stihl 4 mix overhaul tools

Discussion in 'Mechanic and Repair' started by clc19chase, Jan 2, 2014.

  1. larryinalabama

    larryinalabama LawnSite Fanatic
    Messages: 19,635

    I did have to put it back and adjust the valves I hate these 4 mix machines.
  2. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Messages: 789


    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!
  3. Roger

    Roger LawnSite Fanatic
    Messages: 5,943

    Jeff, thanks for chiming in here. I stand corrected. Your kit number for an FS90 is not the same as I posted above, but my purchase was several years ago. And, yes, it did not only have the feeler gauge, but also the two gaskets you noted. The larger one can be seen in the package.

    As for price, I do remember the larger price paid at the time, but I bought other things at the time. I went back to my QuickBooks records, and found that I had not only the kit, but some other things. So, I was wrong about the price of the kit, but right about having paid more at the time because of buying more things. Thanks for clearing. I still do find the $0.20 interesting for any Stihl part, but will defer to your familiarity. Somehow $0.20 and Stihl don't go in the same sentence.

  4. clc19chase

    clc19chase LawnSite Member
    Messages: 102

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  5. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Messages: 789


    The 4-Mix blowers are the "4282" series units, so the kit you have shown in your picture is for a BR500,550 or 600 only.

    The 4-Mix shafted products all use the "4180" series kits.

    On a side note, I would recommend using 2 feeler gauges stacked on the exhaust valve only on the BR product. Not needed on the hand held units.

    I have been amazed also at the retail price of some of the parts for a Stihl unit. You would be surprised at how many spare parts that are under $1.00!

    I agree however on the flip side that there are some items that are priced sky high!

    Attached Files:

  6. BigFish

    BigFish LawnSite Platinum Member
    Messages: 4,189

    How come the double the clearance?

    Hey, and thanks for sharing some of yer " inside info" !
  7. mds2000

    mds2000 LawnSite Member
    Messages: 73

    I worked at a stihl dealer ship for about a year as a mechanic
    first the guy that says stretch out your valve spring should never touch a machine
    stihl recommends using one feeler gauge on the intake and 2 on the exhaust valve
    I would not recommend taking apart unit unit until it dies to learn the machine . If you run synthetic mix oil it keeps the carbon build up to a minimum.
    usually the main service things to do to a 4 mix are a valve adjust ( the best indicator is when it gets hard to turn the machine over from extra compression ) change the spark plug , fuel filter ,air filter and make sure the spark screen is not plugged (if it is plugged use a propane torch the heat till red and use compressed air to blow out the charred carbon out )

    if you do decide to take apart the motor the basic tools are the 2 torx bits I forget the sizes and a 8 mm socket for the valve adjust and a tube of ultra black silicon or ( dirco is what stihl dealers use )

    best of luck hope this helps
  8. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Messages: 789


    I'm not sure why the double on exhaust, I saw it on Youtube... :laugh:

    Actually, the real reason is that there was an issue with excessive carbon build up on the exhaust valve years ago. Then they changed the exhaust valve to a "bi-metal" valve. This helped with the excessive carbon build up for the most part. Even with the changes, there is still a unit from time to time with carbon deposit issues. However, today it is mostly due to their fuel or running with a broken tube and not getting the RPM's/engine temp up to burn off the deposits.

    The thought process or reason to double up on the exhaust valve on the BR units is to allow a longer seat time to help keep the valve cooler. Even though it is only nano-seconds that it is closed longer, it has made a big difference, combined with other changes to help minimize carbon deposits forming on the valve face and seat. There has been no issue with the trade off of doing so which will cause a slightly lower lift height to the valve when open!
  9. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Messages: 789

    Abrasive pads to remove carbon deposits from valves and seats on the 4-Mix units as well as a pad I use on any and all engines with silicone/RTV sealant...


  10. BigFish

    BigFish LawnSite Platinum Member
    Messages: 4,189

    Good to know on the valve adj!
    Yeah, it's been awhile since I worked for a Stihl dealer, so have not heard much in the way of tech info. The last 4-mix info I got concerned the valve change,( Sept. 09 or so) but no mention of the clearance increase. Thanks again for sharin'.

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