Most definitely Commercial Grade Only Bro . I agree , the cheapo homeowner grade kits are not worth the postage lol . EPDM or the previous Viton kits are the only way to go . Having been rebuilding carbs on various saws . blowers , trimmers , snowmobiles etc for over 25 yrs , u get what you pay for . $3.00 kits do not cut it . I pay $12.00 to $13.00 but they outlast the saw these days . Back in the day tillotson and keihen were the norm unfortunately offshore products have flooded the market . Sometimes you can find retro Walbros carbs on web with viton seals and gaskets for $6.00 to $8.00 , I buy them up immediately when I find them lol .

My 1997 Stihl TS 510 Brazilian made cut off saw (same metal base as a chainsaw, carb's a Tillotson) ran well for 10 minutes, then lost power if under load, but would spin up if not under load and sound ok, but bog down again if loaded. So, I replaced the ignition coil with Stihl part and it coughed once after a couple pulls but didn't start, then I have a very short shot of ether, ran for .5 second, then, no more signs of starting. Pulled carb, looked at hoses, cleaned carb with brake cleaner, diaphragms look good, it ran a second on first pull, then no coughs, nothing. The upper seal on the carb, just below air filter is not completely torn, but is thin and tattered. There is a very small gas leak, a few drips around the hose attachment onto the big rubber fitting that pushes with some effort into the metal hole the hoses run through to the gas tank. IDK if the Tillotson is original, or the last guy had problems? I took the hoses off, blew through them, no visible issues. I think it's a fuel issue. What's my next move?

One of my sisters has that model. Had the same problem couple years ago. Found that the thermal fuse on the blower housing was blown, which is in the motor circuit. It's a failsafe for the air temperature thermistor which is also on the blower housing, so I also replaced that. There's also a belt-break safety switch so check that the belt isn't broken.

rasims (or others): I removed the carb, cleaned it, checked float position as per instructions you gave me. All OK. There's no warping on carb flange. Mower will run for a short time, but after five or ten minutes, it will start to rev up and down, and then stop. Question: Will lack of air cleaner cover do this (too much air-> lean mixture)? I have the foam filter in place only. But, it was doing same thing before I broke the air filter cover (I'm awaiting a new one.) I adjusted the mixture as per instructions (seat, open two turns, etc.) No matter what I do, the rpms rev up and down. Should I clean the jets? Could that be a problem? I think one is on the side of the body, and another under the fine cylindrical metal filter screen? Is this correct?