msbrockman
New Member
I am looking to buy a Stihl MS390. I found a saw that has MS310 decals on it but the owner/seller says it is an MS390. How can you positively tell the difference without disassembly?
I agree.walk away,unless he gives you a good price on a used 310.
I knew this would help someone eventually.
http://www.arboristsite.com/showthread.php?t=98960&highlight=1127+cylinder
Not all 390's have the decomp. Pull the flywheel and have a look, or pull the muffler and measure the bore. If he says no, walk away. 039/390 is 49mm, 310 is 47mm.
A stock 390 will have a decompression button, while a 310 does not. A 310 can have a larger piston & cylinder put in it and it will be the same size as a 390. A stock 390 has a 49mm diameter piston while the 310 has a 47mm (i think) . My first instinct would be to look for the decomp button. If its there, the saw is a 390. If not, it could be a 390, 310, or 290 and the only way to know is tear the saw down and measure the bore. All 3 saws are built on the same chassis.
Some 310 models have decomp buttons.
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