Stihl 193c

[firefighter]

Hey ladies and gents, I was given a 193c rear handle. Has anyone ever ported or built one. This was used by a carver and was well used. I'll post of pic of the top end and piston she was toasted but in the box of parts was a stihl 193c in pieces. The intake side of the cylinder has 3 individual openings. Looks a bit off to me, I'm newer to porting so I haven't been in many smaller saws. Thanks in advance.

 

[Ketchup]

I’ve never messed with a rear handle 193, but several 193t-c which should be identical in all but the handles.
You’re looking at a stratified intake. The upper two ports only move air. They open into the piston windows and then puff air into the transfers so that the exhaust is chased out of the cylinder with air instead of raw fuel. Just ignore them. It’s technology designed to meet emissions requirements. Unfortunately the third port is the fuel intake and it’s bounded by the piston windows, so you can only gain a tiny bit of width there.
The rest of the saw is a pretty classic design. The weird tunnel scoop above the exhaust is designed to make starting the saw easier and unfortunately reduces compression. This is also a clamshell design so it’s very difficult to change the squish.
I recommend you widen the exhaust, raise the transfer uppers 2 degrees, lighten the piston where possible, smooth everything real nice and slap it back together. There’s also a baffle in the muffler (the cage thing on the cylinder side) that should be hogged out, and of course make the outlet bigger.
In the end you’ll have a slightly better 193. The Engineers were very budget minded in this design. You won’t find huge gains.

 

[firefighter]

I’ve never messed with a rear handle 193, but several 193t-c which should be identical in all but the handles.
You’re looking at a stratified intake. The upper two ports only move air. They open into the piston windows and then puff air into the transfers so that the exhaust is chased out of the cylinder with air instead of raw fuel. Just ignore them. It’s technology designed to meet emissions requirements. Unfortunately the third port is the fuel intake and it’s bounded by the piston windows, so you can only gain a tiny bit of width there.
The rest of the saw is a pretty classic design. The weird tunnel scoop above the exhaust is designed to make starting the saw easier and unfortunately reduces compression. This is also a clamshell design so it’s very difficult to change the squish.
I recommend you widen the exhaust, raise the transfer uppers 2 degrees, lighten the piston where possible, smooth everything real nice and slap it back together. There’s also a baffle in the muffler (the cage thing on the cylinder side) that should be hogged out, and of course make the outlet bigger.
In the end you’ll have a slightly better 193. The Engineers were very budget minded in this design. You won’t find huge gains.

Thank you I have a 194t also so that will be getting it also

 

[Ketchup]

Forgot to mention 193 likes a timing advance. 194 less so, but has better compression.

 

[firefighter]

My 194 was changed with the timing advance. After those it's going to be the 400c and 261cm. That 261 is a screamer. Both of those having timing advances too. Actually all my saws do except the 193 and 266se. But that's a whole other story.

 

[Ketchup]

I advance 194, just not as much. 1/4-1/3 off the key.

 

[full chizel]

On my 192T all i did was widen the exhaust and advance the timing. Sounds like the newer ones don’t like TA.

 

[firefighter]

On my 192T all i did was widen the exhaust and advance the timing. Sounds like the newer ones don’t like TA.

Like I said in a earlier post I did a timing advance on the 194 and it completely changed the saw, I did each mod separate to see the differences in them and the timing advance woke it up. I advanced about 6 or 7 degrees and we'll it changed it.