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Hi everyone, well my mm 55 tiller hasn't been running well at all. So I thought it would be time for a carb kit. It seemed pretty simple I was careful and took pics to make sure everything went back just like it came out. Well the same thing it will start and run but I cannot get any power out of it. If I squeeze the throttle it will die. On the high speed ( the screw to the top and right) I have had to screw the needle all the way in to get it to run. Also the idle adj doesn't seem to work at all. Could my filter be plugged? Plenty of spark and seems like good compression but I haven't checked it with a gauge. I can't find any cracks in the fuel lines either. I was hoping someone might of had a problem similar to this and could help me out. Well thanks and I will wait for some feedback.

Have you checked the outlet on the muffler especially the spark screen. If it has the small round exhaust outlet, there is a bee that likes to pack it with mud.

While checking for that mud, check the spark arrestor. It can be clogged and cause poor performance.

Thanks guys I will check those things out

I have found for the cost of a new carburetor when I have a small 2 cycle engine come into my shop I replace the carburetor instead of rebuilding the old one. I also replace the fuel lines and filter. As for myself I have had very good luck in doing so. Just don't have very good luck with rebuilding them small carburetors. Still check for the plugged exhaust, I find if the exhaust is plugged you will lose high speed and power was you described but still will have low speed.

Well if the muffler and lines and filter are ok, I will probably do what you just said get a new carb. I think they are only $30 or so.

Thanks

I rebuilt the carb with success on my MM55. I was having maximum power issues. It would hit the "rev limiter" too soon so to speak. But, sometimes I just replace the carburetor. Much more simple.

Lawnboy18 said:

I rebuilt the carb with success on my MM55. I was having maximum power issues. It would hit the "rev limiter" too soon so to speak. But, sometimes I just replace the carburetor. Much more simple.

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He said he could get a carburetor for 30 dollars. I find as a repair in my shop the cost of a repair kit and my labor its cheaper and a better job for me to replace the carburetor. If its my own equipment I would just try cleaning it without buying any parts first.

reynoldston said:

I have found for the cost of a new carburetor when I have a small 2 cycle engine come into my shop I replace the carburetor instead of rebuilding the old one. I also replace the fuel lines and filter. As for myself I have had very good luck in doing so. Just don't have very good luck with rebuilding them small carburetors. Still check for the plugged exhaust, I find if the exhaust is plugged you will lose high speed and power was you described but still will have low speed.

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Ok, pulled the fuel lines and filter they have no cracks and the filter looks very clean and I can blow thru it easily. I even blew thru the lines with my finger plugging up the other end and no leaks. Pulled the muffler, and unscrewed the spark arrestor. Muffler was empty and fairly clean, the arrestor was very black and I could shine a flashlight thru the screen but looked like it was dirtier towards the end with the nuts on the tube. Can a guy clean the spark arrestor? If so how and what with? Or just order a new one and if that doesn't work order a new carb???????

Thanks

reynoldston said:

He said he could get a carburetor for 30 dollars. I find as a repair in my shop the cost of a repair kit and my labor its cheaper and a better job for me to replace the carburetor. If its my own equipment I would just try cleaning it without buying any parts first.

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Here in Canada a carb kit is 17$. A brand new carburetor is 65$ and add 15% sales tax. That is why I rebuild them if I can.

To clean the spark arrestor:

Wear cloves.
Grab a torch.
Hold the tip of the screen with a vise grip and get that screen glowing red to burn all carbon off. It's ok if the arrestor is dirty in the corners. You want the center to be clean; where the exhaust escapes.

Lawnboy18 said:

Here in Canada a carb kit is 17$. A brand new carburetor is 65$ and add 15% sales tax. That is why I rebuild them if I can.

To clean the spark arrestor:

Wear cloves.
Grab a torch.
Hold the tip of the screen with a vise grip and get that screen glowing red to burn all carbon off. It's ok if the arrestor is dirty in the corners. You want the center to be clean; where the exhaust escapes.

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Ok, I will try that tomorrow thanks for the advice.

No problem! Let us know how it goes!

Lawnboy18 said:

Here in Canada a carb kit is 17$. A brand new carburetor is 65$ and add 15% sales tax. That is why I rebuild them if I can.

To clean the spark arrestor:

Wear cloves.
Grab a torch.
Hold the tip of the screen with a vise grip and get that screen glowing red to burn all carbon off. It's ok if the arrestor is dirty in the corners. You want the center to be clean; where the exhaust escapes.

Click to expand...

This is the reason I hate working on these small 2 cycle engines. The cost of the labor and parts the customer can buy new equipment. No money to be made. Its good that gmacmopar will try to fix his own equipment, but already he's having problems. As you said (I rebuild them if I can) This is the very reason I suggested a new carburetor. I hope him the best of luck on this repair :thumbsup:

Reynoldston, that is the reason that I don't spend more than 15 minutes on a trimmer.. that allows for replacement of spark plug or fuel lines, filter in most cases, or maybe a carb replacement if it is cheap enough.

Past that point and you will be around 75% of replacement cost if not above replacement cost.

ILENGINE said:

Reynoldston, that is the reason that I don't spend more than 15 minutes on a trimmer.. that allows for replacement of spark plug or fuel lines, filter in most cases, or maybe a carb replacement if it is cheap enough.

Past that point and you will be around 75% of replacement cost if not above replacement cost.

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I am very up front with my customers when they want repairs on this style of equipment. My problem is I just can't charge someone for a job not fixed so that makes me the loser. Time lost finding problem and looking up price of parts. Not hard at all to spend well over a hour of time for no money just to tell them to buy new. One of the disadvantages of a one job at a time small one man shop.

Ok, well I took a torch and cleaned the arrestor, Put it all back together and it wanted to flood with the choke. So I cleaned the plug and got it fired up but still it would not keep running. So finally I adj the High speed opposite of what the book says,(clockwise all the way) I turned it clockwise all the way that helped a bit. Then I turned the low speed all the way in cw and it is suppose to be 1 turn out cc. I have the idle speed turned all the way in and it would run somewhat but still would never get to the power it used to have. Well I guess the only other option I have is to get a new carb and see what happens. Like some said it is not worth countless hrs on these small engines when you can get a new part for less. So now tomorrow down to the store!

Thanks garymac

Something is wrong there. I would say reset to factory settings the carburetor. If that does nothing, just get the new carburetor. Much easier.

Keep us posted.

reynoldston said:

This is the reason I hate working on these small 2 cycle engines. The cost of the labor and parts the customer can buy new equipment. No money to be made. Its good that gmacmopar will try to fix his own equipment, but already he's having problems. As you said (I rebuild them if I can) This is the very reason I suggested a new carburetor. I hope him the best of luck on this repair :thumbsup:

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As much as these are small engines, they can be a PITA to fix and diagnose what is wrong excaly.

It will not run on factory settings at all. If you try to choke it on cold start it floods. The only way I could get it to run was what I posted earlier. Then it has no power what so ever and will not idle. This is what it was doing in the first place only harder to start and keep running. I know I put the carb back together as it came apart I took a lot of pics. I think I will just order a new carb and see what happens unless I am missing something that you guys can see? I will piddle tomorrow but go ahead and order a new carb. Does the new carb come complete? Or are there extra's like the idle and low speed screw I have to order separate? Okay guys,

Thanks Gary Mac

Maybe you put something in there the wrong way. Did you use a carburetor rebuild kit or reuse the old pieces? Also, you might have forgotten to clean out a section that may have a speck of dirt. Doesn't take much to get these carburetors to have a fit.

Carburetor comes complete and preseted. Bolt on and run.

Lawnboy18 said:

Maybe you put something in there the wrong way. Did you use a carburetor rebuild kit or reuse the old pieces? Also, you might have forgotten to clean out a section that may have a speck of dirt. Doesn't take much to get these carburetors to have a fit.

Carburetor comes complete and preseted. Bolt on and run.

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Well I used a brand new carb rebuild kit, all new parts. I laid everything out in order as I took it apart, and as I did this I took pictures to make sure I got everything back in the exact place. I used carb cleaner to clean the carb and compressed air to blow out of all the orifices. Not saying I didn't put something in the wrong way, maybe tomorrow I will take it back apart and see with my pics if I indeed did mess up. I know stihl has a lock on all of there tech manuals and diagrams, but is there a way to get a diagram of the carb and how the gaskets line up etc? I know John Deere is this way but you can still get some things on line or maybe know somebody that has access. Anyway we will see maybe I did forget to clean something. The only thing I didn't put in the carb were these little alum caps or whatever they are called because I didn't know how to get them out.

Thanks Gary Mac

gmacmopar said:

The only thing I didn't put in the carb were these little alum caps or whatever they are called because I didn't know how to get them out.

Thanks Gary Mac

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Don't take short cuts. There can be some dirt under them caps causing the problems. Drill a small hole in them and pull them out with a self taping screw.

reynoldston said:

Don't take short cuts. There can be some dirt under them caps causing the problems. Drill a small hole in them and pull them out with a self taping screw.

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Do the new ones just push back in?

gmacmopar said:

Well I used a brand new carb rebuild kit, all new parts. I laid everything out in order as I took it apart, and as I did this I took pictures to make sure I got everything back in the exact place. I used carb cleaner to clean the carb and compressed air to blow out of all the orifices. Not saying I didn't put something in the wrong way, maybe tomorrow I will take it back apart and see with my pics if I indeed did mess up. I know stihl has a lock on all of there tech manuals and diagrams, but is there a way to get a diagram of the carb and how the gaskets line up etc? I know John Deere is this way but you can still get some things on line or maybe know somebody that has access. Anyway we will see maybe I did forget to clean something. The only thing I didn't put in the carb were these little alum caps or whatever they are called because I didn't know how to get them out.

Thanks Gary Mac

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Get the name of who made the carb, and what the model numbers are off of the carb itself. Walbro will be laser etched into the side of the carb, normally in one of the corners. then to that companies website and look up the number there and it will give you a diagram.

Zama will have part of the model number molded into the carb under one of the mounting bolts, will be something like C1Q and the rest of the number will be on the side, should start with an S.

I strongly suggest youtube. There are many videos on how to rebuild a carb completely step by step. Just whatch the video and follow what the person is doing.

Ok, here goes, I went down and they had a new carb so I bought it. Came back home and as hard headed as I am proceeded to take the old one apart again and triple check and redo everything on the carb that I had done before. Put it all back together and whoom it started and had plenty of power. But.... I cannot keep it idling it will die? It starts right up but when you let off the throttle it will die. No matter how I turn the adj. screw it will not stay running at idle. Hmmmmmmmmmm!

Gary Mac

HAve a look at the throttle linkage.
The throttle should stop against an adjusting screw if you actually got the correct carburettor. And if you did that it came with all external parts,sometimes they are missing the idle adjustment screw.

This is still the old carb, I took it apart again and tripled and doubled checked everything again. Got it started and now it has lots of power and it idles?????? But I am not sure this is going to last very long. I have the screw settings a lot different than what they call for but we will see. I still have the new one so if problems arise I will throw that one on and see what it does.

Whatch it with the needles. Don't wanna burn the motor.

I think it is a tad rich I will pull the plug and see how it is burning

Thks Gary Mac

You can get a build up of fuel condensed in the crankcase which will cause it to run strangley till all of it has gone.
So you might just try running it for a while
If this earlier model carb there are 3 adjustments
High speed and low speed mixture screws and throttle stop ( idle screw ).
On top of that the impliment might have an adjusted on the cable which will have to be adjusted very slack before you start adjusting the carb.
You start the proceedure by adjusting the HIGH needle which is the one furthest away from the engine.
Hold the throttle on fully to do this.
The safe way to do it is to wind it out till the engine starts blowing smoke then in very slowly till it just clears up.
This will have it running a little rich
Now let the trigger off slowly if it goes all the way then back of the idle screw till it goes as slow as it can while firing continually.
Then adjust the low speed mixture screw.
Out till it almost dies then in till it almost dies then back midway between the two.

Having the slow jet closer to the engine confuses a lot of people.
Also be careful with the jets thamselves, the LOW IS LONGER.

You will find it helpful to hold the handle of the tiller in a vice so the head is clear of the ground.
The high adjustment must be done with the tynes turning.

Ok guys here goes, I have been working on this old carb with a rebuild and now after taking it apart 3 times the thing runs perfect. Spark plug is not black or lean looking idles fine and has plenty of power. I have no idea what I have fixed or not fixed just that it runs fine now. I have a new carb in the box in case everything goes south. I want to thank everyone involved in helping me to figure this out. I couldn't of done this without you.
Thanks again Gary Mac