Poulan 2550--what's wrong with this dang thing??

[piedmont]

Hi y'all,
My dad recently gave me a chainsaw that's been sitting in his barn for a couple of years. It wouldn't prime, and he had got it to start using starting fluid and it would run great for a couple of seconds until the fluid was gone. So we figured it probably had bad fuel lines.
Sure enough, when I took off the carb I could see the lines were hardened and cracked, including the one going to the fuel filter in the tank. I replaced all of them, and it primes perfectly, only now it won't crank, even with starting fluid. The spark plug is reasonably clean and makes a great spark, so that's not it. The muffler's also clean, and not obstructing air flow. When I had the carb off I also (unnecessarily) took out the four bolts on the bottom of the saw and took the cylinder/head section loose from the crankshaft/piston section. The piston and ring looked ok.
So why the heck am I not getting an explosion in the combustion chamber at all? Is it possible I messed something up when I took the engine apart?

[peter nap]

My first guess is that it was left with gas in it.

Carb clean or more likely, rebuild time. Get out the Varsol!

[Nate Surveyor]

Have you tried cussing?

Or Poulling on it?


Another trick is to place it under a cardboard box, in your street, and blame somebody else.


This is the best I can to to help.

Or place a cherry bomb under it, and go fishing!

N

[piedmont]

My first guess is that it was left with gas in it.

Carb clean or more likely, rebuild time. Get out the Varsol!

peter nap,
It was left with gas in it, but I replaced the gas even before replacing the fuel lines. The carb appears clean, and even if it weren't clean it shouldn't affect starting with starting fluid. And it did crank that way, before I started working on it.

Nate Surveyor, I'll keep those in mind as my last options. Thanks for the "help." 

[peter nap]

Replacing gas doesn't help if it's really clogged. It gets in the circuits.

There isn't much left except valves and I doubt that's the problem unless it's spitting gas back out.

I also wouldn't use starting fluid anymore. It van ruin a salvageable saw. See if you can find a rebuild kit.

[Nate Surveyor]

OK, I'll try to help.

DON'T use starting fluid in it! That stuff is BAD for 2 strokes. I'd Use WD-40, or Silicone spray. I have used that stuff successfully in situations like this.

2 strokes like a little lubrication on the cylinder. So, I'd try the lubricating spray.

That will probably lead to getting it going.

Sorry about the earlier "help". It was the best I could find at the moment!

N

[piedmont]

Thanks guys. The only reason I was using starting fluid was to try to duplicate my dad's results, and determine if the saw is salvageable. What's frustrating is that it won't come anywhere close to cranking. No combustion at all. I'll try WD-40. I just can't understand why bad fuel clogging up in the carb would have anything to do not starting on ether (or WD-40). The airway is fine.

p.s.: Nate, I think I'm fixin' to use your cussin' at it suggestion!

[beenthere]

piedmont
When you say it won't come close to "cranking", that to me means it will not turn over when you pull the starter cord.   

Or do you mean it won't come close to "firing" or "turning over under it's own power" ??

Old cars and tractors that had a crank, one could crank all day and not get the engine to fire and run. 

Is the engine siezed tight, so it won't crank? 

[piedmont]

piedmont
When you say it won't come close to "cranking", that to me means it will not turn over when you pull the starter cord.   

Or do you mean it won't come close to "firing" or "turning over under it's own power" ??

Old cars and tractors that had a crank, one could crank all day and not get the engine to fire and run. 

Is the engine siezed tight, so it won't crank? 

Hey beenthere,
Yes, "firing" is the word I was looking for.  "Making the explosion that makes the piston go down" was as close as I got, but that sounded stupid so I used "crank" or "start."  It turns free, isn't siezed, makes a great spark, and won't fire at all, even though it did fire and run (using starting fluid) even with basically no fuel lines, before I got a hold of it.

[Cut4fun]

Dont laugh, but is the saw ON/OFF switch in the ON position. Been there done that.

Is it a Walbro or the Zama carb?  I have a extra good working order Zama laying around, I replaced it with a before epa Walbro and sold the saw.

Carb rebuilds take about 30mins to a hour to due, carb kits are $3 Dia kit -$10 complete kit  for the carbs for that saw.

[piedmont]

Dont laugh, but is the saw ON/OFF switch in the ON position. Been there done that.

Is it a Walbro or the Zama carb?  I have a extra good working order Zama laying around, I replaced it with a before epa Walbro and sold the saw.

Carb rebuilds take about 30mins to a hour to due, carb kits are $3 Dia kit -$10 complete kit  for the carbs for that saw.

Haha! No, it's in the "on" position!  That was one reason I took the spark plug out and gave a pull on the cord (with the plug still attached to the wire)-- to make sure I was getting a spark and didn't have a bad on/off switch.

It's a Walbro carb. I may rebuild it but I just don't know if the problem is in the carb. I'm wondering if the problem is compression. Maybe I messed up the ring?

[Cut4fun]

Compression tester can be had for $20.  Pull till the psi reading stops.

Piston shows no signs of scoring? How about a stuck ring in the groove?

Coil come loose? Check with index card between contacts and tighten down or a business card or a piece of paper folded to make 3 layers. Place between contacts, Loosen coil, index card etc between contacts, then tighten back for correct gap. Check for spark. Spark testers I use cost $3, go to plug and then to wire with a little light inside, pull over and can see light flickering.

[piedmont]

Compression tester can be had for $20.  Pull till the psi reading stops.

Piston shows no signs of scoring? How about a stuck ring in the groove?

Coil come loose? Check with index card between contacts and tighten down or a business card or a piece of paper folded to make 3 layers. Place between contacts, Loosen coil, index card etc between contacts, then tighten back for correct gap. Check for spark. Spark testers I use cost $3, go to plug and then to wire with a little light inside, pull over and can see light flickering.

Piston looked ok from what I remember-- I'll check the compression and if that's it I'll take it apart again. Spark is definitely not the problem. It sparks great. Just no "boom."

[scottr]

 When you took the piston out of the cylinder did the ring expand or was it stuck in the piston groove? Did you have to compress the ring to reinstall the piston in the cylinder?

[Nate Surveyor]

A friend has a worn out Ford Diesel. You have to coast start it. Because compression is so bad.  Now I know that a diesel is a compression engine. But, a DRY 2 stroke will do something similar. I did some study on BEST oil/fuel ratios. Turns out that something like 22:1 works best, but fouls the plug bad. So, 32:1 allows the plug to work better. This is an OLD study, made during the air cooled motorcycle era. (1978 RM 80, & RM 125).

So, if this were my engine, I'd add some oil to the cylinder, and circulate the oil well, and prime it with fresh gas, with a NEW spark plug, and see what happens.

Just giving ideas.

Nate

[piedmont]

When you took the piston out of the cylinder did the ring expand or was it stuck in the piston groove? Did you have to compress the ring to reinstall the piston in the cylinder?

I don't think it expanded, because I definitely didn't have any trouble getting the piston back in the cylinder. I even said to myself "huh, that was easy."


Nate, it looked pretty oiled up, but I'll add a little more (through the spark plug hole, perhaps?) and see what happens.

[logwalker]

Sounds to me like the ring is stuck. Whenever the piston is out I remove the ring and clean the groove carefully. Also start with a new plug. You should feel a strong compression in the pull starter. Pull it slowly and see if it holds compression for a few seconds. I think it is the plug. Even though it sparks out of the head it won't necessarily do it under compression. Joe

[Al_Smith]

Whoe ,you guys are making this way too complicated .If the little saw has spark the only thing left is fuel delivery .

If the fuel lines are ok the only thing left is a funky carb.90 percent of the time just a clean up of the stale gas gets em going.Although it could stand perhaps a carb rebuild which is relatively easy to do. All the carb makers have tutorials on their respective web sites.

[stonebroke]

In a internal combustion engine you need fuel, spark and compression. If you do not have one  nothing will happen. You need the proper fuel air mixture in the cyliinder. (He should have had that with ether, but I would use a squirt bottle on gas mix). You may have a strong spark but it has to occur at the proper time, It might have gotten mistimed when you took it apart. Compression  has to be high enough  to turn the engine over. I have seen worn out diesels that would only start on ether but than would run. If the compression were very marginal than messing with the piston and ring might have put it below what even ether would start. Just my thoughts on the subject.

Stonebroke

[piedmont]

I haven't had a chance to work with it today, but I'm thinking the ring may be the issue. I don't think it could possibly be a timing problem on a 2-stroke, since there aren't any valves and the timing of the spark comes from when the magnet on the flywheel moves past the coil. I'll take it apart in the next couple of days and see. I don't have a compression tester, so I may go but one if they're not too pricey.
Thanks, y'all! This has been super helpful!