Echo CS-590 Hard to start - Low Compression

[Blueacre]

I have an Echo CS590 with 20 inch bar I use for cutting firewood. It is just over a year old – bought it at the local Home Depot – it was the last one in stock and had it on a fall clearance at a great price. I used it first time for 5 or 6 hours last winter - ran great with no starting issues. I only use premium no ethanol gas and I drained all the fuel and ran it till it died before I stored it in the spring of 2020 and pulled plug and put some oil in cylinder. Didn’t use it again until January this year to start to cut my firewood. It was real hard to start when I first got it out. Thought it was flooded so I ended up pulling the plug and cranking it over with no plug in it and then put in a new plug and got it going after quite a few pulls. It ran fine after I got it going so I headed out to cut some wood. Went through the first tank of fuel and ran perfect – cut like new. I shut it off a few times to move between trees and started right up first pull. After I stopped for about 15 minutes to refuel, fill bar oil and adjust the chain tension it wouldn’t restart. Tried for about 15 minutes to start it and finally pulled the plug I had put in earlier and put the original plug back in – started second pull.

Have been using it for 3 or 4 hours a day all week and same thing happens every time. Cold start is usually 4 pull – 2 pulls with choke on and decompression button pushed in and it kicks a little on second pull– push choke in and push decompression button again and usually starts on second pull. Runs perfect once it is going. I can shut if off for a couple of minutes and restarts first pull. If I shut it down for 10 or 15 minutes, which is normally to refuel, it wont start – usually try to restart by pulling choke out and then pushing back in to set high idle – if no start after 5 or 10 pulls try a couple pulls with choke on and then choke off but still nothing – no kick from motor – decompression button never pops out the whole time. If I let it sit for an hour or two it will usually start in 4 or 5 pulls.

I figured it should be covered by the echo 5 year warranty so I took it to the local Echo dealer that does servicing. Paid $35 for a diagnosis that would be refunded it problem was covered under warranty. Got a call a week later that they had checked it and only had 40 pounds compression and in their opinion the piston and cylinder were damaged and would need replacement. Said it had no warranty because it was purchased as a clearance item. (wasn’t told that when I bought it at Home Depot). The dealer wanted 80% of the retail cost of a new one to do the work so I brought it home and decided to pull it apart myself and see what I could do with it. I have rebuilt several GM V8 engines over the years but a newbie to working on 2 stokes. I was looking for a service manual on the internet and found a post where someone else was looking for a manual on this site and Ray Benson had sent one. I joined the site, contacted Ray and he was good enough to send me a copy – thanks very much.

With the manual I had the cylinder off in about 20 minutes – real easy on this model – basically pull top cover, carb and muffler and the 4 cylinder bolts are accessible from the top.

I was expecting to see a lot of piston and cylinder damage inside based on other photos I had been looking at on line. My first time inside a 2 stroke but looked like minimal damage to me.

I have attached pictures of the cylinder and piston

• · The piston has some discoloration on the exhaust side in the ring area and one narrow line that runs the full length to the bottom of the skirt – the discolored area doesn’t feel rough – if I run my finger over the narrow line the finger nail will catch a little so there is some shallow scoring where the line is.

• · The intake side of the piston has a discolored area near the rings – doesn’t feel rough

• · The top of the piston has a uniform coating of carbon – no visible damage

• · The cylinder has a uniform coating of carbon on the dome except for a crescent shaped area in the intake side of the cylinder.

• · I don’t see any damage or aluminum transfer on the intake side of the cylinder wall.

• · The exhaust side of the cylinder has one small area that might be aluminum transfer just below the exhaust port – I circled it in red in the picture – I ran my finger over it and doesn’t feel rough. I am sure that is easily polished out.

Being a 2 stroke Newbie I would appreciate anybody’s comments on what might have caused this so I can try and prevent it from happening again.

Also any input on the repairs to get it running again. I am thinking clean up the one small mark on the cylinder, new piston/ring kit and cylinder gasket but welcome any comments.

 

[Blueacre]

Followup - forgot to mention that the piston ring moves freely in the piston groove

 

[Nutball]

Sorry if I missed it in your original post, but did you use 2 stroke oil in your gas? At a glance it doesn't look ruined, but the pictures are out of focus.

 

[Blueacre]

I have been using Huisqvarna HP 2 stroke oil - I mix it 45 to 1 to be a little on the conservative side. I will try and get some better pictures and post them.

 

[Pincher]

At first glance it appears the 40psi compression was with the decomp pushed.

 

[Cooper264]

I'm not a big diagnoser, more of a trial and error replacer kinda guy, but it kinda looks like she sucked something up through the intake side since there is no easily noticable damage to the top of the piston. Doesn't seem like it was anything huge, try scraping your fingernail over the damaged spot, if your nail catches its probably where the comp loss is. The changing spark plugs things makes me think that it's flooding itself when you try to start it back up (dry spark plug fires 10 to one better than a wet one). Some could say it's operator error when starting the saw the second time but most of the saw's i've ever dealt with aren't that finiky about starting back up unless there is some other sort of issue, so I rule out operator error and definitely vote that something else is wrong. If it's flooding than i doubt it's anything with a clogged fuel filter. If the nick in the C/P is of decent size, I'de replace either the piston or both. If that doesn't solve anything i'de look into the carb

 

[Cooper264]

Go buy a comp tester (good to have one around anyways) and see what the comp is on that C/P

 

[Steve]

At first glance it appears the 40psi compression was with the decomp pushed.

It sure is!

I have been using Huisqvarna HP 2 stroke oil - I mix it 45 to 1 to be a little on the conservative side. I will try and get some better pictures and post them.

Has this saw ever been tuned properly or is still on the factory tune? Damage looks like it is running a little on the lean side.

The decomp valve is probably stuck open and needs replaced

I bet polishing the piston lightly with 600 wet sanding and clean the cylinder and a good tune will have you back up and going.

 

[Blueacre]

Posted some better pictures of piston - having trouble getting good pics inside the cylinder.

Interesting comment by Pincher that the decomp may have been pushed in for the compression test - I am pretty sure it was pushed in when I dropped but I thought a compression test is supposed to be done after warming up an engine so it should have popped out - hard to believe a good service guy wouldnt have checked the decomp valve was working before saying it had poor compression but you never know.

I have a compression tester for cars - will have to see if I have the correct adapter for this size plug or get one if I dont. I was puzzled when changing the plug worked because the plug I took out didnt look wet like I have seen in a typical flooded engine unless by the time I go the plug out of a hot engine the fuel had all evaporated.

I thought it might be a little on the lean side - both the Hi and Lo needles were out to the limiter stops out of the box and I hadnt pulled them off yet thinking it was still in warranty Now that I know there is no warranty I will pull them and try to tune it better.

I think I will just clean up the worst spots with something like 600 wet paper, reassemble with new cylinder gasket and do a compression check. If I get decent compression then tune it and see if hot starting is better.

 

[67L36Driver]

Tip: The two ring piston for a 620 is a direct fit.

Worthwhile substitute.

[emoji108]

I did that on two saws for a tree service several months ago. The cylinders were quite nasty but serviceable.

 

[Steve]

Tip: The two ring piston for a 620 is a direct fit.

Worthwhile substitute.

[emoji108]

I did that on two saws for a tree service several months ago. The cylinders were quite nasty but serviceable.

That's good to know.

 

[Cooper264]

Comp tester for a car should have the right bushing/adapter in it for a chainsaw spark hole. Check to see if a piece of the decomp came down into the cylinder. I havn't really seen that happen outside of old ass 372's and the china 660's though. Worth a shot. If the decomp is bucked, then that would explain being a little lean lol

 

[Ford3000]

Piston ring turning should not be happening, the locating pin has got to have failed, that is a warranty issue.
If you ran straight gas you would have different images, you don’t.
Contact the Echo distributor for your area personally, email the images
and ask where the locating pin is, and why the ring can rotate freely.

 

[Blueacre]

Thanks for the info on the 2 ring piston - I saw a 2 ring one on ebay being sold by Lil Red Barn but wasnt sure it was a direct replacement - has anyone used their pistons kits ?

MY compression tester doesnt go small enough but a friend of mine has one with the 14mm adapter so I will borrow that tommorow.

Maybe a stupid question but is there any reason to reassemble the carb and muffler to do a quick compression test ? I figured they are open anyways so shouldnt impact the reading ? Also the local dealer wont be able to get a new cylinder gasket for a few days so I was wondering if OK to put the cylinder back on without removing the old gasket just for the compression test.

 

[Cooper264]

Piston ring turning should not be happening, the locating pin has got to have failed, that is a warranty issue.
If you ran straight gas you would have different images, you don’t.
Contact the Echo distributor for your area personally, email the images
and ask where the locating pin is, and why the ring can rotate freely.

I second that. In the first set of pics it appears that the keyway pin duflatchey is gone.

 

[Cooper264]

Thanks for the info on the 2 ring piston - I saw a 2 ring one on ebay being sold by Lil Red Barn but wasnt sure it was a direct replacement - has anyone used their pistons kits ?

MY compression tester doesnt go small enough but a friend of mine has one with the 14mm adapter so I will borrow that tommorow.

Maybe a stupid question but is there any reason to reassemble the carb and muffler to do a quick compression test ? I figured they are open anyways so shouldnt impact the reading ? Also the local dealer wont be able to get a new cylinder gasket for a few days so I was wondering if OK to put the cylinder back on without removing the old gasket just for the compression test.

Spray the case full of eather and throw a match in there for extra compression

 

[Ford3000]

Thanks for the info on the 2 ring piston - I saw a 2 ring one on ebay being sold by Lil Red Barn but wasnt sure it was a direct replacement - has anyone used their pistons kits ?

MY compression tester doesnt go small enough but a friend of mine has one with the 14mm adapter so I will borrow that tommorow.

Maybe a stupid question but is there any reason to reassemble the carb and muffler to do a quick compression test ? I figured they are open anyways so shouldnt impact the reading ? Also the local dealer wont be able to get a new cylinder gasket for a few days so I was wondering if OK to put the cylinder back on without removing the old gasket just for the compression test.

Make a rubber gasket from a bicycle tube, cut holes to fit over muffler bolts, if you have a flat plate to bolt over this rubber well and good, else bolt the muffler over the rubber tube to seal the exhaust.
Do something similar to close the inlet port / where the carb sits.
You can easily block the impulse pipe that enters the case below the carb, some people actually use it to vacuum test the engine and leave the plug in to
block the plug hole, I take it your vacuume and pressure testing the case with
the cylinder sealed up, this will test the case and crank seals for leaks.
Make sure your boot is good and tight if you leave it on the case and just block where the carb goes into it, that will tell you if the boot is ok.

If your reassembling the engine to do a compression test via a compression tester, I doubt it will hold unless you clean the cylinder, fit a new ring at least,
but what’s the point when the piston is missing the pin to retain the ring.

NOTE, that impulse line came loose on a new saw and the guy had issues like
you describe regarding starting, it would start cold as it was choked, but when
you didn’t and couldn’t use the choke for obvious reasons it was a pig to start,
don’t know where I read it, but it’s happened more than once, maybe during assembly,
as these owners did not work on their saws, they went just like yours, but no piston
ring pin was involved, that is obviously another issue.

 

[Blueacre]

I checked and the piston still has the locating pin. The ring expands enough when out of the cylinder to be able to rotate it over top of the pin. I just rotated it to make sure the ring was free in the groove and hadnt turned it back to the proper location.

As far as the compression test I was only planning to put it back together and do a quick test to see if I got more than the 40 pounds the dealer said they got - if I get a lot higher compression without a new ring or piston than it probably confirms that they did the test with the decomp pressed in. I wasnt planning to run it without a more permanent fix so that is why I thought it would be easy to do the compression with out replacing the carb, muffler or cylinder gasket.

 

[Ford3000]

I checked and the piston still has the locating pin. The ring expands enough when out of the cylinder to be able to rotate it over top of the pin. I just rotated it to make sure the ring was free in the groove and hadnt turned it back to the proper location.

As far as the compression test I was only planning to put it back together and do a quick test to see if I got more than the 40 pounds the dealer said they got - if I get a lot higher compression without a new ring or piston than it probably confirms that they did the test with the decomp pressed in. I wasnt planning to run it without a more permanent fix so that is why I thought it would be easy to do the compression with out replacing the carb, muffler or cylinder gasket.

That’s different. You don’t need the carb or exhaust for that. Try and gently clean any build up off the cylinder, and the piston, the piston is soft and will easily clean and polish up.

 

[Ford3000]

Hope the OP does a leak down test to be safe, no point in loosing all his hard work and cash because of a leak.