Originally Posted by clc19chase
I was wanting to tear into a few of my 4mixes and maybe clean the valve seats and faces. What tools will be needed and parts if any? Im mechanically inclined but needing to know if theres anything to be aware of from the ones with experience. I had a guy tell me one time to stretch the intake spring.
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First off, what 4-Mix models are you wanting to tear into?
Why do you want to tear into them? Is there a specific problem with each one of them?
If it ain't broke, why fix it?
In my opinion, unless there is a specific problem you are having with ANY unit, only general maintenence would be expected which would include adjusting the valves on the Stihl 4-Mix units.
As with any post/thread/reply, there always seems to be a certain amount of BS sprinkled into the mix, which has been shown here also...
I would disregard any and all information from the person that told you to "stretch the intake spring"!
The "Valve Adjusting Kit" for the BR500,550 and 600 is part number 4282 007 1001. This kit includes the valve cover gasket, sealing washer on the valve cover screw and the feeler gauge. MSRP on this kit is $3.11!
The "Valve Adjusting Kit" for an FS90 is part number 4180 007 1005. This kit includes the valve cover gasket, sealing washer on the valve cover screw and the feeler gauge. MSRP on this kit is $3.60!
The feeler gauge (included in above kits) is the same for ALL Stihl 4-Mix units and is part number 4180 893 6400 and has a MSRP of $0.20!
You also have the option of using EDTA which you could get from your Stihl Dealer. It's sole purpose is to loosen, disolve carbon build up in engines. To use in the 4-Mix units, simply rotate crank shaft to get to the end of the exhaust/beginning of intake stroke (both valves will be slightly open), then fill the cylinder through spark plug hole with the EDTA and leave sit for for upto 24 hours. Then pour out remaining ETDA through spark plug hole, reinstall spark plug, check/adjust valves and then you are good to go!
I do have a complete set of cleaning pads in different "grits", styles and sizes for the 4-Mix units, but NEVER use them unless I am tearing the unit down anyway for another reason!