Mantis tiller won’t stay running

[Ranchito]

Ah yes entire batches of parts that don't play nice. A few years ago, I bought a trailer sprayer for the sole purpose of spraying my gravel drive with glyphosate and it worked flawlessly. Then one day the pump failed and after taking it apart, I found the diaphragms were swelled to the point where the "rubber" was wrinkled. I ordered 3 replacements and after doing the job and flushing the pump found the same problem at the next use. Changed it out and sprayed, flushed and put it away for a few months. Again at the next use I found the same problem. All the "new and improved" replacements were wrinkled. Now the original lasted for years even when I got lazy and didn't flush the pump with water. But to my surprise, the wrinkled parts, when left sitting on the bench, returned to their original shape and could be reused. I am still using the same chemical from an original large quantity purchase. Does the chemical change over time?
On ethanol fuel, years ago I built and flew an experimental aircraft and used premium auto gas until the day I noticed the fuel cap gaskets swelling and wondered what else was going on that I didn't see. After draining the fuel from the tanks, I pulled up to the 100LL avgas pump and was happy to pay the hugh price jump for the peace of mind. Inspection showed the ethanol had not attacked the fuel lines or carburetor parts yet, but I shudder to think about your internal collapse of a fuel line that may escape a visual inspection. Guess that's why I buy the expensive non-ethanol fuel for the small engines, to avoid that Mayday.

 

[StarTech]

I think it depends on what manufactures are using for materials of course they should testing the materials before making a huge run but they don't always. Here I even have plastic fuel to swell so much that it take large pair pliers to get them off. It just that the plastics used are not compatible with gasoline.

Leaving just component of a mix can cause problems. It just like when my former doctor left out the HCTZ out my Losartant blood pressure pills. Everything was find until he change the prescription but he refused to put me back on the med that was working fine. Now I got to hunt for a new doctor that will plus I am on a self imposed crash diet trying to get the BP back down to a manageable BP.

 

[sgkent]

Last week I pulled an old carb off an edger, and replaced it with a new one. Works fantastic. Pulled the old carb apart, and the float seal was all swollen. Left it on the bench for a week to decide whether to toss or rebuild as a spare, and found out the seal had shrunk back to its original size. Never seen anything like that before. Lots of weird things going on these days.

 

[StarTech]

Last week I pulled an old carb off an edger, and replaced it with a new one. Works fantastic. Pulled the old carb apart, and the float seal was all swollen. Left it on the bench for a week to decide whether to toss or rebuild as a spare, and found out the seal had shrunk back to its original size. Never seen anything like that before. Lots of weird things going on these days.

I know Tecumseh fuel bowl o-rings do that. Both oem and after market.

 

[sgkent]

I know Tecumseh fuel bowl o-rings do that. Both oem and after market.

that is what it is. OEM seal about two years old. Came in a Tecumseh rebuild package. Even after two or three rebuilds I could not get the edger to start easily and stop leaking down when it sat for a couple weeks. Replaced everything from the float and needle / seat down to the bowl and special bolt on the bottom. Done thousands of carbs in my life, this one threw me. Even got the special tools to rebuild it properly. Just sold my mantiss tiller. Those Zuma carbs only lasted 2 seasons for me. I could use it in say June, ran perfectly, drain the fuel like I do with all the 2 stroke engines I have to prolong their life, come back to use it again in November and the carb would not work right. Stick a rebuilt one or new one on in 10 minutes and it would fire up and run right for a season, maybe two, then back to the same problem. The gasket that also acts as a valve for a fuel pump would be warped and the flaps not seal properly. Have a similar type issue with a B&S engine pressure washer that uses a thin gasket under the carb as a fuel pump valve also. Even how they sit in packaging sometimes kinks them to where they don't seal right.

 

[Tdj2591]

Thanks for all the helpful responses everyone! I ordered another new carb which my son replaced (since he had the tiller at his home in another town). When he described what was happening when he pressed the primer bulb and how quickly the engine would die, I said it sounded like the fuel lines were crossed. Once he switched the lines he got it running. After adjusting the carb it’s now running great.