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.

 

[DavidP71801]

I’m still fighting with this 064 I had a friend of mine bring his 064 I built for him over so I could swap parts and try to figure it out and honestly, I’m now more confused both saws are pretty much identical The only difference being his is built with a Stihl branded 066 cylinder. Mine is a Mahle branded 066 cylinder. The timing on both is very similar mine is 99-121-79 and his is 98-119-80 I built both saws at the same time They both are running the same ignition, the same flywheel the same carburetor but his tunes properly and mind doesn’t I have swapped the carbs his still tune properly and mine won’t so it’s not the carbs so I was thinking it had to be something in the linkage so I swap the trigger the linkage rod, the master control level and everything his still tuned properly. Mine wouldn’t I have done a pressure and vacuum test on both mine’s been holding 10 PSI pressure for over 20 minutes now and it held 10” of vacuum the entire time I was gone to lunch. What am I missing? Both carbs tune perfectly on his saw and both won’t tune properly on mine.

 

[Stump Shot]

I’m still fighting with this 064 I had a friend of mine bring his 064 I built for him over so I could swap parts and try to figure it out and honestly, I’m now more confused both saws are pretty much identical The only difference being his is built with a Stihl branded 066 cylinder. Mine is a Mahle branded 066 cylinder. The timing on both is very similar mine is 99-121-79 and his is 98-119-80 I built both saws at the same time They both are running the same ignition, the same flywheel the same carburetor but his tunes properly and mind doesn’t I have swapped the carbs his still tune properly and mine won’t so it’s not the carbs so I was thinking it had to be something in the linkage so I swap the trigger the linkage rod, the master control level and everything his still tuned properly. Mine wouldn’t I have done a pressure and vacuum test on both mine’s been holding 10 PSI pressure for over 20 minutes now and it held 10” of vacuum the entire time I was gone to lunch. What am I missing? Both carbs tune perfectly on his saw and both won’t tune properly on mine.

How is your exhaust screen?

 

[DavidP71801]

How is your exhaust screen?

I’m not running one but I think I figured it out. Apparently, I have a mismatch of parts because when I tighten down my air filter base I think it’s bottoming out against the car box before it gets the carburetor push tightly against the intake boot. I was trying to think of anything that I hadn’t swapped and wasn’t there for a pressure vacuum test so I reassembled both saws and reached through the hole for the adjustment grommet to see how tight the carburetor was and his is quite a bit tighter than mine. Both saws have the same intake boot, same carb box, same air filter base so manufacturing defect maybe

 

[Stump Shot]

I’m not running one but I think I figured it out. Apparently, I have a mismatch of parts because when I tighten down my air filter base I think it’s bottoming out against the car box before it gets the carburetor push tightly against the intake boot. I was trying to think of anything that I hadn’t swapped and wasn’t there for a pressure vacuum test so I reassembled both saws and reached through the hole for the adjustment grommet to see how tight the carburetor was and his is quite a bit tighter than mine. Both saws have the same intake boot, same carb box, same air filter base so manufacturing defect maybe

I'm not the most knowledgeable person on the ins and outs of these saws; however, I do know that it went through some changes in the area you describe, having an old and new version. The old, required gaskets as I recall. So, you might want to look at some IPL's and see that you aren't mixing and matching to a failure between the two different carb boxes.

 

[DavidP71801]

I'm not the most knowledgeable person on the ins and outs of these saws; however, I do know that it went through some changes in the area you describe, having an old and new version. The old, required gaskets as I recall. So, you might want to look at some IPL's and see that you aren't mixing and matching to a failure between the two different carb boxes.

I think I have seen a TI about it do you know someone that might have it?

 

[redline4]

I think I have seen a TI about it do you know someone that might have it?

There was some discussion about the different carb boxes, intakes and the flanges in my 064 build thread.
Maybe the pictures in there will help?

Thread 'Ugly Stihl 064 overhaul'

Nov 12, 2023

It seems my 064 decided to stop oiling the bar.
It still oils the bench, the shelf it sits on, the back of my truck or the bucket of my skidsteer from the case half gasket.
So, I've decided to give it a full tear down.
This will be in real time. It's deer season and im also working on an engine build for my car, so expect this to be like a trip to the Department of motor vehicles, slow, aggravating and totally unsatisfying.

I did order a gasket set, but now that I'm thinking, I did not order bearings...

Now, if you see me doing something wrong, let me know. Being a dumbasś is second...

• redline4
• Replies: 219
• Forum: Chainsaws

• 

My saw is an older model that originally had the flat air filter and I converted it to the HD2.

 

[DavidP71801]

I have found the problem. It appears to be a manufacturing defect in the intake boot. I ordered both of them at the same time they are part number 1122-141-2201 and are both marked 1122/01 the flange the carb seals to on the one off his saw measures 0.118” and the one on my saw is only 0.088” And the ring that goes around the outside of it is 0.080” so the boot only stands 0.008 proud over the ring on mine and almost 0.040” on his. I put both saws back together the way they were except for the intake boot now mine tunes properly and his doesn’t.

 

[Stump Shot]

I think I have seen a TI about it do you know someone that might have it?

@ray benson

 

[ray benson]

@DavidP71801 not sure these are what you need. Post up a T.I. number and I will check. There are quite a few T.I.s for the 064 that I do not have.