Stihl MS280 Chainsaw Piston Replacement
* 8mm socket
* 3" extension (I used 1/4" tools during the repair)
* 1/4" ratchet
* T27 torx tool
* gasket scraper
* o-ring pick(used to remove and install piston wrist pin circlip)
* Stihl Dirko sealant
* cylinder hone and hone oil
* drill (for cylinder hone)
* small impact driver(really speeds up disassembly and reassembly)
* torque wrench(inch-pounds)
Next the four cylinder screws were torqued to specification after a Google search to find out how Newton meters(Stihl only lists their torque specification in Newton meters) converted to inch-pounds. The top engine cover, handle, carburetor and intake, and muffler were all reinstalled. While doing the reassembly I went ahead and replaced the impulse hose and fuel line due to the ethanol in fuel these days causing so many issues on small engines, after the rebuild the chainsaw will be fed a healthy diet of non-ethanol 89 octane mixed with Stihl's Ultra synthetic 2-stroke mix. The old fuel line was hard rubber from age and ethanol whereas the new fuel line was a softer rubber(a Stihl brand fuel line was installed). A few pulls of the pull rope with the spark plug out of the cylinder to help lubricate the piston rings against the cylinder walls and to make sure everything was moving smoothly and then I reinstalled the spark plug.
I then set the engine to the choke position to start the chainsaw and quickly flipped it off the choke position to the run position to let the engine idle for a minute to check for any possible issues. I then used a tachometer to check the low and high idle and adjusted as needed so the RPMs were within Stihl's specification.
Overall this repair could be completed in a few hours for the average wrench-turner and isn’t too terribly hard to do with some basic tools. The other tools I ordered specifically for this project was the 46mm cylinder hone & the honing oil but I can use both tools in future projects. Disassembly and reassembly was quick but you want to spend the most time using the muriatic acid & cylinder hone to make sure there isn’t any scoring left on the cylinder walls or it won’t take long for the engine to have problems again.
View attachment Stihl MS280 Chainsaw Piston Replacement.pdf