Stihl MS200T Rebuild

[TheManOfStihl]

So last winter I picked up a Stihl MS200T as a parts unit. Completely torn down, all pieces in a box, and everything was there. Guy told me: "40 bucks if you want that damn thing." I didn't hesitate to open my wallet instantly.

The back story was that it was owned by a tree service and just quit, so they just traded it in. Didn't care what the problem was, just bought a new one. This dealer tore this one down to individual components to see what the deal was, and left it that way in a box so they could sell the used parts if need be. Well they never sold any of the parts, and it couldn't have been there a month and they were tired of looking at it. So when I asked if they had any basketcase or non running saws for sale, they showed it to me. Yeah, forty bucks, no brainer.

The crank was grooved on the clutch side where the bearing rides on it. Took out the seal and stopped running. Had mild scoring on the piston, but the jug looked fine. I put it all back together with new seals, used crank and a few little new parts, and tried to start it.

Nothing. Won't even fire on mix sprayed in the carb. Checked the compression, it was like 15-20 PSI. Crap.

At that point, the budget was getting thin so I put this saw on the shelf to look at later. Well two nights ago was later.

I bought a ring and piston kit from a company for $25. Yeah, it's aftermarket but I'm on a budget. Well when I got it in the mail, they sent me a jug kit with the piston and rings. Said they were out of just the piston kit, here you can just have this. Score!

I put everything together with the new jug and piston and built the saw back up. As soon as I could, I pulled the string to try to start it. 3 pulls and it ran! Very stout compression according to the pull rope, I really have to hold this thing! It runs smooth and starts very easily now! This is the first time I'd ever heard it run! I thought just for fun I'd check compression again with the new setup.

20 PSI! Are you kidding me?!

I went up to the Stihl store and talked to my guy up there, he said not to worry about the compression on it as long as it runs. He said compression tests are more suited for 4 cycle and don't tell us much really about the health of a two cycle. Hmmm. Do you agree with that? I don't want to say he's wrong, but I thought it took like 60PSI or better to ignite gasoline in any gas engine? I also have an 029 that's been slowly losing power, checked it out at 35PSI of compression. It starts well and idles great, just can't tune it to perform up high. I'm going to use it for smaller jobs until it quits, and put the 039 kit in it.

So, my questions are about the compression readings I got. It's a new Snap on compression guage that I bought recently so I believe I can trust it. But, as the dealer told me, it runs so what are you worried about? I'm worried that this 35cc saw won't perform to it's full potential, and I just rebuilt it. As he said the compression can only escape past the rings or past the spark plug threads after the ports are covered. Well this is a new jug, piston and rings. Is it because it's aftermarket? Any thoughts?

 

[naturelover]

Hmm, I don't believe it'd run on that low of compression.

You should be able to feel the difference between 20psi compression and enough compression for it to start.

Are you pulling it until the gauge stops rising? Is the Schrader valve for your gauge on the end of the hose?

 

[TheManOfStihl]

That's what I thought, the string pulls really hard, even slowly, as though there is a great amount of compression. But my tester says otherwise. Yes, the Schrader is in the hose, and I pull even a few more times after the needle reaches top reading. I don't want to believe the tester since the engine is so stout. My previous small engine knowledge says this has to have more compression than the tester is telling me.

 

[Frank Boyer]

Try a different gauge and/or that gauge on a different motor. Change the Schrader valve.

 

[Zombiechopper]

Uh, you have a gauge problem No engine is going to run at 20psi!

Are you pulling the rope hard and fast over and over until the gauge stops rising? You can't be prissy about it, really have to show that rope who's boss

 

[7sleeper]

Clearly you gauge is wrong! Nothing under ~80 PSI is going to run. But if you compare the results to your 290 all is well. The 290 has 35 and the rebuilt 200 has 20. Now if you consider that the rings have to seat there is absolute room for improvement. An air leak test would be more interesting in my eyes.

I have to agree with the store guys who cares what readings you are getting just go cut wood.

7

 

[TheManOfStihl]

Thanks for the input fellas, I appreciate it. I am wondering if there is something amiss with my gauge. I'll give it back to Snappy and see what he can do with it.

I was pulling the rope quickly, as I would to start it. There's no dilly dallying around with this, without a brisk pull the compression catches and almost pulls it out of my other hand. I really hafta hold on to start this little thing. I had attributed that to it being so light and also being a little awkward holding a top handle to start it, but I think you guys are probably right, it's gotta be more that it's telling me. And that's what I thought I heard forever ago, someone told me ~60PSI min to run. Anyway yeah, 20 should then be out of the question.

I am going to take that advice given to me by the store guys, and just ignore it. It runs so who cares what the reading is until it stops running. Thanks guys.

 

[jus2fat]

Thanks for the input fellas, I appreciate it. I am wondering if there is something amiss with my gauge. I'll give it back to Snappy and see what he can do with it.

You've definitely got a screwed up gauge - just because it's a Snap-On doesn't mean it's a good gauge.

A quality name..but still sometimes crap gets out the door..Not every unit is checked though it should be.

16 yrs.in QC for an international company...if you're over 95% good on product...that's good enough.

The 5% bad...just give them their $$ back or offer another new unit for free...best you can do..!!

Sort of like 95% of folks I deal with are "cool"...5% are azzholes...!!

J2F

 

[Matt_M]

Did you find the cause of the original problem as to why is just stopped working?
Might wanna investigate.

You would hate it to seize in a few more weeks because of an unsolder underlying problem.

Just my thoughts.


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[Wood Doctor]

My Bicep Measures Compression...

... better than your compression gauge. Your comp gauge is a dud. I wager that engine is kicking out higher than 120 psi with your new parts and probably higher. All the Stihl engines that I have rebuilt deliver about 150 psi compression and a few are even higher. I have seen a few guys squish these things up to 180 psi. I've never done that, but it is possible.

You can buy a decent compresssion gauge for less than $50 that would work better than what you have.