Stihl 039 rebuild

[Aufdy's lawn]

I picked up an 039 for next to nothing, but it is trashed. I'm looking to rebuild and I was wondering if I should just replace the top end, or order an entire engine that is ready to install. The Piston is scored, and the rings are stuck. The jug is scored as well. I'm just wondering if I can trust the bearings on the crank, or if I should replace it all. I looked at the flywheel, and it isn't marked up like it was rubbing the coil, so I personally think the bearings are alright. Any and all recommendations on what to do, and brands to use would be greatly appreciated.

 

[Leerod83]

First things first. Figure out what cooked it in the first place. Than access the damage....... Can you salvage the cylinder? (Pictures would be helpful). Then go from there. An aftermarket motor most likely won't be as strong as the original and changing bearings and seals while you have it apart that far is pretty easy. I'd try to clean it up and throw a meteor piston in it and bearings and seals. You have to remember these are clamshells. To pull the cylinder you pretty much have it apart anyhow.

 

[Aufdy's lawn]

I have it all apart. It scored the jug and piston on the exhaust side. I'm not going to try to salvage the cylinder. It's too far gone

 

[Leerod83]

You'd be surprised at what will clean up. Search YouTube( or here) for mastermind cleaning up a scored cylinder. As long as it doesn't get into the plating you can clean it up. Basically raised spots you can get off. Gouges are bad.

 

[Mustang71]

Those kits are cheap. Get a cylinder kit and some new seals a long with some motoseal or equivalent and rebuild it. It's a long process for those saws they are complex.

 

[Aufdy's lawn]

The cylinder is gouged. And I've been looking at the different kits. I like to think that I'm rather mechanically inclined, so it shouldn't be too hard for me to do everything. @Mustang71 I'm going to school for HVAC, and I'm crazy about my saws, so I may have to pick your brain from time to time

 

[Mustang71]

I've been doing hvac for 8 years now. I work residential and we do some new builds. I've been messing with saws for a bit over a year now but I've been in the garage and the woods since I was a little kid.

 

[Sleepy]

If you're not in a hurry, HL Supply put's the Cross Performance kit's on sale occasionally.
http://www.hlsproparts.com/Stihl-039-MS390-cylinder-kit-p/cp30390.htm

 

[Aufdy's lawn]

I've been in HVAC for 9 months, and started school in August. We mainly do commercial and industrial. I've been tinkering with Stihl products for the past few months to try to help pay for school. I won't mess around with the other brands because Stihl is all I've ever known. I started doing landscaping and lawn care my junior year of high school and I never bought anything besides JD, Stihl, and Snapper Pro. I'd kinda like to get this saw done in the next few weeks and sell it to put money towards my student loan

 

[Mustang71]

Ya know what, once you rebuild that 039 any other brand will be a dream. That's a messed up series of saws.

I never did any schooling just got paid to learn. Hopefully it all works out for you the real field experience isn't anything like what they teach you. I started out doing commercial there's a lot to know and a lot of fears you need to get over.

 

[Stihlbillie]

https://m.ebay.com/itm/46MM-CYLINDE...3Aea11674015e0aa46a914f53fffff00c0%7Ciid%3A17

Whole sha bang for $45

 

[Aufdy's lawn]

I agree. It is a messed up series of saws. I moved parts from an 036 to an 034 to make 1 good saw, and it was much easier to understand what was going on. I'm going to put a 49mm kit on the 039 because there is noticable difference in power between it and the 46mm

 

[rd35]

The 46mm is for the 029 saw. The 49 is the correct size for the 039. Otherwise the engines are identical as are the saws. I recently repaired an MS310 (also the same series 1127 saw as the 039) that had been straight gassed. The customer was wanting a cheap fix and was fine with aftermarket parts. I ordered piston/cylinder kit. When I went to install it I discovered the bearings were shot due to all the aluminum that had gotten in them. They felt smooth and tight at first....until I cleaned them in the parts washer. When all the blackish grey aluminum dust came gushing out of the sides of the bearing they became loose and very rough/noisy as they spun. Rod bearing on crank was not much better. At that point I discovered I should have just bought a complete engine. So, I would suggest you disassemble your engine and check out the bearings and crank. If the bearings are bad, you may want to consider just getting an entire pre-assemble new engine. Will save you time as well since you won't have to wait 24 hours for the pan sealant to set up.

 

[jltrent]

As Leerod said use acid and clean it up. I haven't clean one up yet that I couldn't get at least 140 lb compression out of with a meteor piston. Go ahead and buy a POS china kit and learn like I have as plating is as thin as cigarette paper and poor quality all the way around.. Don't throw away the cylinder send it to me as I will pay shipping.

 

[Aufdy's lawn]

I guess I'll have to try the acid treatment. I never knew how to do it. I'll see about getting some muriatic acid

 

[Outdoorguy1979]

I don't know how old this thread is but im rebuilding a 039 also, I have alil play in the crank needle bearings and was wondering if im suspost t to or not? I can rock the rod just a little and if not how hard is it to replace?

 

[Leerod83]

Side to side is ok if it's minimal. Up and down play is no bueno. You can't replace that particular bearing as the crank is pressed together. If it's suspect then get a new one. They're cheap. Most likely it's ok.