OK as is or More Tuning ?

[frontporch]

I have a Stihl 024 Yard Boss made in VA. Not sure of its age, but older.

It was bogging down on throttle badly, so I changed the carburetor with one from Amazon

New carb responds well to throttle but idled VERY high and smoked when I ran the speed up.

I turned out the idle screw and now its slower, but seems to not return to the low idle all the way after exercising the throttle.

The smoking is my primary concern. I believe the gas/oil mixture should be good, but I can go through that again with newer gas.

I could probably also stop the chain with the break when it is at that idle where the chain might spin a little.... I understand the danger in a moving chain.

All thoughts for any steps that I can take to improve this saw are appreciated. I don't plan on using the chainsaw much but I might cut down a small tree or two, so it would get a few hours of use here and there.

 

[Bob Hedgecutter]

My guess- it has a massive air leak- do NOT continue to run the saw or it will run no more.
It could be the unbranded Amazon carb- these can be good or they can be shocking- they are usually no where near spec when it comes to tuning and some need two full turns out to run anywhere near rich enough on the H circuit.

So I am picking you are WAY lean because of the carb- or WAY lean because of an air leak.
Best carb to ever go on a saw is the one they came with. If you still have that carb- clean it and put a kit in it, odds are it will be 10X better than the Amazon replacement.
Then you need to go through possible air leaks of the intake manifold between carb and cylinder, fuel line to carb, impulse line and if you do not find any cracks/splits/pinholes or tears there- suspect the main oil seals on the crank- pressure and vac test those.
If you are not confident doing this, take it to a shop that will do it for you.

Could be, trying to tune out an air leak is already scoring the piston- remove the muffler and look at the face of the piston through the exhaust port of the cylinder- if it is scored up- you have bigger problems.

The 024 is a nice wee saw and deserves looking after- smallest magnesium cased saw Stihl made that was still a rear handle saw.

Another thought- when you took the old carb off to put the new one on- you didnt end up with a couple of funny looking washers still on your bench?

 

[frontporch]

Hello Bob. Thanks for your reply.

I did break down the carb that came with the chainsaw. it was bogging down badly when the throttle was run up. It was so bad it couldn't really be used. On carb disassembly I didn't turn any screws, just took it apart to look for what didn't look right. Overall it was pretty clean except for a screen that was covered in muck. I sprayed that clean and reassembled. I didn't replace any seals/diaphragms, but none were torn. Unfortunately I lost the small screw that holds the spring and lever on the fuel valve. I found something close and put it back together. I don't think the replacement screw made it any worse. It still had the same issue of bogging down.

The Amazon carb is a Chineese walbro. I have read about chainsaw tuning, but didn't want to make any changes to any settings with the hopes that they got it right. I have had pretty good success with other replacement carburetors, but mostly on 4 stroke engines.

Honestly I didn't change anything else in the saw. The carburetor came off with some issues... the linkage was a challenge, but for the most part I cleaned and reassembled. No funny washers were left from the removal. I didn't replace any seals. The kit purchased was meant for a more recent saw, so fuel lines and other parts were not right. It came with a new intake ( I assume the rubber boot was that part) but I didn't break down the saw any further.

Like the original post said, it started easily, ran fast but nice. Good reaction to the throttle, fixing the original issue and the only issue was idle speed and smoke. Smoke was present when I used it last. I cut a few small trees and it seemed to have issue running for a while making a horizontal cut.

 

[Bob Hedgecutter]

Racing at idle, excessive smoke, high revs = air leak.
This is still very much the diagnosis I am leaning towards- but you can never trust an aftermarket carb either.

If the fuel screen in the original carb was blocked with fines- the rest of the carb very likely is as well and a good cleaning will probably sort that carb back out, fitted with a new OEM carb kit, it will probably outlast you.
I would take the saw and original carb to a trusted Stihl shop and ask them for their diagnosis, have them clean and kit the carb and repair any air leak.
In my opinion- if you continue to run it as is- I believe in a very short period of time you might end up with an uneconomic repair type door stop.

I also do not trust Amazon type aftermarket rubber component kits- they usually do not last for long- but when the carb comes off these Stihls there are two small metal components (washers) that seal the carb to rubber manifold joint- if these get lost and or go missing, the saw will suck air at that point.

If it were my saw, or here for repairs- all those rubber components would be checked for damage first and foremost.

 

[frontporch]

Any sources for OEM parts or carb rebuild kits? I had trouble finding parts for the 024AV.

 

[Bob Hedgecutter]

Any sources for OEM parts or carb rebuild kits? I had trouble finding parts for the 024AV.

Sorry no- I live on the other side of the World and I am not much use at suggesting local shops that might help over in your part of the World, however if the saw is running a Walbro carb- a Walbro kit will be available for it.