Paul Bunions
ArboristSite Operative
I decided to try and tune my CS590 with a 620 carb, no limiters, a Gearhead deflector, and the Gearhead flywheel key that bumps the timing 6 degrees. The saw runs easily, but the top RPM is way too high. Either that or I'm making some kind of tachometer mistake.
Today I put in a new deflector and a key to bump the timing 6 degrees. I set the idle so the chain was still. I tried to find the point on the L screw where the speed started to drop.
I put a cheap tach on the saw and set it so it read 1 RPM every time the plug fired. I got something like 14K RPM, which is just a wee bit high considering that Echo says 12-13K.
I turned the H screw all the way in, and the saw didn't slow down.
Any ideas what I'm doing wrong? I had a 20" bar on it, and the chain was adjusted so about 3 whole pullers or whatever they're called were exposed when I yanked on it. I tested the saw warm.
Here is a summary of the tips I used, copied from Steve's Small Engine Saloon:
Today I put in a new deflector and a key to bump the timing 6 degrees. I set the idle so the chain was still. I tried to find the point on the L screw where the speed started to drop.
I put a cheap tach on the saw and set it so it read 1 RPM every time the plug fired. I got something like 14K RPM, which is just a wee bit high considering that Echo says 12-13K.
I turned the H screw all the way in, and the saw didn't slow down.
Any ideas what I'm doing wrong? I had a 20" bar on it, and the chain was adjusted so about 3 whole pullers or whatever they're called were exposed when I yanked on it. I tested the saw warm.
Here is a summary of the tips I used, copied from Steve's Small Engine Saloon:
- Have your bar and chain on, as well as the air filter.
- Start it and warm it up.
- Turn idle screw CW until chain moves.
- Turn L back and forth. Speed will drop at extremes. In the middle, there is a top speed. Find it.
- Loosen L just until you hear the speed start to drop.
- Adjust idle until the chain is still.
- Go to H screw and use a tach to set the max RPM.