"Porting" a Stihl 021

[CWME]

Been doing a lot of reading on the subject. I have a suitable(read that it was free) saw to play with so here goes nothing for my first try at it.
My goals are to widen the ports by about 1/8" and clean up the casting. Thats it no timing changes etc for now. Do a little grinding and put her back together to see how or if it will run again.

I started by marking the piston ring pins on the skirt. I then transfered this to the cylinder for the intake and exhaust so I know the limits of what I can do before risking catching a ring. I can't really do much to either port. For one the ends of the rings and two there isn't a whole lot of meat for either flange.

Anyway here are some pics of my layout etc.

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Edit: The carbon buildup was pretty unreal. The saw was way out of tune when it was given to me. I have progressively opened up the mufler so it can breath. Cleaning out the carbon that was on the top of the piston and coating the entire exhaust port would probably give it a "port job". You can still see some of the carbon on the top of the cylinder.

 

[CWME]

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Roughing in the flange on the intake and exhaust.

 

[MnSam]

Looks like you took out quite a bit. Of course make sure you can fully adjust your carb when your done, not sure what comes on the 021's. Good luck, I'll be anxiously awaiting your finished product.

 

[acguy]

OK, now what?

Post a vid on youtube so we can all feel that 021 adrenaline....

 

[logging22]

I like the 021 myself. Got one that runs pretty good. Wins most every time in the small class. Takes alot of prep to make it run well.

 

[CWME]

I still need to widen the actual ports. I need to get some new bits before I can do much more.

Not sure how much 021 adrenaline there will be:hmm3grin2orange: Running is a good goal for my first try. Shoot for spanking a Wild Thing later

 

[Stumpys Customs]

Looks like yer on the right track. I kinda like messin with the "cheapie saws" myself. It's amazing what you can git out of one.

 

[CWME]

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Found a carbide dremel bit at HD so I could finish up the ports. I still need to smooth them out a little but this is as far as I am going with this saw. I need to get the muffler cut out to match the new port dimensions. I won't get to that until tomorrow. Going to try to figure out how to film a movie and post it once I get it back together.

 

[ccicora]

If you look back far enough I stroked an 021.... worked well...for what it was

 

[MechanicMatt]

I still need to widen the actual ports. I need to get some new bits before I can do much more.

Not sure how much 021 adrenaline there will be:hmm3grin2orange: Running is a good goal for my first try. Shoot for spanking a Wild Thing later

Watch what you say, there's a few Wild Things I wouldn't mess with. Good Luck with your stihl!

 

[blsnelling]

Looks like you've perhaps lowered the exhaust floor, and in the process, made it convex. You're liable to catch a ring on that. If you've get enough piston skirt to keep it from free porting, I'd lower the center to get it shaped right.

 

[blsnelling]

Also, you don't want to go any bigger on the intake opening than what the boot is. Any more will just cause turbulence.

 

[diggers_dad]

Also, you don't want to go any bigger on the intake opening than what the boot is. Any more will just cause turbulence.

Brad,

How much does it need to be polished? Are his modifications too extreme or within an acceptable range that won't change timing or cause other issues? I have an 021 I'm considering a similar modification on. Thanks for your input.

dd

 

[CWME]

Looks like you've perhaps lowered the exhaust floor, and in the process, made it convex. You're liable to catch a ring on that. If you've get enough piston skirt to keep it from free porting, I'd lower the center to get it shaped right.

I see what you are saying. I was very careful with the top of the exhaust port but obviously not with the bottom. In straightning out the wall I hogged out the corners.

10-4 on the intake. I got carried away with making it smooth and a straight shot into the cylinder.

Thanks for the tips and words of encouragement guys!

 

[blsnelling]

It's VERY easy to do what you did on the exhaust port floor. Don't polish the intake.

 

[BloodOnTheIce]

If you look back far enough I stroked an 021.... worked well...for what it was

In one ear and out the other, they got no idea what you're talking about.

I think I may have parts to make one of these laying around the shop.

 

[Saw Dr.]

If you look back far enough I stroked an 021.... worked well...for what it was

Yeah, me too. I have a Big Bore and stroked 021. It is called an 025. I have a stroked STD bore one too. It is says 023L on the top.

 

[CWME]

Do you have a link to what you did to stroke a 021 CC? I checked your posts and tried a search and found nothing.

 

[CWME]

Got it back together and it is running. So I met my goal. Been trying to get some video of it ruuning through some red oak but not having much luck. The camera shuts off when the saw is runing and has a message on the screen. I assume it is due to noise. Cannon T2I.

The throttle response is better. I had the 16" bar burried in oak and I had to lean on it pretty good to stall it out. It is in no way my MS460 but I am pretty impressed with it so far. It had been moth balled as a backup but might get some more time in the wood.

 

[diggers_dad]

Glad to hear it's back together and running. Good work, especially for a first attempt!:msp_thumbup: