Slow to no acceleration on Mantis 2-cycle tiller

[wannabegreener]

Hi,

I have a mantis tiller (2 cycle) that I left the gas in over the winter. I had a hard time starting it and once I did, it was tough to keep running. I managed to get it to till 1 of my 6 raised bed gardens but it was tough. I did some reading here, in the mantis manual and on other web sites and this is what I did:

Emptied the gas
bought new air filter, carburetor diaphragms, and spark plug, and fuel filter
took the carb off and cleaned it using carburetor cleaner (The parts place said the carb was in good shape and not really dirty or gummed up)
put carb back together with new parts
checked the anti-spark screen and it had no crud on it.
Took the muffler off and no carbon build up
bought new gas and mixed in stabilizer and 2-cycle oil

Tried my best to adjust the carb low and high. On the mantix, there are stops on the low and high so you only have minimal adjustments. Maybe only 1/2 a turn on each. The Mantis manual said to turn the high all the way counter clockwise and put the low 1/2 way between the 2 stops.

After all of this, I got it to start and run for a while (2 - 3 minutes). I then squeezed the throttle and it would bog down. The manual said if that happens to turn the low adjustment counter clockwise. I did this in steps (again, the stops don't allow this to move that much) until it was all the way to the counterclockwise stop. It still bogs down when giving it throttle. I managed to till 1 more garden, but if I stopped while tilling I would have to remove the tiller from the dirt and rev it while it was out of the soil. Once going again, I could manage to keep it going. It did till, but with limited power.

I was guessing that I needed to somehow remove the stops so I could adjust the low a little more, but wanted to see if anyone here had any other thoughts. I figured it is just a 2 cycle engine so it should not be that different than a chainsaw.

Any help would be appreciated.

Thanks

 

[bogydave]

MY guess, only a guess.
Sounds like it is starving for fuel. Piece of dirt or varnish from storing it will fuel for
a long time, the gas evaporates off leaving behind a varnish. Could be in the carb, but not knowing the engine, tough
to say where.
Follow the fuel from the tank to the spark plug. (fuel lines, needle valve etc)
Again just a guess.

 

[jharkin]

I think Dave is on the right track. Even if the diaphragms are clear you could still have Jun in the needles etc.

1/2 turn on the needle of a walbro type Carb is a lot.. A screwdrivers width turn can make a diference. Hesitation on acceleration is a low speed needle issue...if itbogs then speeds up you are rich, if it stalls you are too lean.

One way to tune. Set both scwews rich. Kept gunning it and slowly lean the low end until it transitions smooth. Then set the high end. At idle to mid throttle it gets fuel from the low jet only, at full throttle both jets feed.

 

[wannabegreener]

Thanks for the replies. I read some more last night after posting and it looks like the stops on the low and high jet screws can be pried off. With the stops on it, I can only move the screws about 1/4 to 1/2 of a turn. Moving the low screw doesn't seem to do much while the engine is running.

As for 'rebuilding the carb'. I just took the diaphragms off and sprayed it all down with carb cleaner. I didn't take the needle valves out - too afraid I wouldn't get them back the same way. I'm pretty handy with taking things apart and putting them back together, but if this requires any special tools, I wouldn't have them.

Couple of more questions:

1. if I run it for a while will the new gas clean up any crap? My guess is no, especially if it is dirt, but what if it were varnish?
2. if I manage to take the stops off of the screws and take the low and high screws out, do I just spray carb cleaner down the screw holes?
3. how difficult is it to take the needle valves out and get them back in? Are there springs in there I need to worry about?

Thanks for any help.

 

[woodsman23]

Try and blow out the air line with compressed air and a low setting and also use some seafoam this is the only additive i have ever seen that actually does something. Worked for my royobi....

 

[Singed Eyebrows]

As most said it is low speed fuel(95 percent sure). Take the LS needle out & look.//// Many 2 cycle carbs have a very fine mesh inlet screen, carefully pry it out & look through it. You may need to poke a fine wire through the jet, be carefull you don't open up the bore./// I just bought a generator that was surging at idle & I needed to run a .015 wire through the removable jet as carb cleaner would not do the job. It ran like new afterwards. Todays new envirnmentally friendly carb cleaner doesn't cut like the stuff of old, Randy

 

[maverick06]

I have the tiller, not that problem though.

Lot of people have issues with the tiller though (its an awesome tiller). The engine is quite temperamental and leaving gas in it over winter can mess it up (I assume that varnish clogged the carb). ALWAYS use gas stabilizer with any gas that this machine takes, its cheap insurance.

Other possibilities you appear to have already checked for:
Did you mix the gas correct? I *think* the machine wants 1:50, The oil I have recommends 1:32, so i do that, no problems with any of my tools (some what that ratio anyways). If you have too much oil it will bog down, too little and you will burn it up.

If in the past it had run with too much oil, the exhaust port could be plugged with carbon.

I have a green machines weed wacker that, if you give it any throttle, will bog down really bad. But if I let it warm up for 3 min, it runs great. So that is all i bother doing with it.

Good luck, I bet it is the carb....

Rick

 

[wannabegreener]

Maverick06 - I love the machine. I have tried different small tillers (one that goes on the end of the stihl weed wacker, another brand mini tiller that I think was a husky or something) and they all worked like crap.

I have a friend that has a mantis and he let me borrow it for a weekend. WOW what a great machine. His is 23 years +/- and he always puts it away with gas in it. He never had a problem starting it. Before I gave it back to him I took a hose to it and cleaned it all up for him, I removed the tines and took all of the crap in there out. When I went to give it back, I wanted to show him that it still ran and when I pulled the cord, the cord broke. The look on his face was priceless. I told him that I would take it back home and get him a new cord. I ended up finding a complete used cord enclosure for $5. Put it on and gave it back to him.

>Lot of people have issues with the tiller though (its an awesome tiller). The engine is quite temperamental and leaving gas in it over winter can mess it up (I >assume that varnish clogged the carb). ALWAYS use gas stabilizer with any gas that this machine takes, its cheap insurance.

Yeah - I guess you can say I learned this the hard way. It's working better after taking everything apart, but still not right. I just want to get it right. The small engine place that works on them wants about $100 to fix it so I figured I would try it myself. It's a great learning experience and with the help from forums like this, I'm hoping I can get it working.

>Other possibilities you appear to have already checked for:
>Did you mix the gas correct? I *think* the machine wants 1:50, The oil I have recommends 1:32, so i do that, no problems with any of my tools (some what that >ratio anyways). If you have too much oil it will bog down, too little and you will burn it up.

The best thing is that all of my 2-cycle engines use 50:1 so I only have one can with mixed fuel. I use the same fuel in my Stilh chainsaw and string trimmer, and my echo leaf blower. It works great in those. No problem at all, so I think the oil is mixed correctly. Maybe a little on the weak side since I probably put a little more than a gallon in, but not much more.

>If in the past it had run with too much oil, the exhaust port could be plugged with carbon.

I took the muffler off to check the spark arrest and everything was clean. No carbon build up anywhere that I could notice.

>I have a green machines weed wacker that, if you give it any throttle, will bog down really bad. But if I let it warm up for 3 min, it runs great. So that is all i >bother doing with it.

Before taking everything apart I managed to till a garden about 10x8 and it still ran like crap after it was done. I'm sure it was warmed up after tilling that (twice).
After taking everything apart, I managed to till a 3x13 garden and it ran better, but reving the engine after tilling (definitely warm again) it would bog down.

I'm going to go with everyone here and take the carb apart again. This time I'll play with taking the needle valves out to see if I can get any varnish/dirt out of it. I know everyone is saying the Low valve is the likely culprit and maybe the fact that the primer bulb didn't want to prime when I took it out makes sense. When I took the tiller out the primer bulb was empty. I must have pumped it about 100 times before getting it wet. Does anyone know if the primer bulb uses the low valve to get the carb primed? If so, then this is sounding real promising.

Thanks for everyones help. I'll update after taking the carb apart.

 

[heat seeker]

While you have it apart, check very carefully for a cracked fuel line. They get hard and crack, making it run lean or not at all. Also make sure each hose fits tightly on its nipple, as hardened hoses will not seal well at the nipples.

 

[maverick06]

Oh, if you really want to, you can change the grease in the gearbox. I think that the manual says to replace, or maybe "top off" every year. I suspect no one does. But its worth considering if you are doing lots of maintenance for it. But you probably should get the motor running first...

 

[wannabegreener]

I looked for the grease while I was getting carb cleaner but they didn't have any. The 'not so bright' person working at the auto store wanted to sell me lithium spray. Nope - not the right stuff.

I took the carb apart again today and took the needle valve out. It was pretty easy. I also pried off the stops on the low and high screws and was able to take that apart also. The high port was very large and seemed wide open. The low port seemed open as well. I didn't put any wire through it to test it, but the carb cleaner went right through to the inner part of the carb.

What I didn't realize was that the high and low screws were different. I don't remember which one, but I had first put the wrong screw in the the wrong port. One went in easy, but the other was not right. I was very careful screwing them in so I don't think I did any damage. After I put them in I think I backed them out too far and gas was leaking out of the inner part of the carb. I screwed them in until it stopped and got it to run, but not long enough to adjust anything. I also kept taking the plug out and it was damp every time I took it out. I also didn't have much time today to play with it. Hopefully I can get it running long enough tomorrow to get it adjusted. I'm keeping the stops off right now until I get it adjusted.

I probably only have about 3-4 hours on it so I'm guessing the grease is ok. I will replace it once I find some new grease for it.

I'll post more the next time I play with it.

 

[heat seeker]

If I remember right, the gearbox is a worm drive type, and the proper lube is critical to its lifespan. There is a lot of friction inherent in a worm drive, so a lube with good shear strength is required. I could be wrong on that, but then again, I might be right…. :-S

 

[wannabegreener]

Here is my update - still fighting with it.

I set both high and low screws to 2 turns out from bottomed out and gas was leaking out of the carb. I then turned them in until they were it was no longer leaking. I also thought the low screw was the high screw and the high was the low. I wanted to get it to run at idle first so I screwed in the screw I thought was high all the way (it was actually the low screw). I actually got it to run this way, but not very well. After looking at the owner's manual and the air filter cover (which I had off to do the adjustments) and after seeing a mantis carb adjustment note on some other website, it said to start with the low screw out 3/4 of a turn and the high to 1.5 turns. I did this today and no go. I also read that the exhaust could be plugged. It wasn't when I was first playing with it, but maybe it was now. I took the muffler off and the tiller will now run but not stay running. I didn't have much time to play with it this morning, but I could get it to run and to rev a little. The transition was not very smooth and when I reved it too high it would bog down and when I let go of the trigger it would sometimes run and sometimes die. This was all with the muffler off.

Can I clean the muffler with carb cleaner? If so, should I just soak it?

When I took the muffler off and tried to get it running there was lots of blue/black smoke coming out of the exhaust port. Should I try to clean the cylinder with carb cleaner and then try to blow it out with compressed air, or will this damage the rings and such. Once I got it running it didn't smoke at all, but when it died I would remove the plug to look at it and it was usually a little wet and a little oily? I would think that this would mean 1 of 2 things:

1. too much oil in the gas
2. running too rich

Now that I have this much time invested in this I really want to get it running myself, but I have thought about bringing it in to have someone else do it and get it running. I have 3 other 2 cycle engines and really want the knowledge on how to take care of these types of things instead of paying $100 each time I need to bring them in.

 

[wannabegreener]

Played with it some more tonight. Couple of things I found:

I got it to run temporarily but not smooth at all. When it was running, I thought there was an air lead near the carb. I could feel all kinds of air there. (Ok - here is where you all see I'm a newbie at this). It was not an air leak, it was the flywheel (or whatever you call it) cooling the engine.

Anyway, I took the carb off again thinking I messed up the gasket between the carb and the next piece. I took that next piece off also. Cleaned up the base of the engine where the carb mounts and decided to take the carb apart again. I'm getting real good at that. I found that the needle valve was stuck open. I don't know why, but once I touched it, it was fine. I took it out and sprayed it pretty good with carb cleaner than I put it back together. Still no go or barely running. My neighbor came over and tried to get it going. Still no go. I then remembered that the parts dept where I bought the diaphragm thought that it was the right part, but wasn't sure if the height of the 'pin' in the new one was not the same size. Since the old diaphragm was soft and pliable, I just put it back in. We set the screws at 3/4 for the low and 1.5 for the high and it was running pretty good with the muffler off. We were able to get it to wide open throttle and it ran great. It was getting late so I put the muffler on and it started and ran decently. It smoked for a while with the muffler on, but it cleaned up after running it for a couple of minutes.

I think/hope it is pretty close. It still has the air cleaner/filter off and the spark arrest screen off, so I'll add 1 at a time to make sure it still runs and see how it accelerates. Once I get it with the complete exhaust and air filter on, I'll put the tines on and see if I can go to town.

Thanks - I think mostly it was just dirty and plugged. I probably didn't need the new carb rebuild kit and getting the wrong diaphragm was probably key to me not getting it running right until I put the old one in. I found the owners manual and it lists the carb rebuild kit by part number. Next time I'll make sure I get the right kit.

I hope to be happily gardening soon.