Carb adjust on Stihl Blower/Vac

Discussion in 'Mechanic and Repair' started by TRUCKGUY1, Jan 27, 2014.


    TRUCKGUY1 LawnSite Member
    Messages: 4

    I bought a Stihl blower/vac last Spring. I THINK the big model - BG86 or something like that - not the CE model. I am a homeowner, but pretty handy with tools.

    I always run STIHL oil and use gas stabilizer. I probably have a total of 10-12 hours on the machine. Last summer, the unit started acting up, not wanting to speed up when you pull the trigger, but stall out unless you keep blipping the throttle to bring up the RPMs. I adjusted the carb per the owner's manual several times but it seems like I come up against the adjustment stop before any positive perfomance change occurs. I called the dealer where I bought it, quite a distance away, and he said there was a special tool he has that can be used to remove the "LIMIT, or BLOCK" or something like that that allows more adjustment travel. It sounded like he wanted me to come in and pay for the adjustment. Is there an explanation on the web of how to do this adjustment, or what the tool or adjustment components look like, so I can make my own? Post help here, or PM me if you have any suggestions.:confused:
  2. ernieknows

    ernieknows LawnSite Member
    Messages: 69

    Check (chuck) the spark arrestor. If plugged will cause those symptoms.
    Could pull cold muffler and run water thru it, if a white/yellow paste
    comes out too much water in your fuel. Clean out paste and dry.
    Running wot after warmup helps prevent problems.
  3. rlitman

    rlitman LawnSite Bronze Member
    Messages: 1,764

    After that, the carb might need service/replacement.
    There is a screen inside the carb that is known to clog.
  4. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Messages: 789

    As mentioned prior, check muffler screen and or remove screen if desired... Unscrew exhaust port and the screen will be on the port.

    There is a tool (several actually) available to dealers only which are used to remove different style limiter caps. There are also several different tools used to adjust the different carburetor H&L screws. These are also not available to the public (at least they are not supposed to be).

    The reason for this is that the EPA had decided for you that the only amount of adjustment YOU can make is within the limiter stops! This in turn keeps the emissions within the specs. of the OEM per the EPA.

    After all, what good does it do to have limiter caps in place if anyone could adjust the screws...

    Just a little FYI for ya... Being that you are a home owner, you have at least a 2 year warranty on that unit. Before you start messing with it and possibly void any warranty, you just might want to make that long trip to the dealer.
    While I cannot say 100% it would be a covered repair/warranty, it would be up to your dealer as to what they find and if/how they would cover it.




    TRUCKGUY1 LawnSite Member
    Messages: 4

    Will check the spark arrestor & let you know.

    TRUCKGUY1 LawnSite Member
    Messages: 4

    OK, checked the screen - its clean, just a little blackened - no clogging or carbon buildup. Inside the muffler is very clean. Sparkplug is ok.

    Jeff - does that tool depress the sides of the limiter so it will pop off the screw? Or do those prongs fit into holes to allow it to pop off?
  7. Jeff in AL

    Jeff in AL LawnSite Senior Member
    from Alabama
    Messages: 789

    The legs on the tool go under the limiter cap and "pop" it off... Any time a limiter cap is removed, it is supposed to be replaced due to the original being damaged on removal.
  8. rlitman

    rlitman LawnSite Bronze Member
    Messages: 1,764

    I can't be sure from just the picture, but the primer bulb in Jeff's picture looks mighty "dark". They darken like this as they harden and slowly get "crunchy". Eventually they crack and suck air. The vacuum leak makes the machine run lean, like you're describing. Is your bulb nice and squishy? Even if you don't see a crack, it might be there, just not easily visible until you flex the bulb.

    TRUCKGUY1 LawnSite Member
    Messages: 4

    Thanks for the help everyone!

    Jeff - I think I understand now.

    rlitman: Will check the bulb, but the machine is new last spring - hoping it's not getting rigid yet.
  10. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,592

    Just cut the plastic with wire cutters making sure not to bend needles.

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