038 super top end rebuild

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Madprofessor you are the man! I went from stuck to done all from your tips and pics :clap::bowdown::clap:
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Ok one last question before I call it a night...big wet ash to dismantle tomorrow so better get some rest: -

I’ve put the piston and rings in dry, the crank turns nice and smoothly as it is. Should I spray a misting of oil into the cylinder to keep it all smooth and prevent a dry start when the saw is back together, or is the dry build good for helping the new rings bed in?
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I’ll do a pressure and vac check in the next few days.

Thanks for all the help to this point guys :cheers:
 
I would have suggested to put the piston and rings in with some oil, you need that oil in there, rings will bed in with oil present, but with no oil, you will damage your saw.
hope you put oil in the case bearings, and crank and piston gudgeon too.

no oil = wear= damage= do it all again.
 
I would have suggested to put the piston and rings in with some oil, you need that oil in there, rings will bed in with oil present, but with no oil, you will damage your saw.
hope you put oil in the case bearings, and crank and piston gudgeon too.

no oil = wear= damage= do it all again.
Hello, thanks for the info. I oiled the crank bearings, even though they came pre-greased from the looks of it, and I greased the new OEM wrist pin bearing. Piston and rings were dry install though; I should be ok oiling through the intake and exhaust ports though yes?
TIA
 
Hello, thanks for the info. I oiled the crank bearings, even though they came pre-greased from the looks of it, and I greased the new OEM wrist pin bearing. Piston and rings were dry install though; I should be ok oiling through the intake and exhaust ports though yes?
TIA
Would have been far better to have oiled them before fitting the cylinder, I would have suggested to oil the piston wrist pin bearing liberally with oil tho, not assemble with grease.
Can you take the jug off and assemble with oil ?
If others think greasing the wrist pin bearing is ok, then you could oil it thru the exhaust port to soak the rings and piston, dont worry about too much, it will just burn off as smoke, too little on the other hand is where wear will occour.
 
Would have been far better to have oiled them before fitting the cylinder, I would have suggested to oil the piston wrist pin bearing liberally with oil tho, not assemble with grease.
Ah ok...I will chalk this down to lack of experience and will do it better next time. Such a satisfying learning curve. Thank you for your input
 
Ah...I see. Sneaky :sweet: Isn’t it great how we’re thousands of miles apart and never to meet but we’re able to do this together. Thank you for the help :numberone:

You are welcome. Those 038 are great old saws. Take care of them and they never seem to wear out.

Looks like the piston has enough room to delete base gasket. 1mm ~0.040".

Good luck!
 
You are welcome. Those 038 are great old saws. Take care of them and they never seem to wear out.

Looks like the piston has enough room to delete base gasket. 1mm ~0.040".

Good luck!

Yup I left the base gasket off.

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Vac test complete and passed, no drop after 5 mins even with turning the crank back and forth plenty. I did notice as I turned the crank the needle on the gauge went up and down slightly but at the end was at 17in-Hg.
Now for the pressure test...but I am led to believe that after a successful vac test, a pressure test in normally a formality. Rebuilding the saw and trying to start it draws closer :clap:
 
Well, it’s back together and hopefully ready to run tomorrow. I also renewed the carb gaskets etc but didn’t adjust the screws or anything so it might take some fiddling to get it running nice...assuming it starts and doesn’t explode.
Only one thing left over lol, I really can’t remember where it came from! Any ideas guys?
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It’s plastic and about 12mm long and 5mm wide. My instinct is it is a guide that fits around a plastic shaft, like the choke, run, off plastic shaft but I couldn’t see where to fit it. It might also be something my son was messing about with that ended up in the 038 box of bits...but I don’t think so
 
F5FD596F-1680-445C-BF6F-6403F8D485B4.jpeg Just to make sure the piston pin circlip physics is understood . . . I wish I had CAD software to illustrate, but I'll have to do it verbally. At chainsaw rpm the piston is going up and down hundreds of times per second. This creates tremendous acceleration forces. Remember that force = mass x acceleration. Now if we have a circlip with the gap at 3 or 9 o'clock and the piston is going up, the top half of the circlip is being pushed down. The fulcrum point will be at the midpoint of the circlip and the outer half of the clip will be bent away from the fulcrum point and also away from the groove that it rests in. At this point it will be the least confined by the groove and more subject to any sideways forces that would move it out of the groove and in a worst case scenario pop it free from the groove. Now imagine that there is an "ear" on each half of the circlip. You now have much more mass at the outer edge of the circlip, which by F=ma means the circlip will bend even more and be more susceptible to popping out. This is the rationale for (1) not using circlips with ears, and (2) lining up the gap at 12 or 6 o'clock, where the forces will cancel each other out. Hope this is clear.
 
View attachment 768752 Just to make sure the piston pin circlip physics is understood . . . I wish I had CAD software to illustrate, but I'll have to do it verbally. At chainsaw rpm the piston is going up and down hundreds of times per second. This creates tremendous acceleration forces. Remember that force = mass x acceleration. Now if we have a circlip with the gap at 3 or 9 o'clock and the piston is going up, the top half of the circlip is being pushed down. The fulcrum point will be at the midpoint of the circlip and the outer half of the clip will be bent away from the fulcrum point and also away from the groove that it rests in. At this point it will be the least confined by the groove and more subject to any sideways forces that would move it out of the groove and in a worst case scenario pop it free from the groove. Now imagine that there is an "ear" on each half of the circlip. You now have much more mass at the outer edge of the circlip, which by F=ma means the circlip will bend even more and be more susceptible to popping out. This is the rationale for (1) not using circlips with ears, and (2) lining up the gap at 12 or 6 o'clock, where the forces will cancel each other out. Hope this is clear.
Thank you, that is very clear and makes perfect sense. Thanks for taking the time; no more eared circlips for me again
 
Right, I've finally pulled my finger out and uploaded a video of the rebuilt saw running...how does it sound to you...have I got the carb adjusted correctly? I think its fine on idle and it seems to cut well enough (even with a dulled chain and no dawg contact) but I'm not sure about how it should sound on WOT. Any advice much appreciated.

In the video it is running a 20" bar.



Thanks
Karl
 
Right, I've finally pulled my finger out and uploaded a video of the rebuilt saw running...how does it sound to you...have I got the carb adjusted correctly? I think its fine on idle and it seems to cut well enough (even with a dulled chain and no dawg contact) but I'm not sure about how it should sound on WOT. Any advice much appreciated.

In the video it is running a 20" bar.



Thanks
Karl


Very nice !
 
Thanks mate. Do you have an 038?

No, I have a copy cat kit along with a mountain of parts I ordered from around the world to replace all the parts I was not happy with in the kit, such as; crank axles, crankcases, bearings, clutch cup/sprocket, cylinder kits, oil pumps, etc...
No oem parts except the chain adjuster (ms381), but I'm still not sure if I put it back together with the 381 case or as a "038".
I just ordered a new 381 case from aliexpress that looked like a different production than the ones I got from the hustle site previously, if I'm happy with it (not likely) it will be somewhat of a mix because I like the side chain adjuster on the 381 case but I very much prefer the tank fuel/oil caps on the 038.
I have one 038 crankcase that is quite nice and I have at least one crank axle that is usable (slight throw in it on the clutch side but acceptable compared to the bad ones I got), and I have one crank axle that I've not tested yet.
If I use a 381 crankcase I will make new threads for the oil tank cap in composite so that I get the 038 oil/fuel caps, the reason I would like the side access chain adjuster is because it makes it easier to use with the Granberg minimill.
The side access chain adjuster and a decomp valve in the cylinder and the fuel caps is basically the only difference between the 038(magnum)/380 and the 381.

I love the 038 basic design, it's just really solid. The only saw except the 100cc+ saws with a twin needle cage/bearing on the clutch cup/sprocket. Plenty of solid good old fashion torque at a wide rpm range.
My plan is to use the best parts of the lot that I have collected, I have parts enough for two saws at least. It will never be the same as an original Stihl but it might become a pretty good saw in the end still.
 
I've rebuilt a couple of 038 Supers. My method for putting the cylinder on is first to squirt a little 2-cycle oil on the big end crank bearing and then by moving the crank around, get access to the points where I can squirt a little oil into the crankshaft bearings. Turn the crank around a few times to distribute the oil. then put the piston, wrist pin, and that pesky circlip in. Turn the unit over and put a couple of drops of oil on the wrist pin bearing. I don't oil the rings or the piston. The cylinder also goes on dry. The mating surfaces are squeaky clean. I use Yamabond 4 on both mating surfaces and gasket if used. I want the sealant and mating surfaces completely free of oil. After the cylinder bolts have been torqued, I turn the crank around a couple of times by hand, dry, just to make sure everything is OK and there is no binding. Then I leave it a couple of days for the Yamabond to set up fully. At that point I put a few drops of oil on the front cylinder surface through the spark plug hole and on the back surface through the exhaust port. Then turn it around a few times and everything is oiled and ready to go for startup. Also, if you forgot to oil the big end bearing, you can turn the crank to where the bottom of the piston is above the intake port and dribble oil down the connecting rod.
 
No, I have a copy cat kit along with a mountain of parts I ordered from around the world to replace all the parts I was not happy with in the kit, such as; crank axles, crankcases, bearings, clutch cup/sprocket, cylinder kits, oil pumps, etc...
No oem parts except the chain adjuster (ms381), but I'm still not sure if I put it back together with the 381 case or as a "038".
I just ordered a new 381 case from aliexpress that looked like a different production than the ones I got from the hustle site previously, if I'm happy with it (not likely) it will be somewhat of a mix because I like the side chain adjuster on the 381 case but I very much prefer the tank fuel/oil caps on the 038.
I have one 038 crankcase that is quite nice and I have at least one crank axle that is usable (slight throw in it on the clutch side but acceptable compared to the bad ones I got), and I have one crank axle that I've not tested yet.
If I use a 381 crankcase I will make new threads for the oil tank cap in composite so that I get the 038 oil/fuel caps, the reason I would like the side access chain adjuster is because it makes it easier to use with the Granberg minimill.
The side access chain adjuster and a decomp valve in the cylinder and the fuel caps is basically the only difference between the 038(magnum)/380 and the 381.

I love the 038 basic design, it's just really solid. The only saw except the 100cc+ saws with a twin needle cage/bearing on the clutch cup/sprocket. Plenty of solid good old fashion torque at a wide rpm range.
My plan is to use the best parts of the lot that I have collected, I have parts enough for two saws at least. It will never be the same as an original Stihl but it might become a pretty good saw in the end still.
Well good luck with all of that, it sounds like mix of a fun project and a nightmare, depending on your character. Whichever it is for you, you’re going to have a strong saw at the end (as you know) as you say a classic bruiser. Atm my 362c is relegated to the rack whilst I enjoy the 038S.
You’re position with a load of parts is similar to one I find myself in, albeit ms200t instead of 038. Yesterday (rain stopped play) I stripped 5 200t’s that over the years have been put away for whatever reason (long forgotten)...I’m going to use the best parts to make a good saw. I’ve got 4 good cylinders, 5 good cranks, 4 good pistons, two good case pairs etc etc. Maybe over Christmas on a wet day I’ll set the parts out and start by picking the best of each, I’m looking forward to it :clap:
 
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