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Chainsaw repair

MikeD

MikeD

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Any small engine repair gurus here?

I have a Poulan 50CC chainsaw that I just cannot get running. It had run great for me every time I've used it and I just had it running back in Nov and it started on the second pull. I did not cut anything with it in Nov, I was showing it to a friend who was interested in getting one. I tried it a couple weeks ago and it was dead.

It will not even fire with starter fluid, canned gas (Stihl brand) or from either of my two cans.

Gas has always been drained between uses.
Compression is good, as per compression guage 115ish psi
Piston looks like new as viewed from exhaust port, no scoring whatsoever.
Spark is good and will jump a 4mm gap with nice violet color (with plug installed)
Carb is working and pumping gas
I can't get the flywheel off yet, but appears to be close to TDC when coil magnets align. Saw really has not been abused and only used a couple times. I Can't imaging it has sheared a keyway but I will continue to try and get this pulled to confirm.
I've tried two different coils - Both brand new and multiple spark plugs.

I have removed the carb and cleaned it well, nothing obstructing the airflow.

I find it odd that it won't even ignite the starting fluid.

I'm kind of at a loss as to what else it could possibly be, there isn't much to these engines.

I have since bought another smaller saw (Stihl!!!) for light work but this has become a personal challenge now.

Any ideas's
 
MikeD said:
Any small engine repair gurus here?

Spark is good and will jump a 4mm gap with nice violet color (with plug installed)
Click to expand...
First, I am not a guru, chainsawspeakingwise. I'm having a problem understanding what you wrote above. How did you see the plug's spark when it was installed?
 
My best guess from ýour description: Timing
 
My guess is timing too. . . . maybe the flywheel has slipped on the hub. Happened on my motorscooter.

When 2-strokes quit you sometimes have a big air leak at a crank seal or case gaskets or (most likely) at the carb mount itself.

But even then, if you're spraying fuel in it it should pop and try.

Are you getting any action at all? Does it even try to run a little?
 
Alcohol in modern day fuels can wreak havoc on fuel lines. The lines can be tricky to replace but it is a CHEAP fix--just be sure to get the correct size hose. About $2-$3 worth of hose--you can get it at Ace Hardware (for example). That would be my guess if the saw just suddenly "stopped working". You'll see the fuel filter just flopping around in the tank...

You could probably pop the carb off and check the diaphagms but first make sure the carb is not loose.
 
Absolutely true about alcohol, and that little hose and filter in the tank cause about 1/3 of all chainsaw problems when they plug or collapse.
BUT, it would try to run with starting fluid.

Maybe it does...
 
I have not replaced the fuel lines because it will not even pop by adding gas or starting fluid straight to the cylinder. Even if you remove the lines it should still pop and run for a second but its completely dead. I will have to confirm the timing. I've eliminated almost everything else.
 
I would certainly change the Condensor. They're cheap and they do fail.
 
CaddmannQ said:
I would certainly change the Condensor. They're cheap and they do fail.
Click to expand...
Done, twice.

I figure its got to be something stupid im overlooking.

Going to set it aside for a few days, I seem to have contracted the plague and its kicking my behind. Too much stress right now has weakened my defenses.
 
I am a chainsaw guru, you covered all the bases ......I would have to have it in my hand to be any help at this point

you have spark , fuel and air......if your carburetor is not atomizing the fuel/air ratio properly than that's the only thing left ......I have never seen timing issues just develop....timing has never been an issue in all my saw time

if you have spark, you use starting fluid and get no fire....the only way that is possible is if there is not enough oxygen, something doesn't make since

are you spraying into the cylinder or the carb?

you can just put a bit of mix in the cylinder also

How do you know the carb is working ?

How wet is the plug after attempting to start?

Check the plug by putting it on the head and pulling the starter cord , then try a new plug anyway......i have had plugs spark on the head and not under compression both in motorcycles and in chainsaws.....plugs under hard use can break internal

ETA, I saw your cord thing you used to check spark.....as long as your confident in it. I havent seen one.....rebuilt a handful of saws in my time, they are simple as hell
 
oli700 said:
I am a chainsaw guru, you covered all the bases ......I would have to have it in my hand to be any help at this point

you have spark , fuel and air......if your carburetor is not atomizing the fuel/air ratio properly than that's the only thing left ......I have never seen timing issues just develop....timing has never been an issue in all my saw time

if you have spark, you use starting fluid and get no fire....the only way that is possible is if there is not enough oxygen, something doesn't make since

are you spraying into the cylinder or the carb? I tried both

you can just put a bit of mix in the cylinder also

How do you know the carb is working ? I do not, but I thought it should still at least pop by manually priming it regardless. I can look at this

How wet is the plug after attempting to start? Depends on how much time i spend trying to get it going.

Check the plug by putting it on the head and pulling the starter cord , then try a new plug anyway......i have had plugs spark on the head and not under compression both in motorcycles and in chainsaws.....plugs under hard use can break internal I've done this as well.

ETA, I saw your cord thing you used to check spark.....as long as your confident in it. I used it in conjunction with just grounding the spark on thw cyl head. The dial allows me to increase gap to help determine how strong the spark is. I haven't seen one.....rebuilt a handful of saws in my time, they are simple as hell
Click to expand...


I agree this is probably the most simple motor I've ever seen, that's why it is bugging me so much that I can't get it going. I've tried so many different things, perhaps I just need to go back to square one and eliminate each part one at a time. If that doesn't work I'm driving out to OR!!
 
I'm grasping here but just take that kill switch completely out of the circuit incase it is leaking voltage internally.

Have you verified the timing, NOT by the timing marks but by dipstick method? (Use a depth gage on the piston top)

I have a two stroke that I stopped suddenly and would not start again. It turned out that the hub rivets had sheared nearly off from the flywheel.

Timing was off. WAY off. :(

I didn't figure this out until I tried to start it enough times that the rivets sheared completely through and flywheel came loose.
 
Oh, and make sure your fuel is new and perfect out of a CLEAN container. A few oz. of water in the bottom of a fuel can can cause ALL sorts of problems. Use hi-test or better yet, alcohol-free gas (if you can find it). Mix the CORRECT oil precisely and mark the container with the ratio--"50:1" for example. I use Sta-Bil in a gas can as soon as it is back in the shop. I don't keep a lot of fuel on hand (unless it is an emergency) and I'd burn the 50:1 in the riding mower if it got too old (say 4-6 months).
 
Living in the 'burbs, I use one so infrequently that I bought the 4.5 hp ElectraMac 16".

No more gasoline, & can get to all my trees with a cord.

Nowadays, it's just in case a branch falls off & I need to move it now. I dont burn wood except to smoke BBQ.
 
I win!!!!

Felling a little better today so I broke it down again.

Pulled the flywheel just to rule it out, nothing wrong here, keyway is in perfect shape. I'm calling timing good.

Plugged the spark plug in, no spark. What the hell, it had spark before.

Went through 3 plugs and 3 coils but could not get visible stark by grounding it to the cylinder head. My neighbor who had come over to see what I was doing asked how I had tested for spark before. I put the plug back in, hooked up my spark tester gave it a pull and the damn thing popped. Removed the spark tester, put it back together, and it started fine and idled perfectly. I started it 3 or 4 more times and it was perfect every time.

Still not sure exactly what the problem was but I will at some point go back and swap out one component at a time to try and narrow it down.

I'm just happy it runs now. Damn small engines can be frustrating.
 
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