Tuning CS-590 With New Air Filter and Muffler Holes?

[Paul Bunions]

Yesterday, I stuck an air filter sealing kit on my Echo CS-590. I also drilled 6 3/16" holes in the muffler under the spark arrestor. I also broke my OEM air filter while trying to clean it, and I replaced it with one that has a plastic screen instead of the fluffy stuff.

The saw already had a Gearhead deflector, a new key to advance the timing, and an HDA-327 carb for a CS-620P. The carb has no caps, so any information from the manual about using "stops" to set the screws seems useless.

It was running well before I drilled the holes, added the seal kit, and installed the plastic air filter.

I could not get the saw to run yesterday, so I have been trying to tune the carb today. I have gotten to where I can tune a saw that already runs, but starting from nothing is not my thing.

The saw will start with the throttle stop thing engaged (choke pulled out and pushed back in). It will then either idle way too fast or die, depending on the L screw. If I touch the throttle to release it, the saw dies.

A while ago, I had it running well, except that it would not rev up. It didn't die when I revved it, but it probably ran at something like 6,000.

Give me some clues here.

It's funny, but no one on the web seems to provide info on getting a saw to idle as part of the tuning process. They all start with, "Once the saw is running and warmed up..."

Google's unwanted AI overview butted in and told me the throttle valve should be cracked 1-2mm at idle. That would pretty much max out my idle screw.

I didn't really understand what the idle screw does until today. Apparently, it just cracks the throttle valve so the L screw can feed enough gas to make the saw idle.

 

[Chevboy0167]

https://www.walbro.com/wp-content/uploads/2016/01/HDAseries.pdf

 

[Marley5]

So it was running fine before the new air filter, seal kit and a couple of holes drilled in the muffler ?
Recheck everything including the venturi, possibly compromised when air filter broke.
Did you remove the muffler before drilling holes.
If not shavings can migrate to the piston on the down stroke..... not good.

 

[Paul Bunions]

Thanks for the link.

I used 1-1/4 turns out on H and L, as indicated in the Walbro manual, and I got the saw going. I had to adjust the idle speed screw to get the saw to idle so the chain was barely moving, as the gurus tell us to do.

The saw acted strangely after this, revving up to almost full throttle by itself.

Eventually, I got it to settle down. Then I started adjusting the L screw. In the past, I moved it in and out on idle, looking for the fastest speed between two extremes that would kill the motor. This time, it kept going faster when I opened it up. It will slow down and die if I keep closing it.

Not sure what's happening.

Update: I fired up the saw, and it ran fine. I left it idling for a while to warm it up. I goosed the throttle, the saw ran up to high RPM's, and then it died.

It ran fine before I added stuff yesterday. I removed the muffler to drill the holes. I put it in a sink full of hot soapy water and rinsed it out thoroughly. The air filter I tore was torn while being washed. It wasn't in the saw.

I am going to remove the air filter kit and see if it helps. It worked fine without it. I wonder if I have an air leak. I have taken the carb out and done my best to re-seat it. This saw has no gasket between the carb and the body.

 

[Paul Bunions]

I removed all of the air cleaner stuff except the O-ring closest to the carb, and the saw seemed to run normally. I don't know what I'm doing, but I think the balance between the idle speed screw and the L screw was off. I backed the idle speed screw out a lot, and the saw seemed to get it together.

I was trying to get my new tachometer to work, and I think I turned the idle speed down too much. Not sure. Anyway, the saw idled for 5 minutes and then croaked. Now it doesn't want to start.

In case anyone is wondering, the right setting for a Proline Solo Tach on a chainsaw is 1p1r. The idle speed on a CS-590 is 2600-3200 according to the service manual. Some idiot on the web said it was more like 1000, so I may have gone too low trying to get to the wrong figure. WOT is 12,000-13,000 fresh from Home Depot.

 

[Wood Doctor]

I let the saw's engine tell me what the correct idle speed is. Start the saw with a higher than normal idle speed setting. Then when the engine is running, back the idle drop down slowly. As you adjust, check to see that it accelerates up OK. When the chain stops spinning on its own and the engine sounds comfortable, do not back it down further. Just leave it alone. More than likely, you are good to go.