Strange behavior Stihl 028

[Turd Ferguson]

Ok here goes! I picked up a running Super AV Woodboss 028 a couple of weeks ago. When I arrived at the owners' address - I should have suspected something when I saw him coming back from the woodpile with the saw. We talked a little about it and he told me that it just ran out of gas. I asked him if I could take the air filter cover off - he agreed and I immediately noticed a piece of regular fuel line wrapped up around the air filter and slightly pinched off on the end in place of the correct tank vent. I'm immediately thinking rigger at this point - although I would do the same thing in a pinch. I ran it some more - cut a few pieces with it and it wandered at idle a bit - but came up to speed pretty strong. As the saw was fully warmed up, I borrowed his carb adjustment screwdriver (funny how he just happened to have one in hand) and fiddled with the carb settings a bit but it wouldn't run on its side or above my head, so I also suspected crank seals and/or possibly needing a new Chinese carb. The saw was complete so we agreed on a price and I took it home. After getting it home, just being me, I replaced the tank vent, fuel line and filter, impulse line and NGK7BPMR plug at .020". The air filter was completely matted over with a mixture of caked-on dust and fuel. The air filter cover on this saw is 1118 141 1000 version that has the screw that goes through the air filter onto the left carb stud. Not having the type of air filter that this set up requires, I took an aftermarket Forester flocked air filter and removed the receiving screw for the 1/4 turn knob type cover, put everything back together along with a new Chinese carb and took it for a spin. I also disassembled, burnt out, cleaned and straightened the muffler and installed with a new gasket (this saw looks like it fell off a truck or something). The previous owner was running Rural King bar oil and it sure was oiling plenty with this thinner oil. It also has a very sloppy on/off/choke lever - but workable. Saw started fine and allowed me to go through the initial throttle settings, then to L/H and it was doing great. Smoked a bit, but he was running 32:1 fuel mix or so he told me - I run 40:1 but don't want to get anything started on oil mix ratios. It picked up good and took high rev with little or no problems. Then after idling for a few minutes it seemed to bog down at pickup and would lose power under high rev that no amount of carb adjustment would correct. Here is the funny part - when I loosened the air filter cover screw 3 or 4 turns it smoothed out and ran better. When I remove the air cover completely - you would swear that it runs like a new one. When I reinstall the air filter cover and tighten the screw - back to the bogging and up and down running. I have another 028 with the 1/4 turn knob on the air filter cover so I replaced the air filter with another Forester brand flocked air filter (with the metal receiving socket for the 1/4 turn pin) installed the other 1118 141 1001 1/4 turn knob type cover and it also ran great. If I go back to the old-style cover and altered filter it will run if I only tighten the air filter cover up a turn or two. Obviously, something is going on with the filter and air filter cover and possibly blocking off the air filter so it can't breathe - but that is strange to me. I would like to ditch the old cover and get another 1/4 turn pin cover but I can't find one for love nor money. Since I only run one at a time - I either have the option of trading covers between the two or only tightening the old air filter cover screw a turn or two. I plan on doing a teardown/ rebuild on it this fall since I just can't leave anything alone. Anyone have any suggestions or any old covers laying around that they don't need?

 

[Creaky limb tree care]

Hi, it may be doing the same, as what happened with my 038, the choke flap was sucking closed on higher revs, due to a weak spring,
Took me ages to work it out!
Regards, Toby.