Stihl FS-85 won't start

Ortis

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Feb 20, 2017
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Hi - I have a Stihl FS-85, 2-stroke-cycle, string trimmer, an echo chainsaw, and other tools with small engines.

The current problem is with the FS-85. It quit, and upon looking into it, I found that the piston was badly scored. So, I bought a piston & cylinder kit, replaced the damaged units, and figured I was home-free. It didn't work out that way. It has good spark, feels like it has compression, and yes I did put gas/oil mix in the tank. It won't even try to start. I even tried ether and got nothing.

Do those symptoms ring any bells to the hordes of users on the forum?



Thanks in advance,
Ortis
 

bertsmobile1

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1) was it a genuine Stihl kit or a cheap Chinese "oem copy" .
A lot of the stuff sold on evilbay / craigs list is the stuff that was made by the supplier to Stihl quite truthfully.
However it is the stuff that Stihl rejected as being below production standards.

Next , crankcase prssures are more important than cylinder compression so do a pressure & vacuum test on the crank.
If the crank can not maintian a vacuum then it can not suck the new charge from the carb.

Blue smokes can be a regular bugger to break in rings.
I some times have to run the crank off my drill for quite a while before I get acceptable compression
Remove the pull start & drive the engine off one of the crank shaft nuts, backwards or forewards makes little difference without a plug.
 

Ortis

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Feb 20, 2017
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Thanks to all for ideas-

It's running like a champ now. After about a million pulls, I put a few drops of oil in the cylinder, pushed the primer bulb and realized it was sucking as much air as gas, tilted the engine so the fuel pickup was in a deeper spot, pulled once, and off it went. There seems to be a leak in one of the fuel lines, so I am getting new ones. It must have been failing for a while, since now it idles nicely, which it has not done in several years. Whew!
-Ortis
 
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