Which saw to rebuild MS290 or 029 Super

[joelbert]

I have two saws, an MS290, and an 029 Super that I want to make one saw out of, which do I rebuild?

Quick inspection found that the MS290 has good compression (150psi), but a scored piston, the 029 Super has low compression (120psi) and the piston looks perfect except for some heat discoloration. Looking at the cylinder bore on the 029 I can still see cross hatching. The MS290 will start and run ok. I could not get the 029 to start. I have not done a pressure leak down test yet.

Which do I rebuild? Will a set of rings bring the compression back up in the 029? Is the heat discoloration a scary sign. It looks like the 029 has more heat damage (melted plastic).

Below is a bunch more history on these if anyone cares.

I picked these up about 2 years ago from a rental place that put an ad on Craigslist giving away a Stihl hedge trimmer. When I got there the guy gave me a pair of Stihl HS60AV hedge trimmers, and these two saws. I have been using one of the hedge trimmers since then, but never quite got around to poking at the saws. That was when I first found arboristsite.com looking for an IPL for the HS60AVs. Istill have not found that IPL for the HS60AV.

I have a Stihl MS250 I picked up at a garage sale that generally does everything I need out of a chainsaw for my homeowner use, and maybe in the future some work clearing blow downs on local hiking trails if I ever get to the park's mandatory safety certification course. But I do like to tinker with small engines, and getting a couple of cheap crappy 14" garage sale chain saws running got me to start looking back at this project.

Okay enough history, onto the saws. They are a MS 290, and an 029 super that came from a rental place that was done with them. When I first got them I I gave them a quick look, and neither of them came with a bar, chain, sprocket, sprocket cover or air filter cover. I occasionally looked at CL and won an auction for some miscellaneous MS 290 parts that included an air filter cover (what I was looking for), and a flywheel, carb, brake handle, some brake parts, a recoil starter, and some spare plastics I don't really need. I didn't try to run them because I figured the centrifugal clutch would not enjoy having no sprocket over it if the thing did try to run.

Looking at them more closely this past week I see just how abused they are. The biggest abuse was apparently being used by idiots, or at least people with no clue as to how these saws work. The engine housing on both saws show that the chain brakes have generated huge amounts of heat. I am guessing that people rented these started them, and didn't know there was a brake so they just gave them throttle and couldn't figure out why the chain didn't move, and the thing stalled. They probably then tried giving it throttle real slowly to try to keep it from stalling. I wonderif it stalled, or the stopped when the melting smell got too strong. Maybe the rental place rented them with the idle turned up too high, and people just engaged the brake to keep the chain from moving while it idled, and that lightly engaged clutch just let it cook. In any case the engine housing on both has significant melting around it. On the 029 the chain brake is inoperable because the pivots for the brake mechanism have moved/deformed too much. The MS290 the brake is operable, but the lever is only about 3/4" in front of the handle when the brake is released because of the same deformed plastic issue. The brake handles are even melted down where they engage the brake, but fortunately the parts collection I got on ebay a while ago included that. I bought an engine housing off of ebay, and now have to figure out which engine to rebuild.


I picked up a sprocket on ebay, and tried to fire them up. After the MS290 tried to rip my arm off I found the flywheel key sheared. After aligning the flywheel where it belonged and tightening the nut I got it to run. I figured I am not putting the 'good' flywheel I got in the parts collection on until everything else is done and stable. The 029 won't start with either carb on it, the MS290 will run with either of the carbs on it, but one of them runs pretty smokey. I assume that will go away with adjustment.

MS290 photos

029 photos

Lastly a photo of my photo studio for getting all of those nice exhaust port photos.

 

[JimmyT]

joelbert, it all depends on how much you want to spend. The cheapest way is to put a aftermarket piston and rings from Northwood Saw for $28.95 in the 029.Be sure to check with your local Stihl Dealer or e-mail Stihl support with your serial number to see if you have the 45mm or 46 mm piston. You might get by with a ring job but since the 029 Farmboss was first produced in 1993 at Virginia Beach VA. it is probably going to need a piston.


http://

northwoodsaw.com/store/index.php?l=product_detail&p=72

 

[JimmyT]

I think the Stihl MS 029 super uses the 46mm piston and is the same as the 290.


http://
northwoodsaw.com/store/index.php?l=product_detail&p=76

 

[joelbert]

You might get by with a ring job but since the 029 Farmboss was first produced in 1993 at Virginia Beach VA. it is probably going to need a piston.

Is there a history of piston problems with saws made in Virginia Beach? Any way to tell if the piston is problematic?

Thanks,
joelbert

 

[JimmyT]

Not that I am aware of. I am assuming that Stihl is using Mahle pistons that are made in Trumbull Connecticut. Mahle is a German based company but they are global and produce pistons in Germany,Austria,U.S.A.,Brazil and China. Stihl makes 33 models and only the 5 largest saws the 440 thru 880 are made in Germany,the rest are made in Virginia Beach. I found a service station that sells all 3 grades of ethanol free gas plus I am using Stihl HP ultra oil and my saws are running cooler. It gets down to good lubrication to overcome heat and friction.The EPA phase 3 regulations aren't helping the small engine life expectancy.

 

[joelbert]

The way you phrased it I thought you were implying it would likely need a new piston because it was made in VA.

Is the decision about new piston vs reuse old piston just based on visual inspection, or are there other concerns? In the 'what brand of aftermarket piston ' thread several people suggested they would opt for a used oem piston over an aftermarket piston. If my used oem piston looks okay am I better off just reusing it?

Does anyone have any experience with the chinese pistons and cylinders on ebay? I am generally leery of chinese knockoff stuff, but I figured I 'd ask if anyone has any first hand experience? Either 'I tried one and it is running great', or 'I tried one and it exploded, didn't fit, etc'.

Thanks,

Joel

 

[JimmyT]

My neighbor has a 1994 029 Farmboss with 120 lbs. compression. After 17 years of use and many hours and cords of wood it needs a new piston and rings.Generally when a saw gets that old the piston skirts are worn too.Lets say that you drop the 28.95 (Episan-Made in Turkey) piston in it and get the compression up to 145 lbs. and you get another 5 years out of the saw then you can't ask for anymore than that. My neighbor does not want to spend the money for a new piston,cylinder or a new saw. I guess he going to have to listen to one of my new saws running this October. If you decide not to repair them put both of them on e-bay and sell them for parts and get the new Husqvarna 562XP that is coming out.

 

[JimmyT]

Joel, I was just thinking you can go to plan B. Pull the cylinder off of the 029 and install it and the new piston on the 290 since it is a newer saw.

 

[joelbert]

Jimmy,

I suspect I will end up with a bucket of all of the parts, and I will just pick the better of the two I have to choose from for each part, to make a true frakensaw. Since the markings are on different plastic pieces I have to decide whether it ends up saying MS290, 029, or both, or neither.

Thanks for your advice

 

[sefh3]

Here is what I would do. Order a set of rings for the 029. Order a new piston and rings for the 290. While your on line with Northwood saws, order 2 sets of fuel lines and seals. Build both saws. Sell one and run the other. These saws are known to have a quirks with fuel lines cracking. Seals are under $5 and it's great insurance. If you need help building these, PM me or post here. I have built a few of these over the years. While your at it, stop by the local Yamaha store and get some Yamabond or a local hardware store and get some fuel resistant sealant. You'll need that when you reinstall the crankcase. OH yeah, go steal the wifes doohickey that she uses to get jar lids off with. You'll need that when you remove the rear bar studs. And last but not least, I have a thread in my signature where Mr. Hall assembles one. It will help you.

 

[JimmyT]

It would be nice to get both saws back on line but the 290 cylinder wall looks badly scored. You could get the 029 running then keep looking on e-Bay for a cylinder head for the 290. Something is bound to pop up between now and fall. I priced a Stihl OEM piston for my neighbors 029 last year and it was like $90

 

[Evan]

How bought you just send me that picture rig and ill send you my 026 pro

 

[joelbert]

It is tempting to try to get both saws working, but for a start I will get one running, and then see how close I am to getting the second one back together. I'll take a look at the scoring on the MS290 cylinder, and maybe even experiment with some acid for the learning aspect of it. Some of this is just the fun of playing with different little engines. I have spent years playing with lawn mowers, weed whackers, snowblowers etc, but on those it isn't worth rebuilding the engine. This will be my first time replacing a piston and rings, so it is fun getting this far into these. Spent some time today looking over the service manual I got from atpchas from the manual begging thread.

I know I am short some parts for getting both back together. I'm actually short a few parts from even getting one back together, like a clutch/sprocket cover. I have only one flywheel with an intact key. I know I have seen threads here saying you can get away with just lining up the keyway with the spot where the key should be on the flywheel, and tightening up the flywheel nut. That is how I got the MS290 running, but I am not sure how 'durable' that solution is. I have only one air filter cover, and brake dust cove between the two of them. After one saw is done I will look at what parts I have, and what I need and decide whether to fix the second saw or part it out.

sefh3 the links in your signature were helpful.

Thanks,

 

[sefh3]

I have both a MS290 and MS310 that are running without keyways. Those are there for timing. Line them up and tighten them down. I would order and new set of rings and seals and work on that one first. That one looks most promising. Once you get it going the get some acid. Acid is great for cleaning these cylinders up. Doesn't take much to clean the transfer off.

 

[joelbert]

How bought you just send me that picture rig and ill send you my 026 pro

I might end up with the better end of that deal.

The camera is an older 8 megapixel DSLR. It always bothers me when I see cameras like mine on CL going for less than half of what I paid. And I'd be happy to send you the half bug eaten hemlock I was using to hold the saw at the right angle to get good lighting in it, but the postage might get kind of steep.

 

[joelbert]

I have both a MS290 and MS310 that are running without keyways. Those are there for timing. Line them up and tighten them down. I would order and new set of rings and seals and work on that one first. That one looks most promising. Once you get it going the get some acid. Acid is great for cleaning these cylinders up. Doesn't take much to clean the transfer off.

I'll certainly start with the easier one first, but I will experiment with the acid even if I am not going to fix the second saw, just as a learning experience. Always good to add new tricks to the bag.

Good to know I don't need to worry about finding another flywheel. I was concerned that it might not hold up too well to the chain brake. Inertia of the flywheel vs sudden decel of the crank.

Thanks,

 

[joelbert]

Okay, I have both completely apart. I doubt I can rebuild two saws from the collection of parts. Too many heat damaged parts. The back handle/housing plastic on the 029 was too melted. The intake manifold and the impulse line were also melted on the 029.

I tried using some acid on the MS290 cylinder, but did not get much results. I may have been too timid in my application. I may search around this site a bit more for tips on using acid on a cylinder.

I think I have all of the parts together, and should be able to try the assembly later this week if time permits.

 

[JimmyT]

Joelbert, after looking at the P/C pictures again I would focus on the 029. I still would go with a new piston and rings.

 

[JimmyT]

Okay, I have both completely apart. I doubt I can rebuild two saws from the collection of parts. Too many heat damaged parts. The back handle/housing plastic on the 029 was too melted. The intake manifold and the impulse line were also melted on the 029.

I tried using some acid on the MS290 cylinder, but did not get much results. I may have been too timid in my application. I may search around this site a bit more for tips on using acid on a cylinder.

I think I have all of the parts together, and should be able to try the assembly later this week if time permits.

How did the 029 get the heat damage.

 

[JimmyT]

If there is to much heat damage on the 029 then swap cylinders with the 290. Put the 029 cylinder with the new piston on the 290.