Coco 5 #1 Posted May 5, 2023 I inherited a 1990 520H about a year ago. Only about 500 hrs on it, but it had sat for upwards of 15 years prior. New filters and oil (all Toro/Onan spec'd), as well as new fuel filter and line (1/4" aluminum hardline with PTFE rubber hose to engine this year). I also cleaned the carb last year, although did not do a full rebuild, which is in the works. Problems are as follows: -Stalling. After about half an hour of mowing, I begin to lose vacuum and the engine starts surging badly. I suspect this is a carb issue, but I don't know why it would run fine initially. I would think a dirty carb would cause it to run poorly all the time. Of note, I run 100LL avgas in it, no ethanol. When it finally stalls I can wait maybe a minute and it'll run fine for another half hour or so. Not a huge deal, just a little befuddling. -PTO popping out. I've adjusted it looser and tighter, but I just can't get the PTO to stay engaged. Pops out every few minutes when mowing. I grease the deck (and everything else) religiously, but it doesn't want to stay engaged. Clutch disk doesn't look bad, but should I replace it anyway? I'm not mowing roots or anything that should overload it. Very annoying. -Hydro temp. This year I've noticed toward the end of my yard the hydro temp light comes on. I seem to remember there being a fan over the right rear tire, but there's nothing there. I'm pretty sure there should be, and it looks like there's a stub shaft for one. Am I crazy, or did it eject the fan? Hasn't been a problem so far, but I'm worried that when it gets to be 100+ outside I'm either going to be waiting for it to cool down or lock up. Sorry, I'm not super familiar with these tractors. Mostly dealt with older Cubs and bigger Onans. Thanks Share this post Link to post Share on other sites
953 nut 59,051 #2 Posted May 5, 2023 The stalling problem is probably cause by a plugged vent in the fuel cap. As fuel is removed from the tank a slight vacuum is created in the tank if there is no vent. Once this vacuum equals the ability of the fuel pump to pull fuel out the engine is starved for fuel and surges then quits running. A new fuel cap should solve this problem. The Eaton transaxle has a plastic cooling fan that is secured to the input shaft with a 1/4-20 bolt. Your Toro dealer should stock that or it can be found on . keeping grass clippings cleaned off the top of the transaxle will help the coolin problem too. 1 Share this post Link to post Share on other sites
lynnmor 7,680 #3 Posted May 5, 2023 There is no need to use special gas as long as it is fresh. I don't know why you want extra connections in the fuel line, seems like asking for more problem areas. Remove the seat, fender and fuel tank, then flush the tank and clean up the entire area. Replace the broken or missing fan. The shutdown problem could be a bad ignition module or coil, check for spark IMMEDIATELY after shutdown. Follow the PTO adjustment procedure in the manual, install the trunnion with the hair pin up. Share this post Link to post Share on other sites
