How I Adjusted the Carb on My Mantis Tiller So It Would Run and Run Smoothly

Last year I paid a small engine mechanic $65 to rebuild the carburetor on my then 7 year old Mantis Tiller/Cultivator when I couldn’t get it to start. This Spring I couldn’t get the tiller to start for some time. Then it would run rough for 10 minutes or so and cut out again. Frustrating!! I read up on it, and made some easy adjustments and in about 5 minutes had the tiller working perfectly! See what I did. I hope if you are having problems with your tiller, you can get it fixed. Maybe this will work for you.



46 thoughts on “How I Adjusted the Carb on My Mantis Tiller So It Would Run and Run Smoothly

  1. Unfortunately, Jason, the number of turns on the screws is not an exact science. I do understand your frustration though.
    Turn the one marked H counterclockwise and the one marked L clockwise–several turns each. It will be necessary to play around with it.
    I turned the screws a lot so that I was sure my playing around with it would been backing off what I just did.
    Good luck!

  2. I was about to get rid of my mantis with its pesky 2-cycle engine….wouldn't start and/or would cut off if I even breathed on the handle, but your suggestions helped tweak it so now it runs just fine. Thanks for the video! ūüôā

  3. Lisa and others, just buy non-ethanol fuel if there is a station nearby. I have a few by me that have it and it's all I run (also in all my fam's pre-2002 vehicles as well). Google " pure gas" to find the locator website. Reply if that works for you. Cheers!

  4. Thanks for the tip! I just Google "pure gas", but there are no pure gas stations close by!! Does sound like a great idea!

  5. Zama factory instructions: (google mantis zama carburetor adjustment)

    Note that it suggests that you turn both the "L" and "H" screws in all the way and then back them each out two turns. Consider driving to your nearest general aviation airport and filling up a 5-gallon can of either 90 MOGAS or 100LL AVGAS which are extreme premium fuels that have zero detergents, ethanol, or other BS mixed with them. They are the purest form. Caution with storage as avfuel is more volatile.

  6. Rebuilding carb is easy. Just take your time and lay out parts in order you remove. Clean the main casting, Replace the gaskets, replace Bulb (mine dies & cracked. Replace fuel filter. I got kit on eBay.
    Also you can buy pre-mixed gas with no ethanol at Lowes (probably any hardware or big box that sells 2-cycle equipment) Not cheap but if you can't get 100% gas locally this is an option. Also if you plan to mix your own be sure to add Stay-Bul if you plan keeping gas over 30 days.

  7. what you gotta do is turn them both out about 1/12 turns the low speed is for the fuel to air mixture at idle and the high speed is for when you have it throttled up. I have a good ear to tell when it is running at the right mixture but what i just recommend is to just play around with it till it runs like it used to. I obviously can tell that you have gotten it but if not a mower shop will usually not even take it in a mechanic will come out and do it for you and charge little money for it.

  8. Lisa I watched your video went play with it got nowhere went back and work . Mine is oldest mantis but now kicking dirt again,thanks so much, mantis not running ruins the day. Ans

  9. Truck Mech58 has it right but I would add this important difference:
    Once engine is warm adjust "L" screw for best idle. The haflway reference means to open screw counterclockwise till idle drops then go clockwise till idle drops count the turns between these settings and split the difference.¬† For the "H" screw you need a helper to run the tiller in the dirt full speed under load while doing the same adjustment procedure.¬† You can do this out of the dirt but it's hard on the engine and not as accurate.¬† When setting the "H" screw it is VERY IMPORTANT to err on the rich side……..this means don't set so the engine is screaming cleanly (too lean).¬† You want to go a little more counter clockwise from screaming cleanly to where the sound blubbers slightly (slightly rich).¬† This setting protects the engine from expensive heat damage.
    It's good to write down your final settings for future reference (exact number of turns).
    These settings can change slightly from summer to winter and with different fuel and oil mixes.  It helps to be consistent with your fuel and oil mix and drain or stabilize the fuel when your machine sits for extended time.

  10. Wow, way too wordy, get to the point already. Also $65.oo rebuild the carb is a rippoff. You can buy a new one for $40.00 and install it yourself, totally easy

  11. I have a new mantis tiller and have only been able to use it for thirty minutes. It cranked up and cut off have not been able to use it since, I have the 4 cycle and I use the gas and oil that is not mixed together. I have no problems getting push mowers to run. I am going to have to return mine it I can't get it to run. Very disappointed I have one twenty years ago and it worked great.


  12. look uo Chipjumper … down about 10 comments lower… it WORKED !!!!!
    i screwed both all the way in then backed them out like he said …

  13. I have had to adjust my H/L needle screws every year.My tiller is about 5 years old and has the plastic limiters on the screws which allows you to turn the screws only so far.The third year I had to remove the plastic limiter caps so I could get a little more out of the screws.I popped off the caps and then put the caps back on so more counter clockwise adjustment was possible.This year same thing,wouldn't stay running.I adjusted the H screw to full counter clockwise position that the limiter would allow.Still wouldn't stay running.I was going to adjust the limiter caps again,but decided to do a google search for gum/varnish remover.I found one that sounded pretty good.Star Tron Enzyme Fuel Treatment.I went to Home Depot this morning and got a bottle.It recommends 1 fl oz per 6 gallons.I got home,put about a quarter oz in the mantis tank and shook the whole tiller.Choked it and got it started for a second or 2.Started it again.I had to get some of the treated fuel to the carb.It stalled.I started it again and it started screaming the way a 2 stroke should.I adjusted the idle screw half a turn to keep it idling.I'm headed out to do some tilling in a bit.Should run even better after a while.I should also tell you that I put in last season 2 stroke mix.I know,always use fresh fuel,I just hate wasting gas.The previous years,fresh fuel had been used and still had the starting/running problem before adjusting the screws.That Star Tron stuff claims to refresh old fuel.We'll see.I have the bigger 4 stroke mantis xp also.That one started fine yesterday.That thing is a beast!

  14. I had my mantis carb. rebuilt at a place in Sioux City.. got it home after shelling out 72 bux…It would not start… I pulled on the rope 18 maybe 25 times before it would offer to start and then another 10-15 pulls to get it started.. So i watched your video and adjusted the high & low needles now it starts and runs like it should have .Thank You so much for this video !!!

  15. Great video! I'm rebuilding a Mantis 7222m tiller for a friend. He's giving me a Honda 4-stroke tiller in exchange for my labor. However, the Honda tiller does not run. After no success in getting the Honda to start, I discovered the cam belt was broke, so no wonder he offered the Honda to fix his Mantis. I purchased the new belt and twp seals, so I have my work cut out, as this is only a hobby of mine. Many thanks for some of your details, as they should help.

  16. Just a note, do not pay to have the carb rebuilt. You can buy a brand new carburetor, with the gaskets, a new set of fuel lines and gas filter, an air filter, and a spark plug all together in a kit. They sell on Ebay or Amazon for $30-45.

  17. There are a number of places to buy non-ethanol gas. I've purchased it in cans at Lowe's, Home Depot and Sears. You can buy pure gas, or an oil and gas mix of 40-to-1 or 50-to-1, depending on your machine. My Mantis takes 50-to-1. It is expensive, but cheaper and less aggravating over time than the break-downs and repair expenses caused by the corn ethanol that is added to gasoline. As for carburetors, a rebuild is nothing more than cleaning it and swapping out a few disposable parts. There are many videos on YouTube showing how it's done. Although having rebuilt the tiny 2-stroke carb on my Mantis, I wouldn't bother again. By the time you buy the rebuild kit and a can of cleaner, you may as well buy a new carb direct from China, incredibly cheap, free shipping and no tax. Just make sure you look at your carb to get the correct brand and model,which is stamped on the carb, probably it's a Zuma brand. Also, use PayPal to order it. Don't send your credit card number to a foreign country!

  18. Thank you so much for this! I had changed my carburetor; the mantis turned on quickly, but the tines wouldn't move properly. This did the trick!!!

  19. Mantis tiller with plastic choke started.after about twenty pulls, ran ten seconds then quit. Now will not start at all.

  20. Thank you very much, your video was excellent, close up shots, captions and no fluff. My old mantis is running and digging like a champ. I can't thank you enough!

  21. you were lucky to get it started. what it was referring to turn the L screw half-way was when the red and white caps are on. with those off you are on your own.

  22. Yeah. I got one of these "easy start" mantis tillers and it wont start and yes the tines wont start when it does run for less than 2 minutes then dies. Brand new last year–it started 3 times and I was never able to finish anything. This company is horrible. This product is so much work to own. Who the hell wants to screw around with a tiller like this when there is work to be done? Getting rid of this pos tomorrow and purchasing a real tiller.

  23. Rebuild the carb yourself, rebuild kits are cheap and it's an easy job. Don't like ethanol gas? That's understandable, it gums stuff up bad if you don't run the carb dry at the end of every season you're back to non-starting and rough running. Use engineered, canned 50:1 fuel instead of mixing your own with unleaded gas that will contain 10% ethanol in most places.

  24. Use premium non-oxygenated gas only. Any gas that has ethanol in it will gum up the carb over time. Learned that lesson the hard way. Since I've switched gas I haven't had a problem with my small engines.

  25. one thing to check that slips by a lot of people on any 2¬†cycle engine¬†,, "check the muffler spark arrester screen" if it has one and make sure its not plugged with carbon clean it if it is ,,¬†after sitting in storage¬†carbon will harden¬†restricting the exhaust flow and it will never run right if it is,,¬† The diaphragm carburetor on most mantis tillers is¬†made by Zama and they¬†have an adjustment procedure¬†listed on there website simply search "¬†How to adjust typical diaphragm carburetors – Zama — I will add always perform adjustments with the tines removed for safety ,, and adjust¬†the throttle¬†idle speed setting screw¬†(not the low speed mixture¬†needle adjustment)¬†so the engine idles without the tine shaft revolving¬†, if the engine bogs when you go to give it throttle¬† your low speed mixture¬†needs to¬†made slightly richer ,,¬†use care¬†when adjusting the high speed mixture to adjust¬†for highest engine¬†speed¬†"then turn the high speed screw out counter clockwise slightly¬†until the engine just barely starts to 4 stroke the change in sound will be¬† noticeable" as¬†an adjustment that's too lean can cause a lack of¬†proper 2 cycle¬†engine lubrication and damage the engine,, when the engine is working¬†under load that is the correct adjustment.

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