Author Topic: Poulan 4620  (Read 1424 times)

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Offline Cut4fun .

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Re: Poulan 4620
« Reply #40 on: April 30, 2015, 12:55:04 pm »
Owner got new b+c and cut yesterday for the 4620. He was smiling saying she does run and cut good for his uses. 

Also told him another friend we work with that could use those 2 new carlton 3/8LP chains and 16" new bar.  Seen him handing them to him today.
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Offline Chris-PA

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Re: Poulan 4620
« Reply #41 on: April 30, 2015, 12:58:02 pm »
There are some advantages of the chromed piston/bare bore approach:

There is less surface area on the piston, so it makes some sense to give it the harder coating.

The chrome plating will reduce thermal conductivity a bit.

The rings run on the bare cylinder which would seem to be a disadvantage, but in practice does not seem to be a problem.

The worst aspect is if foreign objects get into the cylinder (carbon chunks, etc.), as then they get dragged along the unplated cylinder walls by the piston/ring and plow grooves into it.

Offline Eccentric

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Re: Poulan 4620
« Reply #42 on: April 30, 2015, 01:53:22 pm »
Actually on this series of saw (P600) they have all been plated cylinders.  It's the other series (mostly 42cc) like is used in the Wild Thing and PP260 that were only plated for Poulan Pro versions (maybe Partner in Euope too?). 

I have seen bare bore cylinders (and plated pistons) for a few of these 46cc saws.  I would not have said they existed if I had not seen them.  I also know the difference between this series and the one that includes the WT.


-Aaron

For older saws:
Tune the H side so that it 4-strokes (burbles) at WOT unloaded and just cleans up when under load.
When you lift cutting load, the saw should immediately revert to 4-stroking.  Fine tune the transition point for the wood you're cutting.

Offline Eccentric

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Re: Poulan 4620
« Reply #43 on: April 30, 2015, 02:15:02 pm »
For example.....


Plated cylinder, bare piston.  What we're used to seeing in this series.


http://www.ereplacementparts.com/poulan-2900-type-gas-chainsaw-parts-c-16962_17147_130237.html





http://www.ereplacementparts.com/assycylcrankcase-p-641198.html





http://www.ereplacementparts.com/piston-kit-p-248120.html





http://www.ereplacementparts.com/piston-ring-p-248131.html



Bare bore, plated piston.  Seen in the 2900 Type 3 and 4, 2775 Type 3 and 4, some Craftsman 46cc saws, and maybe others.  Seems to be most common in Craftsman versions from what I've seen.  Cylinder, piston kit, and ring are all different part #'s.

http://www.ereplacementparts.com/poulan-2900-type-gas-chainsaw-parts-c-16962_17147_17278.html





http://www.ereplacementparts.com/assycylcrankcase-p-248612.html





http://www.ereplacementparts.com/kitpiston-p-248611.html





http://www.ereplacementparts.com/piston-ring-p-248131.html


Unfortunately, these pics don't show the cylinder bores.  I've seen ebay listings for new 530071491 cylinders with clear pics of the unplated bore.
-Aaron

For older saws:
Tune the H side so that it 4-strokes (burbles) at WOT unloaded and just cleans up when under load.
When you lift cutting load, the saw should immediately revert to 4-stroking.  Fine tune the transition point for the wood you're cutting.

Offline Chris-PA

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Re: Poulan 4620
« Reply #44 on: April 30, 2015, 02:47:21 pm »
Interesting - my 2775 is chromed bore.  I wonder if it's just the replacement sets? 

Offline Eccentric

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Re: Poulan 4620
« Reply #45 on: April 30, 2015, 03:25:04 pm »
Look at the MN/SN decal.  There should be a Type #.  IIRC, it precedes the SN.  For example, 1-12234556 would be a Type-1. 

The 2775 Type-1 and 2775 Type-2 both have the normal plated bore and bare piston.  Type-3 and Type-4 are the bare bore, plated piston versions.  Don't think they made many 2775 and 2900 Type-3 and Type-4 saws. 

My guess is that Poulan built those versions to use up the excess bare bore/plated piston sets left over from the Craftsman saw production runs.  I've seen far more bare bore Craftsman 46cc saws than their Poulan branded brothers.

Only reason why I knew the bare bore/plated piston versions exist is because I've researched this series pretty thoroughly.  I put the 46cc engines into the Husky 36-141 chassis, and needed to figure out what would be good donors (and what new/NOS parts on ebay to grab) for my PoulVarnas...  8)
-Aaron

For older saws:
Tune the H side so that it 4-strokes (burbles) at WOT unloaded and just cleans up when under load.
When you lift cutting load, the saw should immediately revert to 4-stroking.  Fine tune the transition point for the wood you're cutting.

Offline Chris-PA

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Re: Poulan 4620
« Reply #46 on: April 30, 2015, 04:22:38 pm »
Thanks, that's good to know and I stand corrected - I had not run into any of the unplated bore versions in this series yet.  It's something I'll have to pay attention to if I ever get any Craftsman versions. 

Oh, and my 2775 is a Type1 so that is consistent.

Offline aclarke

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Re: Poulan 4620
« Reply #47 on: April 30, 2015, 05:41:02 pm »
Seems like a neat  set up.  Is the bore fairly rough when new for oil retention?  Normal cross hatch?

Offline Eccentric

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Re: Poulan 4620
« Reply #48 on: April 30, 2015, 06:27:44 pm »
Thanks, that's good to know and I stand corrected - I had not run into any of the unplated bore versions in this series yet.  It's something I'll have to pay attention to if I ever get any Craftsman versions. 

Oh, and my 2775 is a Type1 so that is consistent.

I'm not surprised that you hadn't ran into any of them, as they seem to be uncommon.

Seems like a neat  set up.  Is the bore fairly rough when new for oil retention?  Normal cross hatch?

There's some sort of hard coating process.  Something to do with high silicon content aluminum.  If it's like the Briggs and Tecumseh engines with the same sort of finish, then it's only a few thousandths thick.  Not really cross-hatched, but more of a 'frosted' look.  Poulan has produced many 2-stroke engines with this same bore finish. 

The 3400 and 3800 CounterVibe saws, most of the Micro series saws, many of the 33-42cc series consumer saws (including the WildThing), and many blowers and weedeaters have this finish.  It's proven to be much more durable than we'd expect.  Just seems "wrong" to have steel rings riding in a bare aluminum bore..............but it has held up very well over the decades.  Technically, the rings are supposed to ride on a film of oil rather than the bore anyways.  Only thing that seems to kill them is severe 'dusting' from dirt ingestion and running WAY too lean due to air leaks and/or incorrect adjustment.  The 4-stroke lawnmowers with this bore finish seem to be less durable than the Poulan 2-strokes, at least from what I've seen.
-Aaron

For older saws:
Tune the H side so that it 4-strokes (burbles) at WOT unloaded and just cleans up when under load.
When you lift cutting load, the saw should immediately revert to 4-stroking.  Fine tune the transition point for the wood you're cutting.

Offline aclarke

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Re: Poulan 4620
« Reply #49 on: April 30, 2015, 06:40:37 pm »
Thanks Aaron,  maybe be some sort of chemical conversion process that creates a hard oxide layer? I'll Research this more and pass on any info...

 

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