064 Carb tuning

[DavidP71801]

I have a 064 with a thin base KS 066 piston and cylinder and I need some advice on tuning. I am very hard of hearing because of injuries I received in the Marine Corps so I have to use a tach for tuning which usually isn’t a problem but the 064 manual doesn’t have a procedure for tuning with a tach but a ms660 manual does and when I try to follow it I’m running into problems and I don’t know if it’s because the 660 procedure won’t work on the 064 or there is something else wrong. I have tried it with both a Bing and a Wj-34 and got the same result when I try to follow the procedure in the picture below I can’t get the highest idle below 3500 even with the LA screw backed off all the way. I have done a pressure and vacuum test and it held both perfectly. So I’m lost any advice would be great appreciated

 

[DavidP71801]

Everything is stock except the 066 cylinder and a muffler mod. It has the 0000-400-1300 coil and dual key flywheel using the “B” keyway.

 

[Mastermind]

Very strange. Are you sure that the throttle is not being held open a bit somehow? Throttle rod bent maybe?

 

[el33t]

Very strange. Are you sure that the throttle is not being held open a bit somehow? Throttle rod bent maybe?

Or perhaps its end is not placed in the intended hole and is pushed by the "flat part" of the throttle trigger.

 

[DavidP71801]

Very strange. Are you sure that the throttle is not being held open a bit somehow? Throttle rod bent maybe?

It’s doing the exact same thing with the Bing and WJ-34 I’ve looked at the carb off the saw and the throttle blade appears to be closed fully. I’ve also checked the linkage and it’s not putting any pressure on the throttle arm in fact the 1st 1/4” of movement is taking up slack before it starts to move the throttle arm.

 

[DavidP71801]

Or perhaps its end is not placed in the intended hole and is pushed by the "flat part" of the throttle trigger.

It has that slot the hook on the throttle rod hooks into the 1st 1/8-1/4” of movement is taking up the slack before the throttle arm begins to move

 

[Mastermind]

I have no idea then.

 

[DavidP71801]

Could there be an air leak in the carbs somehow? Maybe sucking air back down the impulse line? Just thinking about the carb is the only thing not in the system when I pressure/vac test

 

[el33t]

It has that slot the hook on the throttle rod hooks into the 1st 1/8-1/4” of movement is taking up the slack before the throttle arm begins to move

Have you checked that the throttle is not stuck in the fast idle position?
Does the LA screw turn the butterfly at all? Does it touch the arm? Does the engine rpm change?

 

[Brad Button]

Something else to check, pull the carb off and work the throttle, watch the throttle plate. Sometimes, not often the screw that holds the plate in place comes loose and the plate gets cocked at an angle and won't let the throttle plate close down all the way.

 

[bogieboy]

Stupid question, but when your saw is idling at 3500 rpm, is the chain moving? Wondering if your tach is not exactly reading right?

 

[gorilla]

Lots of layers between air filter and cylinder on 064's make sure nothing is perished or a bit of sawdust inbetween any of the layers. Also impulse line may not shoe signs of holes but give it a blow to check for leaks.

 

[Mastermind]

Stupid question, but when your saw is idling at 3500 rpm, is the chain moving? Wondering if your tach is not exactly reading right?

Not stupid at all.

 

[gorilla]

Also 064's have a mild propensity to shearing woodruff key as they have some kick, if this has occured, your timing could be out a little. And their coils go goosed after a while. Don't know if this would give the symptoms which you are describing?

 

[el33t]

Not stupid at all.

It may be that the tachometer is set for a four-stroke engine (to put it simply). Then the rpm reading will be twice what it should be.
Although I don't think that's the case, because if everything was right, the engine should rather die when the LA screw is fully unscrewed.

 

[Nutball]

I don't know if you can hear if it is a steady idle or a surging one like if it's running out of fuel. Surging would indicate an air leak in the fuel system.

 

[DavidP71801]

Stupid question, but when your saw is idling at 3500 rpm, is the chain moving? Wondering if your tach is not exactly reading right?

Yeah the chain is moving so I don’t think it’s the tach but that’s definitely not a stupid question or idea

 

[DavidP71801]

Have you checked that the throttle is not stuck in the fast idle position?
Does the LA screw turn the butterfly at all? Does it touch the arm? Does the engine rpm change?

If I turn the LA screw in it will increase the rpm I backed it off till it no longer touches the throttle arm. To eliminate throttle linkage I took it completely off and still the same thing I’m honestly baffled

 

[DavidP71801]

Something else to check, pull the carb off and work the throttle, watch the throttle plate. Sometimes, not often the screw that holds the plate in place comes loose and the plate gets cocked at an angle and won't let the throttle plate close down all the way.

I’ve looked at the throttle blade that was my first thought as old as the carbs are I’m sure they have been apart and maybe not reassembled properly. I shined a flashlight down the bore of the carbs and both throttle blades appear to be sealing off

 

[DavidP71801]

I don't know if you can hear if it is a steady idle or a surging one like if it's running out of fuel. Surging would indicate an air leak in the fuel system.

I really can’t hear it I am legally deaf in 1 ear and have 80% loss in the other but the tach reading is pretty stable stays at 3500 plus or minus 25 rpm. An air leak in the fuel system is something I haven’t checked I can easily check the lines but how can I check the carb? I have pressure tested the carb and it passed but that only checks to the needle could it be past that?