how to set the carburator with a tach

[RIDGERUNNER30]

got a question for you guys, I ordered a tachometer the other day and plan adjusting the carbs on two chainsaws i have, done some research on the matter, but still have a question on setting the H setting screw on the saw, should this screw be set under a load or can you just rev up the engine and get a accurate reading with the tach.

 

[smokinj]

Both lol, but find your max load for your saw should be some where around 12,000 this is without a load. Setting rpm's in the cut would be more of set- up for racing. Tuning by ear
you can auto tune through every cut. (Band geeks) What Saw you tuning?

 

[Dingeryote]

The easy way with an un modified saw is to set for no load max, then turn rich 3-400RPM's under, and then verify by ear in the cut that it is "Cleaning up" under a load.
From there sneak up a bit untill it cleans up with light pressure in the cut, and verify with the Tach.

 

[HittinSteel]

Only thing I would add is make sure the saw is sufficiently warmed up. If you set the max RPM's by tach and the saw is still cold, you will gain several hundred RPM's when the saw warms up...... could take you in to the danger zone.

 

[Jags]

From there sneak up a bit untill it cleans up with light pressure in the cut, and verify with the Tach.

Dinger - when you say sneak up a bit - do you mean to lean it out from there?? Or am I backwards? Just clarifying.

 

[HittinSteel]

he's saying a little lean..... clockwise on the H screw just a hair

 

[Jags]

he's saying a little lean..... clockwise on the H screw just a hair

Got it - I thought that was the meaning, but wanted to clarify (for both me and anyone else that was scratching their head )

I don't tach tune, but find it interesting none the less.

 

[smokinj]

I run fat, let it lean out under more pressure. With sharpe chains you will get nice rooster tail.

 

[Jags]

I run fat, let it lean out under more pressure. With sharpe chains you will get nice rooster tail.

Zactly! But I do it by ear. I want to hear a diesel under no load, but clean out when it hits wood. VROOOM VROOM.

 

[HittinSteel]

I was listening to a friend cut with my 372 the other day.......as soon as he lifted the saw at all out of the cut it would 4 stroke and then immediately clean back up when he touched the wood again. Perfect place to be IMO

 

[smokinj]

I was listening to a friend cut with my 372 the other day.......as soon as he lifted the saw at all out of the cut it would 4 stroke and then immediately clean back up when he touched the wood again. Perfect place to be IMO

Yes sir and a big saw I like it to lean out with the dawgs set and a good amount of pressure (not when it first torches it.)

 

[smokinj]

I run fat, let it lean out under more pressure. With sharpe chains you will get nice rooster tail.

Zactly! But I do it by ear. I want to hear a diesel under no load, but clean out when it hits wood. VROOOM VROOM.

me too. Taught about putting a tac on my 880 for milling but much quicker just to listen...

 

[HittinSteel]

I was listening to a friend cut with my 372 the other day.......as soon as he lifted the saw at all out of the cut it would 4 stroke and then immediately clean back up when he touched the wood again. Perfect place to be IMO

Yes sir and a big saw I like it to lean out with the dawgs set and a good amount of pressure (not when it first torches it.)

I run a little on the edge as my saw only has about 140lbs of compression. the piston is nearing the end of its life and I have a new one ready to go in. Gonna lose the base gasket as well when I replace it.

 

[smokinj]

I was listening to a friend cut with my 372 the other day.......as soon as he lifted the saw at all out of the cut it would 4 stroke and then immediately clean back up when he touched the wood again. Perfect place to be IMO

Yes sir and a big saw I like it to lean out with the dawgs set and a good amount of pressure (not when it first torches it.)

I run a little on the edge as my saw only has about 140lbs of compression. the piston is nearing the end of its life and I have a new one ready to go in. Gonna lose the base gasket as well when I replace it.

Yep, 140 it should not be long. You will be in the 190lbs range. That will a whole new Beast!

 

[Dingeryote]

Yeah the guys nailed it.

Set it a smidge fat on the tach so you know where your are, then tinker with going more lean in the cut. It should 4 stroke untill light pressure is applied.
I always err on the side of a little fat myself, just in case I get some crappy fuel, develop an air leak and that sort of thing.
Just verify with the tach when you find the sweet spot, and write it down. Then you can always tune back to that point.

 

[JeffT]

Not always ideal but a good starting point is the manufacturers recommended max rpm on a stock saw.

 

[smokinj]

Not always ideal but a good starting point is the manufacturers recommended max rpm on a stock saw.

That is idea for a tach guy.