old 028WB up and running, need some advice

[STIHL-KID]

I finally fixed the pull cord on my newly aquired 028 Wood Boss power head. I also replaced the broken recoil spring. To my surprise the saw started in the "choke" position on the third pull. The saw seemed to idle roughly by itself for about 8-10 seconds. Next, while the saw was in the "choke" mode running I moved the switch to the "start" position and the saw instantly went wild with the rpms. The saw basically sounded like it was "redlined", then I used the throttle trigger to kick it down. The throttle lever did kick it down. Once the rpms came down, I used the throttle trigger and reved it up. The response was excellent, however the saw would also die after 2-3 seconds after using the throttle trigger. I'm guessing that this thing needs a carb rebuild or fuel filter to be looked at. The saw is unknown as to how it ran before I bought it. What is the first thing I should check in this case? The air filter is not clogged or obstructed. The carburetor looks varnish free and the throttle butterfly works correctly. I don't have a compression gauge or anything, but I can say that when I hung the saw in mid-air from it's pull cord, the saw did not drop. Good compression? Hopefully I can get this saw dialed in and use it this fall.
STIHL-KID

 

[Four Paws]

Most definitely a carb rebuild. Those tiny diaphragms go bad and still 'look' good when you pull it all down. $9 and you will be ahead in the end!

 

[Lakeside53]

Replace your fuel filter, look real carefully at the fuel line and if soft/gummy replace it. Your carb is likely blocked at the inlet screen. Just rebuild it.

 

[Dan Forsh]

Probably as the above have suggested, but given you haven't said anything to the effect, are you sure the carb settings are correct before you start tearing in to it. I bought my 028 as spares or repairs stated as not running. First off the kill switch wire was grounding on the casing and second off, once I got a spark, I got it to run and rev up as you have, but it wouldn't idle. Checked the H, L and idle settings and found them to be totally screwed up. Set them to standard settings and the saw idled fine.

If you haven't already, I'd start with the simplest first.

 

[STIHL-KID]

Current Results

Yesterday I took my saw down to the local small engine repair shop. The owner helped me find some of the parts that were missing on my saw. I basically was hooked up with a inner bar shield, chain tensoner screw, and new spark plug. I also picked up a carburetor rebuild kit. I went home and installed the new rebuild kit and put everything back together. The new spark plug is properly gapped. I was able to start the saw in the choke position. The rpms seemed to move up and down by themselves. The saw only ran for 5-7 seconds. I had much difficulty trying to start it again. I did get it started again in the "choke" position. As soon as I flipped the switch to "start", the saw rpms sky-rocketed and then steadily came down and died. So far I have $65 bucks into this saw and it's still not usable. Things done and checked so far........

1. Took muffler off and inspected piston......no scratches and very clean!
2. Installed new carb rebuild kit
3. Had small engine repair shop owner inspect carburetor fuel lines, looks good
4. Inspected fuel filter in the tank, not clogged or damaged
5. New spark plug installed and gapped
6. Checked for spark, shockingly good
7. compression good? Saw seems to hang from it's own cord and doesn't drop
8. Checked air filter, no debris and clean
9. Checked choke linkages/butterfly positions........good
10. dumped all fuel out of tank and put clean fresh "mix" in

This is basically what I have checked so far. I have not messed with any of the carburetor settings since I bought it. I don't have any directions on setting it to factory specs. I have no idea if they are way out of tune. The other thing I noticed is that the fuel tank vent tube is missing. All you can see is the little brass fitting. Does anyone have any suggestions to add? I know this saw is totally usable, but just need to get it running. STIHL -KID

 

[Lakeside53]

If it's starting, it's probably not it the seals, but the possibility remains. Could be impulse line feed.

You need to replace the fuel filter if it's more then a year old. The old style disintegrate and you could have re-blocked the inlet screen in the carb.

At some point after doing the obvious, all you can do is get the saw pressure and vacuum tested.

 

[STIHL-KID]

Note:

While rebuilding the carburetor, I did remove the screen inside and found no debris or material that would cause blockage. More specifically I took the fuel filter apart and was able to pull out the foam insert. Nothing looked questionable. The impulse line is located where on my saw? Need a diagram to show where both ends go. I would like to check all lines and make sure they are clear of obstructions. STIHL-KID

 

[Dan Forsh]

Basic factory settings for the carb should be about 1 turn out on the H and L screws from lightly seated. That means turn them both gently clockwise until they stop. Make a mental note of how far you've just had to turn them to get there. Then turn both back out anticlockwise one full turn. The idle you can check out later, at least now you will have a starting point to work from. Try starting the saw again and see where your at.

 

[Lakeside53]

The impulse line goes from just below the cylinder base to the back of the carb mount. The crankcase pressure changes drive the fuel pump diaphragm on the carb