028 Problem

[doc874]

Just got an 028 super WB, owner said gas was coming out the carb when it ran, Stihl mech thought gas blowing past piston likely piston gone or rings wore out or cylinder problem. I stripped the saw today and can find no reason why the gas would come out the carb, the piston and rings look great, no scoring etc... The cylinder looks good as well ( see pics. ) Could it have been that the piston was put in wrong? and not ran long enough to hurt it? The saw doesn't seem to have much use on it. Thanks.

Doc

 

[THALL10326]

Just got an 028 super WB, owner said gas was coming out the carb when it ran, Stihl mech thought gas blowing past piston likely piston gone or rings wore out or cylinder problem. I stripped the saw today and can find no reason why the gas would come out the carb, the piston and rings look great, no scoring etc... The cylinder looks good as well ( see pics. ) Could it have been that the piston was put in wrong? and not ran long enough to hurt it? The saw doesn't seem to have much use on it. Thanks.

Doc

Its normal for saws to have some gas blow back through the carb. Must remember 2 strokers have no valves to so its a open shot to the cylinder. As for the piston being put in wrong, nope, if it was put in backwards it would run a few seconds and the rings would catch the exhaust port and kaboom. So are you saying the carb was leaking gas or gas was blowing back out the back of it???

 

[rahtreelimbs]

Was that saw that clean when you got it...wow!!!

 

[doc874]

028

The saw was in good condition when i got it, i cleaned it as much as i could without stripping it all the way down ( yet ) I have not ran the saw, the owner posted them here in this forum, nobody made a decent offer so i did ( their loss ), i took a gamble and so far its paying off, the people that sold them to me are straight shooters and described them excellently. The original owner stated it was soaking the filter so i assume it blew back out the carb into the filter. When i got the saw the filter was wet and smelling of fuel. I am stumped as to why this is happening, i bought a new piston kit for both saws so if i have too i will put them in and i have a flex hone if needed, but i hate to do this as the original piston looks great. Any other takers or ideas??

Doc

 

[Lakeside53]

Blowback is mainly a function of piston skirt wear. It might look good, but measure it... Amazing how a new piston cleans up idle and other problems in a saw!

MIght be the pictiure, but the piston looks worn to me.. Highy polished... a dead giveway...Take out the rings (carefully). Insert them in the cyinder and measure the ring gap. That will tell you how much the rings are worn.

 

[doc874]

Lakeside, the piston isn't polished its the flash from the camera i have several other pics, take a look. The little ridges that a new piston would have are also still there also. Must be the rings are worn?

Doc

 

[doc874]

Here are some pics of just the rings lying inside the cylinder, sorry if abit blurry. I don't have a feeler gauge to measure. They seem snug enough. Thanks.

Doc

 

[Lakeside53]

hmmm... I can't quite see the gap.... The ring end radius is misleading in the pictures you took.

Hard to say...

The 028 is a bit of a spitter anyhow... That carb gushes gas and the filter has no sheild.