CS590 surging

[a. palmer jr.]

Working on an Echo CS590, owner says it surges. I started it up and he was right, it seems to have a lean surge to it. Wondering if the carburetor might be the cause. I'll probably do a pressure/vac test on it anyway but right now I don't have the block off plates. I know those carburetors are fixed from the factory so that you can't run them too rich. Any help would be appreciated.

 

[singinwoodwackr]

Working on an Echo CS590, owner says it surges. I started it up and he was right, it seems to have a lean surge to it. Wondering if the carburetor might be the cause. I'll probably do a pressure/vac test on it anyway but right now I don't have the block off plates. I know those carburetors are fixed from the factory so that you can't run them too rich. Any help would be appreciated.

You are doing what you need to do…find the obvious air leak.
if you don’t have plates and rubber, make them…quite easy.
that said, you can test the carb by itself first. If it leaks, fix or replace, including checking/replacing carb gaskets. If an air leak persists, vac/press test the case.

 

[ballisticdoughnut]

Working on an Echo CS590, owner says it surges. I started it up and he was right, it seems to have a lean surge to it. Wondering if the carburetor might be the cause. I'll probably do a pressure/vac test on it anyway but right now I don't have the block off plates. I know those carburetors are fixed from the factory so that you can't run them too rich. Any help would be appreciated.

Lean surge at idle? I’m definitely thinking carb but check fuel and pulse hoses, intake boot, etc. Also be sure to inspect the high speed nozzle, HDA carbs are known for having check valve issues.

 

[Vintage Engine Repairs]

Main nozzel

 

[a. palmer jr.]

I found the problem, well, sort of. I took the muffler off and noticed the piston was already terribly scarred so I might assume the cylinder probably needs work or replacement. I went ahead and did a pressure test just for the heck of it and it had a fairly large air leak. I didn't bother to find out where because at this point I'll have to return the saw to it's owner. The repairs on the saw were gonna be more than it is worth. The saw is an older one and it's pretty beat up. Thanks for your replies..

 

[a. palmer jr.]

By the way, I just needed a small metal plate to block off the exhaust and a rubber cork for the intake. I ran the air through the impulse hose. I didn't bother to take off the side plates since I knew I wasn't going to repair the saw.

 

[singinwoodwackr]

eBay, parts saw…

 

[a. palmer jr.]

eBay, parts saw…

Not many parts, possibly the crankcase and crankshaft, nice muffler, maybe the carb. Everything else looks well used. All the plastic is beat up.