Outdoor Power Equipment and Small Engines - 2 Cycle Mantis Tiller - No Start - Flooding

Mantis Tiller Model 7222-02-02
Kioritz 21.2 cc SV-4/B Type 1-E
Zama Carburetor

I need some help from the 2 cycle engine experts. My Mantis tiller is 6 years old. I use it 2 - 3 times per year. I run the carb dry after each use. Each winter, I clean the air filter, spark plug, and add a teaspoon of oil to the cylinder. Spark plug was replaced in 2006.

This spring, the tiller would not rev to full throttle. I removed and inspected the muffler and screen; they were not clogged. I replaced the in-tank fuel filter and cleaned the fuel line and return line with compressed air. Once these items were completed, the tiller would run at full throttle, but it was not turning the RPMs that it normally turned.

The tiller was started today (first time since spring) and it would not run at mid - full throttle. It idled fine, but would not rev. I adjusted the HS screw (approximately 1/2 turn ... limited by the plastic cap) with no change. I adjusted the LS screw (again, limited by plastic cap); no change. I returned both screws to original position.

I removed the air filter and fuel line. I sprayed automotive carb cleaner into the carb throat. I also sprayed carb cleaner into the fuel inlet (using a spare piece of fuel hose). I let it sit for 30 minutes and started the engine. It ran perfectly (even at WOT). In fact, it ran better than it has in years.

I let it cool down, sprayed it off with the water hose (like I always do) and tried to start it. It sputtered on the 4th or 5th pull, but would not start. I have not been able to start it since. It floods very badly (approximately 4 -5 pulls of the starter cord will cause gas to start dripping from the exhaust).

I'm assuming that I will need to rebuild the carburetor. Is this correct or is the carb just in need of major adjustment (via the HS/LS needles)? Why did it run perfectly for 15 - 20 minutes? Did the aerosol carb cleaner dissolve the metering diaphragm?

In para. 4 when you said it ran perfectly, even at WOT, did you have the air filter installed ??
Why are you spraying it off with a water hose ?? I was always afraid of doing this, didn't want water to get in muffler, soak the air filter, and even get in the atmospheric vent of metering cover, plus possibility of getting coil wet.
Soaked air filter might flood engine as well as metering pin not shutting fuel off as it should.
If it doesn't run well with clean, dry air filter, I'd opt to rebuild carb.
You can download the Zama service manual for your carb from the http://www.zamacarb.com/ site. They also have a cross reference file that tells kit nums for your carb.
hope this helps,
thanks,

If you haven't had to replace anything in 6 years, even if used very little, the fuel lines are breaking down and so are the diaphgram and other non metal parts in the carb. I would suggest getting a diaphgram/gasket kit and new fuel lines soak the carb in bath type carb cleaner then blow all holes,cracks and crevases with brake parts cleaner(it doesn't leave residue) reassemble and you will be good for another 6 years. After 6 years it is due for a treat. Have a good one. Geo

GlenM,

Yes, when it ran perfectly, it was with the air filter and cover installed. I tilled with it for approximately 15 - 20 minutes; no problems.

I don't think the water hose is the problem; I always wash the mud, dirt off with the hose. Just to make sure there is no damage to the coil, I'll check for spark, but I'm leaning towards a problem with the carb. It is allowing way too much gas to enter the cylinder (and get blown out the exhaust port). I've owned it for several years and never saw it flood this bad; the muffler will be dripping wet after 4 - 5 pulls of the starter cord.

Excuse my ignorance, but where is the "atmospheric vent of the metering cover"?

I'm a decent home mechanic, but I've never been inside a small carburetor. I'll do some research on the Zama web site and see what I can find.

Thanks

On a Zama carb, the vent is usually just a tiny hole in the metal cover. I doubt water entering it would interfere with engine operation. I think you dislodged some buildup inside the carb when you sprayed the cleaner into the inlet. This probaby got stuck between the inlet needle and its' seat. This would casue the flooding you have. I reccomend disassembling the carb and cleaning it, and replacing the diaphragms if needed.

Another problem common with the Zama s, is the welch
plug comes loose inside the carb, causing it to flood as well.
It would be that, or like cheese said, the needle has a
piece of crud keeping it open.
When reinstalling the welch plugs they are concave shaped
so when in place, the top is lightly "punched" in so the
seating area spreads out and sealing. A light coat of fingernail polish, allowed to dry completely to finish. Zama
plugs can be in some bizarre shapes, not like the normal round ones.
Also, any parts for the machine can be found at an echo dealer, as the engine is an echo. Zama kits can be bought
at any mower/saw shop.

Fish

Fish, Cheese, and Geo,

Thanks for the information. Last night, I spent about an hour looking over the Zama Service Tips and Technical Guide. I have a better understanding about diaphragm carbs now. I think you guys are correct; spraying the carb cleaner loosened some gum and deposited it under the inlet needle. Now the needle can't seat and it sucks massive amounts of gas into the intake port.

I was concerned that my aerosol carb cleaner solution had messed it up (dissolved the diaphragms or seals).

I'm going to get a carb rebuild kit and dissassemble the carb. If I goof it up, I can always just get a new or rebuilt carb (I won't need the tiller till spring). Does anyone have an illustrated "how to" for diaphragm carb dissassembly?

Also, I'm going to take a look at the welch plug. Hopefully it will be in place and sealing properly.

Thanks,
Xterra01

The Technical Guide beginning page 7 shows disassembly.
thanks,

It's been over a month, but I finally had time to complete this project.

I purchased a carburetor rebuild kit (Zama RB-71) and rebuilt the carb. I disassembled the carb, cleaned all passageways with spray carb cleaner, and reassembled with new metering lever, pin, spring, inlet needle, gaskets and diaphragms. I also replaced the purge line and fuel line. I did not remove the high speed needle, low speed needle, strainer or welch plug.

The tiller runs great. Thanks for all the help and advice. This was my first carb rebuild and the advice on this page make it easier.

I highly recommend the Zama technical guide; it explains (in detail) the operation and service procedures for their carbs. Of particular importance for me: 1) the procedure for setting metering lever height, and 2) position of gaskets and diaphragms. I don't think I could have successfully completed this project without the technical guide.

Thanks,
Xterra01

Good news! Glad you got it fixed, and thanks for the update!