Stihl 028 AV Wood Boss Carb trouble

[HarleyT]

Leave the tank vent alone. Take a small screwdriver and turn each screw to the right until it lightly seats,
counting the number of revolutions, i.e. 2 1/4 turns, or 1 1/2 turns.
The low speed screw is the one that is closest to the piston/cylinder, the high is the one closer to the air filter.

I am hoping that your mixture screws are set too far out and the saw is just running rich.

The back each one to 1 1/2 turns out to start.

 

[bottomcat]

Leave the tank vent alone. Take a small screwdriver and turn each screw to the right until it lightly seats,
counting the number of revolutions, i.e. 2 1/4 turns, or 1 1/2 turns.
The low speed screw is the one that is closest to the piston/cylinder, the high is the one closer to the air filter.

I am hoping that your mixture screws are set too far out and the saw is just running rich.

The back each one to 1 1/2 turns out to start.

Well, i kinda screwed this one up. The low speed screw took less than 1/2 turn to seat. The high speed screw took between 1 1/2 and 1 3/4 turns to seat. I then backed the high speed screw out 1 1/2 turns. However when I began to back out the low speed I got distracted and was going to start over by reseating the screw and then backing out again. When I first started backing it out I kno I didn't go over 1/2 to 1 full turn but when I began to reseat it, it took at least 2 full turns maybe more to reseat. I don't know why it felt seated the first time. Perhaps the edge of my screwdriver wasn't fully on the screw and caught on something, i don't know. But the first time I seated it the screwdriver groove as pointing at about 1 and 7 o'clock, the second time it was at 12 and 6 o'clock just like the high side was when it was seated. Sorry.

I cranked it up and fuel is still coming out of the carb throat. It is still idling about like it was last night but I may have missed something that I didn't know. Today I disengaged the chain brake and initially it ran much better, almost perfectly. It would rev up and down with the throttle but it seems to be "stuck" in high gear. As soon as the chain brake is disengaged the chain starts moving at a much higher rate than "I" think is normal. But I didn't play with it much because as I worked the throttle back and forth it seems to progressively run worse so I just shut it off.

And here as a couple of gratuitous pics cause I like taking pics.
I am assuming that the yellowish tube is the tank vent. I didn't mess with it.

 

[huskihl]

Sounds to me like both screws (but particularly the h) need to go in a1/4 - 1/2 turn. Try turning h in a bit and check if it's better

 

[bigbadbob]

Have you tried backing the LA screw a bit , it is on top of the airbox .
It controls the idle speed, not the mix,, but they do go hand in hand.
BBB

 

[bottomcat]

Sounds to me like both screws (but particularly the h) need to go in a1/4 - 1/2 turn. Try turning h in a bit and check if it's better

When I first turned the hi side in 1/4 turn it wouldn't even crank. When I backed it back out to 1 1/2 it did crank. After it cranked I then turned it back in 1/4 turn and it would crank then but with the same effect. When I disengage the chain brake it seems to go to full throttle on it's own. And now the throttle trigger seems to have no effect at all. Earlier some one mentioned that it sounded like it was sucking air in somewhere. I'm wondering it that misformed intake sleeve is still a suspect.

i took a video of me cranking it and it running but couldn't figure out how to upload it. after watching it myself i'm not sure it would help much anyway.

 

[JonCraig]

Take pics of each needle themselves. Sometimes the needles can be damaged.

Also, what's the exact model number of the carb? Walbro has at least one oddball whose initial adjustment is something weird.

 

[bottomcat]

Take pics of each needle themselves. Sometimes the needles can be damaged.

Also, what's the exact model number of the carb? Walbro has at least one oddball whose initial adjustment is something weird.

May be a few more days before I can mess with it again.

How do I get to the needles? Are they under the set screws?
And where do I look for the model # on the carb?

 

[bottomcat]

Have you tried backing the LA screw a bit , it is on top of the airbox .
It controls the idle speed, not the mix,, but they do go hand in hand.
BBB

sorry bob, missed this earlier. No I haven't done anything to that screw but I can't speak for the feller that previously worked on it. What does LA stand for?

 

[JonCraig]

May be a few more days before I can mess with it again.

How do I get to the needles? Are they under the set screws?
And where do I look for the model # on the carb?

The set screws are the needles. Take one out and you'll see.

There aren't red & white plastic things on the screws, are there?

 

[Brettl]

The LA he refers to is a idle adjustment screw. It contacts the throttle lever, letting It open more or close.It doesn't change the fuel to air mixture.

 

[HarleyT]

The model number is beside the fuel inlet nipple.

Should be this one. Click on it to make it big.........

 

[Scott Kelly]

Can someone give this fine gentleman instructions to upload the video? I would but I'm not sure how either.. I think that will help us greatly to diagnose the running issue.

 

[bottomcat]

The set screws are the needles. Take one out and you'll see.

There aren't red & white plastic things on the screws, are there?

No there aren't red & white plastic things on the screws. I'll be a bit nervous taking them out. Do i need to worry about small parts that will drop off or dislodge making reinsertion difficult?

The model number is beside the fuel inlet nipple.

Should be this one. Click on it to make it big.........

That blow up "looks like" mine from what I've seen. Here is a pic of what I think you're talking about. In case you can't see it well on the left side are the letters WT and underneath them the numbers 16. Center of the body next to the nipple inlet are K3.

 

[bottomcat]

Well i figured out how to upload a video but i don't think it's going to be much help. If anyone wants a better one I'll retry.

 

[JonCraig]

Nothing will fall out. There's probably a spring around the outside of the screw. Just don't lose that.

You might search on YouTube for "Walbro carb rebuild" or something like that. Video is way easier to learn from than pics, much less words.

 

[bottomcat]

Nothing will fall out. There's probably a spring around the outside of the screw. Just don't lose that.

You might search on YouTube for "Walbro carb rebuild" or something like that. Video is way easier to learn from than pics, much less words.

thanks jon, i'll pull them and post when i can.

 

[Adirondackstihl]

I think a few things are going on there.

1) Air leak - on a saw of that vintage, I recommend replacing the impulse hose, fuel hose & fuel filter. When you're replacing the impulse hose, inspect the intake boot for rips or tears. You'll need to remove the fuel tank to do this. It sounds scarier than it is.
I just rebuilt an 028 that had a torn intake boot and rotten crank seal.

2) Clutch problems - could be a bad sprocket bearing or broken clutch spring(s).

 

[Adirondackstihl]

Another possible air leak could be a crank seal. This is from the 028 I just finished......

 

[Scott Kelly]

A pressure/vacuum test would tell the tale pretty quickly.. sounds pretty hokey I know but, get a small piece of hard plastic tubing and a few vacuum fittings from o reillys. Hook the hose up through the impulse line, plug the intake with your finger, cut some inner tube to go between the muffler and exhaust flange.. Suck on it or pressurize it gently with a compressor (regulator). At least then you'll know if you have a bad seal impulse line ect..

 

[Adirondackstihl]

A pressure/vacuum test would tell the tale pretty quickly.. sounds pretty hokey I know but, get a small piece of hard plastic tubing and a few vacuum fittings from o reillys. Hook the hose up through the impulse line, plug the intake with your finger, cut some inner tube to go between the muffler and exhaust flange.. Suck on it or pressurize it gently with a compressor (regulator). At least then you'll know if you have a bad seal impulse line ect..

By the time he did all that he could have changed the $7 hose