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

[stonebroke]

Sometimes on small engines the key that locates the flywheel to the crankshaft sometimes shears and that affects the timing.

Stonebroke

[Nate Surveyor]

IF the flywheel nut is loose, just a bit, and by spraying starter fluid, you get a backfire, you can shear the flywheel key, and mess up the timing of the spark. You may be able to remove the flywheel nut, and SEE if it is sheared, But, sometimes it can be partially sheared, and NOT easlily detected, without REMOVING the flywheel.

And, a puller is recommended to pull it.

Anyway, I think starting fluid is bad medicine for most motors.

Use as WEAK of a fluid as gets the job done. I personally am a fan of silicone spray. Plenty of umph, and a little lube.



Nate

[logwalker]

What is complicated about swapping a plug? The plug can spark outside the cylinder and not under compression. I have seen it many times. Besides he gave you a strong clue when he said it quit firing on the ether. It was firing before he tore it down and replaced the fuel lines. The plug is cheap and easy to change. This is a process of elimination. I am still betting on stuck ring. Could put a couple tablespoons of rust reaper in the top end and let her set. Might loosen the ring.

[sawguy21]

Did you properly re seal the crankcase when you re assembled the motor? There is no gasket and you could have a serious air leak. How quickly does the saw drop when you suspend it from the starter handle? If it falls like a stone, compression is weak.

[piedmont]

Update:
I replaced the plug and although that didn't fix the problem, at least I have a new plug.

I then took the motor apart again. The ring has some very shallow grooves worn into it, not deeper than the width of a human hair, I'd say. There are matching grooves worn into the cylinder.

There was also a silicone gasket (the kind you make yourself with the squeeze tube) that I didn't notice before where the two parts of the motor come together.

I plan to clean all the parts really well with WD-40, make a new gasket, and put it back together again. Should I worry about the grooves? Should I try to make sure they line back up again so they don't carve more grooves, or perhaps sand or file them down on the ring?

[Cut4fun]

Grooves sounds like light scoring to me, jmo though. I would clean up Cly with fine Emery cloth like doing a hand hone to clean up and knock off glaze and put a new ring in it.

Silicon on a set up like the clamshell design. I have never used anything for that (just tighten the 4 bolts to the Cly and tighten around the crank rubber seals real good., silicon sealant could be adding to your problem. Good luck.

[piedmont]

Cut4fun,
The saw has "rebuilt" where the serial # should be, so I'm guessing the rebuilder may have added the silicone. Since it was coming off in little pieces, I think you may be right about it adding to the problem.
I'll try honing the cylinder, and the ring may be salvageable with the same treatment. The scoring is really shallow.

[olyman]

when he pulled the barrel--end of crankcase seal--no compression--cause no fuel pull--------------------if you pull the jug again--go to dealer to get a new jug gasket---dont use silicone--none of it tolerates gas---------------------------itll get in places you dont want it to---

[Nate Surveyor]

Olyman is corrrect. Silicone will dissolve in gas.

ONLY use it where there is no gas.

Gotta have a better gasket.

While you are at it, are the REED valves stuck?

They are metal things that allow air to ENTER the crankcase, but NOT go backwards. One way check valves.

N

[piedmont]

I don't think there are reed valves on this engine, but I'm not sure I would recognize them.
In other news, I polished the ring and cylinder with 2000 grit sandpaper, then broke the ring while fooling around with it.  So I'll get a new one from the small engine shop and be more careful with it. On the plus side, by the time I get it fixed, I'll know this saw like the back of my hand. 

[sawguy21]

That is a piston port engine, no reeds.

[logwalker]

And it will be running like new.

[ladylake]

 Put a new plug in first, then go over the carb again.  Is the plug soaking wet or dry after trying to start it?     Steve

[scottr]

Piedmont, there is a locating pin in the groove of the piston that is used to keep the ring from rotating and breaking. Were the light scratches on the intake side or the exhaust side?

[piedmont]

Piedmont, there is a locating pin in the groove of the piston that is used to keep the ring from rotating and breaking. Were the light scratches on the intake side or the exhaust side?

The ring broke 'cause I was squeezing on it-- didn't have it on the piston at all. Kinda dumb, I know. 

The scratches were mainly on the exhaust side. There was one light one on the intake side.

ladylake, I tried a new plug before disassembling the motor again. Good spark, as before, and fuel was getting to it, as before, but no firing. Plug was wet with fuel.

[Cut4fun]

IPL for your saw  http://www.odref.com/poulan/pdf/poulan/gas-saws/2550-TYPE1.PDF

Also dont forget to line ring ends up right on the piston with the pin in the ring groove to keep the ring in place.

[logwalker]

What is the update on the saw?

[clousert]

Wow - is a Poulan worth all of this effort?

[Cut4fun]

Wow - is a Poulan worth all of this effort?

IMO, YES!
 That Poulan is built just like the Stihl 290,250,310, etc. and the Husky 455 etc that have the Plastic crank cases with the clam shell design. Just the Poulans cost 1/3 less.
Todays poulans are crappola (yes I agree), but they were pretty good saws at one time IMO. Plus the cost less to buy back then and cost A LOT less to repair. I cut my teeth on the magnesium cased Poulans and I loved them. I bought one plastic cased poulan to just find out how they were and it passed the test with flying colors for a homeowner saw too or to cut firewood. Now a pro logger is a whole different story.
I owned Poulans 3750, 330, 3300, 305, 2000, 1800, XX, plastic cased 220, 2250 (built from 2 basket cased).

A few that was in a group pic once.

[XJ99]

Silicon on a set up like the clamshell design. I have never used anything for that (just tighten the 4 bolts to the Cly and tighten around the crank rubber seals real good., silicon sealant could be adding to your problem. Good luck.

I'm working on the same saw, and found
this thread. So from what I've read, do not
use any RTV when I assemble the jug, and
make sure to keep the ring lined up with the
groove. I also found some silicone on my saw,
and it was bought new in 2000. (was not rebuilt)
I still need to order ther ring, so it'll be a few days
before I finish working on the 2550.

BTW, the reason why I'm rebuilding it is because
it was ran with out oil in the gas. I used the same
gas can, and have it marked "mixed" but I think my
wife filled it up with regular gas for the lawn mower.

Anyway, it ran great for about 20 minutes, then the
idle started to pick up really high, and it started to bog
down. It still had 1/2 tank of gas, and that's when I
check the gas in the can and found out it wasn't mixed.

Thanks for any tips on this rebuild..