MS192T acting up - doesnt drop to idle immediately

WolfpactVI · Mar 22, 2013

Well, I got the filter base replaced. Didnt make a difference. Tried retuning the saw tonight, and I noticed a few things. First, the top end seems to be fine - I can get it just at the 4-stroking point no problem, and it cuts fine when I tested it in some elm logs.

Now for the weird stuff. First, I couldnt get it to idle nicely. No matter how much I would fiddle with the L and LA screws, it either idled really fast, or died. Just couldnt get a happy medium. That could be chalked up to my inexperience at tuning though.

Second, it would take a while for changes to take effect (like Windows) to any turns of the L and LA screws. It would be idling fast, I'd turn it a bit, nothing. Bit more, nothing. Bit more, nothing. Then all of a sudden without me touching it, it would slow down and die. Then it wouldnt restart until I had turned the screws back a bit.

Third, it would die if I turned it on it's side. Which renders a climbing saw pretty much useless. I made sure the tank was full. But without fail, when it was idling (fast) as soon as I turned the saw onto it's left side (filler caps down, adjustment screws up) the idle would drop really low and die.

Fourth, sometimes it would not drop to idle immediately (like previously), other times it would. Seemed to be random whether that would occur or not.

I'm going to tear the thing down this weekend, look at the fuel lines, etc, since I wont need it for the next 3-4 weeks. I hope someone has some idea what's going on, because I'm about ready to through the thing in a pond. That could partly be due to a long week though. I'll keep you posted. Thanks everyone for the help so far.

- Justin

Stihl n Wood · Mar 22, 2013

Sounds like air leak caused by a bad crank seal or seals. Especially that you mention it changes when turned on its side like that.

jwp · Mar 23, 2013

There are two things to try before tearing everything down. Run the idle needle to the bottom and then back to its correct setting and see if this fixes the problem. If there is still a problem spray wd40 around each crank end seal with the saw idling and see if there is a change. If the idle changes it is probably a crank seal leaking. You can also spray wd40 on anything that you think may be leaking air. If the idle changes then you have an air leak.

Cracks in the fuel line will cause the saw to go lean when tilted on its side if the crack in the line comes out of the fuel.

I am not a saw mechanic so try these ideas at your own risk.

WolfpactVI · Mar 25, 2013

I am definitely beginning to suspect an air leak somewhere, with the tilt-sensitive behavior. I'm also thinking that the root cause of my woes is the saw having been dropped. I never gave it a second thought because 1) there didnt appear to be any damage, 2) the saw seemed to run fine afterwards, and 3) I didnt use it for a while after that, and it's been so long now that the whole thing was out of my mind.

I realize now it must have landed on it's butt (specifically, the air filter cover). I discovered evidence of that on the filter cover, and that would explain the messed up filter base. It also means that anything in the vicinity of the carb could have been flexed, jarred loose, cracked etc. I dont know if the crank seals could have been damaged by that type of fall, but I'm sure hoping not. I've not had it in a situation where the bar has been wrenched around relative to the body that I can remember. Nevertheless, I guess I've got to check everything now. Thanks for the WD-40 suggestion. That sounds like a great way to do some diagnostics before I just randomly start replacing parts.

- J

WolfpactVI · Mar 25, 2013

jwp said:
Run the idle needle to the bottom and then back to its correct setting and see if this fixes the problem.

Are you referring to the L or LA screw?

Stihl n Wood · Mar 25, 2013

Well now you mention it was dropped pretty hard on the back of the saw. In that case it probably is Carb area related. Air leaking from boot or something got jarred loose. Crank seals probably not so likely from a fall. The crank sits very tight in the main bearings and would not flex enough to damage them. But you never know. I'd start by stripping the Carb system back to the jug and make sure you have a good seal. Using the Wd-40 trick is a good first start.