Mantis 2-cycle tiller: stalls under load

I have a Mantis tiller - only 4 years old. This spring it would only run by operating the choke repeatedly. Then quit altogether. Seemed obvious that it was a carburetor problem. Replaced fuel filter and installed carb kit with no results. Took it apart again and sprayed carb cleaner into all holes to discover there seemed to be a blockage that I traced to the "high" and "low" screws. In trying to remove these I wrecked the white "stop" cap. I searched online to find specs for how to install these again and thought I'd found the answer, but no success. So, I started experimenting and now have it idling perfectly. However, it now stalls as soon as load is applied. Any suggestions? Would it be the settings for these screws? or might I have some other problem?

 

Try backing out the high speed screw a bit. I like to set the high speed first, then the idle, then back to high speed fine tuning, then back to idle fine tuning.

 

Manage to get back to trying to get a fix today.

Tried adjusting the high speed from one edge of the stop to the other with no difference. It can rev up for a couple of seconds, then starts to stall. I can keep it running by throttling down, but as soon as it revs up again, again it tries to stall.

I'm wondering if my focus on it being a carburetor problem is ignoring the possibility of another issue. What kind of a clutch system is on these things? When I rev it up, (I have the tines off) the axle doesn't seem to turn appreciably faster. I have checked the grease in the gear housing, so that's not a problem but I'm wondering about how it engages the gears (clutch?).

 

IF you can get a good idle on it, go to your high screw and turn it in as far as you can without killing it. Then turn it out about 1/16 turn while you trigger the throttle a couple of times quickly. Each time it tries to die out go out another 1/16 and see if you hit a setting on the high speed that lets it accelerate well. When you hit that setting (hopefully it's there), hold the throttle wide open and turn the screw out to get the highest rpms, then back in until it drops the rpms slightly (about 1/16 to 1/18 turn). Leave it at that setting and go back to the low speed screw, turn it out for max rpms, then back in to drop the rpms.

By going back in after max rpms on either screw you'll be making the mixture a little richer. On a two stroke you want the mixture a little richer, rather than lean, which is death on a two stroke. the richer mixture will let the engine carry a load.

If you can't get it to accelerate, check the fuel cap for vent blockage, the exhaust for blockage, the air filter, and the fuel mix for too much oil.

 

Should I take the red plastic off the screw so I can allow it to open/close more than the stops allow?

 

You might have to in order to get it running right. Usually you can open it enough to clear whatever trash is blocking it, then put it back close to where it was.