Stihl 028 AV

[coldfrigman]

Hello. Was given an old Stihl 028 AV. I went through it replacing air cleaner, new Carb Tilletson, gas filter, plug. I get the unit to idle, but when trying to set the high rpm speed, I can get it to 13K, but machine runs lousy. It doesn't run well, or cut well, seems way too slow. When I lean out the mixture slightly , I am able to get it to 14K to 15K, and it seems to run great. I am using a chainsaw tach to do this. The carb set screw is still more than 1 & 1/4 turns out from bottoming out. Is there any harm running it to a higher rpm, and if so, any ideas how to correct it? I am going to put on a gasket when mounting the new carb (even though one was not on the original) to the motor head, to see if that makes any difference. Thanks for any help.

 

[Wood Doctor]

At 13K you are already above the MFG recommendation, You are aware of that? Are you trying to kill this saw by running it at at 15K or use it to cut wood? Please check this out:

 

[buzz sawyer]

I've had to replace the coil/module on two of these due to poor running.

 

[Wood Doctor]

I've had to replace the coil/module on two of these due to poor running.

Interesting. I have owned at one time or another six Stihl 028 chain saws and never had to replace an ignition module on any of them. I still own two of them. They are both very dependable.

 

[coldfrigman]

Not trying to kill the machine. The 028 is 12,500, and the 028 AV Super , which I have calls for 13,000 rpm max. That is my problem, when I set it to below 13K, it bogs out, even with low idle set well. Any thoughts ? thanks

 

[buzz sawyer]

Interesting. I have owned at one time or another six Stihl 028 chain saws and never had to replace an ignition module on any of them. I still own two of them. They are both very dependable.

I was surprised too. Both were cutting out when hot. Replacing coils finally corrected them. There have been other posts on this.

Not trying to kill the machine. The 028 is 12,500, and the 028 AV Super , which I have calls for 13,000 rpm max. That is my problem, when I set it to below 13K, it bogs out, even with low idle set well. Any thoughts ? thanks

I'm wondering if someone has modified something in the past, like timing. Can you hear it 4stroking when it's running good? Have you used the tach for setting other saws and has it given correct readings? Just trying to cover all the bases.
As long as you can hear it 4 stroking out of the cut and hear it clear up in the cut, I'd probably run it awhile and keep listening. Also check the plug for color.

 

[coldfrigman]

Ok, I was able to get carb settings straight on my 028. Have high rpm under 13K. Problem now is when I try cutting anything the saw bogs down, slows chain down, etc, won't cut. Any more thoughts?

 

[TheTone]

Checked for air leak?

 

[buzz sawyer]

OK, I'm brainstorming.
I'll ask the dumb question - is the chain sharp?
Does it still rev ok out of the wood right after it bogs?
What is the compression? What does the piston look like through the exhaust port?
Any chance the flywheel key was removed and timing altered?
Do you still have the old carb to try, even if it needs a kit?

 

[Wood Doctor]

You replaced the fuel filter and the fuel line seems OK, right? If so, now replace the carburetor, assuming that you still have good compression as Buzz asked above in post #9. Verify that compression.

 

[coldfrigman]

I can try swapping to the old carb. I did replace the fuel filter, but not the fuel line. I will try to get an oem fuel line to use, since I heard the aftermarket are garbage. It runs pretty regular at most rpms, but once I hit a piece of wood, it trys to die, and would if I left it in contact with the wood.

 

[coldfrigman]

also air leaks....where would I look ?

 

[coldfrigman]

I checked for air leaks around new carb to engine (cut a gasket), but besides the old fuel line to new carburetor inlet nipple, is there anywhere else I should be looking? Thanks

 

[dmb2613]

yes, pull the muffler and look at the piston

 

[dmb2613]

I am betting it is toast

 

[coldfrigman]

don't mean to sound to stupid, but what am I looking for on the piston? how would I see air leaks, if that is the case?

 

[67L36Driver]

Spark screen plugged up some?

 

[coldfrigman]

cleaned screen, was not bad

 

[Mad Professor]

don't mean to sound to stupid, but what am I looking for on the piston? how would I see air leaks, if that is the case?

Scoring on piston.

Leaks can also be impulse, air boot, or seals.

Did you replace fuel line yet? Sometimes cracks are not evident until you bend it some.

 

[coldfrigman]

I replaced the fuel line. I was able to start to cut wood, then saw rpm bogged down. I noticed now even when not under load, the saw has a hard time to maintain the proper rpm on high idle throttle up. Once the unit really heats up, I notice the rpms start to slow and won't maintain once hot. Again, when not under load. Could this be a bad coil symptom ?