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Stihl 4Mix valve adjustments - when, if at all?

Discussion in 'Mechanic and Repair' started by Roger, Jul 22, 2008.

  1. Roger

    Roger LawnSite Fanatic
    Messages: 5,937

    I bought a Stihl FS90R string trimmer a few weeks ago. It was my understanding that the valves should be adjusted at about 50 hours of operation. I think my trimmer has had at least that number of hours.

    When I left the dealer with the new piece, I looked at the service tech standing there who had fueled it, and got it running. I said, "check valves at 50 hours?" and he said "yes." I asked, "... instructions in the manual?" I was holding the bag with the Operators Manual in my other hand. He replied "yes."

    Now that the time has arrived, I look in the manual, and find nothing about "how to." I see it on the chart of things "to do."

    I did a search in this Section and found some threads discussing the topic. The responses ranged from "never have done it," to "it is absolutely necessary." And there were some others that said "it was important on the early models, but not so on the later ones." Some of these posts were a couple of years old. Nothing on the topic was very current. Also, I think the manual says 0.002" clearance on both intake and exhaust. But, I see some other values in threads posted here, 0.006, 0.008, and 0.010.

    My question for the new buyer in 2008: Is it important to do? If so, are there good instructions someplace? I see somebody mention a kit of tools, that includes a feeler gauge. If I buy a kit, will the kit have instructions?

    I have feeler gauges, but one of the posts said a very narrow one is needed for the job -- either get the kit, or modify an existing one with cutting.

    Now that the 4Mix engines have had much more use, maybe some of the comments in the older threads of a couple of years are not appropriate any longer because of engine changes. I'm just asking .... Thanks.
  2. Yuanding

    Yuanding LawnSite Member
    from England
    Messages: 82

    Have a look at this link :
    What is not explained is how to locate top dead centre.
    Can anyone give us a blow-by-blow account of this valve adjustment process?
    Why doesn't Stihl want customers to be able to do it themselves? It would save a lot of messing about.
  3. Den69RS96

    Den69RS96 LawnSite Member
    Messages: 96

  4. sawman65

    sawman65 LawnSite Senior Member
    Messages: 754

    take it back to the dealer its coverd under warranty. stihl used to give ya a new gasket and a guage and a paper telling ya how but people got it so messed up they just made the desicion to cover it under warranty.
  5. Roger

    Roger LawnSite Fanatic
    Messages: 5,937

    Thanks for the tips. The video on the website could be more useful. It does not provide specifics. Giving information on taking off the shroud, disconnecting the plug wire, taking out the spark plug, ... is not the kind of information I was seeking.

    I called my dealer this morning, taking sawman65's suggestion. After talking with the man who sold it to me, their prime floor sales person, he clearly had little idea about what I was speaking. I put me on hold, and was gone a long time. When he came back, he said "we don't do the valve adjustment as part of the sale." He had a copy of the operator's manual, and started reading to me. I told him I had read this part, but the tech who fired it up at the shop at the time of purchase said the information was in the manual. He agreed it was not there.

    Then he said something really strange. This is a dealer that just does not dabble in Stihl products, but rather sells quite a lot. I think they do a good chain saw business, but all the other products are there too, trimmers, hedge clippers, pole pruners, etc. He said that he has worked there for more an a year, and I was the first person to ask about the subject of valve adjustments. He further said he cannot recall anybody bringing in any 4Mix gear for a valve adjustment. When I asked about a kit for doing the adjustment, he said he had never seen or heard of one.

    What does this say? For me, it says that nobody takes the topic seriously, ignoring the suggestion of the manual.

    For the record, the manual says to do the valve adjustment at 139 hours. Yes, 1-3-9 hours. What is significant about such an odd number?
  6. wildbilly1113

    wildbilly1113 LawnSite Member
    Messages: 154

    If your trimmers starter cord is hard to pull it is time to adjust valves. SO If you keep breaking the cord it probably is the valves.
  7. sawman65

    sawman65 LawnSite Senior Member
    Messages: 754

    run!!!!! dont walk away from that dealer and find you a new one that sells stihl. they will be able to help you if not go here and send them an e-mail
    ask them why their dealer can not take care of you after the sale. i have been to the VA.beach plant for my gold level training and stihl will not put up with crap like this.
  8. haybaler

    haybaler LawnSite Senior Member
    from ma
    Messages: 511

    the first 110r I bought came with the gasket and tool to do the adjustment, and the dealer explained it to you at time of purchase. also maintanece chart says "about" 135 hr's. new km130 no gasket or tool dealer says NOTHING about it. mantanence chart says "about" 139 hr's. What the heck!!! why would they bother changing it 4 hr's?? is it a misprint? my km130 pulls hard, does that mean it needs adjustment, or has it been that way since new, seeing the size of the engine?
  9. Fisher40037

    Fisher40037 LawnSite Member
    Messages: 36

    Roger, send me your e-mail address, and I will send you the mechanic
    manual for that engine. Keep in mind, the clearances are in metric.

  10. GravelyNut

    GravelyNut LawnSite Bronze Member
    Messages: 1,594

    What he said. Stihl does stand by their equipment.

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