How we do it

Al Smith

Mac Daddy
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Mar 6, 2005
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Northern Ohio
The subject on this one is the Stihl MS 200 T . I recently did some improvements to mine with very good results so I thought I'd give a few hints in case anybody was interested .

As with any saw engine the biggest improvement can be realized by improving flow out the exhaust ,this model is no exception .

The muffler on these things is not a true pressure can but just a baffled muffler .First remove the baffle plate .Then increase the hole the baffles set in by about 50 percent or more .

In the photo of the muffler half note the diverters .Remove the side tabs on the side nearest the outlet .This will tend to force the flow out the exhaust better .
 

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The rest of the thread I don't expect that everybody can do but this is how I did it .

The base was cut down to set the final clearance at around 20 though or so I thought .As it turned out I messed up and didn't remove enough material so I replaced the standard 20 thou thick gasket with a 5 thou one made from a sheet of paper .

The piston was domed around 12 thou ,should have been more but it works well just the same .
 

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Now had I not screwed up with my measurements the ports would still be pretty close with the pop up piston and cut base .Because I miscalculated I had to raise the ex port to set it to factory specs of 96 degrees after top dead center in order to maintain the speed these things run at .

The port was then widened to around 50 thou material left on both sides of the piston skirt .The exhaust was belled out and polished with craytex .

The muffler and gasket had to be shaped then to match the new ex port shape .

By shaving the cylinder base and using a thinner gasket the intake was automatically dropped by the 27 thou I removed from it .

That port was widened somewhat internally and also polished up .
 
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After fiddling with this tiny thing I now see why so many so called engine porters are reluctant to rework these little gems .They are tiny ,everything is in miniature .Just a few thou on something this small can make a big difference in the final outcome .

The picture shows the size of the piston,which had also been reworked regarding the windows there in to improve the flow .

The piston shown for comparison is from a Mac 10-10 .The other cylinder is a Stihl 034 .
 

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I didn't drop the intake just did some widdening inside the cylinder ,about standard stuff just a lot smaller .

The transfers still were around 30-31 blow down .I did just a little around the base and just a tad in the uppers ,not much .

For it's tiny size this saw engine has large transfers .I was surprised .With 30 or so so blow down factory set it explains why they run so well even in a stock condition .

This was just an experiment on my part .I had an idea about what the final outcome would be and it came out pretty close to my expectations . Then too I wanted to maintain the torque so the saw would still be good as a working saw .

In looking over the design it occured to me that possibley some improvement might be had if the transfers were more angled regarding the roof .. I imagine the engineers at Stihl might have already looked at that possibilty.

Perhaps the flat angle stops short cicuiting or something .You can tell by the flow pattern though they aren't quite right .
 
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Could you get me a link to what a crayex for polishing part is and for sale at or post a pic and explain what it is. Thanks.
McMaster -Carr page 2594 .Unmounted silicon carbide rubberized points . I use item 477A61 and mandrel 477A34 .Medium grit .

You get 25 in a pakage for 12-13 bucks and 3-4 bucks for the mandrel .

Not bad considering mounted points are 3-5 bucks a pop or more .

These do so well I seldom use felt fobs and rouge any more .
 
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I usually go bonkers on these things .

I think however on this model of saw if a person just made a thinner gasket or used sealant you could raise the comp enough you really wouldn't have to fiddle with the porting if you aren't sure of how to do it .

With sealant I imagine you could lower the cylinder around 18 thou which would put the exhaust opening at around 100 after I imagine more or less . This would likely slow it down a tad bit but increase the torgue a lot or at least it should .

With a gutted muffler this would be a simple way to pep one up .If it didn't work out just stick the gasket back in .Nothing harmed in any way .
 
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