This is a record of the internals of a SX25 top handle or arborist chainsaw purchased for about $100 on eBay, and used for about 50h for home yard maintenance.
I have owned three of these.
- The first was disposed of after 100h use. The chain sprocket was replaced (only slightly grooved), new clutch springs, new chain, bar dressed and it worked flawlessly. Early in its life, most of the fuel hoses and the primer bulb had to be replaced as they were sucking air… fatal to two strokes if left unfixed.
- This is the second, I purchased it as a spare for the first and when the first was sold, it was used for about 50h before a helper dropped it and cracked the oil tank… effectively making it a bucket of spares. No faults during its life. The engine was run in with three tanks of 25:1 mineral two stroke and zero Ethanol unleaded fuel. Then always run on Amsoil Sabre 50:1 with zero Ethanol unleaded fuel.
- When this saw was damaged, a new one of the same type was purchased and it now has 30h run time, no faults.
Here are some pics with a borescope of the engine internals, they are very telling of the engine condition. Before stripping it down, a crankcase vacuum and pressure test was conducted and a pressure test of the carburettor and fuel system… all good.
Looking in through the spark plug hole
Above, all pretty clean and a tribute to the Amsoil Sabre oil @ 1:50.
Looking in through the inlet port
The inlet side of the piston is clean and no sign of scoring. It is excellent given that this saw is used for short bursts and is not usually warmed up… so cold seizure is a risk.
Looking in through the exhaust port
The exhaust port on this engine exits at 90°, so it results in ‘different’ views.
Above, the ring is free, so sign of adhesions or scrapes.
A little ‘varnish’ in the port, no lumps of carbon, it is pretty clean.
Above, a little ‘varnish’ on the piston side below the ring, no scoring.
Above, the bottom of the skirt is clean, no scoring.
Above, a view across to the other side of the bore.
Above, a closer view of the bore from the exhaust port, it is clean and no sign of scoring.
Evaluation
All three of these saws I have owned have been stunning value. The first suffered the common Chinese problem of low quality ‘rubber’ parts, but once they were replaced it was good.
At an eighth of the price of a Stihl top handle saw, and parts readily available at low cost on Aliexpress, they are stunning value.