064 Carb tuning

[DavidP71801]

I’m heading out to the shop I’ll take a bunch of pictures maybe someone will see something. Is there a way to post a video?

 

[Agent Smith]

If your vac/pressure test was good, two carbs produced the same result, I'd be looking at the intake boot or impulse line. Is the intake boot sleeve/ring present? Thats the area I'd inspect after the impulse line. Dont be afraid to take the intake boot off and bend it around. I've had them look fine till i bend them and cracks suddenly appear. Just my thoughts and hope you get it figured out.

 

[Coupe]

Have you got someone or a mate close handy that knows a bit about tuning saws to have a listen for you.
You really need to tune by ear to get the best out of them and tuning by ear is the best way to do it.

 

[Wood Doctor]

Last fall I ran into a chainsaw carb that would not idle down. I found an obstruction with the throttle control linkage from the trigger to to the carb that kept the spring from moving the throttle back to the idle position. I found it only by removing the carb and locating the obstruction. That fixed it and the saw started and ran fine thereafter. Take a shot at finding that obstruction.

 

[DavidP71801]

I ran it without the air filter base so I could see the linkage when running and I’ve never seen this before but when running the saw is pulling in enough air to overcome the return spring and crank the throttle just a bit kill it and it instantly closes fire it up and it cracks even with the throttle rod removed. Do I have 2 carbs with similarly weak return springs or is this thing just moving that much air? It’s always been a really strong saw but it’s just a Stock thin base 066 ks cylinder on a stock 064 the only thing that has been done to it is a muffler mod I think the numbers are ex 101 tr 123 and intake 79 squish is 0.023”

 

[bogieboy]

I wonder if the throttle return spring needs another wrap around the shaft on both carbs?

 

[Nutball]

Throttle shafts can wear and waller out with enough cycles, maybe that is part of the problem if not the spring?

 

[Merkava_4]

If the idle speed screw is not holding the throttle open, then what is?

Is the butterfly a slide in type? If so, make sure you don't have it installed switched around.

There should be stops on the butterfly that bump up against the throttle shaft if it's the slide in type.

 

[Stump Shot]

If no leaks are present, the low side is most likely leaned out to get the saw to run with the throttle completely closed shut.
Crack open the throttle with the LA screw and enrichen the low side by turning counterclockwise. Watch your tachometer and look for it to start dropping and stumbling, reverse the screw and lean it until it does the same, right in the middle should be your tune. Test by checking throttle response, if enriched properly engine should speed up near instantaneously, if not enrichen until it does. The low speed is now set, now you should be able to drop to the proper idle RPM with the LA screw.
As for another note, if your tachometer is adjustable, be sure it is set for one firing per revolution(one cylinder two stroke). A different setting may alter your readings.
Best of luck with resolving your issues.

 

[DavidP71801]

If no leaks are present, the low side is most likely leaned out to get the saw to run with the throttle completely closed shut.
Crack open the throttle with the LA screw and enrichen the low side by turning counterclockwise. Watch your tachometer and look for it to start dropping and stumbling, reverse the screw and lean it until it does the same, right in the middle should be your tune. Test by checking throttle response, if enriched properly engine should speed up near instantaneously, if not enrichen until it does. The low speed is now set, now you should be able to drop to the proper idle RPM with the LA screw.
As for another note, if your tachometer is adjustable, be sure it is set for one firing per revolution(one cylinder two stroke). A different setting may alter your readings.
Best of luck with resolving your

I’ve tried something similar but I’ll try this method. Thanks any suggestions where to start with the LA screw

 

[DavidP71801]

Thank you to everyone that is trying to help it really means a lot to me. Everyone PLEASE PLEASE PLEASE Protect your hearing. Everything becomes so freaking difficult when it’s gone.