CS-4600 no start

Sean2202

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Greetings,

Last weekend I came upon a used Echo CS-4600 Echo chain saw at a swap meet. It looked to be in decent shape and had a tag on it "pops but doesn't run" ($45). Upon pulling it a few times I indeed got it to pop a few times but did not run. A few hours later of thinking about it and I went back to get it. So when I got it home I checked the spark, dumped out the old gas and put new in, tried it and nothing, no pops. Then I threw a shot of start fluid in it and it did nothing. No pops this time either. The plug is a BPMR7A. Good spark. Put a new fuel filter in it. No change. Tried a new plug, nothing. Inspected the carb lines and they look decent. Thinking it is a carb or fuel issue I looked up the carb on jacks small engine. Not available. My carb states Zama C3 on one side then K5 with 24S underneath it on the other side. It also has C3 on the top. Checked on e bay with the number from jackssmall engine and there was nothing for sale. Checked compression 110 psi.

What else could be wrong with this saw?
Where could I get a carb if I needed one?
What do these numbers on the carb mean?
What should compression be?

Thanks for any help
Sean
 

bertsmobile1

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Firstly these engines are very small so the amount of starting fluid needed to make the fire is tiny.
Most spray way too much in the engine and effectivly flood it
My GuESS is the flywheel key has sheared and the engine is out of time,
Check the operation of the carb by sliding it off the mountings but leave the fuel lines on.
Turn it sideways and blow through the carb.
If you can use high volume low pressure air
If you get a good flow of fuel coming out the engine side then the carb is working well enough for the engine to fire.

If the carb checks out OK pull the muffler and try starting muffler off.
The exhaust port clogs up with carbon, particularly if the owner ran too much oil and loaded the saw too heavy.
Muffler also clog so the motor chokes on its own exhaust.
Generally a blocked exhaust will cause the carb to spit back because the pressure built up in the crankcase can not enter the engine so will blow back out the carb when the inlet port is opened.

If both of these check out then pull the flywheel & check the key.
Most are cast into the flywheel so if it is broken then replacement is the only option.
 

jp1961

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Hi Sean,

Does the "primer bulb" (actually a purge valve) look OK with no cracks? Chainsaw carbs are different than weedwhacker carbs as the primer bulb isn't mounted on the carb, but on the saw housing.

Try removing the fuel line(s) and shooting carb cleaner into both fuel line fittings.

It's possible the spark arresting screen, in the muffler is clogged with carbon too.

I converted an Echo chainsaw engine to model airplane use and after mounting it in the airplane discovered the engine wouldn't run (actually acted like your issue, a few pops but it wouldn't start) and think it was due to me not plumbing the purge valve. I swapped carbs off a weedwhacker with the purge valve on the carb and it ran.

The Echo chainsaw I converted was a CS-3000 (30cc) and it had a Walbro WT 941 4028 carb. I can't guarantee this carb will work on your CS-4600 though.

Fuel lines that may look otherwise ok, can develop a crack or split right at the end of the fuel nipple or brass tube.

Regards

Jeff
 
Last edited:

Sean2202

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Thanks for your replies.

There is no primer bulb on this carb, just two lines one that runs to the fuel tank and filter and one that runs to the block which I assume is a pulse line. You are correct, cracks are hard to spot. I may replace these as PM. I have not tried the exhaust port screen removal yet. An interesting thing that I forgot to mention is when I pulled the fuel line from the tank at the carb fuel had a continuous stream and I had to plug the fuel line so fuel did not continue to run. Is this normal? The plug that is in the engine seems to be wet all the time so I am thinking there may be something in the carb that is not stopping the fuel flow? I tried a few different plugs and held the saw wideopen and throttle locked it (no bar and chain) and pulled like crazy and finally got it to fire. It would run a little with the throttle locked but as soon as I let off it would die. Did this a few times. Same result.

So flywheel key is probably good. Also there is a high and a low screw on this carb with a idle screw. At what factory point should these screws be set? The saw will not idle at all.

Thanks for your help
Sean
 

jp1961

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Hi Sean,

I would try using carb cleaner in both lines on the carb. Also if the carb has both High and Low needles that can be removed (mine didn't), try removing both needles and spraying carb cleaner in the holes. Unless the guy heated his home with wood, chainsaws don't get a lot of use, with a lot of extended periods of time where they don't get used, allowing the fuel to gum up the carb. Certainly the case with my chainsaw.

I'm no carb expert, but feel diaphramg type carbs are even less tolerant of dirt and gum deposits than a float type carb.

Echo makes a quality product and would be REALLY surprised if you couldn't get it running good.

One and 1/4 turns from a lightly seated position, should get you in the ballpark for both the high and low needles. I feel the Low mixture needle controls starting and idling, with the High for wide open throttle. I'd tinker with the Low more than the High to see if you can get it to start and idle. Someone with more knowledge can correct me if I'm wrong. Also, turning either needle 1/4 turn is a lot in a diaphragm type carb, don't go crazy with adjustments.

Regards

Jeff
 
Last edited:

bertsmobile1

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Yes a line coming from the block is the impulse line to power the fuel pump..
The 2 lines you are seeing are the pick up & return lines.
The fuel tank runs at pressure of around 7 to 10 psi.
Any higher and the fuel cap or tank vent should bleed it off.
So just loosen the cap to drop the pressure.
It is easier to push fuel than pull it so the pump pressurises the tank to get the fuel to flow to the carb.
Inside the carb is a spring loaded needle that works against the tank pressure to cut off the fuel supply and prevent the carb flooding the engine.
You could have either a Walbro WT or a Zama C1Q fitted
the initial settings are
Walbro H=3 L=1.25 I=1.5
Zama H= 2.25 L = 1.5 I = 2
Note H & L are turns out from lightly seated, Idle is turns in from flush with the inside of the bracket.
 

Sean2202

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Thanks for the help here. I have gotten the CS-4600 to run good. It seems to have an interesting starting pattern which I found by tinkering around. Not sure if this is factory starting procedure as I don't have a manual for it.

1. On cold engine pull choke out and pull until it tries to fire
2. Lock throttle wide open then pull and a few pulls fires it right up. Let lock off and it will idle just fine. Top end seems good as well.

Runs good, cuts good. Used it to cut a few large uncut log pieces and it even cuts straight! Not bad for $45!

Sean
 

jp1961

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Hi Sean,

Thanks for the followup. Yep, you got a saw that cost several hundred dollars for 45.00,,,good deal.

Regards

Jeff
 
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