Author Topic: CS-590 carb help  (Read 395 times)

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Offline graywarrant

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CS-590 carb help
« on: January 23, 2018, 10:30:12 pm »
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

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Offline 660magnum

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Re: CS-590 carb help
« Reply #1 on: January 24, 2018, 03:12:30 am »
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.
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Offline Cut4fun .

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Re: CS-590 carb help
« Reply #2 on: January 24, 2018, 07:40:27 am »
Sounds like air leak. WAG crankcase seals etc?
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Offline graywarrant

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Re: CS-590 carb help
« Reply #3 on: January 24, 2018, 02:25:10 pm »
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?

Offline 660magnum

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Re: CS-590 carb help
« Reply #4 on: January 24, 2018, 02:27:55 pm »
Sounds good. Once you get set up for this routine, it is easier on the next chain saw.
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Offline graywarrant

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Re: CS-590 carb help
« Reply #5 on: January 24, 2018, 07:22:27 pm »
Cut4fun:  What is a "WAG"?
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Offline farmboy

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Re: CS-590 carb help
« Reply #6 on: January 24, 2018, 11:24:09 pm »
I'm not Cut but WAG= Wild Ass Guess.
Shep
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Offline graywarrant

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Re: CS-590 carb help
« Reply #7 on: January 25, 2018, 07:58:25 pm »
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

Offline 660magnum

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Re: CS-590 carb help
« Reply #8 on: January 25, 2018, 08:43:56 pm »
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?)
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Offline graywarrant

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Re: CS-590 carb help
« Reply #9 on: January 26, 2018, 05:44:57 am »
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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