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#Post#: 81011--------------------------------------------------
CS-590 carb help
By: graywarrant Date: January 23, 2018, 9:30 pm
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First post:
Echo CS-590 C25812082968 (built May 2015)
Bought the saw off of CL, story was it was used clearing around
some land, put up on the shelf for several months, pulled down
and couldn't get it to crank w/out starting fluid, would not
continue to run and he didn't have time to mess with.
Once home and looked over, the PO had been all in the thing,
blown head gasket, missing parts, basket case.
After ordering the gasket, new piston ring and various bolts, I
put the saw back together.
I'm now fighting getting the carb adjusted correctly. Starting
with 1 3/4 on L and 3/4 on high with TAS 1 turn in just past
touching. These settings are based off of Echo Service Data
90-ZCA-00 (European specifications) so may be a bit out of wack.
I've tried various "factory default" settings for the L & H
mixture screws with those above being the ones that have at
least gotten the saw to crank and run (poorly).
Symptoms now are something I haven't seen in my limited
experience: I can get the saw to run and it will immediately
run up to near WOT, I can pull the throttle in half way and
bring the saw down to high idle (chain still spinning) and
attempt to adjust. Adjustment has little affect other than to
kill the saw if I run the L screw all the way in. Oddly if I
pull the throttle in all the way the saw runs up to WOT again.
Thought maybe the jets were swapped, so looked them over and
compared to other 2 strokes I have and it appeared that the jet
with the taper is on the L side and the more stocky jet is on
the high side - I have tried both and this configuration gets me
started and running poorly. Can anyone confirm this
configuration to be correct?
I've checked the metering and fuel pump diaphragms and appear to
be good to my untrained eye. Also checked the vent, fuel filter
and fuel flow (no blockages).
Looking for ideas before dropping $100 on a new carb as I am
suspecting the needle seats may be toast. thought about a
rebuild kit and may try that before a new carb.
Thanks -
Ray
#Post#: 81013--------------------------------------------------
Re: CS-590 carb help
By: 660magnum Date: January 24, 2018, 2:12 am
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At this point being as the history of the engine is a complete
mystery, I would run a pressure/vacuum test on the engine.
A lack of crankcase vacuum will make the carburetor mixture
needles unresponsive - especially at lower speeds.
#Post#: 81014--------------------------------------------------
Re: CS-590 carb help
By: Chainsawrepair Date: January 24, 2018, 6:40 am
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Sounds like air leak. WAG crankcase seals etc?
#Post#: 81022--------------------------------------------------
Re: CS-590 carb help
By: graywarrant Date: January 24, 2018, 1:25 pm
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Thanks for the feedback. I took a look at my Mityvac this AM and
it will do both pressure and vacuum. Need to source a pressure
gauge and figure out how to block everything off. Looks like
best option is pieces of inner tube at exhaust and intake and
hack up a spark plug to attach the vac/pump to.
Sound like the right direction?
#Post#: 81023--------------------------------------------------
Re: CS-590 carb help
By: 660magnum Date: January 24, 2018, 1:27 pm
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Sounds good. Once you get set up for this routine, it is easier
on the next chain saw.
#Post#: 81025--------------------------------------------------
Re: CS-590 carb help
By: graywarrant Date: January 24, 2018, 6:22 pm
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Cut4fun: What is a "WAG"?
#Post#: 81027--------------------------------------------------
Re: CS-590 carb help
By: farmboy Date: January 24, 2018, 10:24 pm
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I'm not Cut but WAG= Wild Ass Guess.
Shep
#Post#: 81036--------------------------------------------------
Re: CS-590 carb help
By: graywarrant Date: January 25, 2018, 6:58 pm
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Thanks Shep.
I was able to spend an hour or so tinkering with the saw
tonight. I got the block off plates made, used contact cement
to layer on a bit of innertube and tried them out. I was able
to pull, but not hold vacuum and was then called in by the Wifey
for other chores, so I'll have to get back out and try to
pressurize the case and see where she is leaking.
Thanks for the help so far, feel like I've made some progress.
Ray
#Post#: 81037--------------------------------------------------
Re: CS-590 carb help
By: 660magnum Date: January 25, 2018, 7:43 pm
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The spec is not for the engine hold the full vacuum forever!
There are many variations on how to go about pressure testing a
chainsaw crankcase.
If you have a repair manual for your chainsaw, there is likely a
crankcase pressure testing tutorial in the repair manual. If you
have several different manuals, you may find several different
ways to perform the pressure test?
The basic factors are:
The chainsaw must have the cylinder sealed to the crankcase.
The muffler and carburetor must be sealed off. This can be done
with solid gaskets, inner tube, plastic or metal pieces, or
combinations of these.
The pressure used is 1/2 atmosphere which is .5 KPa or 7 lbs
pressure or 14" of vacuum.
Pressure is easiest to do as any leaks can be found with dish
washing soap bubbles.
Crankshaft lip seals should also be checked with a vacuum due to
their design. A chainsaw can check OK under pressure but
absolutely fail the vacuum test due to the crankshaft seals.
The pass/fail parameter is that the crankcase should not loose
more than 1/3 of the test pressure within 30 seconds.
There are a lot of ways to create the pressure or vacuum.
The most accepted way is to use the automotive tester for
bleeding brakes and checking vacuum switches.
The Mity-Vac 8500 is the definitive tool (Ebay?)
#Post#: 81042--------------------------------------------------
Re: CS-590 carb help
By: graywarrant Date: January 26, 2018, 4:44 am
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660 - Thank you for the detailed reply. Unfortunately, I have
been unable to locate a service manual for the CS-590 - all
googling points to it being only available in digital format to
dealers/service centers. I will call my local dealer today and
see if it is available for purchase. I hadn't found another
service manual, some service manual supplements, but no straight
out service manual. If you have a link to one, please let me
know as I suspect that the pressure/vacuum procedure should be
near universal across all 2 strokes.
As for my post, I may have been misleading when I stated "able
to pull, but not hold". When I Pulled the handle of the vac
pump in, the vac gauge deflected a slight amount and then went
away as quickly as it started. by pulling vacuum I meant that I
could see some deflection of the needle. It didn't hold vacuum
for any length of time.
I will dig in deeper with the pressure test as last night I
didn't have the time to take the saw all the way down.
Hopefully I can find time between other projects this weekend.
Thanks again for the feedback and guidance.
Ray
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