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Lessons I learnt the hard way during my Stihl 044C rebuild...

Started by Andy171361, January 12, 2016, 05:41:55 PM

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Andy171361

Here are a few things I learnt along the way during the recent rebuild of my Stihl 044C.  Some will amuse you, I hope, and others might help.  Anyway a picture paints a thousand words, so here goes.

Lesson 1 Stihl OEM parts do NOT always cost more than reproduction parts and they are pretty much guaranteed to fit.

Here is a picture of 2 Stihl 044 cylinder gaskets.  The smaller one is Stihl OEM, the larger one is an aftermarket part.  They actually cost about the same but the postage was cheaper for the aftermarket part.  Of course that does not help if the part simply does not fit.  The supplier sent me identical (too large) gaskets 3 times before giving me a full refund.  I returned the gaskets as they were no use to me but the ordering, waiting, complaining, waiting, complaining again and eventually ordering an OEM part wasted me about 2 weeks.



Incidentally it is possible to reuse a cylinder gasket (if you have to) but if you do it is VITAL to reuse it the same way round and the same way up, so mark it in some way before you remove it.  Otherwise there is a 3 in 4 chance that you will put it back the wrong way round and then you will have a good chance of an air leak - even if you use some liquid gasket.  That was why I had to remove the cylinder the second time...

ZeroJunk

I had the same thing happen at the Stihl store and had to make a return trip. Had the 046 MS460 gaskets in the wrong place.

Andy171361

Well that's interesting. Maybe the same thing happened here?

Andy171361

Lesson 2  Keep your work clean.

I know that sounds obvious but...  Initially the 044 was a non runner with a scored piston.  The cylinder looked OK and the impulse line was obviously unserviceable so I flushed out the crankcase to rinse the bearings, gave the original piston a moderate polish with fine emery paper, fitted a new impulse line,  piston rings and cylinder gasket and rebuilt it.  The saw ran quite nicely, felled one tree easily but then was reluctant to start when warm.  Having previously destroyed a 038 Magnum by ignoring the warning signs and continuing to run a saw that clearly did not want to run I decided to strip the saw a second time and check for damage.  As it happens there was nothing obviously the matter but I decided to replace the piston as a precaution.  While waiting for the new piston to arrive I spent some time polishing the intake and exhaust ports of the cylinder (by hand with more very fine emery paper) but crucially did not clean the cylinder as thoroughly as I should have done - especially the transfer ports. 



At this point I had the cylinder gasket problem from lesson 1 and rebuilt the saw with the reused gasket.  The saw seemed to run quite nicely but I simply could not fine tune it.  I think this was probably due to an air leak around the reused cylinder gasket.  Anyway a further strip was obviously in order and this is what I found...



So I removed the piston, gave it a further polish with very fine emery paper, rinsed the crankcase again, cleaned everything thoroughly and reassembled using a new cylinder gasket.

What happened next was quite interesting.  The saw started very nicely, idled nicely and ran nicely.  The only thing that was unusual was that while tuning it with my tacho after approx. half a second at WOT I could hear the revs beginning to increase.  I was tuning it deliberately low at 12,500 rpm to give a margin for error.  When I tried cutting with it the revs would die after a couple of seconds.  I could sort of cut with it at half throttle but full power, under load was unobtainable.

Andy171361

Which led to lesson 3 If your chainsaw won't operate at full throttle when cutting, stop using it and find the problem

Even though the saw was obviously not working correctly I kept cutting logs at half throttle for a while. Next day I removed the cylinder (again) and found that my new piston, which had run for only 20 mins total, showed distinct signs of lean-burn scoring.  The cause of this problem turned out to be the fuel feed hose as you can see in this picture. When I had re-fitted the carb the pipe had been pushed back leading to a kink just behind the collar.



To be fair to me there was a bit of a gotcha gotcha here.  I had assumed that this fuel hose was complete and intact but, when I replaced it, the new part had a small lug on it which stopped it being pushed back when the carb was installed.  Without the lug the pipe gets pushed back and kinks, allowing enough fuel for starting and idle, and even enough fuel for WOT not under load but for about half a second, but not enough fuel for cutting.  Hence also the rpm creeping up after approx. half a second at WOT not under load.  Here's a photo of the piston.



At this point I decided just to do the job properly and do a full rebuild...


Andy171361

Lesson 4  You can remove a flywheel without a puller

Possibly the greatest benefit of this forum is learning really useful practical techniques for rebuilding  and maintaining chainsaws without going to the expense of buying all of the Stihl service tools.  In this respect I am particularly indebted to Joe Indi who has posted many top tips and practical suggestions.  One of Joe's tricks is removing a flywheel by loosening the nut, so it stands proud of the threaded end of the crankshaft, holding the flywheel firmly and then giving the nut a sharp tap wth a hammer.  The trouble is that my finger tips are clearly not as strong as Joe's!



As I bashed harder and harder at the nut I realised that what I actually needed was to suspend the flywheel using a piece of strong tape.  With the flywheel suspended from my garage ceiling all my puny finger tips needed to do was hold the piece steady, as the picture shows.  One sharp tap like this and the flywheel came free, plus the added bonus that my fingers are still intact too.  I used a spark plug socket to keep my punch lined up in the small indentation in the end of the crankshaft.

Andy171361

Lesson 5 The serial number is stamped internally on the crankcase

There are several threads on FF asking where the serial number is on various saws.  Having stripped both types I can confirm that on Stihl 038 and 044 the serial number is duplicated on the mating surface of the clutch-side half of the crankcase.





These shots also demonstrate Lesson 6  The dishwasher does a great job of cleaning crank cases

Andy171361

Lesson 7 While the chainsaw is in pieces re-build the oil pump and replace the oil hose



If you are planning to use the "heating the crankcase" method in order to fit new bearings you MUST first remove all rubber components.  Oddly the Stihl 044 Service manual states that you should remove the O ring at the end of the curved pipe and also the plastic plug, but does not say that you should remove the two O rings that are fitted inside the pump.  Removing the screw which controls pump output is not particularly difficult - just a bit fiddly.  I used an old 2mm drill bit as a drift.  It is common sense to replace all 3 O rings because they cost literally pennies each.

Replacing the oil hose is easy with the crank case parted but I imagine it is a nightmare job when the saw is intact.  A new pipe only costs a few pounds, about $5?

Andy171361

Lesson 8 Installing oil seals

Seals can be a bit fiddly to fit unless you manage to apply even pressure.  I found a socket in my collection that matched the size of the seal and then used a second, long-reach socket, to push the first one down.  Tap tap with the hammer and in the seal goes.


Andy171361

Lesson 9 A stitch in time really does save nine

This is the first time I have deliberately bought a non-running chainsaw with a view to rebuilding it.  Having done so I would certainly do it again but next time if the piston is scored I would simply do a complete strip and rebuild.  I would renew all the rubber parts, as a matter of course and , if there was any doubt, the bearings too.

Here endeth the lesson(s)...

The finished article,



which came fitted with a catalytic converter.



Al_Smith

Nice job .Some points to ponder just as an observation .

An after market  flywheel puller for a Stihl is rather inexpensive .I make mine from a metric hydraulic bango fitting but I'm not the average bear in the woods in a manner of speaking . ;)

As far as the piston ,two things .A scored piston like shown is not usually a problem .I've saved many that were far worse .A low spot will not hurt you .A high spot however breaks the surface tension of the oil film and will fail given enough time .

Which once again says something about oil mix ratios .It would make  sense that slightly richer mix ratios with more oil than the popular 50 to one would provide more protection .Some don't subscribe to that theory and some do .I'm among the later group .

Andy171361

Hello Al.

Thank you for your kind words.  Thank you also for your posts elsewhere on FF about using the freezing the bearings/heating the crankcase method for installing crank case bearings.  I have used your method twice, on my Stihl 038 mag and now my 044, and it has worked really well both times.

I hear what you are saying about a flywheel puller and have now ordered a proper one!  I posted lesson 4 because when I dismantled my 038 Joe Indi's technique worked very well and the flywheel came off quite easily.  This time, with the 044, it was much harder and using some webbing to suspend the flywheel was very simple (once I had worked it out) and made all the difference.  As I have learnt so much from your postings, and Joe's, I hoped my refinement of Joe's technique might help somebody else.

What you say about the piston scoring is very encouraging.  The original piston was scored much worse than this but I did get the saw running just by smoothing the piston down and fitting new rings.  What worried me about this light scoring on this new Meteor piston was whether it was being caused by some debris floating around in the crankcase or a lean mixture.  In the end as I replaced everything, and was very careful with cleanliness, I hope I have eliminated both problems.

As for oil mixes it is clearly a subject which generates a lot of heated debate!  The Stihl 044 manual says use 1:50 and that's it.  But my MS361 manual says 1:50 using Stihl oil or 1:25 if using "Other high-quality two-stroke engine oil".  I would have thought any ratio in between should work.  I simply use 1:50 for general chainsaw work and 1:25 for milling and it works for me.  As I have some 1:25 made up I am using it on the 044 for a couple of tanks, while the new piston and rings bed in.


Logger RK

Couple years ago I split my O44 to change crank bearings & seal's. Somebody told me I would'nt of had 2 split it if I had the right tools. Wondering if that's true? Also when I split it that painted on coating inside was peeling off in a few spots. I took the loose stuff out & put back 2gather. Seems like it runs fine. Wondering what that stuff 4? Heat shield like? It's been about a year & only use for oversize trees my shears can't cut & maybe 20-30 cord firewood if my 066 is dull or forgot 2 put in the pickup. Anyone think With some of coating not there,there will b issues with it?

sawguy21

Perfesser Andy, that was a good tutorial. ;D Some lessons have to be learned the hard way but those are the ones that stick. I have no idea how the crank bearings could be removed without splitting the case. As far as the coating goes I wouldn't worry about it, there is nothing that can be done in the field short of replacing the crank case.
old age and treachery will always overcome youth and enthusiasm

Andy171361

Hi logger RK

I don't see how you could replace the bearings without splitting the case.  Maybe, just maybe, the clutch-side one could be extracted somehow, because when you install the clutch-side bearing the maintenance manual tells you to fit the oil pump to ensure the bearing stops in the right place when you place it in its pocket.  But I can see no way how that would work for the flywheel-side because the casing forms the bottom of the bearing pocket.  Here's a picture of the flywheel side.



I had assumed that the coating on the inside that you refer to is just the same paint as the rest of the crankcase.  I guessed that it was a slightly darker colour due to years of contact with a mixture of oil and fuel.  But that is only my best guess and not a fact.  Maybe one of the technical experts could tell us more?

Sawguy, thanks for your kind words too.  The simple fact of the matter is that I rebuilt my first chainsaw (038 Mag) in 2015 and there is no way I would have attempted that job without learning so much from this website.  It is generous of you to call this a tutorial as it is simply an account of what I did.  But I like the sound of Professor Andy - it has a certain ring to it! 

You are right about lessons sticking when you have learnt them the hard way - I will certainly apply Lesson 9 to all my future rebuilds!



Logger RK

That's what I thought about changing the crank bearings also. This was a younger guy with a small engine shop that said it didn't need 2 b split. Being 55 I've worked on a few things & didnt think they could b changed with out the splitting. Unless he sends them out 2 have changed & hasnt done it? This info May have been told 2 me at The Pub. And we all know only truth is told in them placed. Also more wood is cut there then the mills could ever handle😄

Logger RK

Guess I didn't check that last one all the way over good. Suppose 2 say,Place's

Andy171361

I understood what you were saying anyway.  I think we are agreed that either this chap was talking about a different model of chainsaw or he had never actually done the bearings on an 044 himself.  As you said, there are a lot of experts on hand in The Pub!

Al_Smith

That guy might have confused Stihl with Husqvarna .They claim some models of Husqvarna can have a bearing change without splitting the case .181-281 maybe 2100 --forgot which models

Now the rest of the story.It takes a special bearing puller that has fingers that go between the balls in the bearing that costs a couple hundred dollars . I for one am not going to rush out and buy one . :o

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