Stihl 020 Super Surging at High RPM

[bulletpruf]

Fellas - Finishing up the build on an 020T Super. Rebuilt the Walbro carb. New rings. New fuel lines and fuel filter. Did not split the case and did not change crank seals. Running fresh pre-mix fuel. Had points ignition with weak spark so swapped to electronic from a parts saw. Set flywheel gap at a thin business card. About the only thing that is sub-optimal is the spark plug wire; it's a bit sketchy, but no bare wire showing.

It tuned fine on the low speed jet - idles at 2,800 but when I went to tune the high it was surging at high rpm - basically from about 8,000 - 14,000.

That's a new one for me. Any ideas? I do have a spare carb that I can rebuild and swap on.

Thanks

 

[Dean-O]

Have you done a pressure and vacuum check? Could have an air leak.

 

[Vintage Engine Repairs]

It’s my understanding air leaks will present themselves at idle too, which yours doesn’t seem to be doing?

What is your tank vent like? it may be worth taking the vent off or tank cap off and see if at WOT the problem persists. Doesn’t hurt to swap carbs if the vent isn’t your issue if you have a known good one.

 

[trains]

Sounds like a possible issue with the pointless ignition system you installed, remember that issue you had with one of your earlier saws Vintage Eng rep ?

 

[Vintage Engine Repairs]

Sounds like a possible issue with the pointless ignition system you installed, remember that issue you had with one of your earlier saws Vintage Eng rep ?

Hmm the 07? That one didn’t surge, but actually wouldn’t hit WOT and misfired had no power in the cut. I wish I still had my old videos, I deleted them all!

 

[bulletpruf]

Have you done a pressure and vacuum check? Could have an air leak.

No, I have not. I might go ahead and change the crank seals since I have some new ones here.

Thanks

 

[bulletpruf]

It’s my understanding air leaks will present themselves at idle too, which yours doesn’t seem to be doing?

What is your tank vent like? it may be worth taking the vent off or tank cap off and see if at WOT the problem persists. Doesn’t hurt to swap carbs if the vent isn’t your issue if you have a known good one.

I was thinking the same thing. I'll run it today without the cap on before I dig too far into it.

 

[bulletpruf]

Sounds like a possible issue with the pointless ignition system you installed, remember that issue you had with one of your earlier saws Vintage Eng rep ?

If I end up tearing it down again, I'll swap the plug wire and tighten up the flywheel gap a tiny bit. Right now it's at the thickness of a thin business card, but I think that's just slightly looser than the factory spec.

 

[bulletpruf]

It’s my understanding air leaks will present themselves at idle too, which yours doesn’t seem to be doing?

What is your tank vent like? it may be worth taking the vent off or tank cap off and see if at WOT the problem persists. Doesn’t hurt to swap carbs if the vent isn’t your issue if you have a known good one.

Was working on another saw after work but I did fire up the 020 and run it without the fuel cap to see if that helped. No joy. Looks like it's time to swap carbs, replace plug wire, and install new crank seals. No biggie. I have some time before I'll need it.

 

[Vintage Engine Repairs]

Any updates on this saw mate?

 

[bulletpruf]

Any updates on this saw mate?

Not yet. I’m out of town for a few days.
Thanks

 

[huskihl]

It’s my understanding air leaks will present themselves at idle too, which yours doesn’t seem to be doing?

What is your tank vent like? it may be worth taking the vent off or tank cap off and see if at WOT the problem persists. Doesn’t hurt to swap carbs if the vent isn’t your issue if you have a known good one.

I’ve seen them idle all day, and rev up to the screw setting for a split second before screaming lean. It’s always an air leak. Usually the seals

 

[Vintage Engine Repairs]

I’ve seen them idle all day, and rev up to the screw setting for a split second before screaming lean. It’s always an air leak. Usually the seals

Ah ok! Thanks for that, I haven’t experienced it, but really good to know it happens, another piece of info to add to the knowledge bank.

 

[bulletpruf]

Back apart again. Got the flywheel side crank seal replaced. PTO side is out, but it's a lot bigger than what I have in the Stihl gasket kit. It looks like it's 26mm OD and 18 mm ID. Need to source that before it can go back together.

 

[axeman088]

If you have one of those old style square body 020 Super 's that crank seal is NLA from Stihl or anybody else for that matter . Good luck finding one. Been down this road myself. FYI the 020 Super never had points for ignition . The early older 38mm 020 did have the points ignition. The flywheels are not the same as the electronic version of that saw. Might be your problem. The Super is a 40mm engine and a couple different versions of electronic ignition. There really isn't much difference between the Super 's and non Super's . The mm bore is stamped on the cylinder so you can tell which 020 you have.

14,000 rpm is permissible for a 40mm Super 020 saw at WOT no load. The same as the present day ms 200's/201's T. the The old 020 never had that T after the numbers .

Not trying to be arrogant or some kind of know it all but I have several of those older 020's and 200's in both top handle and rear handle versions. When that T is put into the model number it is confusing as to which saw someone is talking about .

 

[bulletpruf]

If you have one of those old style square body 020 Super 's that crank seal is NLA from Stihl or anybody else for that matter . Good luck finding one. Been down this road myself. FYI the 020 Super never had points for ignition . The early older 38mm 020 did have the points ignition. The flywheels are not the same as the electronic version of that saw. Might be your problem. The Super is a 40mm engine and a couple different versions of electronic ignition. There really isn't much difference between the Super 's and non Super's . The mm bore is stamped on the cylinder so you can tell which 020 you have.

14,000 rpm is permissible for a 40mm Super 020 saw at WOT no load. The same as the present day ms 200's/201's T. the The old 020 never had that T after the numbers .

Not trying to be arrogant or some kind of know it all but I have several of those older 020's and 200's in both top handle and rear handle versions. When that T is put into the model number it is confusing as to which saw someone is talking about .

I have a crank seal on the way. Should be here in a few days. Appears to be the right one, but we'll see when it arrives. Also found some in Europe (UK and Germany) if this one doesn't work.

The saws are both 40mm.

Easy enough to swap ignition, so if these were both Supers originally and all Supers came with electronic ignition, it certainly could have been swapped at some point.

When I swapped ignition, I swapped flywheels too.

Thanks

 

[bulletpruf]

All fixed! But it was painful!!!

I did end up with an NOS crank seal that worked fine.

Also got the ignition wire fixed.

But then I ran into serious carburetor and flywheel issues - the carburetor was getting pulled into the flywheel as the magnets passed the carb. I tried several different ways of clocking the carb, making sure carb nipple was fully seated in the fuel line, making sure flywheel was fully seated, etc.

Those of you who mess with these know how much of a pain this is -- to remove the carb, you basically have to split the saw in half. You don't split the case, but you do have to remove the tank and recoil assembly from the rest of the saw. Then you have to pull the flywheel to get the carburetor off!

Anyway, I thought that the intake boot was the problem, so I swapped those around. And then I tried the other carburetor. And then I got a new intake boot, and it made matters worse!

And each time I tried a new fix, I had to put the flywheel back on, put the saw back together, etc.

If I had to guess, I would say that I took the saw apart and reassembled it about 40X!!! By now, I think I could disassemble and reassemble the saw blindfolded, sound asleep, hands tied behind my back, while whistling dixie.

Anyway, it's running great now! Idles well, tuned to 4 stroke slightly at WOT. Sunk it in some wood this weekend and it did great.

All I'm missing now is the operator presence handle piece for the throttle. If anyone has one to sell, please let me know.

Thanks for all the input!

 

[ajshoe]

All fixed! But it was painful!!!

I did end up with an NOS crank seal that worked fine.

Also got the ignition wire fixed.

But then I ran into serious carburetor and flywheel issues - the carburetor was getting pulled into the flywheel as the magnets passed the carb. I tried several different ways of clocking the carb, making sure carb nipple was fully seated in the fuel line, making sure flywheel was fully seated, etc.

Those of you who mess with these know how much of a pain this is -- to remove the carb, you basically have to split the saw in half. You don't split the case, but you do have to remove the tank and recoil assembly from the rest of the saw. Then you have to pull the flywheel to get the carburetor off!

Anyway, I thought that the intake boot was the problem, so I swapped those around. And then I tried the other carburetor. And then I got a new intake boot, and it made matters worse!

And each time I tried a new fix, I had to put the flywheel back on, put the saw back together, etc.

If I had to guess, I would say that I took the saw apart and reassembled it about 40X!!! By now, I think I could disassemble and reassemble the saw blindfolded, sound asleep, hands tied behind my back, while whistling dixie.

Anyway, it's running great now! Idles well, tuned to 4 stroke slightly at WOT. Sunk it in some wood this weekend and it did great.

All I'm missing now is the operator presence handle piece for the throttle. If anyone has one to sell, please let me know.

Thanks for all the input!

need to get some drive and flywheel seals. have drive seal as 9640 003 1890 (17.8 x 26.2 x 3.6) and flywheel seal as 9640 003 1190 (12 x 20 x 5). does anyone have a cross for these seals ?