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.

 

[Paul Bunions]

I got it to run without dying. I ran it at around 4,000 idle, where the chain barely started to move. At this speed, I moved the L screw back and forth, and it died at two points, so I shot roughly for the middle. This is what people on the web say to do.

I started fooling with the H screw. I figured I had to tighten it to get peak RPM. I was looking for a point where it ran rough and had to be backed off a little. Before the latest mods, I got about 13,000, although that was with a cheap tach, so it could be off.

While I was tightening, the saw dropped from 13,300 to somewhere in the 12's. It ran smooth the whole time. Should I back it out to 13,300 and leave it alone as long as it sounds good?

The idle is at about 3,000 now, within spec. My guess is that with a saw that has died a lot on me, I am more comfortable with the high side of spec than the low side.

 

[Paul Bunions]

I think maybe I got it.

I turned H CCW to get more fuel and raise the top RPM. Then I leaned it out 1/8 at a time. Now it farts a little with no load, but if you were to turn the H CW a small amount, it would smooth out. The tach says 13,400.

 

[NSEric]

Turn the high CCW until the rpm drops to 11000-12000rpm and it sputters then go CW until it gets up to about 13000rpm.
Those echos dont rev that high so there's no point going over 13000rpm. 13400rpm is likely the rev limiter.
If it gained rpm when you turned it CCW it was so lean it couldnt rev properly.

 

[Paul Bunions]

Thanks. It seems okay, but it does not like to start. I took it out and cut the only convenient 10" oak log, and it flew through it.

It's nice when a chainsaw has all the typical homeowner issues fixed. Sharp chain with full chisels, good tune, fresh fuel, and so on. It's like moving up to a better model.

 

[NSEric]

It sounds like it's too lean, that will make it get hot and start hard.

 

[Paul Bunions]

I will keep checking it. I didn't think about listening to it when I was cutting the log.

 

[Sidecarflip]

When I purchased mine, first thing I did before I even started it for the first time was, I modded the muffler and removed the top baffle entirely but retained the spark screen and rotated the deflector so it dumps the exhaust to the side towards the bar and I canned the stock air filter (which tends to pass fines through the center fixing hole to a Nick Stokel oiled foam air cleaner - velocity stack assembly. Then I fired it up with the limiter caps removed and tuned it to 4 stroke when free revving, just a tad and cleaning up when put into the wood cutting. Runs fine, starts right up and sounds real nice to boot. Of course I run it on canned fuel (Echo Red Armor 50-1) and the infamous Poulan bar oil that Menards had on sale so I bought quite a bit. I run the Echo 20" greaseable roller nose bar and full tooth chipper, razor sharp of course.

One thing I don't want is to lean it out too much, not into scoring powerheads and I don't desire to take it apart and have to fix it either.

I'll most likely at some point, install the offset flywheel key and possibly replace the ignition with the 620 unit, maybe.

It runs fine as it is so maybe not. Time will dictate that. I will most likely fab up and add a roller chain guide as well and can the stock solid guide.

I always set my saws to 4 stroke a tad when free revving and to clean up when put in a cut.

It pulls the 20" bar, full chipper, just fine, even in a ripping cut in oak. Far as I'm concerned, modding the muffler is the best mod and allows the unit to breathe much better and the oiled foam air cleaner, while a PITA to oil, does a much better job of keeping fines out of the carb. I did add an extra 'O' ring to the fixing stud, just in case.

Good saw at a very competitive price point.

 

[Paul Bunions]

Last night I realized I wasn't sure whether I had replaced the check valve. This carb is from Ebay, so l don't even know if it has the check valve that makes tuning hard. I'm going to pop the saw open today and find out.

 

[Sidecarflip]

I've never purchased a used saw as they aren't that expensive new anyway. I have purchased used farm tractors but only after I have them inspected by my good friend who is also the head tech at the dealership I deal with.

Far as saws are concerned, my philosophy about being used is probably abused as well. If they get abused, I want to be the initial abuser....

I have purchased used vehicles in the past, in fact my daily one is used but I always practice due diligence when buying a used car. I want a low mileage still under warranty and service records as well and I prefer an off lease ride.

 

[Paul Bunions]

I bought the saw and carb new. All the damage and wear are on me!