Stihl 170 mods

[C George]

Just looking for feedback on this as I know this is a basic consumer saw , not a competition hot saw.
If the intake insert is removed out of the air box , it really turns this little saw into a screamer. It even smokes more as I suspect the impulse port is cycled better.

 

[J D]

Assuming you're referring to the circled piece in the picture, which I believe serves to hold the filter element in place. That should have no influence on the impulse but removing it will likely lead to a less restricted (& probably less filtered) intake.
I would suspect all you are doing by removing the insert is offsetting other issues within the carb

 

[C George]

The insert fits inside the intake tube and has no affect on af sealing , its strictly a restrictor for air and impulse port that it mostly covers up

 

[C George]

We always use fleece 2 stage filters in the shop and lightly grease the edges

 

[C George]

Since most dont realize the dirt / debris is collected on the bottom of the filter

 

[J D]

If this is the "impulse" port you are referring to, that may make more sense. That is compensation not impulse & by removing restriction to the intake you alter the pressure on the back of the metering diaphragm in turn changing the mixture

 

[C George]

I agree 100% , the saw has noticeably more power and revs. It also
seems richer as it
smokes slightly more

 

[C George]

We have also been installing gaskets on the air filter housing mount to carb . That makes no sense to skimp on a 20 cent gasket

 

[Sportfury70]

Maybe taking it out reduces air velocity, not volume? If it does, then it reduces fuel atomization and an incomplete burn, resulting in more smoke. Just a thought..

I built one of these. Get a wt215 carb so you can actually tune it, and shave a few thousandths off the flywheel key to advance the timing. Top it off with a MM. I used a 14” bar with 3/8 chain and it was a little ripper. Not much else to do as I don’t think these respond well to porting and being a clamshell you can’t change port timing much or delete the base gasket.

 

[J D]

In leu of replacing the carb you can get replacement jets in around 0.05mm increments. If you have teenie weenie drill bits you can enlarge them a fraction too

 

[cookies]

Play with the needle lever height (raised mine a hair) and adjust the a/f needle after opening the muffler up, they are quite restricted for air, fuel and exhaust. A oiled foam air filter instead of the thin fiber one helps too. Never bothered to adv the ignition since it upped the grunt enough to bury the 14" bar and lean on it with lowered rakers in hardwood

 

[stihltech]

Nitro

 

[C George]

So This is how Im running my saw in todays tune . I ditched the intake insert and the spark arrestor. Opened up muffler louvers slightly, dont drill your muffler. Removed carb cv top and silicone plugged o ring side. Drilled 1/32 hole below that so carb diaphram can move. Changed plug to 1 number hotter ngk and run 25:1 fuel mix. I gasketed both sides of air filter housing and run a 2 stage Stihl fleece air filter greased on the sides. I opened up air intake passages on the chain saw main cover. With the stock carb, but now no vacume from air filter housing , this saw now turns 1500 rpms higher and will cut a 12" log with little to no bogging .
Many can laugh and thats fine but this has really transformed this little saw.

 

[C George]

So This is how Im running my saw in todays tune . I ditched the intake insert and the spark arrestor. Opened up muffler louvers slightly, dont drill your muffler. Removed carb cv top and silicone plugged o ring side. Drilled 1/32 hole below that so carb diaphram can move. Changed plug to 1 number hotter ngk and run 25:1 fuel mix. I gasketed both sides of air filter housing and run a 2 stage Stihl fleece air filter greased on the sides. I opened up air intake passages on the chain saw main cover. With the stock carb, but now no vacume from air filter housing , this saw now turns 1500 rpms higher and will cut a 12" log with little to no bogging .
Many can laugh and thats fine but this has really transformed this little saw.

Yes with stock 16" bar

 

[J D]

So This is how Im running my saw in todays tune . I ditched the intake insert and the spark arrestor. Opened up muffler louvers slightly, dont drill your muffler. Removed carb cv top and silicone plugged o ring side. Drilled 1/32 hole below that so carb diaphram can move. Changed plug to 1 number hotter ngk and run 25:1 fuel mix. I gasketed both sides of air filter housing and run a 2 stage Stihl fleece air filter greased on the sides. I opened up air intake passages on the chain saw main cover. With the stock carb, but now no vacume from air filter housing , this saw now turns 1500 rpms higher and will cut a 12" log with little to no bogging .
Many can laugh and thats fine but this has really transformed this little saw.

I have no doubt your mods have given your saw more power... however, with a stock carb feeding a less restricted intake & exhaust I'm pretty sure most those gained RPM & some of that extra power will be as a result of it running lean

 

[C George]

I have no doubt your mods have given your saw more power... however, with a stock carb feeding a less restricted intake & exhaust I'm pretty sure most those gained RPM & some of that extra power will be as a result of it running lean

Agree and thats part of my 25:1 theory.
Im very open minded that I'm an old guy that knows enough to be dangerous

 

[C George]

Agree and thats part of my 25:1 theory.
Im very open minded that I'm an old guy that knows enough to be dangerous

It smokes enough that im not too concerned about blowing it up , plus wo getting into oils , I have alot of confidence in the oil im running

 

[J D]

Agree and thats part of my 25:1 theory.
Im very open minded that I'm an old guy that knows enough to be dangerous

By adding more oil to the mix you lean the fuel out MORE!
The bearings will be better lubricated but your cylinder will be running even hotter!
Additionally, the use of a hotter plug to help burn the additional oil will increase cylinder temperature further.
I'm honestly quite surprised none of these saws have seized yet

 

[C George]

By adding more oil to the mix you lean the fuel out MORE!
The bearings will be better lubricated but your cylinder will be running even hotter!
Additionally, the use of a hotter plug to help burn the additional oil will increase cylinder temperature further.
I'm honestly quite surprised none of these saws have seized yet

So why do you think the lubrication is ok on the bearings but not the piston ? I do get the theory about a higher viscosity fuel mix and it being leaner with the same jetting

 

[C George]

So why do you think the lubrication is ok on the bearings but not the piston ? I do get the theory about a higher viscosity fuel mix and it being leaner with the same jetting

Im running a hotter plug but not a projected tip like stock