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Mantis Carb adjustment

Posted by exmar 6 SE Ohio (My Page) on
Tue, Apr 1, 14 at 15:54

Hi Folks,

Have a 2cycle mantis, it's about 3 years old, and probably has 4 hours on it. The reason is two fold, one I DON"T LIKE MANTIS, and the other is it's so flipping hard to start!!

Anyway, due to being on the "sick list" due to dropping a heavy carving board on a toe and not being able to do the outside stuff I need to, decided this spring I would conquer the beast.

Prepared myself by watching youtube videos on carb adjusting for them, read the book, etc.

Air fiter is clean, checked plug, checked gas filter, etc. New "medium" unleaded with 50:1 oil mixed in.

Prime, choke, pull till it fires, open choke, pull and it starts-NOT! It did start, but only ran about 3-4 seconds and died. Will not idle.

Two hours later, here's the results. If the "H" screw is adjusted fully CW it will idle all day but will not accelerate without "bogging" down. If the "H" screw is adjusted fully CCW accelerates, idles, plenty of power, etc.

What I seem to be looking at is to start and idle this to let it warm up, the "H" screw has to be fully CW, then to operate, it must be reversed to fully CCW. Note: This has the plastic stops on the adjusting screws, so limits are determined by them as to CW and CCW. Carry a small screwdriver with me when I'm going to operate this? :-)

"L" screw has relatively little change on things other than "fine tuning" high speed operation..

I'm open to suggestions at this point. Ready to blame partially blocked fuel circuit due to ethanol, but as soon as it's warm, it works great. Shut it off and if it hasn't cooled down will start right back up. Temperature sensative fuel circuit blockage?

I've got a barn full of two and four cycle engines, not counting the diesels on the farm tractors. Everybody is happy, including a 25 year old homelite chainsaw. This thing just doesn't want to play nice.


Thanks for your time,


Follow-Up Postings:

RE: Mantis Carb adjustment

1. Was the Eng stored with untreated fuel (Stabil/Etc) for a period of time?
2. Are the fuel lines “good, soft, solid and tight”?
3. Have you pulled the carb, disassembled, inspected, verified no varnish or debris with compressed carb cleaner or fine wire??
4. Have you tries running 2 oz of carb cleaner in a fresh tank of fuel?

Please share what you find the final issue to be. Two Cycles can be Monsters IMO compared to four cycles.

RE: Mantis Carb adjustment

  • Posted by ericwi Dane County WI (My Page) on
    Wed, Apr 2, 14 at 21:57

If it starts and runs better when it is warmed up, it could be that the compression is improved when the piston has gotten hot, and therefore makes a better seal in the cylinder. I suppose that you could put a heat lamp on the engine before you try to start it up. Does this engine use reed valves?

RE: Mantis Carb adjustment

  • Posted by exmar 6 SE Ohio (My Page) on
    Wed, Apr 2, 14 at 23:03

All my stuff is fed a regular diet of stabil, also ran dry every fall, also part of spring start up and about August is a good shot of Sea Foam. This thing has been a bear to start from day one!!

After much discussion with a buddy in RI who is small engine mech and who also has the same machine I finally got it running. Specifically I found adjustments which would allow a cold start, idle and accelerate smoothly. Where it's now adjusted is "far and away" from the instruction manual or any online info suggests. However, it works.

Decided I'm too old to put up with the aggravation. I'm putting it on Craigs List and someone else can have fun with it.

I've never really believed in the "lemon" theory but this particular machine has me wondering.

I mentioned that I don't like the Mantis, before the "hordes" of Mantis owners arrive to lynch me, the following is offered. Have only used tillers with rear wheels or rear tines and drive wheels. Small two cylce and larger 4 cycle depending on the size of those machines. The mantis just has the tines spinning-period. If you're in perfect loam and cultivating they steer and track nicely. However, if you hit a small rock, they bounce. INVARIABLY they go into the row of veggies, and not into the "balk" of the row. :-( I'm used to guiding/steering power equiptment, not wrestling with it.

IMHO, the intended audience for the Mantis is the gardener who has small flower beds or raised beds and wants to graduate from a spading fork but doesn't want a large tiller. That audience and "perfect" soil would probably work well. Just my two cents.

Thanks for the responses.


RE: Mantis Carb adjustment

Ev lot of people like mantis I would just sell it see if you can get most of your money back.. I do above ground gardening now and I got electric mantis for this. IMO has more torque than the gas models and the carb never plugs up or malfunction.

I too sold off all my front and real tine tillers. For me it was driven by Gofers the Boxes has wire screen across the bottom so they can't eat the roots of my tomato's and pepper plants plus I don't have to do a lot of tilling in the spring which makes the elect. mantis prefect for me.

RE: Mantis Carb adjustment

  • Posted by exmar 6 SE Ohio (My Page) on
    Sun, Apr 13, 14 at 11:06

Listed on Craig's for $225, first caller came out, I started it, he played with it a little and handed me the cash!! We were both happy.

That's a happy ending, I think I paid $279 on a day after christmas deal that Amazon was having 3+ years ago. That's the best return I've ever had on buying something new and then selling down the road.

Well, my 15+ year old sears "cultivator" with a tech two cycle is still running so until it finally dies. Won't think about what to replace the Mantis with.

I do know that whatever I end up with, it has to have rear wheels for ease of steering, control and just general convenience.

RC, I know a lot of folks that have gone to electric tillers for the small units. If my garden wasn't 1500 ft. from any electricity I would have gone that way. Had an electric chain saw years ago which was cheap and strong, good combination.

Be well,


RE: Mantis Carb adjustment

Done good. I wish I could do that good selling my used stuff.

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