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CS-590 will not idle

Started by Dave41A, April 18, 2020, 03:35:34 PM

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Dave41A

Quote from: Hilltop366 on April 20, 2020, 04:23:31 PM
Where is your high speed (H) set?
H is set at 1-1/2 turns open.  Thank you for your continued help.  Dave

Al_Smith

If this link works try this .I couldn't get into the Walbro site or just lack the patience for it .This should be the service for a Tillotson model HS which is a common carb and they all work the same ----https://tillotson.ie/wp-content/uploads/2015/07/techinfo_hs_us.pdf

Dave41A

Quote from: Al_Smith on April 20, 2020, 05:06:41 PM
If this link works try this .I couldn't get into the Walbro site or just lack the patience for it .This should be the service for a Tillotson model HS which is a common carb and they all work the same ----https://tillotson.ie/wp-content/uploads/2015/07/techinfo_hs_us.pdf
OK thank you.  The download worked.  That is very good information. 
The only thing I see in common between the "will not idle" and the "will not accelerate" (mine won't do either) is the needle valve lever setting.  I will look at this carefully--sort of like setting the float in a bowl carb.  I am thinking the metering chamber is not getting enough fuel.  I will also double-check the needle valve passage for obstructions using the WD-40 method.  I will dig around a little and see if I can find the lever setting for the Walbro HDA 268A.  Thanks again.  Dave

Dave41A

Quote from: Al_Smith on April 20, 2020, 05:06:41 PM
If this link works try this .I couldn't get into the Walbro site or just lack the patience for it .This should be the service for a Tillotson model HS which is a common carb and they all work the same ----https://tillotson.ie/wp-content/uploads/2015/07/techinfo_hs_us.pdf
I removed the lever & needle on the metering side and the inlet screen on the pump side.  I probed this hole with a fine wire and looked through and could see a pinhole of daylight.  I also blew WD-40 through it and it went through in both directions.
Based on what I read in the manual provided by Al, I was able to search for the equivalent guide from Walbro, which is their C-1022 service manual.  I was able to download a copy of this manual from an RC aircraft site.  Setting the lever on the HDA series carburetor normally requires use of the walbro 500-13 gauge, but for the HDA series, which this is, the lever is simply set flush with the flat surface of the carb.  I used a machinist rule and verified that this was correct.
I re-assembled and set the lever as described above, then installed the carburetor back on the saw.  Both L and H are set at 1-1/2 turns out, which is the starting position specified in the C-1022 manual.
I have re-assembled the saw, and taken it outside.  It will fire on the first or second pull at full choke.  I then push the choke in (e.g. half choke, throttle set), and pull again.  On the first or second pull, it will fire, run fast for 3-4 seconds, and then die.  I am not touching the throttle lever at all when doing this.  If I squeeze and release, the engine dies.
The C-1022 manual is very helpful, and explains the differences between diaphragm and bowl carburetors on page 5, which makes this more understandable to me.  However, I do not feel I am any closer to a running saw.
Thanks again to everyone who has contributed to this effort.  Dave

Dave41A

As an update to what is going on, I worked on the saw a few more hours this evening.  One test I did is as follows:  I removed the carburetor from the saw, and with the sparkplug out, turned the engine over by pulling the starter cord.  I felt at the end of the impulse pipe and felt no spurts of neither pressure nor vacuum from this hose.  I then removed the diaphragm from the carb, and reconnected the carb to the fuel hose and impulse pipe.  I then turned the engine over as before, while depressing the metering lever with my finger (e.g. needle valve open).  I then cranked the engine several times by hand, expecting to see fuel come from the needle valve area.  Nothing.

I then blew into the impulse pipe (hose) and air blows right through it.  I turned the engine to several positions to ensure the scavenge & exhaust ports were blocked/closed, but it made no difference.  It is as if the crankcase end of the impulse pipe/hose has broken off or become disconnected.  There is plenty of vacuum at the crankcase bellows intake, but none at the vacuum line, even if I partially cover the intake bellows with my thumb.

It will take me some time to dig into how and where the impulse line connects, but my reasoning is as follows:  When the engine is at full or half choke, there is enough vacuum in the carb barrel to pull fuel all the way from the fuel tank--through both check valves and the needle valve--despite a non-functioning fuel pump.  However, when the choke is released, this vacuum drops, and then the engine dies.

I am new to this so this is just an educated guess based on what I observe.  Is there a more reliable way to test for a functioning fuel pump?  Should I be able to blow through the impulse pipe like I describe?  This is number "8" in the attached diagram.

 

Any insight is appreciated--especially an easy (easiest) way to access the other end of the impulse hose.  Thanks for the pointers from everyone so far.  I am definitely learning about saws.  Dave

Dave41A

Yet another update:  I once again removed the metering diaphragm from the carburetor.  I connected a small syringe to the impulse connection on the carburetor.  I pumped the plunger of the syringe while holding the needle valve open with my finger.  Sure enough, fuel began to pool at the needle valve seat.  Repeating this test with the impulse line connected did not cause fuel to pool, even with repeated pulls of the starting cord.  So I am making progress.  Somehow this impulse line is not doing its job.  It is not plugged, so it is either broken or disconnected.  Thanks to everyone still reading.  Dave

Hilltop366

Sounds like you are making progress, not pumping fuel will certainly impede performance. :)

I always try to try to look on the bright side, just think of all the new things you have learned that you hope to never have to use again! 

Dave41A

Quote from: Hilltop366 on April 21, 2020, 10:08:32 AM
Sounds like you are making progress, not pumping fuel will certainly impede performance. :)

I always try to try to look on the bright side, just think of all the new things you have learned that you hope to never have to use again!
Thank you for your continued interest.  I was able to remove part of the rear handle of the saw and peek in between the handle assembly and the crankcase.  Sure enough, there is the impulse hose, dangling there, connected to nothing!
I can also see the little hose nipple where it is supposed to connect.  Somehow it worked itself free.
Right now the only thing holding the two halves together is the bellows.  This is part 12 in the diagram I posted earlier.  It looks like it is a press fit into the rear handle assembly, but I am not sure.  Having never taken one of these apart before, I do not want to force it and break things.  These are not the most expensive parts on the saw, but I do not need more down-time waiting for another parts order.  I am (and have been) burning good daylight, as the saying goes.
Any insight as to how to disconnect the intake bellows from the rear handle assembly on a CS-590 is appreciated.



 
Edit, 12:30 PM:  I figured it out.  Got the bellows disconnected--there is a little metal retaining ring that keeps the bellows expanded into the rear handle assembly intake opening.  This ring slips out, then allows the rubber bellows to be collapsed down to fit through the hole.

Here is a picture after the cleaned off some of the sawdust and oil.  The impulse hose and crankcase nipple (at screwdriver tip) are both clearly visible.  The disconnected hose also probably least reduced my crankcase vacuum at idle, making it harder for the carb to provide the right mixture to the engine, anyway.  This would be true even if the carb was being supplied with fuel--which it clearly wasn't.  I'll have to see if I have a small hose clamp I can put on this line.

I have to work on a few other things for the next few hours but will get back to it this evening.  I will post back when I have a running saw.

Thanks to everyone for the help here.  Dave

Dave41A

As of 7:40 this evening, I have the saw back together.  It starts OK, and will idle.  I can rev it to full throttle and it runs at high speed fine as far as I can tell.  However, after releasing the throttle it drops back to idle but it only idles for maybe 7-10 seconds before quitting.  It restarts without problems. I assume this is a carburetor tuning problem or one of the other issues already identified (old diaphragms/gaskets, fuel filter, etc.).  However, any insight would be appreciated.

Thanks again.  I would not have made it this far without the insight provided here.  Dave

PS:  As an aside--either I have huge feet or the CS-590 was made for people with feet like bananas.  I cannot get my foot in the rear handle with work boots on!

sawguy21

 :D I hold the wrap handle in my left hand and push the saw away as I pull. The big bruisers go on the ground. Being a southpaw I developed a bad habit of holding the saw with my right and pulling with my left, I quickly learned the folly of that method, saws did not yet have chain brakes.
old age and treachery will always overcome youth and enthusiasm

Hilltop366

Start and warm up the saw then adjust your low speed mixture and reset your idle speed to see if you can improve it.

If it smokes a bit when you restart it after stalling (no choke) it is likely too rich, turn L in a bit.
If it restarts a bit hard and may requires some choke it is likely too lean, turn l out a bit.

Turning either mixture screw effects the other a bit so it can be back and forth a few times to get it balanced out.

Be careful not to set the high speed too lean, how I set mine is when running at full throttle turn the H mixture screw out until it just starts to "4 stroke" usually it will "clean up" when the engine gets a load on it (cutting wood), if not turn the H in a tiny bit and try again. I would rather it run a bit under max and not chance over heating.


Dave41A

Quote from: Hilltop366 on April 21, 2020, 08:43:09 PM
Start and warm up the saw then adjust your low speed mixture and reset your idle speed to see if you can improve it.

If it smokes a bit when you restart it after stalling (no choke) it is likely too rich, turn L in a bit.
If it restarts a bit hard and may requires some choke it is likely too lean, turn l out a bit.

Turning either mixture screw effects the other a bit so it can be back and forth a few times to get it balanced out.

Be careful not to set the high speed too lean, how I set mine is when running at full throttle turn the H mixture screw out until it just starts to "4 stroke" usually it will "clean up" when the engine gets a load on it (cutting wood), if not turn the H in a tiny bit and try again. I would rather it run a bit under max and not chance over heating.
Hilltop:  Thank you.  I'll do what you suggest.  By "tiny bit," how much of a turn do you mean?  I have been using 1/4 turns.   Thanks, Dave

Hilltop366

A quarter of that quarter turn, when things get close to right it does not take much.

Dave41A

Quote from: sawguy21 on April 21, 2020, 08:21:29 PM
:D I hold the wrap handle in my left hand and push the saw away as I pull. The big bruisers go on the ground. Being a southpaw I developed a bad habit of holding the saw with my right and pulling with my left, I quickly learned the folly of that method, saws did not yet have chain brakes.
Thank you.  Good suggestion.   This is definitely easier.  Dave

Dave41A

Quote from: Hilltop366 on April 21, 2020, 11:21:31 PM
A quarter of that quarter turn, when things get close to right it does not take much.
Thank you.  I started with "L" at 1-1/2 turns open per the manual, and slowly crept all the way up to 2-1/4 turns open.  There does not seem to be any effect on performance.  I can rev the saw to full throttle, release, and let it idle.  It idles for 12-13 seconds every time, then quits.  The idle speed seems to slowly creep up during the 12-13 seconds, and peaks just before it quits.  I am thinking this is still a fuel delivery problem.  Maybe a pinhole in the impulse tube or a pump check valve leaking prevents fuel from pumping at idle, or even a pinhole in the fuel line allowing the pump to suck air.  Any thoughts appreciated.  Thanks again, Dave

donbj

If it revs up before dieing when idling that's for sure it's running out of fuel in that circuit. It's slowly leaning out and quitting. Something going on in that circuit for sure.
I may be skinny but I'm a Husky guy

Woodmizer LT40HDG24. John Deere 5300 4WD with Loader/Forks. Husky 262xp. Jonsered 2065, Husky 65, Husky 44, Husky 181XP, Husky 2100CD, Husky 185CD

Air Lad

Would definately put the L adjustment back to 1 1/2 -1 3/4 turns out to begin diagnose.Still could be air leak,seals ?

brewdog

Just had about the same with 61 huskie,had 3 different carbs on it /that wasnt the prob. couldnt get it to run past idle new gas line all is fine.

Dave41A

Donbj, Airlad, Brewdog:  Thank you. I have some parts on order.  I am going to start with new gaskets in the carb, then move to new fuel line, filter, and impulse line.  The saw obviously works, but one or all of these components is not up to full performance.  I am guessing the impulse line is the main problem, but the others are probably contributing, too.  As a whole, they add up and slowly starve the carb of fuel.

Air Lad

At the end of the day,if you go this way 
you know that once you solve the problem
all the other perishables have been updated to new and you 
should get good service from the machine for
years to come.
It's my way of doing it
smiley_thumbsup

kenskip1

David, Try this trick.On the end of the impulse line that is coming from the crankcase,put a dab of grease on the line. Just enough to cover the end of the tube.Now give the rope a few pulls with the spark plug installed.. The grease  should be drawn into the crankcase.From your well detailed analysis, I will make an assessment and say that the fuel pump diaphragm is beginning to stiffen and not pulling the gas in at lower RPM. Best of luck, Ken
Stihl The One
Stihl Going Strong
Stihl Looking For The Fountain of Middle Age

Dave41A

Quote from: Air Lad on April 23, 2020, 04:24:24 AM
At the end of the day,if you go this way
you know that once you solve the problem
all the other perishables have been updated to new and you
should get good service from the machine for
years to come.
It's my way of doing it
smiley_thumbsup
Thank you.  Getting a sense of what is "perishable" on these saws and in need of periodic replacement is a big part of what I am learning.  I have the fuel system from tank to carb on order, as well as a new o-ring for the fuel cap (which is almost impossible to turn now).  All good experience.  It will be 10 days before anything arrives, so now I just need to be patient.
Thanks again, Dave
PS:  The ship I was on at the time pulled into Sydney, Melborne, and Hobart back in '95-'96.  I went to see the blue mountains when ashore.  Is this anywhere near where you are?

Air Lad

No Dave. Sunny QLD. To the north
Cheers smiley_beertoast

Dave41A

Update as of 27 April 2020:  The carb kit shipped separately from the rest and arrived.  I installed new pump gaskets, new diaphragm and diaphragm gasket, new needle valve, lever and pivot, removed Welch plug, cleaned idle jets, and replaced with new Welch plug.  Adjusted needle valve lever per Walbro carb manual--flush with carb body gasket surface.

Saw starts & runs at full throttle, but when releasing throttle it will drop to idle and now only run for 7 seconds before quitting.  Adjusting low idle up and down 1/2 turn makes no effect. 

I did the grease check at the impulse line and it generates good pulses of vacuum and pressure.

New impulse hose, fuel filter, fuel line, grommet, o-ring, etc are all on backorder and are at least 10 days out.

Thanks for all the feedback so far.  Still scratching my head on this one.  Dave

Nolan1030

Have you done a compression check on this saw? If you have cylinder damage this would cause low speed issues. I work on two stroke outboards for a living and we always start with a compression check. A saw(or any motor) with low compression will have trouble pulling fuel at lower speeds.

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