Thanks Bert

PTmowerMech

Lawn Addict
Joined
Apr 16, 2018
Threads
170
Messages
1,053
After reading what you wrote in the "echo carb kit" thread, I'm scared to take a chainsaw carb apart. lol :p

CS-305. Customer says it just needs a primer. Difference being, this customer doesn't seem to be the kind to use his saw once a year. This one looks used regularly.
None the less, after replacing the primer, it'll only run until the fuel from the priming is gone. Not to mention, the primer bulb won't fill up. It sucks some fuel. But very little. I've filled the tank with fresh mix and cleaned out the filter.

There's limiters on this carb, inset like I've never seen.
 

Hammermechanicman

Well-Known Member
Joined
Jan 10, 2020
Threads
2
Messages
839
You really need the tools to pressure test carbs. It sounds like the bulb check valve may not be working. When you push it does it stay compressed? If so then fuel pump or metering problem. When you press it does it rebound but doesn't fill with fuel? Primer outlet check valve leaking. Some of the echo needles need a special tool to adjust.
 

PTmowerMech

Lawn Addict
Joined
Apr 16, 2018
Threads
170
Messages
1,053
You really need the tools to pressure test carbs. It sounds like the bulb check valve may not be working. When you push it does it stay compressed? If so then fuel pump or metering problem. When you press it does it rebound but doesn't fill with fuel? Primer outlet check valve leaking. Some of the echo needles need a special tool to adjust.
Yes, the primer rebounds immediately. And has some fuel sucking up into it. But not much.

And after thinking about this, if the primer wasn't rebounding, that would mean a clog. Rebounding quickly, with mostly air, makes it a leak somewhere.

I've got that fancy MityVac, the one that @bertsmobile1 told me about. I use it when I take carbs off and they don't have any fuel in them. Scared to use it with fuel in the system, because it'll screw mess it up.
 

Hammermechanicman

Well-Known Member
Joined
Jan 10, 2020
Threads
2
Messages
839
Put a translucent fuel line on the output of the primer and pump the primer bulb. You should not see fuel flow back into the carb. If you do rhe check valve is bad.

Assuming your mighy vac does pressure and vacum

Hook up the might vac to the fuel inlet and pressurize to 7 psi. Carb shoul hold pressure. Depress the primer once and when you release the bulb pressure should drop and hold again.

Connect mighty vac to the primer outlet. Pump bulb repeatedly. Pressure should build and hold.
 

PTmowerMech

Lawn Addict
Joined
Apr 16, 2018
Threads
170
Messages
1,053
Good news. Got a kit for it, US cleaned it for about 30 minutes. And bam, she's working like a champ. Now I just got get the oiler to work and she'll be finished.
I'm scared to death of chainsaw and trimmer carbs. I don't know why. To the pro's they're easy. So when I rebuild one, and it comes out right, I get so happy.

Do you know anything about the oiler in this saw?
I've taken the little screen out and clean it. Blew a little (low PSI) through the lines. Unscrewed the oiler adjustment screw a couple of turns.
I suppose I could try spraying some WD 40 through it and see if it's just clogged up.
 
Last edited:
Top