028 WB Piston / Cylinder condition

[shimanok2]

Hello All,

First post here although I've been using this site for quote a while now.

As the title implies I've got a few questions about what my next steps should be in rebuilding an 028 WB picked up off CL for $60. The saw ran, barely, but was very clean so I figured why not. After more cleaning, replacing the impulse line, fuel line/filter, carb boot, plug and installing a new electronic coil I cleaned the carb and test ran. It idles and accelerates well after tuning but doing a few test cuts it seemed to bog down some. I'd say it had the same, maybe even less power than the 024WB I just rebuilt which didn't seem right. In checking the compression it was consistently 130 (024 was 145) which many opinions deemed OK at best, some low though, so I removed the cylinder and piston for inspection and hopefully some cleaning! I haven't torn into something like this in a while either so I figured it would be a good learning experience as well. The rings aren't stuck and there's only mild scoring on the piston and cylinder. It doesn't seem too bad though. Oh, it's the 44mm version, not 46mm, and does have the full chain brake.

So what are your thoughts here? Am I looking at something worse than I think? In my readings on this site I saw a lot of "150+" compression numbers to have a great running saw. I'm sure it varies with the models but does this hold true for the 028?

What about cleaning everything? is there a best practice for doing this? I have at my disposal a paint can of carb cleaner, a baking soda blaster and a plastic media blaster (via work). Obviously any other chemicals could be purchased as needed.

Thanks in advance for all of the input!

 

[Wood Doctor]

I have rebuilt several 028 WB chain saw top ends. It's worth it. The new piston and cylinder will make the saw run like a dream. It's rather rare that the crank seals are gone. Just rebuild the top end with a new piston and cylinder kit. It's a pro saw, so it will be rather easy to work on compared to a clam shell.

 

[shimanok2]

Thanks for the reply Wood Doctor. If I’m replacing both the piston and cylinder should I just upgrade to the 46mm / super top end? Would I be able to keep the same carb and tune it properly?

 

[Wood Doctor]

Thanks for the reply Wood Doctor. If I’m replacing both the piston and cylinder should I just upgrade to the 46mm / super top end? Would I be able to keep the same carb and tune it properly?

I would vote for that upgrade. That's what I did. Yes, you can likely keep the same carb. I have replaced carbs on these saws as well. They do not last forever. Likely, your engine is 20 years old or more and could have run for hundreds of hours.

 

[shimanok2]

Will do. I was just planning on ordering an OEM base gasket unless told otherwise. What about break-in of the new Piston/Cylinder? Tune it rich or maybe run 40:1 for the first couple tanks?

Thanks again for your input!

 

[Wood Doctor]

I always run 40:1 most of the time. Just let it fast idle for a minute and then cut wood to your heart's content. Tune carb as needed. Many have reported here that the Stihl 028 AV Super should never have been discontinued. I must admit that I agree, even though I own a pair of 026 PRO's.

 

[67L36Driver]

I don’t generally mess with an 028. It’s just 45cc and there are plenty others out there that size worth some effort.

OTOH, an 028 super is almost as good as an 026. [emoji106] It’s the size & weight penalty.

Be careful of 028 mufflers and AF covers as they have become scarce.

 

[pioneerguy600]

I don’t generally mess with an 028. It’s just 45cc and there are plenty others out there that size worth some effort.

OTOH, an 028 super is almost as good as an 026. [emoji106] It’s the size & weight penalty.

Be careful of 028 mufflers and AF covers as they have become scarce.

The 028 earned a reputation of being dead nuts reliable, they still are for many weekend firewooders but the 026 is a more modern platform, just becoming outdated as faster lighter saws come on board. I to have taken a liking to the 026, they are my go to saws of the 50cc class. Once ported they cut well beyond what they were stock but not quite as fast as the quad port saws are now. Well built, parts are cheap and easy to find, easy saw to work on so not a lot not to like.

 

[shimanok2]

HI all,

Thanks for the advice. So I ended up putting an aftermarket 028 super top end on and even tuned rich it seems to run better. It definitely start better too, as in first pull choked. It would be 2-3 pulls prior. I read so many different opinions on break in I just chose to idle it for 5 minutes while adjusting the carb and idle speed then a cool down. An hour or so later I let it warm up again and then cut some small stuff I had lying around for about 20 minutes. I'll probably keep on doing this with longer cutting times and just keep re-adjusting the carb as needed.

Speaking of, I noticed in the manual the max RPM is 12,500 but increases to 13,000 for the 028 super. Should I tune to the latter now given the upgrade? On a tuning note I've never been able to tune by ear, so typically tune to RPM and keep it on the rich side by a few hundred.

Thanks again for all of the input!

 

[Wood Doctor]

Either 12.5K or 13K should work fine. Congratulations on the workmanship. Here's one of mine.

 

[shimanok2]

Thanks again Wood Doctor. Your muffler looks different, I'm guessing that's either a "super" addition or maybe a later year switch?

The saw came with a Stihl Bar and Chain but I now realize the chain is a low kickback version with double bumpers. A coworker said it's the older style green chain too which he thought was even worse. It's not in bad shape so could I just file down the bumpers some?

 

[Wood Doctor]

Thanks again Wood Doctor. Your muffler looks different, I'm guessing that's either a "super" addition or maybe a later year switch?

The saw came with a Stihl Bar and Chain but I now realize the chain is a low kickback version with double bumpers. A coworker said it's the older style green chain too which he thought was even worse. It's not in bad shape so could I just file down the bumpers some?

Yes, but that will induce more bite and likely you will notice rougher cutting. Here's an even older version of he 028 WB that I sold for $200. The new owner loves this classic:

He says he really doesn't miss not having a chain brake. I outfitted this one with an 18" bar. I think it had the original top end but very few operating hours. it might be five years or so older than the one I pictured in post #10.