Sears saw won't run

[Alleycat]

I got myself into a mess when my neighbor said he was having trouble with his craftsman 12" chainsaw. He said it would start, but only run a few seconds and quits. Being the wonderful guy, great neighbor, and fool that I am, I offered to take a look at it. I figured a good cleaning and tune up would get the job done. WRONG!! So far I have put a kit in the walbro carb, new plug, tightened the muffler and the cylinder bolts, checked for a good spark, and it still isn't much better than when I started. It runs for 30 seconds and quits. Cranks up on the 3rd pull, runs 30 secs. and quits. Help, my arm is tired.

 

[computeruser]

Does it have a plugged tank vent? Will it run properly with the fuel cap slightly loose?

 

[Alleycat]

Does it have a plugged tank vent? Will it run properly with the fuel cap slightly loose?

Thanks for your reply. Tank vent is in cap but doesn't matter if cap is on or off. Same either way.

 

[havvey]

sears

check compression should be over 120 over 150 optimal. (pull muffler look at piston/jug for scores) this can cause what you describe. Do a leak down test for bad seals/gaskets. check fuel an d pulse lines for problems.

 

[Kenskip1]

Sears won't run

Alley cat,
I would bet you a six pack that the gas filter is simply clogged. Either that or you have a kinked gas line. Before you give this thing a major overhaul, put in a new gas filter. If this saw has been setting for a while be careful about removing the filter. The gas line my be soft and fragile. Ken

 

[Alleycat]

Thanks to all for your input. This morning a new development arose. It won't start at all. It is getting plenty of gas, so much that it will flood in a heartbeat. I'm now using a 3/8 drill motor to turn it over and it kicks back sometimes but no start. I checked the spark and it seams ok, put a jumper on the spark plug lug and grounded the other end to the engine. I get a white spark, but it is very tiny. Barely visable in Daylight. Is this normal? I think I have all the vacuum/ pressure leaks stopped, but havent looked at the piston. That could be it. The saw looks like it has seem some hard use and little care.

 

[scottr]

Craftsman 12" Saw

Alleycat , I think you have a Poulan Micro top handle saw that has a horizontal cylinder . Two things that will be easy to check will be to remove the side cover and the screw that holds muffler cover on the saw and look for a scored piston and cylinder . The other is a worn crankshaft , grab the crankshaft at the clutch threads and give it the wiggle test .

 

[Four Paws]

Similar problems

I have had similar problems with other sears products over the years - most recently a weed eater. I too, rebuilt the carb, new plug, cleaned the muffler, etc. The damn thing runs strong for a few minutes and quits when it gets hot - like it runs out of gas. It will restart after a few minutes, and run for a minute or so, and do the same thing all over again. It is annoying and I never found out the answer to my problem, although I determined it was somewhere in the fuel system - almost like it was vapor-locking. I no longer buy Sears JUNK that is made by XYZ manufacturing company and labeled by sears. I have a new Husky 232R Brushcutter to handle my trimming needs now - this is a first class machine!

 

[pallis]

You might want to check the coil. Clean the coil and flywheel real good. Try moving the coil a little closer to the flywheel (a few thousands) and see if that improves your spark. It might make the saw start again, but it will die when the coil gets hot. If moving the coil closer works to get better spark, and the saw still dies, replace the coil. I hope you get it figured out to impress your neighbor, then talk him into buying a better saw.

Pat

 

[Kenskip1]

white spark

Here is a question, Why would anyone want to mess with a saw that has a White Spark? Spark comes in three colors. Yellow, Blue, and White. Yes White is the hottest spark of the three! Why make unnessary changes? This is taking a step in the inapproiated direction.
As to using a 3/8 drill to turn it over, forget it. If the drill is able to spin it over with the spark plug installed,I would suspect this saw has been run on straight gas and the cylinder and piston are now toast.
I would recommeend a compression evaluation to try and eliminate the anomolies.

 

[gaetoune]

My jonsered acted like that... I pulled the cylinder off and the ring was done, it was half toasted on exhaust side... I bet you that your problem.

Cheers
Gaetoune

 

[retoocs555]

As to using a 3/8 drill to turn it over, forget it. If the drill is able to spin it over with the spark plug installed,I would suspect this saw has been run on straight gas and the cylinder and piston are now toast.
I would recommeend a compression evaluation to try and eliminate the anomolies.

I use routinely use a drill to turn saws or shortblocks over and measure compression. Never had a problem, even with a weak cordless turning up near 200psi.

 

[retoocs555]

I get a white spark, but it is very tiny. Barely visable in Daylight. Is this normal?

Yes, typical for that type of saw.

 

[Justsaws]

Have a lot of small Craftsman saws, almost all are poulans. Check the compression. It should be making a popping sound(for lack of a better word) when it is pulled over. If when it is running a lot of gas comes back out the carb, it is either to rich or low on compression.

If it runs for short periodes of time and then dies, it could also be flooding or leaning out. If it speeds up before it dies it is leaning out and probably needs the metering level adjusted. If it boggs out and dies with a lot of gas ending up in the muffle it is to rich. Could also be metering level.

Check to make sure that all the screws are tight and take a look at the reed valve under the carb.

My bet is compression but it is late and I hope that I am wrong. Good luck

 

[Alleycat]

Thanks to all for your help. You saved me much time and further aggravation. The cylinder and piston looks good, so did a compression test. All it will muster is 50 lbs. Saw now resides in the spare parts (junk) pile.
Alleycat

 

[hornett22]

carbon under the rings?

carboned up exhaust port? or a bad coil or plug wire.