Mantis tiller

[Meadowlark]

Carb is probably clogged.

IMO, the Mantis model I had, which lasted less than one growing season, had a fatal design flaw...the carb was located too close to ground level where the dirt is all stirred up.

That process gets fine dirt in the carb, no way around it with their design, and the result can be poor performance and eventually engine failure. "Eventually" was less than one growing season, in my case.

 

[DirtMechanic]

welders tip files are excellent for unclogging carb pipe.

 

[hcccs]

Yes, gas with no ethanol. I think the LOW speed (or idle) mixture screw is important only if you're idling. I have half throttle so the Mantis should run. The carburetor is new so that wouldn't be the issue. I'm disassembling the muffler to see if that'll help.

 

[DirtMechanic]

Yes, gas with no ethanol. I think the LOW speed (or idle) mixture screw is important only if you're idling. I have half throttle so the Mantis should run. The carburetor is new so that wouldn't be the issue. I'm disassembling the muffler to see if that'll help.

You checked the two most important tubes, the impulse and fuel lines? Have you done a leakdown test to see if the case seal is capable of holding a vacuum? The mantis is old you said?

 

[hcccs]

What case are we talking about?

 

[DirtMechanic]

What case are we talking about?

The main body is split into two halves. There is a case seal. It has a size\volume relative to the movement of air by the piston. The action of the piston is powering the fuel pump action... Utilizing what amounts to a one way valve the pressures created in the sealed space are manipulated into becoming the motive force for pulling fuel into the carb. Thats why they have the primer bulbs etc. The case seal is the core of the whole system. everything else will be stuff like punky lines collapsing under vaccuum and sealing off or gaskets, especially those cardboard type, letting in air and destroying the pulling vacuums.The return line to the tank should be equalizing or even pressurizing the fuel tank for an easy draw.

 

[hcccs]

I cleaned the muffler and it was rather clean. Even the screen looked OK. I cleaned it and put it back. After that I got gas into the bulb and I could run the machine. I was happy with that and left it for a couple of days. Today I had mustered some enthusiasm for it and intended to get the idle and running speed correct. I could not pump up any gas into the bulb. I could start it with the choke but it died. So the mystery remains - if there's no gas in the bulb it can't run, right?

 

[DirtMechanic]

So yes basically. That is the inlet side anyway so something is cracked, plugged, collapsing etc probably on that side of things. Here is a detailed description of the ubiquitous walbro 2 cycle carb. Since your carb is new as I recall, the lines to and fro become more suspect, as well as the gas tank cap. And ultimately the case seal. But you said it ran so that probably eliminates the case seal leaking badly enough to prevent impulses from being sent.

Walbro Carburetors - So how does this thing work - HeliFreak

This thread is going to cover the internals of the Walbro carburetor that almost all gas helicopter engines use. Specifically the ones found on the

www.helifreak.com