Chainsaw won't start when hot

[jefffarq]

I have a Homelite 18 in. 46cc saw, which ran great the first 2 or 3 years I had it. I will admit that I never drained the gas out when not in use, and so this past spring when I needed to trim some trees and started having problems with it, I figured that was why.

The saw would start very easily, usually on the 1st or second pull, but after it got hot it would die and not start again until it had sat and cooled for at least a half an hour.

After doing some reading on this and other forums regarding this problem and finding lots of advice, I have completed the following:

Rebuilt the carburator

Replaced fuel lines, filter, primer bulb

Fresh, high-octane gas

New spark plug

New air filter

Adjusted mixture 1/4 turn richer

After each of those adjustments, the saw still started easily when cold, but after it got hot it would die and not start again until it had cooled off.

The last time I used it I checked the spark after it died (after more reading on the forums), and sure enough, no spark. Forums said "bad ignition coil."

I replaced the coil with a new one, set the gap per instructions found online using a business card. The saw will not start at all now. Thinking I got a bad coil, I put the old one back on, set the gap, but it still won't start at all. In performing the spark test, I get what looks to me like a very weak spark, but a spark nevertheless. But it won't start.

I've searched all over, and the only "specification" I can find for the correct gap is the business card. I'd bet some money that's not how they set them at the factory, but then again I have trouble believing that a couple of thousandths either way would make a big difference. Does anyone know exactly what the gap should be set at?

But, the cotton-picking thing won't start.

What am I missing here?

Thanks,

Jeff

 

[Toyboy]

Business card, matchbook cover are the usual methods.
Try moving the coil closer. Use a sheet of printer paper to gap it and see what you get. I had a similar no spark issue with a different engine, and that made the difference.

 

[/pine]

Just an off the wall thought...I've read some saws have an issue with the muffler and a plate or something that can cause the no start when hot issue...removing the "plate" or cleaning it is the remedy...
...Also, low compression will also cause it to fail to start when hot...FWIW...

 

[davesl708]

Just an off the wall thought...I've read some saws have an issue with the muffler and a plate or something that can cause the no start when hot issue...removing the "plate" or cleaning it is the remedy...
...Also, low compression will also cause it to fail to start when hot...FWIW...

As /pine mentioned a fouled muffler will give you trouble. Clean the screen and I suspect your problem will improve.

 

[yomax4]

Also check your spark plug cap. I had one with weak continuity. Saw started like crap and not at all when hot. Did the continuity test and then changed the cap. It's a whole new world.

 

[stuckmotor]

I've got a Wild Thing that won't start when hot. I only got around 50 psi when I checked the compression. Thinking it might be the guage, I bought a new one today. I'll try to run another test later in the week.

 

[mddorange]

:welcome:
To the TBN forum Jeff. You are lucky. The Homelite I bought a few years ago started being hard to start after a couple of months.

 

[Mysfyt]

Had the same problem on a Stihl many years ago. Did all the same things you did. Turned out to be a weak flywheel magnet. Replaced the flywheel and was good to go. Saw lasted 25 years. Got the tip from an old timer that did chainsaw repair.

 

[jefffarq]

I've got a Wild Thing that won't start when hot. I only got around 50 psi when I checked the compression. Thinking it might be the guage, I bought a new one today. I'll try to run another test later in the week.

Approx. what should the compression be? I don't use the saw very much, just cut up a little firewood now and then; I'm skeptical that I've used it enough to wear out the cylinder/rings.

 

[stuckmotor]

Approx. what should the compression be? I don't use the saw very much, just cut up a little firewood now and then; I'm skeptical that I've used it enough to wear out the cylinder/rings.

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.