB. I dont know what type of grass. I try to water early in the morning once every 2-3 days. I water about 1/3-1/2 inch. I fertilized with 28-0-3 lawn fertilizer two weeks ago