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  1. #1
    Bronze Member
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    Kubota B7800-HSTF 2005

    Default Mantis tiller - dies when throttle is pulled

    Hey everybody! Long time since I posted here, but I need some help.

    I have a 4 year old Mantis 2 cycle (oil and gas) rototiller. It has worked great until this season. Althought last year I did have some problems getting it running as I left some gas it in over the winter. The small engine repair place donw the road stated it only take a little of the ethanol "improved" gas to really screw up the piston and rings. True?

    Now for this year..... starts with the few presses on the bubble primmer and a few pulls. But when it is running as soon as I lightly press the throttle it dies and stops running. The low adjustment screw seems to work as when I turn it the rpms change. When I turn (either direction) on the high adjustement screw, nothing.

    Everything I have tried will not allow me to give it any gas to get it running full speed.

    Any help / thoughts?

    Regards,
    Paul
    Kubota B7800-HSTF, BL4690B backhoe, LA402 FEL, 60" MMM, Woods GT60 tiller, Woods LA72 rake

  2. #2
    Epic Contributor Bird's Avatar
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    Default Re: Mantis tiller - dies when throttle is pulled

    Paul, my 2-cycle Mantis also turned 4 years old this past month. I bought it direct from the company as a "refurbished" model, although it looked new. Do you have the Owner's Manual for yours? Page 7, item #9 on starting says in part when it starts "Let the engine warm up two to three minutes before using." And they mean that literally! As with yours, any attempt to use the throttle until it has been sitting there running for at least two minutes will result in it instantly dying. If you're standing there waiting to get to work, two minutes can seem like a long time. But then it runs great after it's warmed up.

    The only time I've needed to adjust the carburetor was when it wouldn't start a couple of years ago. I followed the directions on Page 12 of the manual and all was well again. And yep, I've noticed the same thing with the high and low speed adjustment screws. To start with, it says to turn the RED high speed screw counter-clockwise all the way to stop, then the WHITE low speed half way to get it running and warmed up for the final adjustment. Mine has never needed anything beyond that. But it doesn't seem that turning that RED screw changes anything. Oh well, it works fine anyway.

    Incidentally, the first winter, I ran all the gas out of it, then in the Spring, no gas would go through the fuel filter. It seemed to have hardened, but when I took it out and gave it one quick reverse direction blast with the air hose, all was well. So in spite of the horror stories about ethanol, I leave gas in my Mantis year round. I do try to remember to start it and let it run 10 to 15 minutes about once a month.

    I don't know whether this will help you or not, but I guess the only advice I can give you is to have more patience when it starts. At least your "problem" sounds normal to me. It did annoy me for awhile until I learned to give it time. And if you shut it off, it doesn't take long for it to cool and you have to follow that cold starting procedure again on mine.
    Bird

  3. #3
    Epic Contributor Soundguy's Avatar
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    Default Re: Mantis tiller - dies when throttle is pulled

    sounds about right... let it warm then try it.

    I have a couple weedwackers that ar elike this..

    either flood out or starve till warmed up..

    soundguy

  4. #4
    Gold Member
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    JD

    Default Re: Mantis tiller - dies when throttle is pulled

    If, after letting it warm up, it still won't run at high speed or it seems to lack power, check for a clogged spark arrester screen in the muffler. My tiller is a little older than yours, so I can't swear you have a spark arrester screen, but you probably do.

    The restriction in the exhaust from a clogged screen can cause the behavior you're describing as well as a general lack of power. The screen clogs up with oily carbon which is difficult to remove with a solvent. You're better off cleaning it by scratching it with something sharp. I finally took the screen out of mine. I don't use the tiller where there is a fire hazard.

    If none of our other advice helps, you probably need to rebuild (or at least clean) the carburetor. If you can get it apart without tearing any of the gaskets or diaphragms, you may get by with just cleaning it with some carburetor cleaner (my favorite is Berryman Product's Chemtool Carburetor Cleaner).

    A side note in case someone doesn't know, the Mantis tiller is made by Echo sort of like the way a Chevy Prizm is actually a Toyota Corolla.

  5. #5
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    Default Re: Mantis tiller - dies when throttle is pulled

    I'm pretty sure your carb is gummed up with old gas. The engine on Mantis tiller is sensitive to gas being left in it. The engine is made by Echo by the way.

    I suggest disassembling the carb and cleaning it well with carb cleaner. You may buy a rebuild kit for it and install the new parts. Not very expensive. The diaphragm in the carb can harden and not work correctly.

    Because your machine is only 4 years old I bet it's carb just needs a good cleaning. Mine did! These little buggers are irritating as heck when not running right. But when they run man can they dig! While you are in there make sure to install a new air filter.

    Good luck!

  6. #6
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    Default Re: Mantis tiller - dies when throttle is pulled

    At one time I thought I had cornered the Mantis tiller market. Bought every one at auction I could find. They are great tools when running. This said I am sure many people have died trying to start them after several years of use. Even the manufacture offers a Honda engine for about a hundred dollars more. The best - most reliable one I gave to my mother. It was electric.

  7. #7
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    Default Re: Mantis tiller - dies when throttle is pulled

    Thanks for the help and input guys! I will try letting it run for longer at idle than I usually do and remove the air filter and spark arrestor to see what happens. I'll post after I get to mess with it on Sunday.
    Thanks again!
    Paul
    Kubota B7800-HSTF, BL4690B backhoe, LA402 FEL, 60" MMM, Woods GT60 tiller, Woods LA72 rake

  8. #8
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    Default Re: Mantis tiller - dies when throttle is pulled

    No difference in the way it runs after letting it warm up for 2o minutes. I thought it was air starved also so I removed the air filter and cover..... same thing.

    I guess I am going to buy a new carb. If I am understanding it correctly there is no way to pull apart the carb, as it is one single block.

    Paul
    Kubota B7800-HSTF, BL4690B backhoe, LA402 FEL, 60" MMM, Woods GT60 tiller, Woods LA72 rake

  9. #9
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    Default Re: Mantis tiller - dies when throttle is pulled

    try to get some carb cleaner in there (can you get the fuel line off the carb and spray some in there). try and start it to pull the cleaner in, then let it sit for overnight and give it a try. I have used Lucas fuel injector cleaner in the gas for generator with good results, Seafoam has also worked. It is just gummed up..
    2007 Kubota L3130, LA723 FEL
    Land Pride FDR1672 rear finish mower, Frontier RB1172, Koyker KB60 BH
    Pallet forks, Golf cart canopy bolted to ROPS, 9" & 12" PHD

  10. #10
    Epic Contributor Bird's Avatar
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    Default Re: Mantis tiller - dies when throttle is pulled

    Quote Originally Posted by pashworth View Post
    No difference in the way it runs after letting it warm up for 2o minutes. I thought it was air starved also so I removed the air filter and cover..... same thing.

    I guess I am going to buy a new carb. If I am understanding it correctly there is no way to pull apart the carb, as it is one single block.

    Paul
    Darn it, I thought sure we'd solved that one. But I've no experience with replacing, or working on, the carb beyond the 2 adjustment screws.
    Bird

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