Stihl 021 023 025

[toolmaker]

So I recently jumped the gun and bought a Stihl 021.
All I want it for is a "camp saw" for around camp and for the front rack of my ATV for clearing trails.

I found out later that the 021 023 and 025 all share the same "chassis"
The 021 is 2 hp, the 023 is 2.5 hp, and the 025 is 3 hp.
If I am unhappy with the ponies of the 021, I may consider getting a cylinder and piston from an 025 and swap them out.

Will the carb from the 021 be enough to run the bigger displacement of the 025?

Thanks!!

 

[Ozhoo]

Nothing wrong with a knock-around 021.
Yes, the all share the same carb... some variant of a WT, I forget which.

 

[toolmaker]

Thanks for the reply Gary.
My saw arrived today and I am really impressed, I think I got a great deal. It is VERY clean and well-kept.
Fires right up and runs strong. It look it for a ride tonight on my ATV with me and played with it a little. It made short work of some small stuff up to 5 or 6 inches.
I sunk it in to a piece of 10 to 12 inch red oak and there was a lot to be desired though. I also must bear in mind that I am used to much bigger saws.

Tell me. What is the physical difference between the 021 and 025 inside the motor?
Is it just bore diameter or is the crank stroked or both?

Here's what I am thinking:
I see these 025 engine kits on ebay for dirt cheap. I am thinking of buying one and throwing it in. If I can buy another pony for 30 or 40 buck, that's plenty cheap enough for me. If it blows up, I can put the 021 engine innards back in.
Your thoughts?

 

[HarleyT]

No, the 021 is different, innard-wise

 

[HarleyT]

 

[Finnrpm]

Would not fix a good runner, but if needed would try this one https://www.hlsproparts.com/Stihl-025-MS250-023-MS230-short-block-kit-p/h30251-dns.htm

I have 023 and it is a great small saw for light cutting work.

RV

 

[DND 9000]

Will the carb from the 021 be enough to run the bigger displacement of the 025?

Yes it should be possible to use the same carb.
The difference between the fixed jet size of the 021 carb WT-503A and 025 carb WT-283C is 0,03mm. That`s why I think it can be adjusted turning the carb adjustment screws.

 

[tallfarmboy]

I just want to add my $0.02, I purchased an MS250 kit on ebay for a neighbors saw that was toasted... Anyway, I only got the cylinder, not the pan... When I installed the new cylinder onto the Stihl factory pan, the crankshaft bearings could move up and down between the 2 halves. If I were buying a cheap top end, I would make sure that I get the matching pan to hold the crankshaft properly.

 

[nenicu]

The stroke is bigger on 023. The 021 is 40x30mm, the 023 and 025 have the same crankshaft with diferent cylinders: 40mm -023 and 42,5-025. The 023 crank has a stamped steel rod, the 023 has forged rod.

 

[nenicu]

I did a 023 recently and the aftermarket engine pan worked ok. The aftermarket cylinder can be shaved a little .

 

[BB Sig]

So would an 025 short block fit in an 021 body? I assume yes. Is there anything else that would be needed to upgrade the 021 to an 025? It was already stated that the carb from the 021 should work in the swap.

 

[HarleyT]

Otherwise it is the same, they did put out a slightly higher output oiler, but otherwise the same.

 

[BB Sig]

Sounds good. A new oiler makes the juice worth the squeeze.

 

[HarleyT]

I doubt if you would need it, might not be worth the effort.

 

[toolmaker]

I went ahead and pulled the trigger on a short block for an 025. It comes completely assembled except for the pan.
This is gonna be interesting.........
Like I said, I don't have a lot of money in it, so if it blows, I can go back to the OEM 021 engine.

 

[Walter Glover]

Picked up a well used 025 at a shop for the core price of $35.
Needs oversize bar studs, oil cap and replaced the gas vent with a Homelite duckbill
A good cleaning and I have a runner.
Pleased with it

 

[Walter Glover]

Checked the muffler and it seems pretty open. Biggest restriction being the deflector plate.
Runs pretty good for a basket case. I guess with todays shop rates plus parts a saw will quickly get wrote off!
Makes for a pile of fun for guys like us eh!!