Chainsaw won't start when hot

[sdef]

My experiences may be different than yours as I drain all of the stabilized fuel from my 2/4 cycle utility engines when done with them unless I will be using them again soon, such as the lawn mower during the summer time or when cutting large amounts of firewood.

Approaching the hot starting problem only, sometimes my Husqvarna semi pro/pro saws can be hard to start when hot due to me not paying attention to proper hot starting procedures. You may need to verify your hot start procedures if not done so already. When this happens to me I switch to another saw until the first one cools down or... I ensure the choke is open, place the throttle into wide open position and pull the starter rope until it fires, which usually takes 10 or 15 pulls (sometimes more) on the rope; just like starting an old carbureted automobile that was flooded. My oldest saw is ~ 15 years old and never fails me as long as I do my part. The newest saw that uses a computer is more touchy to me following proper hot starting procedures.

You have replaced quite a few parts. In my experience, if my chainsaws start and run fine when cold and run fine when hot, the hot starting problem is caused by me. Of course, whatever is causing your current no start problem could have been causing your hot start problem.

 

[dfkrug]

I'm a little skeptical of the word always.

The intake side of the piston and cyl can get scored from sucking dust. Not as common as the
damage you see at the exhaust port, yes. I have seen it several times, from bad or missing air
filtration.

I am with MYSFYT and YOMAX: weak spark can come from weak magnets, bad cap, or bad wire.
Weak magnets are extremely rare in my experience, but excessive heat can damage them. That
is why you don't use a torch to pull the flywheel.

Also, at least one large saw maker had a recall from hot-start issues. It was due to flooding the
carb when a hot saw was turned off. Tank pressure buildup overwhelmed the rubber valve in the
carb. Some tanks have only one-way vents.

 

[jefffarq]

If I remember correctly, some people on the web said their saws had compression around 150 psi. My Stihl dealer said I didn't need to check compression, just remove the muffler and look at the piston and rings for dammage. He said the dammage always occurred on the exaust side. I'm a little skeptical of the word always.

Tested the compression, it runs between 125 - 140, depending on how well I can hold the saw/tester and pull the rope.

 

[Oldpath05]

Chainsaw won't start when hot<<< Neither will I, sounds like the 1970s Partner chainsaw, guess it was called vapor locking.
I have a 3 year old Husqvarna 550XP with a make believe Auto Tune system, that can start miserable hot or cold, sometimes I don't know whether or not to choke my saw or no or throw it the brush pile, 3 pulls it can flood, gas comes out the exhaust, sometimes, 1 pull and it runs.

 

[jefffarq]

I finally got time to fiddle with this some more, I pulled the muffler and sure enough, the top of the piston is badly scored.

So, in trying to determine what's next, I guess my next question is - what is the likelihood of the cylinder being damaged? I see pistons and rings are fairly cheap, the cylinder not so much. I haven't had time to disassemble the whole engine; and I don't want to just for the exercise, but I know I can't tell whether the cylinder is bad or not without taking the whole thing apart.

 

[Oldpath05]

I'd say since the piston is scored it must of scratch the cylinder and should be fixed to if it doesn't cost more then the saw's worth. The other option is boat anchor or hang it on a limb at 300ft and use for target practice, I'd go with the target idea, tannerite and shotgun slugs.

 

[4570Man]

I had a lawnmower that would die and wouldn't restart until it cooled down. The coil was bad.

 

[4570Man]

I'd say since the piston is scored it must of scratch the cylinder and should be fixed to if it doesn't cost more then the saw's worth. The other option is boat anchor or hang it on a limb at 300ft and use for target practice, I'd go with the target idea, tannerite and shotgun slugs.

Will shotgun slugs detonate tannerite? They recommend a minimum of 2000fps, and their website says shotgun slugs will not reliably detonate it.

 

[stuckmotor]

I had a lawnmower that would die and wouldn't restart until it cooled down. The coil was bad.

I had one with the same symptoms. It caused me so much frustration that I ditched the mower and cut my vines with a swing blade. I used the slasher on the yard.

 

[4570Man]

I had one with the same symptoms. It caused me so much frustration that I ditched the mower and cut my vines with a swing blade. I used the slasher on the yard.

Except I didn't have a tractor at the time which left me little choice except get it sorted out. It also caused lots of frustration and took me a while to figure it out. I could mow about 15 minutes before it shut down.