Friday, September 6, 2013

Poulan Model PLN 1514 Chainsaw Teardown

This old saw was given to me by a guy who cuts a lot of firewood at home for heating fuel. The saw is not well.

It occasionally attempts to start depending, it seems, on the armature's at-rest position when the trigger is pressed, but it will not run. The saw is probably a write-off, but I thought I'd tear it down for a look-see. If nothing else, I'll salvage the chain and bar -- the chain is in better condition than the one that's on my working, similar Poulan saw. Here goes.

Teardown Sequence

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- All screw fasteners are No. 2 Phillips recess, unless otherwise indicated.
- There's a PDF parts breakdown (such as it is) here.
- Exercise great care whenever working with motor armatures and field windings. A mishap can cause irreparable damage in an eye-blink.

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1) Chain-Drive Cap
- Two M4x40mm pan head threading screws.

2) Sprocket Support and Bar W/Chain
- One M4x9mm pan head shoulder screw. (Note the short shoulder -- this is not a common M4 screw.)
- Two M6 flange nuts, 11mm A/F hex.
That gets you to here.

NOTE that the two bar bolts are free to fall out at this point. Remove them. (They're M6x60mm, 11mm A/F hex head.)

3) Front Hand Guard w/Bar Bolt Receiving Items
- Bar bolt receiver (pull it out).
- One M4x14mm threading screw at left side end of hand guard.
- Hand guard.
- Oblong washer plate (it's down inside where the bar bolts go through).
- Two bar bolt sleeves.

Here's a view of what you'll have.

4) Motor Brush-End Cap
- Two M4x14mm pan head threading screws.
- End cap.

5) Chain Tension Adjuster
- One M3.5x12mm flathead threading screw.

6) Right Side Shroud
- One M3.5x12mm flathead threading screw. (Its head is low down in front of the motor at the left side of the casing.)
- Four M4x18mm pan head threading screws.

7) Chain Oil Tank w/Oblong Outlet Seal
- It just lifts out.
- NOTE the orientation of the oblong outlet seal. It resides at the lower front of the tank, and is likely to be much obscured by oily sawdust muck.

8) Chain-Sprocket/Ring-Gear (5 tooth/59 tooth; 9mm bore)
- Just pull it gently straight off its bearings.
- NOTE that there are two small roller bearings associated with it.

9) Chain-Sprocket/Ring-Gear Roller Bearings (8mm cage length)
- Just pull them straight off their 6mm diameter spindle.

10) Motor Output Gear (11 tooth; 8mm D-bore)
- Just pull it straight off the motor's output shaft. It may want a bit of coaxing.

11) Motor Output-End Plate
- Four M4x14mm pan head threading screws.
- Grasp the sprocket/ring-gear spindle and pull the plate straight off. It may want a bit of prying/coaxing.

12) Motor Armature
-NOTE the dark sealing material at the centre of the brushes-end motor bearing housing (pictured below).

- Drill that stuff out to 5/16" diameter.
- Apply a brass punch to the motor shaft's end through the hole you've drilled, and hammer lightly. The armature will dislodge and be free to come out.

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That's where I stopped dismantling the machine, because I could see that one of the brushes was stuck and wouldn't spring out to contact the commutator firmly. On to the parts washer tank.

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'Repair' And Reassembly To Testability

Brush Holders And Cleaning

The brush holders would not come out. They're either cemented in place, or they got so hot at some point that they slightly melted themselves in place. In any event, I did manage to coax the stuck brush to emerge, and move in its holder more-or-less as it should.

The oil-soaked sawdust that accumulates in a chain saw is a devil of a thing to clean away. It took a lot of solvent spraying and brushing and poking and prodding and air blowing to clear it all out of the saw's frame, but I got it reasonably well cleaned up. I've left it out in the sunlight to dry out thoroughly while I go for lunch and a siesta and a coffee.

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One Further Bit Of Teardown

I removed the two long screws and the cover that secure the field winding, so I could blow out all the cleaning solvent that got into the winding. Here's a view down the length of the empty saw frame.

It's not a great photograph, but at the centre of the photo you can see the brass brush holders and the protruding brushes. Both brushes are now free moving, but the brush on the left is appreciably more worn than the one on the right. I've seen that often in these universal motors -- one brush wears much more than the other. I have no idea why that happens.

Poulan does not offer replacement brushes; these saws are meant to be throw-aways.

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The Bearings

Both bearings look and feel ok.

The output-end bearing is an NMB 608Z shielded bearing.

The brush-end bearing is an Outdo 607RS sealed bearing.

Those are common bearings. Identical or equivalent replacements would be readily available were they needed.

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The Armature/Commutator

Judging by the appearance of the commutator, I don't think this saw has seen all that much use. I'll burnish the commutator on the lathe with No's. 600 and 1200 silicon carbide paper, and make certain that all the commutator segment gaps are clean.

Here's a view of the armature ready for re-installation.

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A No-Load Test

I cleaned up the motor's output-end plate, and reassembled the saw only to the point where I could try the motor; it runs. Here's a view of the motor clamped in my woodworking vise, merrily arcing along.

I'll fully clean up and reassemble the saw, and see how it behaves under load.

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Final Reassembly Sequence


- The following assumes perfectly clean, reassembly-ready components.
- The number in square brackets is the teardown sequence number of the item being reinstalled.

1) [10] Motor Output Gear
- The gear is end-to-end symmetrical. It can go on either way.
- A wee smear of grease on the motor's shaft prior to gear installation won't hurt.

2) [9] Chain-Sprocket/Ring-Gear Roller Bearings
- Pack them with a high-quality wheel bearing grease like Canadian Tire's Wheel Bearing and Chassis Grease prior to slipping them back on their spindle.

3) [8] Chain-Sprocket/Ring-Gear
-NOTE that this item was free of grease when you removed it. The ring-gear/motor-output-gear interface does not require lubrication.
- Slip it in place over its two roller bearings

4) [7)] Chain Oil Tank w/Oblong Outlet Seal
- As I was cleaning this item in the parts washer tank, I noticed that it leaked quite badly. The tiny 'nipple' that dispenses oil was torn. I installed the seal with Permatex Ultra Grey, and left it to cure for a few hours. Here's how it looks.

I tried it out in the parts washer tank, and my repair appears to be successful. The tank squirts fluid when the cap is pressed, but it doesn't drip or drool otherwise.

For the most part, I'm quite impressed by the engineering and construction of Poulan's electric chain saws, but these little oil tanks strike me as flimsy. They could have been better thought out, with a proper check valve incorporated.

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The seal came loose on me; the Ultra Grey must have adhered poorly to the materials involved. I let some CA adhesive wick into the seal/tank interface.

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That appears to have worked.[1] What a finicky component the oil tank is. That's marginal/poor design in my estimation.

5) [6] Right Side Shroud
- NOTE that the trigger-switch and its associated wiring must be in place and properly arrayed prior to re-installing this item.

6) [5] Chain Tension Adjuster

7) [4] Motor Brush-End Cap

8) [3] Front Hand Guard w/Bar Bolt Receiving Items

9) [2] Sprocket Support and Bar W/Chain[2]
- The hole in the sprocket support for the shoulder screw looked to me like it had been enlarged by wear, possibly from vibration while running with the screw not fully tightened. I recall that when I went to first remove the shoulder screw, it seemed loose.

I added an external tooth lockwasher, so I'd have a thin washer in place that I could really tighten the shoulder screw down on. I think that was a good move. Here's a view of it.

10) [1] Chain-Drive Cap

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All But Done

Adjust chain tension for 'no slack; no tightness'. Pour in some bar oil and see what it can do.

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A Done Deal

It cuts wood.

I don't know how much life there still is in the saw, but I don't do much chainsawing, so this machine may yet give me long service. (The price was certainly right.)

One wonders how much of this sort of gear is in landfill because of stuck brushes.

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A Parting Word About Poulan's Electric Chain Saws

This is the second Poulan saw that I've torn down and 'overhauled'; I also have an old Model 1420 that I got working.

From what I've seen, Poulan's saws are well-designed and well-constructed machines EXCEPT for the chain oil tanks -- those are cheap, flimsy little leak centres.

I'd be interested to see how other manufacturers deal with the matter of chain oil delivery; surely there are better ways to go about it than Poulan's silly little 'nipple'.

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[1] No it didn't. I could not get the oil tank to work properly. I've got it sort of dispensing oil, but it's still going to leak.

The simplest way to deal with the problem is to hang the machine up by the hole in the nose of the bar when the saw is idle; oriented that way, the oil tank won't leak.

[2] Getting the bar and chain back on can be a clumsy, aggravating chore. It's helpful to have the saw held immobile in a woodworking vise.

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