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Son borrowed my Mantis tiller and complained that it will only run less than a minute then die. It has been completely rebuilt with new carb, fuel lines and filter, fuel bulb and spark plug. He said it appears to die once the gas in the bulb has been used up. He checked the kill switch and found no problem, saying it’s definitely a fuel supply issue.

Any ideas?

Model 7225-00-02 10743117
Serial 09209281
Kioritz 2 cycle engine SV-5C/2

Model # will help. This is a 2 cycle cube carb? It's new, but has it been adjusted? May be too lean.

Model 7225-00-02 10743117
Serial 09209281
Kioritz 2 cycle engine SV-5C/2

those carbs are cheaper new than to rebuild. The ethanol in the gas kills them in about a year. I've managed to extend that by draining the tank and running dry each time it is used. Were it me I'd buy a new carb and put on it. Also the ethanol attacks the hoses in the tank so one of them may be fallen off. The symptoms match that the diaphragm is not sealing that works as a fuel pump under the carb.

Sorry that some people just don't read the posters Posting !!!! If the carb,fuel lijnes, and filter are new sounds like it may be just an adjustment issue. It takes very little turning to adjust these small carbs but maybe you should check there first if it uses HI and Low needles check both adjustments. Don't jump off the deep end until you go thru the basics.

OldDiyer said:

Sorry that some people just don't read the posters Posting !!!! If the carb,fuel lijnes, and filter are new sounds like it may be just an adjustment issue. It takes very little turning to adjust these small carbs but maybe you should check there first if it uses HI and Low needles check both adjustments. Don't jump off the deep end until you go thru the basics.

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I read that but also saw the word "rebuilt." The symptoms are those of fuel starvation. If the parts are "new"like this week and not rebuilt then I would suspect a problem with how installed, or a defective new part. If he wants to bring it here I will be glad to look at it. Those Zama carbs don't last very long. I've replaced them, run a mantis once or twice really well, put it aside for six months, dry, added new fuel and they run exactly like his problem A new carb solves it each time because the diaphragms that provide fuel pressure warp. I used to keep a spare one around because the problem is so common.

Please read it again he stated that the unit was rebuilt with new parts. !!!! It has been completely rebuilt with new carb, fuel lines and filter, fuel bulb and spark plug.

OldDiyer said:

Please read it again he stated that the unit was rebuilt with new parts. !!!! It has been completely rebuilt with new carb, fuel lines and filter, fuel bulb and spark plug.

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why the heck are you shouting? Do you have earwax in your ears? It is a fuel problem. I doubt if the mixture screw is going to solve this. Those ZAMA carbs go bad very fast. Making matters worse, there are plenty of people these days that buy one, swap it and then send the old one back as a return. People brag about it all the time here and on other forums.

From the top
1) where did you get the parts from ?
usually the "full rebuild kits" seen on Amazon & evilpay are total trash
Many of the carbs are QC rejects and most of the fuel lines are not suitable for fuel .
2) you say the primer bulb starts out full then slowly empties and the tiller stops.
That suggests a fuel supply problem
Bad pump
Bad tank vent
broken fuel line
collapsed fuel line

Try it with the Fuel Tank Cap loosened. If it still won't run past 30 sec, Blow fuel line back into tank with cap loose from carb. Replace Filter if there is one. New ones can be plugged.

Sounds like the impulse port is clogged or blocked.

Tdj2591 said:

Son borrowed my Mantis tiller and complained that it will only run less than a minute then die. It has been completely rebuilt with new carb, fuel lines and filter, fuel bulb and spark plug. He said it appears to die once the gas in the bulb has been used up. He checked the kill switch and found no problem, saying it’s definitely a fuel supply issue.

Any ideas?

Model 7225-00-02 10743117
Serial 09209281
Kioritz 2 cycle engine SV-5C/2

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Check the fuel cap, needs to breathe and if you can’t suck from the thread side it’s blocked and the engine can’t overcome the suction caused by it not venting.

I had the same problem with my Mantis. The tank vent was not working and the fuel would only flow if the fuel cap was loose. Try looking at the vent fitting.

As far as I know this engine's fuel cap is not vented or at least the IPL of the SV-5C/2 shows the Echo style fuel tank venting system which item 11 is the vent assembly.

StarTech said:

As far as I know this engine's fuel cap is not vented or at least the IPL of the SV-5C/2 shows the Echo style fuel tank venting system which item 11 is the vent assembly.
View attachment 59855

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Yes, item 11 was the source of my problem. Thanks for the clarification.

OP is MIA

sgkent said:

OP is MIA

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As too often happens. Sure is helpful to future followers of a thread to find out what solved the problem and it only takes a minute to extend that courtesy.

What is Courtesy? My doctor office had none so now he is now "Fired" and I am looking for a new doctor that might care.

Star, Yes, sadly, courtesy is a rare commodity in today's world. People of my (our?) generation are appalled at the change for the worse that is happening before our eyes. And don't get me started on doctors who no longer practice medicine, but instead blindly follow the marching orders of the AMA and various trade publications. Sorry for going so far off topic.

I am guilty of dragging us off topic. Doctors have never got it right yet as they just keep practicing at being a doctor instead being a full time doctor.

Now back to those little vent modules. I had a batch of aftermarket ones several years ago to swell so the internal duck bill valve inside couldn't operate. I ended up having to change vendors to get problem resolved. At one time it was strange to me that things happen in batches but no longer. It getting a NOS string trimmer where the fuel lines have complete disintegrated before fuel has ever been in the tank yet there people that would blame that on ethanol fuel. And I had the Tygon LP-1100 fuel lines to have the internal liner to collapse and block fuel flow. I even regular 1/4 rubber type fuel to have an internal collapse. I have seen it at three times lately.

Ah yes entire batches of parts that don't play nice. A few years ago, I bought a trailer sprayer for the sole purpose of spraying my gravel drive with glyphosate and it worked flawlessly. Then one day the pump failed and after taking it apart, I found the diaphragms were swelled to the point where the "rubber" was wrinkled. I ordered 3 replacements and after doing the job and flushing the pump found the same problem at the next use. Changed it out and sprayed, flushed and put it away for a few months. Again at the next use I found the same problem. All the "new and improved" replacements were wrinkled. Now the original lasted for years even when I got lazy and didn't flush the pump with water. But to my surprise, the wrinkled parts, when left sitting on the bench, returned to their original shape and could be reused. I am still using the same chemical from an original large quantity purchase. Does the chemical change over time?
On ethanol fuel, years ago I built and flew an experimental aircraft and used premium auto gas until the day I noticed the fuel cap gaskets swelling and wondered what else was going on that I didn't see. After draining the fuel from the tanks, I pulled up to the 100LL avgas pump and was happy to pay the hugh price jump for the peace of mind. Inspection showed the ethanol had not attacked the fuel lines or carburetor parts yet, but I shudder to think about your internal collapse of a fuel line that may escape a visual inspection. Guess that's why I buy the expensive non-ethanol fuel for the small engines, to avoid that Mayday.

I think it depends on what manufactures are using for materials of course they should testing the materials before making a huge run but they don't always. Here I even have plastic fuel to swell so much that it take large pair pliers to get them off. It just that the plastics used are not compatible with gasoline.

Leaving just component of a mix can cause problems. It just like when my former doctor left out the HCTZ out my Losartant blood pressure pills. Everything was find until he change the prescription but he refused to put me back on the med that was working fine. Now I got to hunt for a new doctor that will plus I am on a self imposed crash diet trying to get the BP back down to a manageable BP.

Last week I pulled an old carb off an edger, and replaced it with a new one. Works fantastic. Pulled the old carb apart, and the float seal was all swollen. Left it on the bench for a week to decide whether to toss or rebuild as a spare, and found out the seal had shrunk back to its original size. Never seen anything like that before. Lots of weird things going on these days.

sgkent said:

Last week I pulled an old carb off an edger, and replaced it with a new one. Works fantastic. Pulled the old carb apart, and the float seal was all swollen. Left it on the bench for a week to decide whether to toss or rebuild as a spare, and found out the seal had shrunk back to its original size. Never seen anything like that before. Lots of weird things going on these days.

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I know Tecumseh fuel bowl o-rings do that. Both oem and after market.

StarTech said:

I know Tecumseh fuel bowl o-rings do that. Both oem and after market.

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that is what it is. OEM seal about two years old. Came in a Tecumseh rebuild package. Even after two or three rebuilds I could not get the edger to start easily and stop leaking down when it sat for a couple weeks. Replaced everything from the float and needle / seat down to the bowl and special bolt on the bottom. Done thousands of carbs in my life, this one threw me. Even got the special tools to rebuild it properly. Just sold my mantiss tiller. Those Zuma carbs only lasted 2 seasons for me. I could use it in say June, ran perfectly, drain the fuel like I do with all the 2 stroke engines I have to prolong their life, come back to use it again in November and the carb would not work right. Stick a rebuilt one or new one on in 10 minutes and it would fire up and run right for a season, maybe two, then back to the same problem. The gasket that also acts as a valve for a fuel pump would be warped and the flaps not seal properly. Have a similar type issue with a B&S engine pressure washer that uses a thin gasket under the carb as a fuel pump valve also. Even how they sit in packaging sometimes kinks them to where they don't seal right.

Thanks for all the helpful responses everyone! I ordered another new carb which my son replaced (since he had the tiller at his home in another town). When he described what was happening when he pressed the primer bulb and how quickly the engine would die, I said it sounded like the fuel lines were crossed. Once he switched the lines he got it running. After adjusting the carb it’s now running great.