Stihl MS 280: repair or replace?

[Damocles]

Lumerjack, does she have any sisters?

At ant rate, I figure that he can put together a parts list for me and save me some hours figuring out what I need. At least that's the theory. Does anyone know a good source for a repair manual? Online even?

[JohnG28]

Glad that you decided to try to fix er up, will be a good feeling when you get it running at 100% again with your own hands.  As for manuals, member Boobap I believe had some Stihl IPBs and manuals I think, if you look back there is a thread about people in need of these, says Stihl IPBs in the topic.

[Damocles]

OK, got the saw back. The repair guy doesn't know where the leaky seal is so I couldn't buy any seals until I find the problem myself. Boobap was kind enough to send me IPB and manual so I should be ready to roll. I'll start to dig into it soon but I'm wondering if anyone has some specific advice about how to proceed. I would just start taking it apart and reading through the manual and hoping I see something obvious. Probably making lots of extra work for myself in the process.

[joe_indi]

The safety lock plastic guard thing is busted almost off, there is an air leak in the crank case (not 100% positive that's what he said - I was still reeling from the price), a couple bushings are missing (extra vibration may have contributed to the crank case problem), general tune up, and bang... $300.

The couple of bushings you've mentioned  might be the root cause of the problem.
I get to see this condition quite often here.
The saw must have been pushed too much into the wood with its dull chain.Typically on a Stihl when you do this it sets off a chain reaction.
The bushes bust or come off their slots..........
This causes the crankcase  to wobble too much on the tank housing...........
Which in turn causes extra load on the on the components that connect the crankcase to the tank housing.............In this case the manifold and the impulse hose................They might come off or tear............ Which causes air to move in, which strongly resemble a leaking crankcase.
So check the manifold and, definitely, the impulse hose.
By the safety lock thing you must mean the trigger interlock on the handle or the switch shaft (on/off switch).These a simple replacement items. Just check the 'Air Leak' first.

[Damocles]

Thanks, I think you're likely correct. Now that I look at the IPB, I see that what I've been calling bushings are annular buffers with bushings internal.

Last year while cutting I noticed that the annular buffers were fallen off. I have no idea how long I worked with them damaged, but I pushed them back in place with a screwdriver as best I could and kept on cutting all fall and the next spring. So wrong, I know.

"Safety lock thing" actually means chain brake... Easy to replace I think.

Going through the manual it seems there are some tools I'll need. I would like to avoid buying stuff until I actually need it. Do you guys think I have to get a vacuum pump to test at this point? Any must-have specialized tools I need to open my wallet for?

Also, there is something confusing me. Between the two annular buffers on the bottom there is a post protruding into an opening. It looks like spring or something is missing there, but I haven't found a reference to it in the manual or IPB. I couldn't figure out how to attach a JPG so I changed my profile pic to illustrate. How's that!?

[Damocles]

So the real question I have is; what do I do next? I got it mostly apart, ready to replace the chain brake and the annular buffers, but it seems like I should locat the air leak first. Left to my own devices, I would just keep taking it apart and look to see if I see anything obvious like a bad gasket or cracked hose. Something tells me there is a smarter way to proceed though.

Also, there is no mention of an "impulse line" in the manual. It must be called something different.

[JohnG28]

The impulse line should come out of the bottom of the crankcase, and it goes to the carb, I think on the bottom of it as well.  As for the air leak, Id start where joeindi said, possibly around the intake boot.  After that, Im not sure what to tell you though, sorry.

[joe_indi]

Also, there is no mention of an "impulse line" in the manual. It must be called something different.

That is true.There might be no mention of an impulse line. But it is there.
Maybe not in the manual that you have.But it is there in the parts list.And it is there on the saw.Otherwise it wouldn't run.
Since I have never seen a MS280 before, I am going by the drawings in the parts list.
In the case of the MS280, probably the hose connects to a small nipple on the cylinder, just below the manifold.
A tube goes from this nipple to another one on the tank housing, again, just below the manifold.
I think this must be it:


This seems to be a similar configuration to the 1123 series of saws (021/023/025/MS210/230/250).
And, here is the clincher, the 1123 series of saws are notorious for impulse lines coming off at the carburetor end, if you tend to put too much of push or pull pressure on the saw.
With those two busted buffers, I am sure that the impulse hose has come off it connector, that is, if it has not been damaged.
Look between the cylinder and the tank housing, just below the manifold.You should be able to see a bit of hose somewhere.
When you locate it.Use a nose pliers to check whether its fixed at both ends.
Joe

[Damocles]

Got it, thank you! Impulse hose appears to be good but I'm going to remove it and inspect for cracks. I'll take the boot off the crankcasee to and see if it's intact then look at the crank case seals.

[Damocles]

Ok, more questions... Thanks to help from previous posts I got the flywheel off easy and am looking at the oil seals. They look fine to me but I might be looking at a problem and not seeing it. So I figured I should remove them. The manual says I need to buy a special puller for that job. It also says to tap the seals with a punch to free them up. I don't see how tapping them will free them up without damaging them. I mean I could dig them out with a screwdriver - then I would KNOW they were bad! As for the puller, is there another way to get them out? I'll save a dollar wherever it makes sense. Besides, the illustration showing the puller in use has it pulling on the shaft - not the seals. Is it supposed to pull the shaft through and the seal comes with it, then do the same on the clutch side? Sorry, but I'm scratching my head here and figured I'd ask you guys before destroying something.

I will now go destroy something else and see if anyone made sense of my question. Thanks.

[Rocky_J]

You're far beyond my level of expertise. I've worked on saws for over 25 years and never yet had one with bad seals that was still in good enough shape to be worth fixing. About the only way the seals would go bad would be if the main bearings were so far worn that they allowed the crank to wobble. If it's got that much wear then you either split the case and rebuild it from the bottom up or else go buy a new saw. By the time a saw has that much wear on the motor, everything else is worn out as well and repair costs would exceed the cost of replacement.

I'll throw a new top end and carb on a good saw, but bottom end repairs are almost never financially worthwhile. And vacuum leaks are almost always from the carb or intake area.

[Damocles]

Trust me, I am not beyond your level of expertise - I've been working on saws for a couple days... Maybe I should just bet the new buffers, chain brake, make sure the hoses and manifold are tight and re-seated, put it back together, and see if it works!

[Damocles]

Hey guys, I just thought I would post to say thanks to ALL of the advice and input. Got it back together and the saw runs great! I did end up having someone else do the final carb adjustments because I wasn't getting it right. At the end of the day, and after about 6 hours estimated work, including running to the store for little parts, I probably saved about $60...

[JohnG28]

Good deal, got it running on your own and saved some money too.