Stihl 026 sometimes starts super hard and sometimes loses power at WOT

[gary-stihl]

Hey friends. I have an older Stihl 026 and sometimes it starts super-hard (when left cold for a while, or even when it is warm [e.g., put it down for 45 mins after running it for a while]).

It also will lose power at WOT (wide open throttle) whilst cutting - just starts to bog down, then I ease up on the cutting blade, and it revs back up.

All sounds like fuel delivery issues to me. I do keep the air cleaner, spark plug, etc in good shape and run 93 oct 50:1 gas.

My question is - I see TONS of aftermarket carbs made in china claiming to work on the 026... are these worth it or no? Reason I ask is I first see lots of them, and second, I have had luck with some of these with my other equipment (lawn mowers, snowblowers). Or, should I stick with Stihl branded?

I haven't pulled much apart yet on the saw but need to tackle this soon. Also, where can I find the carb model stamped on the carb itself? Not sure if I have WT-22 or WT-194 or something else.
thanks mates.

 

[SteveSr]

Hey friends. I have an older Stihl 026 and sometimes it starts super-hard (when left cold for a while, or even when it is warm [e.g., put it down for 45 mins after running it for a while]).

It also will lose power at WOT (wide open throttle) whilst cutting - just starts to bog down, then I ease up on the cutting blade, and it revs back up.

All sounds like fuel delivery issues to me. I do keep the air cleaner, spark plug, etc in good shape and run 93 oct 50:1 gas.

My question is - I see TONS of aftermarket carbs made in china claiming to work on the 026... are these worth it or no? Reason I ask is I first see lots of them, and second, I have had luck with some of these with my other equipment (lawn mowers, snowblowers). Or, should I stick with Stihl branded?

I haven't pulled much apart yet on the saw but need to tackle this soon. Also, where can I find the carb model stamped on the carb itself? Not sure if I have WT-22 or WT-194 or something else.
thanks mates.

Symptoms could be a lot of things from fuel delivery to roached piston and cylinder.

Before you do anything else pull the muffler cover and post some photos of the piston as viewed through the exhaust port.

 

[ballisticdoughnut]

I agree with inspecting the piston as mentioned above. If that checks out rebuild the carb and replace the fuel hose and filter. No need to replace the factory carb with chicom carb. Also inspect the pulse hose for cracks. Another thing to look at is the choke flap in the air filter. If the spring is missing the flap will close at WOT and choke the saw out.

 

[sean donato]

Another thought on the choke, is the cam worn down that actuates it, it won't close the entire way and makes cold starts a bugger.

 

[alexcagle]

Pressure check your fuel pickup hose through the fuel cap opening. Hook the hose and yank it out. Wallah

 

[alexcagle]

Check for these too. Lol

 

[singinwoodwackr]

Check the muffler screen

 

[ZeroJunk]

View attachment 1088162
Check for these too. Lol

A few more turns and they would have the plug in.

 

[grizz55chev]

A few more turns and they would have the plug in.

Ran when parked.

 

[ZeroJunk]

Hi, the carb model will be stamped on the carb. The Chinese clones work OK, usually. But, you can buy a kit. Not much to wear out on a chain saw carb. The kit parts get stiff with time. Rare to see one worn to the point it is leaking around the shaft, etc.

Worn saws lose compression as everything heats up. Just the way of things.

The choke in the air filter was iffy from the start.

Going back to the original response. Take a picture of the piston through the exhaust port.

That will be key to seeing what your problem is.

 

[gary-stihl]

View attachment 1088162
Check for these too. Lol

What is that crap all over it?!?!

 

[gary-stihl]

Shots of the piston through exhaust port
Tried to get it at various steps along the upstroke

 

[gary-stihl]

Shots of the carb.
- IMG-8051 at idle
- IMG-8052 at choked, starting
- IMG-8053 - WOT
all, obviously taken whilst the saw is not running mind you

 

[singinwoodwackr]

Shots of the piston through exhaust port
Tried to get it at various steps along the upstroke

Dang, that’s a lot of carbon

 

[SteveSr]

Shots of the piston through exhaust port
Tried to get it at various steps along the upstroke

Not great photos but piston doesn't look scored.

It does look like it is covered in either oil or gas. BTW, what are you using for oil and gas? Looks like whatever it is is generating excess carbon which may eventually be problematic.

Before reassembly remove the muffler screen and burn it clean with a torch. It is unlikely this is your problem unless you find it clogged but should be done periodically.

 

[SteveSr]

Shots of the carb.
- IMG-8051 at idle
- IMG-8052 at choked, starting
- IMG-8053 - WOT
all, obviously taken whilst the saw is not running mind you

A compensating carb possibly a WT-426 or WT-394. You will find the model stamped on the side of the carb. Either of these should be rebuildable with a GENUINE Walbro kit.

 

[gary-stihl]

last, best shot I could get of the exhaust screen and also the spring on the air filter is present and operational (second pic)

 

[gary-stihl]

Not great photos but piston doesn't look scored.

It does look like it is covered in either oil or gas. BTW, what are you using for oil and gas? Looks like whatever it is is generating excess carbon which may eventually be problematic.

Before reassembly remove the muffler screen and burn it clean with a torch. It is unlikely this is your problem unless you find it clogged but should be done periodically.

Yeah, sorry, my phone doesn't have a macro mode (iphone 13 mini) so hard to get close-ups. The piston did look smooth.
See picture I just posted of exhaust screen, not clogged, near as I can tell?

For oil, I use the 2 cycle oil for marine engines (used to have a 2-stroke Force 70HP) mixed with 93 octane gas (unfortunately, ethenol-enriched; sometimes I can get lucky and get real gas). I'm pretty careful with the measurements of oil : gas, 2.6oz oil to 1 gal of gas. Use this for my other two cycle engines as well (a few echo leaf blowers, weed whacker, and i have a Stihl 036 that runs super strong and never have an issue). What could be causing the carbon buildup?

 

[gary-stihl]

A compensating carb possibly a WT-426 or WT-394. You will find trghe model stamped on the side of the carb. Either of these should be rebuildable with a GENUINE Walbro kit.

Do I need to remove the carb to find the number? I am thinking "yes" to that question.

 

[singinwoodwackr]

Clogged air filter and it looks like the exhaust port is about 1/4 clogged, or more. It can’t breathe.