Parting Out An Old Chainsaw

[PANDEMICBANDIT]

So here's the story:

I bought a used (doesn't start) Craftsman Chainsaw from someone for like $20. I took it apart and found the fuel lines were rotted and crumbled in my hands when I gave them a tug. Primer bulb was cracked and had a hole in it. The air filter was done, spark plug was toasted and fuel filter was dancin around in the fuel tank. Anyhow, I did a complete tune-up and replaced all those things. She still would not start.

The carburetor was covered in like 3/4's of dirt and the idle and mixture screws had quite of bit of rust on them when I found it. I cleaned it and took it apart and cleaned it some more. And it still does not want to start. Put in a new carb and also fresh gas and still no start. If I put gas down the spark plug hole it starts and runs for few seconds than dies. The ignition timing is good since I'm getting multiple hot sparks when I'm putting the plug in the wiring boot and touching the cylinder. So I know the ignition coil module is working properly.

I've been at it for a week and she still does not want to start. By the looks of the piston, ring and cylinder. None of them are scored when I dissambled them. The cylinder walls and the cylinder itself, piston and ring are as smooth as a baby's butt. I've got compression, fuel and spark but no start. Compression: I don't have a guage so I'm eyeballing it. Starter rope is solid when I pull it and when I put my thumb over the spark plug hole, air pushes my thumb out of the way so that tells me compression is strong. Spark: New plug and the timing on the flywheels magneto is right because I've got good hot sparks. Fuel: With the old carburetor on, the spark plug came out bone dry and I did the same thing with putting my finger down the plug hole and than pulling the starter rope and my finger came out bone dry so that tells me its a fuel delivery problem. Then when I installed my new carb the spark plug comes out wet so I know I now have fuel. The saw looks to be like 20 years old or so and looks like it was stored more than it was used.

Well since this chainsaw is just such an old machine, I think even If I did invest more into it there is still no gurantee It will still start. I think the chainsaw is just done because its just too old. One more thing, the new carburetor is the same part number as the old one and exactly Identical but the old one had 2 fittings on the choke side and the new one has one fitting on the choke side for the fuel line with the filter on it and a 90 degree fitting on the throttle linkage side for the primer bulb fuel line. So my culprit is that every carburetor is designed and built in a way to deliver the right amount of fuel and air mixture to the combustion chamber for that specific chainsaw. So its very possible that my new carb is just delivering the wrong amount of fuel and air mixtue to the combustion chamber.

Anways, since I'm not able to get it to run, at least it was a fun learning experience. I'm just going to use it for parts.

As for the new carburetor since I've just installed it and its never been used. I'm going to just store it as a backup, but does anyone know If I should clean it of all the fresh gas with some carb cleaner and than let it dry and I'm good to go or?......I perfer to do it when the carb is still assembled, I really don't want to take it apart since its brand new and its been in the saw for just a little bit to see if it would start and run.

Any suggestions? I'm going to probably dissamble the entire chainsaw and just keep everything for parts since some parts are universal but not all.

Thanks!

 

[Deleted member 117362]

Will not be able to sleep. Make it run.

 

[buzz sawyer]

What were you doing with the throttle when trying to start it? I've had two of these and they can be a real PIA to start. There is no fast idle setting so I hold the throttle wide open with the choke closed until it pops, then open the choke about 1/2 and try again. You also may have seal problems - have you done a vac / pressure test? Have you checked the reed valve to make sure it isn't bent open slightly? Doesn't take much.

 

[beavis331]

Try another new spark plug. I've had brand new plugs that check good when you test them but won't fire when in the cylinder. Drove me nuts.

 

[a. palmer jr.]

Some of those saws require about 3 turns of the H and L screws to work right. If you just have them at 1 turn or so they won't run. It would also be helpful to let us know what model of saw it is and maybe a picture of the saw.

 

[PANDEMICBANDIT]

What were you doing with the throttle when trying to start it? I've had two of these and they can be a real PIA to start. There is no fast idle setting so I hold the throttle wide open with the choke closed until it pops, then open the choke about 1/2 and try again. You also may have seal problems - have you done a vac / pressure test? Have you checked the reed valve to make sure it isn't bent open slightly? Doesn't take much.

Yeah, I tried just about everything I can think of to try get it to start. I held the throttle (the trigger that revs the saw if thats what it means) at the same time as playing with the choke. Normally what I do is leave the trigger alone and a I set the choke just until its like 1/4 open and then pull the the starter rope a couple of times. And just keep adjusting the choke until it starts.

Where I live is pretty cold, its around 40 degrees. So what I noticed is that when I pour gas down the plug hole and then reinsert the plug. I set the choke to about half way and then the saw sounds like it wants to start. Then I set the choke about 3/4 almost closed, and then it sounds like it really wants to start. And then I give it a few more pulls, she finally starts and runs and then I close the choke to prevent cold air from getting in the engine and then killing it. Then the saw with out me reving it, revs on its own at a high speed and the chain spins pretty fast, again without me pulling the trigger and blue smoke comes out the muffler and then the engine shuts off.

As for your second two questions, I'm still new to two stroke engines, I just learned quite alot pretty quick from watching a whole lot of YouTube videos and a whole lot of browsing.

So what exactly is a vac / pressure test?

And where exactly is the reed valve located?

Sorry for the silly questions, and as for the second person that replied to this thread. I tested 2 brand new spark plugs and still no go.

Another question thats been bothering me lately is that when I installed my new carburetor, I did not adjust any of the screws. So do I adjust the carb as the chainsaw is running or adjust it first then try and start it? I was thinking maybe the carb is just not allowing enough fuel/air into the combustion chamber. Maybe if I adjusted the low screw and made the mixture slightly more leaner it would start and run longer because the piston is moving faster and then I would bring it down to where the engine is idling smoothly. But I'm not sure, I could be wrong

 

[PANDEMICBANDIT]

Some of those saws require about 3 turns of the H and L screws to work right. If you just have them at 1 turn or so they won't run. It would also be helpful to let us know what model of saw it is and maybe a picture of the saw.

Yeah see thats the thing, I did not adjust the screws on the new carb ever since I got it. I just installed it and hoped it would start. Thats the last thought that hit me after everything I tried. I was hoping the carb would be already factory adjusted but once I learned that every carb has to have an exact air/fuel ratio for that specific saw only adjusted by the screws, thats when I realized that that could be another reason why its not starting.

I will get a few pics of the saw and probably a pic or so of the new and old carb as a comparison when I can. And while I'm at it, I'll try and adjust the carb and try and start it, see what happens.

 

[46 Poulan]

Are you sure all fuel lines are on correctly. I had a craftsman saw with lines gone/rotted off. Had a hard time with the proper routing. When I got it right saw ran great and then I got CAD real bad!!! David

 

[a. palmer jr.]

Yeah see thats the thing, I did not adjust the screws on the new carb ever since I got it. I just installed it and hoped it would start. Thats the last thought that hit me after everything I tried. I was hoping the carb would be already factory adjusted but once I learned that every carb has to have an exact air/fuel ratio for that specific saw only adjusted by the screws, thats when I realized that that could be another reason why its not starting.

I will get a few pics of the saw and probably a pic or so of the new and old carb as a comparison when I can. And while I'm at it, I'll try and adjust the carb and try and start it, see what happens.

Try turning both screws in all the way until lightly seated then turn them out to about 1& 1/2 turns and see if that works.

 

[dswensen]

Try turning both screws in all the way until lightly seated then turn them out to about 1& 1/2 turns and see if that works.

Good advice above.

Plus, there is a starting procedure for these saws. You say you are "new" to two strokes. You didn't say what model you have, but the procedure usually is; full choke with throttle lock on for a few pulls until it sounds like it "pops" (hits for one, maybe two revolutions), then choke off, but throttle lock on and keep pulling till it starts. If you miss the "pop" on full choke, and pull a few more times, likely you'll flood it. Even if I don't hear it "pop" on full choke, I don't pull it with full choke on for more than 4 pulls unless I KNOW I'm working with a dry carb and need a few more pulls to get fuel into the lines.

 

[grizz55chev]

Good advice above.

Plus, there is a starting procedure for these saws. You say you are "new" to two strokes. You didn't say what model you have, but the procedure usually is; full choke with throttle lock on for a few pulls until it sounds like it "pops" (hits for one, maybe two revolutions), then choke off, but throttle lock on and keep pulling till it starts. If you miss the "pop" on full choke, and pull a few more times, likely you'll flood it. Even if I don't hear it "pop" on full choke, I don't pull it with full choke on for more than 4 pulls unless I KNOW I'm working with a dry carb and need a few more pulls to get fuel into the lines.

Very good advice!

 

[grizz55chev]

Since your problem seems to be fuel delivery, there a couple of things to eliminate. Start with the simple things, fuel filter is suspect if it’s been in the saw for any length of time, I’ve seen them cause headaches more times than I can count. A restricted fuel filter is easy to test, try blowing thru it and feel how much resistance you get, it should flow free! You’ve already done fuel lines and carb so these are not likely the problem, unless installed wrong or routed the lines wrong. I believe most saws prime the carb buy drawing the fuel thru the carb and then dumping the fuel back to the tank.

 

[a. palmer jr.]

There is a way of routing the fuel lines to eliminate the primer bulb if you want to, or you can just replace yours if it has cracks in it. Just remember the fuel comes into the primer bulb from the carb and out into the tank. If your primer bulb has a long and a short nozzle on it then the longer one normally is the one that goes out into the tank.

 

[buzz sawyer]

Good advice above.

Plus, there is a starting procedure for these saws. You say you are "new" to two strokes. You didn't say what model you have, but the procedure usually is; full choke with throttle lock on for a few pulls until it sounds like it "pops" (hits for one, maybe two revolutions), then choke off, but throttle lock on and keep pulling till it starts. If you miss the "pop" on full choke, and pull a few more times, likely you'll flood it. Even if I don't hear it "pop" on full choke, I don't pull it with full choke on for more than 4 pulls unless I KNOW I'm working with a dry carb and need a few more pulls to get fuel into the lines.

Good advice! I had assumed he had one of the 2.0 or similar saws that don't have a throttle lock.

 

[dswensen]

Good advice! I had assumed he had one of the 2.0 or similar saws that don't have a throttle lock.

True, and some of the newer Poulan variants have the throttle lock built into the choke lever mechanism. If you have a choke you pull out to engage (mine have a choke lever that are almost all blue in color), then the procedure is to squeeze the trigger while setting the choke - this locks the throttle open. Pull only a few times like this or until it "pops". Then, push the choke lever back in, but don't touch the throttle trigger - it should still be locked with the throttle open. Pull till it starts. Once it starts, squeeze the trigger to unlock the throttle and it should idle.

 

[PANDEMICBANDIT]

Well as said before, here are the pictures:

Carburetor Pictures:

 

[PANDEMICBANDIT]

Chainsaw Pictures:

 

[PANDEMICBANDIT]

True, and some of the newer Poulan variants have the throttle lock built into the choke lever mechanism. If you have a choke you pull out to engage (mine have a choke lever that are almost all blue in color), then the procedure is to squeeze the trigger while setting the choke - this locks the throttle open. Pull only a few times like this or until it "pops". Then, push the choke lever back in, but don't touch the throttle trigger - it should still be locked with the throttle open. Pull till it starts. Once it starts, squeeze the trigger to unlock the throttle and it should idle.

This is actually the way my new carburetor works, exactly as you just explained it. I'm going to have try it out and probably continue to play with the mixture screws and just hope that it works. I'm getting close to running out of ideas.

 

[a. palmer jr.]

Try turning the carb H and L screws out another half turn if you haven't already done so..

 

[buzz sawyer]

Do you see fuel in the lines as you try to start it? Is that a primer bulb just above the fuel filler cap? If so, have you pumped it a few times to prime the lines and carb?
I don't believe that saw has a reed valve. Looks good btw.