Stihl 066 magnum switch falls from warm start back into cold start

[Caleb Brooks]

My grandfather has an 066 magnum that he purchased around 1995. It has seen a lot of miles through the years and I’ve taken to using it now that he is getting old enough that the big saws are hard on his back. Recently I’ve been running and 881 my cousin just bought so I left the 066 with my grandfather. He informed me that he flooded it badly and didn’t know why at first. He said it went down into full choke(cold start) perfectly and the motor hit as it should after a couple of cranks. He raised the switch up to half choke(warm start) and started cranking on it to no avail when he realized the switch was all the way down in the cold start position again. He thought it was his mistake at first but it happened time and time again. I know there are only a few things it can be, like the master control switch, trigger assembly, or linkage. I’m just wondering if any of you have ran into this issue before so I will know where to look first. I’ve gotten some good answers(and not-so-good answers from reading these kinds of threads when I google my issues. I’ve never been a member of one of these sites until just today and I thought I would throw a problem out there and see if the internet would deliver. It is mind blowing to be able to ask a question to 1000s of years of combined experience at once. Thanks in advance yall!

 

[NSEric]

Check out this thread.
I had to add a shim to the choke lever on my clone when it lost fast idle.
https://www.arboristsite.com/threads/066-does-not-have-a-fast-idle-on-cold-start.192288/post-5085359

 

[ZeroJunk]

Losing fast idle is common. Dropping back to choke, not so much. Trying to visualize how that would happen.
I may have a control shaft. I'll look.
But, it may be the spring on the choke butterfly on the carb itself.

 

[Caleb Brooks]

Losing fast idle is common. Dropping back to choke, not so much. Trying to visualize how that would happen.
I may have a control shaft. I'll look.
But, it may be the spring on the choke butterfly on the carb itself.

 

[rogue60]

Sounds like he might of forgot to pull the trigger as he pushed down for choke. As a result something is now bent or popped out of place.

 

[Dennisthemenace]

Pretty common on well used 1124 saws I've found. It doesn't take much play in the shaft for it to slip out of the trigger indent. The cause on my 064 was a slightly sloppy part no. 5

 

[Dennisthemenace]

Edit, I meant 1122 and 1124

 

[Caleb Brooks]

Losing fast idle is common. Dropping back to choke, not so much. Trying to visualize how that would happen.
I may have a control shaft. I'll look.
But, it may be the spring on the choke butterfly on the carb itself.

To clarify further, all of this happens when you are in the process of starting the saw but before the motor starts with the switch in the fast idle/half choke position. You can squeeze the throttle and throttle interlock and get the switch into full choke with no issue. After the motor hits, the switch is very finicky about going into fast idle/half choke position. It tends to get in a bind and not move up high enough to reach half choke position OR it goes past half choke and into the run position. When you finally get the switch to sit in the half throttle positions it will feel good but it will almost always slip back down into full choke once you start cranking. If it ever starts in half choke it will go ahead and take off. I think the guy that replied with a similar story is most likely right. I’m willing to bet it is either an issue with the “groove” the switch sits in being worn out or a problem with the throttle interlock being worn and wobbly. The throttle interlock is fully depressed while in the full choke position and is basically totally engulfed be the rest of the handle. I bet there is just too much play to the left and right in it to stay where it is supposed to be while it is getting a knot jerked in it’s butt. I’m sure it won’t be a complicated fix. I hope to be able to keep this safe running the rest of my days. It holds a lot of sentimental value to me. He has talked about selling it before because it is too much for him to handle very much now but I would have to try to buy it if he did. I have access to an 881 with a 41 inch bar and I run a 391 with 25” bar that will cut basically everything I encounter here in south central Kentucky but I plan to keep it running for as long as I can even if I don’t do too much with it. My grandfather’s hands were burned bad in an accident a few years back. Between the burns and age he has a hard time cranking it so once I get this issue resolved I am going to see if I can’t put a new elastostart pull rope on it for him to try. Maybe I will be able to go get it and take a look at it tomorrow and tell y’all what I found. Thangs y’all!

Sounds like he might of forgot to pull the trigger as he pushed down for choke. As a result something is now bent or popped out of place.

After 30 years of use that thing has probably seen every variation of abuse it could get. You may be on to something. Since he burned his hands years ago he has to depress the trigger and interlock with one hand and move the switch with the other sometimes. Instead of the years of muscle memory we all use to set the switch to choke he has to improvise and that leaves room for error. It has performed great for 30 years so I suppose it has earned the right to need a part

 

[Caleb Brooks]

Pretty common on well used 1124 saws I've found. It doesn't take much play in the shaft for it to slip out of the trigger indent. The cause on my 064 was a slightly sloppy part no. 5

Thank you! I will let your know what I find!

 

[stihltech]

Control shaft a and tank wear. This is how my 64/66 hot saw acted. It you don't get the control lever fully up to fast idle, it may pop back.

 

[NSEric]

Did you try the shim behind the control lever yet? Things wear and get sloppy, the shim fixes it.
I made mine out of plastic, it took about 10 minutes to fix it.