FG110 Tiller intermittently will not accelerate enough to turn tines

C

Cfs

Well-Known Member
I am scratching my head on this one! I was given a FG110 Mini Tiller it needed a carb cleaning and new diaphrams replaced and it ran great. Starts right up on first or second pull I sold it to a neighbor who told me it would not run for him. Brought it back to me and it ran fine' I even turned up a mulch be with it. He came back for it and I was going to show him that it ran great and it would start but it would not rev up fast enough to make the tines turn. I kept playing with it trying to get it to rev up and finally it took off and started to rev up. Once it started reading up,it would just run fantastic. It would rev up slow down rev up smooth as silk. I have since let it sit and go to start it and sometimes it revs and run s great and other times it refuses to rev. It starts and idles but pulling the throttle lever will not make it rev and will in fact make it stall out. Its a barrel style Walbro carb and does not have any adjustment needles that I know where and how to adjust. I do have an ultrasonic cleaner I could run the carb through. It is just so strange that it runs like a million bucks when it wants to and then out of the blue it will not rev/accelerate. I am wondering if there could be something with the clutch for the transmission/tines.
Any and all comments and input welcome
Spit
 
You cleaned the carb, what about fuel filters/lines? What about gunk in the fuel tank? Have you tested the spark, especially when it's acting up? What about the throttle cables? Do the work consistently? I've seen throttle cables that don't move consistently, due to drag, or improper assembly. I don't know that machine, but most carbs have an idle circuit and the main circuit, which the throttle controls. If the main circuit is clogged, it will idle, and often die when given throttle.
 
Mark H_NO said:
You cleaned the carb, what about fuel filters/lines? What about gunk in the fuel tank? Have you tested the spark, especially when it's acting up? What about the throttle cables? Do the work consistently? I've seen throttle cables that don't move consistently, due to drag, or improper assembly. I don't know that machine, but most carbs have an idle circuit and the main circuit, which the throttle controls. If the main circuit is clogged, it will idle, and often die when given throttle.
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Lots of good ideas! I will look at them tomorrow, it just doesn't seem like its the throttle cable..seems like it is pulling the throttle open. I should be able to manipulate the throttle by hand, When it is running right it will just flat out scream at full throttle seems like a bad fuel filter would cause issues all the time and prevent the super strong acceleration I get when it is working properly. Maybe a fuel line is collapsing and cutting off fuel
 
I had a mantis, and a leaf blower that used the same design carb. Inside there was a diaphragm that looked quite good. However it had little flaps as part of it, and over time those small flaps would deform. Those flaps act as a valve that controls fuel flow off the main diaphragm. As they start to go bad, the mantis, and the leaf blower would do the exact same thing. This was a once a year occurance. I finally got it to last four or five seasons by using non-ethanol fuel (with the proper oil of course for s 2-stroke) and draining the tank and running it dry between uses.

If you have a small Zama or carb like it, and it has a gasket like this, replace it. It will go bad again if it is left to sit with fuel in it when not in use.

Zama Carb and diaphrams below

zama.jpg

flap.jpg
 
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Thanks for the info. I will remove both diaphragms and run the carb through an ultrasonic cleaner. I will install new fuel pump and fuel metering diaphragms and see what happens. This should eliminate the carburetor from the suspects list. If it continues to have issues I will have to look at other possibilities
Spit
 
yes - those flaps have to properly seal. One acts as an inlet and the other an outlet. when the outlet seals, the inlet allows fuel into the cavity. Then as the diaphragm pumps, the inlet seals and the outlet opens. When they deform, the fuel just swishes back and forth. Sometimes if there is enough suction, like at a good RPM, they will act normal but as soon as the engine slows the fuel stops flowing again and either the engine stumbles along or dies. When they are working right, the mixture, starting, everything works great on those model carbs. But as soon as they deform, the performance totally sucks. I got to the point where I just kept a spare carb, and would swap it in 10 minutes, then rebuild the old one at my leisure. Some of those carbs have an internal spring and/or ball so go slow as you open it. Nothing that will zing off, but they can fall and go into hide and seek mode. There used to be a guy online who sold kits to rebuild that style carb for like $3 to $4 each but he has gone missing in action I think.
 
So I removed and disassembled the Walbro barrel type carburetor. The pump diaphragm and gasket looked perfect, on the fuel metering diaphragm the metal disc with the nub on it that presses on the needle lever was bent… not sure how that happened… I had just installed it but it was definitely bent when I removed it.
I ran the disassembled carb through a 30 minute cycle and reassembled and reinstalled the carb with a new metering diaphragm and the same pump diaphragm and gasket that I had installed 2 weeks earlier.
It seems to have resolved the problem. I am no longer having an issue either it not accelerating. It does seem like once it has started, that I need to take it off of choke before any hard acceleration. Not sure if that is normal for this engine but it seems to smoothly accelerate far better with the choke off.’
 
usually the choke is only needed on an engine to start it. Once an engine is running properly, the choke can be disengaged within 10 seconds to a minute depending on the engine.
 
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