Advice Needed On a Stihl MS 290

[dw8468]

Hey, All!

I've been lurking here for quite awhile and have been able to solve most of my saw issues without asking, but now I need a little expert advice...

About a month ago I picked up a Stihl MS 290 at an estate sale very cheap. It was obviously used, but did not look abused and ran like a champ.

I've cut about six cords with it over the last month with no issues. That is until yesterday...

I had been cutting for about half an hour and it suddenly lost power, and about five seconds later lost compression and quit. I pulled the starter and the pull cord would only go so far and stop.

I had as sneaking suspicion about what happened, so I pulled the muffler. I was right, but the damage was a little worse than I thought. A piece of the piston and ring had broken off at the exhaust port. When I turn the flywheel, it will rotate about 90 deg. clockwise and counterclockwise until the piston hits the top of its stroke. The piston did look a little pitted, but I've seen worse on other equipment.

To answer the question I know is coming, it was fresh, 89 octane gas with the proper 50:1 oil mix (a little heavy on the oil if anything).

I took it to several repair shops and got the answer I expected - It's done, buy a new one.

This is where the advice part comes in.

Being recently laid off (contrary to what the State of Michigan would have you believe, unemployment does NOT pay the bills), but still needing wood for the winter, I'm looking for a low cost solution to my problem that won't lead to more in the future.

The cost of parts at the Stihl dealer will run in the $250 range for the cylinder, piston, rings and seals. This is assuming the crank and connecting parts are not damaged.

I've been looking at several other options, mainly on ebay. I see aftermarket cylinders, pistons, and rings for under $80, but I'm leery of aftermarket products. What brands are best? Do they hold up well? In other words, are they worth the risk?

The other option I'm considering is a whole new engine, since OEM engines with cranks and all are in the $130 range. This would take care of any issues with damaged parts below the engine. My only issue here is that they could be used or rebuilt advertised as new, and I would be buying someone else's problem.

With either option, what should I look out for? What are the pitfalls and potential problems that I may overlook? Any issues reassembling? Since I don't know how old it is, are all 290's the same, or have parts changed over the years?

Lastly, I was told it was probably running lean, causing the failure. Outside of a fuel line, what else could cause this? I'd like to avoid this in the future.

Any help that you can lend will be much appreciated!

 

[nstueve]

running lean is a huge problem with these saws and usually due to the limiter caps on the carb. If you look in the carb adjustment holes are their red caps on the adjustment screws? if so you cooked your saw b/c of the limiter caps.

I've rebuilt dozens of these now... You have the option of possibly cleaning your cylinder with acid... If it cleans up you can put a new piston in it. If not you need a new piston and cylinder. AM P&C's are ok. They definatly aren't stock OEM quality... I've used both and if done right a AM P&C can/might last you just as long even with quality difference in casting and what not.

Bailey's has a 390 engine for $150 made by NWP which will bump you from 57cc's to 64cc's. www.Northwoodsaws.com also has a top end kit that I believe is of good quality after using a couple but they are still Chinese aftermarket P&C's ($90).

You will want to replace oil seals, gas, and impulse lines to be sure you have no leaks that cause a lean condition. You'll also need some Yamabond4 (or similar) to reseal the new cylinder down.

The biggest problem most complain about is that you have to completly disassemble the saw for a decent rebuild to be done. It take time but you can do a good rebuild for under $150+your time.

 

[H 2 H]

......

Bailey's has a 390 engine for $150 made by NWP which will bump you from 57cc's to 64cc's. www.Northwoodsaws.com also has a top end kit that I believe is of good quality after using a couple but they are still Chinese aftermarket P&C's ($90).

........

Here is one I did with a Bailey's 390

IMO make sure you replace all the lines and intake boot and put a kit in the carb and retune your carb. Then you'll have a saw for many years

 

[Fish]

Your damage is not a normal failure, but since you bought it at an auction, who know's what you bought.

Tear it down and see what you have, there is no need to ask advice until you know what you have. Some of these guys might advise you to
perform a pagan ritual involving Amsoil, Klotz, and a dead, headless chicken.

But since your failure isn't a classic lean seizure, tear it down first and see what you have.

 

[Stihlofadeal64]

Tear it down (as already advised). If indeed you decide to rebuild it -- the final decision is up to you. If you are cash strapped you may try to rework the cylinder. If the ring caught in the cylinder and gouged it you have one decision already down - replace the cylinder. If I was going to rebuild the saw I'd go ahead with the larger piston/cylinder size. Bailey's has an aftermarket 039/390 cylinder that some are raving over. (That being said it depends on how much money you have to stick into it at the time...)

I would not even think about breaking it down and rebuilding it without knowing I HAD TO replace the crank seals, fuel and impulse lines. There are many illustrative threads on this site that can aid you in walking through the tear down/reassembly. (If you buy the Bailey's kit the seals are included). Otherwise you'll be in for an interesting time of learning your way around this series saw. Some actually despise them, but to do the rebuild would be rewarding if you're going to keep the saw. My 2 pennies...:msp_wink:

 

[Grande Dog]

Howdy,
I'll be starting another thread on this but, I thought I would mention here because it's on subject. Our SBN 390's are fully assembled and are pressure / vac tested at the factory. We have 4 additional screws to hold the engine pan in place while the 4 main engine mounting screws are removed to facilitate assembly.
So here's the deal. I was shipped 100 of these assemblies that don't have the 4 additional retaining screws installed in them. I've installed a couple to satisfy my own curiosity, and the dirko kept it sealed, or when I tightened the main mounting screws, it re-sealed itself because the pressure/vac test held.
I'm going to release these 100 under the Item# SBNKU 390 described as Short Block Kit Unassembled. If you buy one and don't have a way to pressure/vac test, I would suggest re-sealing. Long story short, they're going to sell for $99.95 until they're gone. It'll be a day or two before they are ready to ship. Both the fully assembled, and the unassembled version will have a 1 year warranty.

Regards
Gregg

 

[dw8468]

running lean is a huge problem with these saws and usually due to the limiter caps on the carb. If you look in the carb adjustment holes are their red caps on the adjustment screws? if so you cooked your saw b/c of the limiter caps.

Please forgive what may be a naive question, but why would limiter caps cook an engine? I thought they were there to prevent those sorts of problems.

And yes, they do appear to be on the saw.

Your damage is not a normal failure, but since you bought it at an auction, who know's what you bought.

Tear it down and see what you have, there is no need to ask advice until you know what you have. Some of these guys might advise you to
perform a pagan ritual involving Amsoil, Klotz, and a dead, headless chicken.

But since your failure isn't a classic lean seizure, tear it down first and see what you have.

You're right, it was a gamble, but for $35 I figured I could at least get that back selling it for scrap.

I'll tear it down tomorrow and see what damage is there. I can guarantee the cylinder is shot just by looking at the gouges on the top cylinder side edge of the exhaust port. The only question is what's below.

Tear it down (as already advised). If indeed you decide to rebuild it -- the final decision is up to you. If you are cash strapped you may try to rework the cylinder. If the ring caught in the cylinder and gouged it you have one decision already down - replace the cylinder. If I was going to rebuild the saw I'd go ahead with the larger piston/cylinder size. Bailey's has an aftermarket 039/390 cylinder that some are raving over. (That being said it depends on how much money you have to stick into it at the time...)

I would not even think about breaking it down and rebuilding it without knowing I HAD TO replace the crank seals, fuel and impulse lines. There are many illustrative threads on this site that can aid you in walking through the tear down/reassembly. (If you buy the Bailey's kit the seals are included). Otherwise you'll be in for an interesting time of learning your way around this series saw. Some actually despise them, but to do the rebuild would be rewarding if you're going to keep the saw. My 2 pennies...:msp_wink:

A larger engine would come in handy, so I wouldn't mind going that route, but that would involve replacing the carb too, wouldn't it?

This is an unbudgeted but necessary expense, so I have to weigh needs vs. wants at this point. Times being what they are, I need to find the best possible repair for the dollar spent.


Thank you all for your replies so far! You've given me a few things to consider and a good jumping off point.

 

[Scooterbum]

Your carb will be fine with the 390 short block.All you'll need then would be intake boot, fuel and impulse line and a fuel filter. presto !! New saw.

 

[sefh3]

Pictures. Post some pictures of the piston damage. Also, in my signature there are some great threads that will help you assemble and disassemble this saw. They are worth fixing. Check out your fuel line also. They are known to crack and seize the engine. I'm wondering what caused this damage. It doesn't sound like it seized. It sounds like something broke. I'm down by the Ohio line so if your close bring it by. I'll help you get it running. That is a great price on those kits from Bailey's also. I would think about upgrading for that kind of money.

 

[dw8468]

It took me a few days to get to this, but here are some pictures.

I couldn't figure out how to get them in to the body of the post, so they are attached below.

The things you see sticking out of the piston are pieces of the rings and piston embedded in to the top of the piston.

There's some carbon build up on the top of the cylinder and piston, but no major pitting except from the damage caused by chunks of the piston and rings. There's also some discoloration on the side of the piston that travels over the exhaust port, but none any where else.

All the lines and intake manifold seem to be solid and not leaking, and there was no foreign material in the cylinder. I don't see an obvious reason for the failure.

After looking at the pictures, what do you all think was the cause?

 

[dw8468]

Also, what is the item in the attached picture?

It was on the shaft under the clutch, but not attached to anything. It just spun freely. The back side is threaded, but not screwed in to anything, and the wire sticking out was not connected anywhere.

 

[Fish]

Also, what is the item in the attached picture?

It was on the shaft under the clutch, but not attached to anything. It just spun freely. The back side is threaded, but not screwed in to anything, and the wire sticking out was not connected anywhere.

All of Stihl saws have a built in "'stud" finder, just spin it and see who it is pointing to....

 

[sefh3]

Also, what is the item in the attached picture?

It was on the shaft under the clutch, but not attached to anything. It just spun freely. The back side is threaded, but not screwed in to anything, and the wire sticking out was not connected anywhere.

That is your worm gear. It screws into the oil pump and the clutch drum has a notch that goes into the wire. When the engine spins, it pumps out oil.

 

[sefh3]

That is some nasty damage. It's on the exhaust side. I'm betting you lost a needle bearing from the crank or a ball bearing from the crank bearings. Inspect those and see if you find something missing.

 

[bluestripes]

looks to me like a ring broke and caused your problems.

 

[Tim Carroll]

That is some nasty damage. It's on the exhaust side. I'm betting you lost a needle bearing from the crank or a ball bearing from the crank bearings. Inspect those and see if you find something missing.

+1 something came loose and ended up between the top of the piston and top of the exhaust port.

 

[Stihlofadeal64]

I couldn't see all of the cylinder but by the looks of the piston, I'd say the top end is done for. Might as well double check the crank (as stated) to make sure none of the bearings in either place are laying on top of the piston, or pieces of them. There was quite a bit of "stuff" in one picture on top of the piston that rammed through the ring lands in the inside wall of the cylinder. It is possible you're going to have to have a crank -- without putting my hands on it - it is hard to tell from here.

 

[sefh3]

The kit that Baileys has sounds like a really good deal now. The crank and bearings are included in those kits.

 

[dw8468]

I couldn't see all of the cylinder but by the looks of the piston, I'd say the top end is done for. Might as well double check the crank (as stated) to make sure none of the bearings in either place are laying on top of the piston, or pieces of them. There was quite a bit of "stuff" in one picture on top of the piston that rammed through the ring lands in the inside wall of the cylinder. It is possible you're going to have to have a crank -- without putting my hands on it - it is hard to tell from here.

The top end is done that is for sure. Most of the "stuff" were pieces of piston ring and piston embedded in the top, as well as pits from that being mashed against the top of the cylinder.

That is some nasty damage. It's on the exhaust side. I'm betting you lost a needle bearing from the crank or a ball bearing from the crank bearings. Inspect those and see if you find something missing.

I plan on taking that apart tomorrow. My son took off with the tools I needed to do that to help his Grandpa with something while I was tearing down the rest of it. Danged kids!

The bearings spun freely and no balls were missing that I could see, but I'll know for sure tomorrow.

That is your worm gear. It screws into the oil pump and the clutch drum has a notch that goes into the wire. When the engine spins, it pumps out oil.

It pulled straight out - I didn't have to unscrew it. Is that normal?

Pictures. Post some pictures of the piston damage. Also, in my signature there are some great threads that will help you assemble and disassemble this saw. They are worth fixing. Check out your fuel line also. They are known to crack and seize the engine. I'm wondering what caused this damage. It doesn't sound like it seized. It sounds like something broke. I'm down by the Ohio line so if your close bring it by. I'll help you get it running. That is a great price on those kits from Bailey's also. I would think about upgrading for that kind of money.

Thanks for the offer. I live about 45 minutes north of Ann Arbor, so I don't get as close as you are to enemy territory very often, but if I can't get it going, I may take you up on it.

 

[dw8468]

The kit that Baileys has sounds like a really good deal now. The crank and bearings are included in those kits.

Yes, it is. I just want to try to nail down the reason for the failure so it doesn't bite me again.