2-cycle engine troubleshooting

zootjs(zone 5 MA)April 12, 2007

The 2-cycle engine of my Mantis rototiller won't start.

Sometimes, it fires and then runs roughly for a few seconds, but then when I push in the choke, it stops. I've tried pushing it in just a little, or very slowly, but it always quits when I push the choke. I've blown through the tubes and nothing is stopped up. The gas filter seems fine. There are no kinks in the fuel line. The gas cap looks okay.

I've replaced the spark plug, air filter, and gas (confirmed that the mixture was correct). I've tried adjusting the two carberator screws per the manual.

I'm leaning towards taking apart the carberator, though this machine has received very little use so I'd be surprised if that was the issue.


My best guess is that I'm not adjusting the fuel mixture properly.

Any trouble-shooting advice would be greatly appreciated.


Thank you for reporting this comment. Undo

We probably need a little more information, Jonathan. Did the tiller run well last year and now won't run after a winter in storage? If so, you're wasting your time adjusting the carburetor, because if it was right before it was still right when you tried to start it this spring.

You're probably on the right track to disassemble and clean the carburetor, but before you go to all that work you might try the lazy man's trick -- remove the spark plug and pour a few tablespoons of fuel directly into the combustion chamber. Then replace the plug and give it a try. You might have to do that more than once.

It's crazy, but for whatever reason it will often get an improperly stored engine running again.

    Bookmark   April 13, 2007 at 12:00AM
Thank you for reporting this comment. Undo

It's likely a matter of getting fresh fuel thru the carb if all worked well when you put it away. You can try keeping it running long enough to do so or cleaning the carb (best having a kit or to replace the carb) I assume your mix was made up with fresh fuel and not from something sitting around?

    Bookmark   April 13, 2007 at 12:02AM
Thank you for reporting this comment. Undo
zootjs(zone 5 MA)

I bought this machine for $50 on Craigslist from someone who got it from his sister. He never got it to start and gave up, but I don't think he tried that hard.

I suspect it hasn't started in at least two years, maybe three or even four. And it never saw heavy use.

I'll try the gas in the carb trick....


    Bookmark   April 13, 2007 at 3:14PM
Thank you for reporting this comment. Undo

I wouldn't use TABLESPOONS! Try about a teaspoon, it's a small engine.

    Bookmark   April 13, 2007 at 3:24PM
Thank you for reporting this comment. Undo
zootjs(zone 5 MA)

Too late, I tried the tablespoons.

It ran for a few seconds, a little better than before, but then quit again. I did this four times, but no improvement.

Gonna try to rebuild the carb this weekend. Let me know if you have any other ideas.


    Bookmark   April 14, 2007 at 7:44AM
Thank you for reporting this comment. Undo

Yeah, good point, Bill. I wasn't thinking about how tiny those engines are. Sounds like a thorough carb cleaning is a logical next step. Hope there's nothing major wrong, like leaking crank seals or poor compression. You might want to check the carb/manifold/engine connections, because anything loose there will cause an air leak that could give similar symptoms.

    Bookmark   April 14, 2007 at 9:23PM
Thank you for reporting this comment. Undo
zootjs(zone 5 MA)

I took apart and cleaned the carburator, but that wasn't the issue. It still won't run. The idle seems very uneven. It never runs for more than maybe five seconds. Other ideas?

Now that I'm more intimately acquainted with the guts of this machine, I have an even stronger belief that it has very, very few hours on it. It looks almost like new, inside.


    Bookmark   April 17, 2007 at 6:28PM
Thank you for reporting this comment. Undo

Sorry Jonathan, it looks like you're in over my head. As a fellow janitor I once worked with used to say, "I taught you everything I know and you still don't know nothin."

Time to get some professional help. Cleanup in aisle 7! Butch, Walt, Fish, Canguy? Anybody out there?

    Bookmark   April 18, 2007 at 10:34PM
Thank you for reporting this comment. Undo

Try cleaning muffler screen , look for air leak, or
replace filter in tank. JIM

    Bookmark   April 19, 2007 at 10:31AM
Thank you for reporting this comment. Undo

DEFINITELY try cleaning the muffler; I'd certainly do that before I tore into the carb. It's held on by two bolts. Take up out, pull the muffler, and clean all the build-up from the muffler and the engine. That's frequently the problem with 2-cycle engines.

    Bookmark   April 19, 2007 at 11:12PM
Thank you for reporting this comment. Undo

it sounds like clogged jets in the carb. It needs to be taken apart & cleaned. The fact that it runs on choke indicates it isn't getting enough fuel. It's a common problem with engines that sit to long with gas in them. The gas evaporates & turns to varnish/gum.

    Bookmark   April 21, 2007 at 9:13PM
Thank you for reporting this comment. Undo
zootjs(zone 5 MA)

Well, I gave up and took it to the shop.

They said that the paper gasket at the carb was bad. Now, it works fine.

Thanks for your help!


    Bookmark   May 1, 2007 at 8:38AM
Thank you for reporting this comment. Undo

I have similar problem on my poulan 3-yr old chainsaw. I did discover a split in the primer bulb, replaced that ensured I have fresh fuel, but still cannot get engine to run more than 3 or 4 seconds. I removed air cleaner and squirted carb cleaner doen carb throat. Engine started in one pull, but died after about 5 seconds..I then noticed a broken fuel line on one port on the carb, but cannot see where other end should go. The fuel circuit seems intact from gas tank to primer bulb and from primer bulb to a port on the carb which is opposite the above-mentioned port with the broken fuel line. I see a small hole in the fuel tank molding which might be for the broken fuel line. Could it be that circuit provides fuel pressure or vacuum to keep the fuel flowing to the carb? Seems like there is no fuel reaching the carb after initial bulb prime burns out.....Am I possibly on the right track? Thanks.

    Bookmark   July 26, 2008 at 4:22PM
Thank you for reporting this comment. Undo

I have a pocket rocket mini bike,the neighbourhood kids threw it in the garbage. I said let me see if I can fix it for them. The carb was plugged the needle valve wouldn't open, the jetS were plugged up solid. I got all that fixed but the kidS must have removed the vacum lines and I don't know where they go? The carb is made hy HUA WANG. Anybody know ? Thanks

    Bookmark   December 13, 2010 at 7:17PM
Thank you for reporting this comment. Undo

Hi, a few days ago I started my two cycle line trimmer. I never had any problems with it. It did not have a chance to warm up and it turned off. Now it won't start. Fuel is going through and there is a spark. I even replaced the spark plug. It still won't start. I am a stickler with starting instructions and have never had any problems. The new spark plug is gapped correctly. Any ideas why it won't start?

    Bookmark   January 5, 2011 at 9:27PM
Thank you for reporting this comment. Undo

Val: 1st ensure fresh fuel and inspect the fuel filter for restriction . Once these are ruled out buy some concentrated fuel cleaner and put 2 ounces within the fresh fuel . Let sit for approx 20 minutes and then spray some carb cleaner within the carb and retry the starting procedure. Once you get it started keep it running until the cleaner reduces the ethanol gumming restriction. On stubborn cases you may have to remove the High and low jets and insert tag wire and use combination of carb cleaner and compressed air to remove the debris . Be patient it sometimes takes a few hours of THC . :)

    Bookmark   January 6, 2011 at 5:36AM
Thank you for reporting this comment. Undo

I have a 2 cycle Weedeater Hedge Trimmer that starts fairly easily but shuts down after it gets hot. I can restart and run a few more minutes but it shuts off again. Any idea what is causing this. Driving me nuts!

    Bookmark   March 3, 2011 at 1:36PM
Thank you for reporting this comment. Undo

Sounds like your coil is breaking down Bro !

    Bookmark   March 4, 2011 at 8:40PM
Thank you for reporting this comment. Undo

I have a back pack blower that runs good. It Like power and will shut down after 30min of use. Change plug and recheck gas mix. Five years old start very easy. I need help.

    Bookmark   March 12, 2011 at 5:02PM
Thank you for reporting this comment. Undo

Normally when a 2cycle quits after it gets hot it is a problem with the coil not getting proper spark to the plug, at least in my experience.

I've also learned to fill all my equipment with gas before storing for any length of time. If not moisture can get in through the breather hole and contaminate your gas when it condensates.

    Bookmark   March 14, 2011 at 1:26PM
Thank you for reporting this comment. Undo

I have an older Toro 2 cycle that gets sent to a repair shop every two years; sometimes for not starting all together; sometmes for starting, performing for a while, but then cutting out and refusing to start again. This year it has started, and even started up again after moving from the back to the front lawn. Recently I was cutting the grass, everything was going fine, when a friend arrived. I shut off the mower to spend a few minutes with him, and when I went back to resume the job the mower refused to start. I waited a few hours; same thing--no start-up. Any ideas as to what makes this machine's performance so erratic..?? I don't want a new mower: the lawns are small, and this thing has all the power and the three forward drives that I wantor need. Thanks for reading thus far--all about my Toro travails.

    Bookmark   May 24, 2011 at 10:53AM
Thank you for reporting this comment. Undo

You might have a little water in the gas tank.
Try draining a little gas from your float bowl by removing your float bowl nut. Be ready for some gas to spill out.

    Bookmark   May 28, 2011 at 5:36AM
Thank you for reporting this comment. Undo

have a question what would cause gas to leak from the carb and drain my gas tank i bought it off of a friend for 60.00 and it has ran fine till today. i drove it for about a mile and it choked out and was leaking gas through the carb. i let it sit for a while and it started back up just to choke out again. what do i do?????

    Bookmark   July 4, 2011 at 6:08PM
Thank you for reporting this comment. Undo

The inlet needle valve is sticking open! Remove the bottom of the carb and check under the diaphram or float to see if the needle is free.

    Bookmark   July 4, 2011 at 6:15PM
Thank you for reporting this comment. Undo

I have a brand new hitachi 2 cycle grass trimmer. has been run only 30 minutes. i have the same problem a person above with only running a few minutes and then cutting off. emptied out the old fue; mix and bought and added fresh, same problem. is a coil the lukely culprit, even if it has barely been out of the box?

    Bookmark   July 12, 2011 at 4:45PM
Thank you for reporting this comment. Undo
earthworm(6 Pennsylvania)

Check the plug after she quits on you. Do not try any re-start..
If wet, then no spark......maybe far, far too much fuel...

    Bookmark   July 14, 2011 at 10:54PM
Thank you for reporting this comment. Undo
earthworm(6 Pennsylvania)

I'm an old two stroker from way back in the 60s.
Now , with a jogged memory (via U Tube), I remember that there should a some bluish smoke at start up.
No smoke, then check the gas/oil mix, it may be too "lean".
I ran my 7229 LB at 50 to 1 when 32 to 1 was much closer to ideal.
Also, this baby is old...pushing 30....the fuel primer is probably weak...
And I can see why LB has such a following.

    Bookmark   July 15, 2011 at 9:34AM
Thank you for reporting this comment. Undo

I have a Ryobi leave blower. It just stopped and I could not re-start. Took it to repair shop and they replaced the carburetor. Still want start unless starter fluid or gas is sprayed in the air intake. Then it runs fine but if I stop it, I have to spray more starter fluid to get it started. Repair shop had no idea what the cause was. Any suggestions? Gas cap, fuel line ?

    Bookmark   October 9, 2011 at 11:39AM
Thank you for reporting this comment. Undo

I have found that many 2 cycle motors have their compression ring collapsed into the piston ring groove and held there by carbon deposits when they set for an extended time. That's why they will run with the choke on, which adds extra fuel that fills the void and builds compression then when you take the choke off you loose the compression and it stalls. Try pulling the spark plug and spray carb cleaner (sea foam my choice ) into head and let it set for a day or two then dump it out and replace plug and give it a try. On the really bad one's I've
had to tear it down and loosen the ring manually.

    Bookmark   January 9, 2012 at 2:21PM
Thank you for reporting this comment. Undo


1. Very Little Us But How Old Is the Tiller's Last Major Maintenance (including a complete carb disassembly/inspection,/soaking/porting with wire/compressed air/cleaning)?

2. Do you use StaBil etc while using and storing?

3. Have you adjusted the carb successfully before?

Personally, when I forget or cut short my new needed maintenance due to gasohol is when I get caught. My engines need more care now vs in the past.

I'll challenge a chainsaw tomorrow that sounds similar. I will trace the fuel line good and add a missing filter due to seeing consistent air in the line. Checking the Carb's diaphragm next will be my order if my stalling continues. I feel our problems will be different since my air is before it gets to the carb. The similarity is choking will allow it to run longer before stopping or using. Good Luck! loger

PS. I hope this was not Jumping Your Post??

    Bookmark   January 9, 2012 at 8:08PM
Thank you for reporting this comment. Undo

Loger: Bro Zootjs problem was rectified over 5 yrs ago with a gasket replacement Roflmbo :)

    Bookmark   January 10, 2012 at 3:24PM
Thank you for reporting this comment. Undo

Thanks Ewalk! I need to pay attention to dates and bottom post. I saw the fix but proceeded with the possible comparison.

After searching Mantis rototiller (which I'm not familiar with) it could relate to my Poulan chainsaw inspection troubleshooting job today. My lack of fuel was one of two problems or both. I started with the Carb and exhaust port since I h/n inspected them (the exhaust and spark arrest were clean).

1. The carb show restricting derbies at the screen under the crab's side held with one screw (if we have the same Walbro Carb) that I cleaned with compressed air due to loose particles vs varnish.

2. I removes the high and low mixture screws (counting my existing turns to seat them since it ran good at these
settings) and blew them out, feeling the air's exit. The fuel was dirty and dark and I did add a filter and fresh
fuel. What are the two elements snapped together on a Walbro filter?

3. With no good results, I added 1/4th turn to each screw and I could see the fuel started to flow (vs my prime)and
the saw continued to run good. I'll tweak the screws 1/8th later "maybe", when I get into some wood.

Another Maintenance Chore And Experimenting! loger

    Bookmark   January 10, 2012 at 5:50PM
Thank you for reporting this comment. Undo

Loger : Usually the two elements on small trimmers and saws with Walbro's are the screen and the filter membrane cage . Some filters are also fitted with a lead or metallic core weight to ensure the filter remains within the bottom of the fuel cell or tank . Keep an eye on your spark plug for proper colouration , don't run it to lean :)

    Bookmark   January 11, 2012 at 3:16PM
Thank you for reporting this comment. Undo

Thanks Ewalk! I felt the disk looking part between the metallic core and membrane was or should have been a screen. I could c/n see any signs of light through it. The membrane showed good sign of flow with the disk removed. I'll get back to the saw and starve it to get a stumble and tweek past that point. I have never lost a piston or etc to running too lean since my 1970 start.

BUT! I feel I have seen some dark signs of heat on pistons from too much two-cycle mix causing carbon and damage but the spark arrest would be spotless. Plus, I have to keep 100 degree Tx heat in mind by cutting mornings only before the heat. Cutting firewood vs yard work is almost history vs acres of free wood from developments 70s - 90s. loger

    Bookmark   January 11, 2012 at 8:34PM
Thank you for reporting this comment. Undo

Loger: No Problem Bro ! Have a Great Day and stay out of the Heat :) Off to the Postal War's Chow !

    Bookmark   January 12, 2012 at 5:21AM
Thank you for reporting this comment. Undo

More Good Info Found:

Replacing the small int carb screen was a challenge but learn to leave them in the many piece kits as the welch plugs. I tried to pay to have one replaced and the Shop said they are too simple to install with the correct punch or pencil�s eraser. I d/n find that to be true but with a punch I finally installed it close enough (the old one cleaned). Seeing that the mechanics under the screen was clean was my objective.

The opposite from another mechanic was, "you do not replace it". This is when you have to be the Judge from your experiences. Which leads me to cleaning vs removing/replacing. It looks simple but I c/n find the touch. loger

PS. A very good displays at the address below will show the welch plugs and screens. Plus, this info address installing the welch but not the screen.


    Bookmark   January 26, 2012 at 10:52AM
Sign Up to comment
More Discussions
cultivator or tiller or both
In the past I've manually tilled and cultivated my...
Edwin Turlington
Temperature alarm app for Android?
I am wondering if anyone knows of an Android app that...
honda snowblower problem
i have a honda 928 snowblower... good machine, but...
Dewalt 3800 pressure washer, open hole between pump and engine.
Hi, I just bought a dewalt 3800 pressure washer gx...
General craftsman tiller gearbox question.
Ages ago in the early 90's, I bought a Craftsman 5hp...
© 2015 Houzz Inc. Houzz® The new way to design your home™