028 Wood Boss

[Pounce2181]

Hello new to the forestry forum.

We have a 028 wood boss that we got off ebay looked great, seller said it ran great, had 100% feedback. Well it runs good for a few seconds then only idles. try to rev it and it bogs. put your finger slightly over the carb opening and it will scream.  Rebuilt carb everything was clean. I am figuring it has something to do with the impulse signal from crankcase. After disassembling the simple things noticed the jug had a price wrote on it and removed the muffler completely and piston and cylinder looks to be new rings look to have seated well. My question is what next? lol  is it worth the trouble? I hear these are great saws thats why we got it. If I need to go into it further I may need to try to find a service manual. I have never had to go this far into a stihl or any saw for that matter. Does anyone know where to get to a online service manual?  Thanks any info would be greatly appreciated. 

[Mad Professor]

Impulse line, intake boot, and/or crank seals.  A vacuum/pressure test will tell the tale.

[Hilltop366]

Hi and welcome.
I don't think putting your finger slightly over carb makes the fuel pump work any better, sounds like there is an obstruction in the carb. or running lean for another reason.

[Rocky_J]

Ditto to the two posts above. These guys are quick, stole my thunder!  :D 8)

[Pounce2181]

I think my problem is i bought something thats already been tinkered with ha ha. It just seems not to spit fuel when trying to rev and with the finger obstructing airflow it spits fuel.   the carb had looked to have been rebuilt before i got it after comparing the new kit with what I took out. The carb when i take off the plate that has the impulse inlet it had the blue plastic against the body then a fiber gasket then the plate. Looking the walbro site at a diagram it shows 3 layers the third being a rubber type. If i recall right. So I might need to research more on the carb. The walbro site seemed to be pretty generic. So I feel lost looking at it.

[rickywashere]

check the kill switch wire may have a place rubbed in it trace it and look close

[sablatnic]

Can't remember, but does the 028 have the choke valve in the air filter. If it does, the problem could be caused by a slack return spring. The previous owner could have tried leaning it on the H, and screwed up the symptoms. Seen it happen to 026's.

[Pounce2181]

thanks for the info pretty sure its a fuel problem now gonna research the carb again before i go any further. From what i see on the walbro site the saw looks like its missing a layer (from my previous post).

[Al_Smith]

Can't remember, but does the 028 have the choke valve in the air filter. If it does, the problem could be caused by a slack return spring. The previous owner could have tried leaning it on the H, and screwed up the symptoms. Seen it happen to 026's.

Actually the 028 does have the choke built into the air filter just like the 038 models .

I always thought that was kind of stupid or maybe just Stihl being Stihl .They can't help themselves at times . :D

[joe_indi]

There is a non return valve also called a valve jet (brass knob sticking into the carb barrel).
Chances are that the disc inside the valve is stuck.
This causes air to blow back into the metering chamber and lean out the fuel.
An easy cure (if it works in your case) would be to start the saw with the air filter removed.
While you blip the throttle, have someone shoot very short bursts of carb cleaner into the carb.
If its your lucky day, this will get the disc clean and get it working again.

Joe

[mike_van]

I think Joe is on the money with the sticking disk, especially if you believe the seller that the saw was a good runner.  Be careful however using any fuel [carb cleaner, ether, etc] right through the carb to run a 2 stroke, as with this method you don't get 2 cycle mix drawn through the crankcase. For the few seconds you'll be doing it, you should be fine. There are those that would run a saw wide open doing this, then wonder why it siezed.

[Pounce2181]

Thanks for all the info. I will let yall know what worked. Hope to get in it more this weekend. Supposed to be rainy won't have much else to do.

[Pounce2181]

Another question...The fuel tank vent...should you be able to notice by blowing through it that it works?  Looks clean, but I am not noticing any leakage when blowing through it.

just one of my discoveries on the way down

[Al_Smith]

 A couple of things .

If you question the tank vent,loosen the fuel cap .That should tell the tale .

Try richening up the low speed jet a tad .Going from low speed to high speed there has to be enough pressure drop accross the venturi to draw fuel from the high speed jet .

If those soft parts in the carb get assembled out of order they can cause you all kinds of grief and believe me it's not too hard to get them out of order .I've certainly done so many times and I'm sure I'm not alone at that if people are honest about it .

The heigth of the fuel lever is very important .Too low and you would not  fill the carb enough for high speed operation .Too high it will flood out .

A little trick when the metering diaphragn gets stiff from old age is to set the lever just a tad high .It's not a cure all but more so a bandaid and only perhaps prolongs a carb rebuild at best for a short time .