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Stihl BR420 Question

Discussion in 'Mechanic and Repair' started by Primecut, Nov 16, 2006.

  1. Primecut

    Primecut LawnSite Member
    Messages: 61

    Great blower. Has worked great for me. About 2 years old. However, recently it will run for about 15-20 minutes on leaf cleanups, and then the power will cut about 30-40%. Why is this happening? Thanks.
  2. khouse

    khouse LawnSite Bronze Member
    Messages: 1,465

    does it just sound like you reduced the throttle and it runs fine but lower rpm's. Or does it sputter and blow black smoke. Or does it act like its too lean and going to die. I don't know really what to tell you except a few cheap things to do. Change spark plug, replace fuel filter (in fuel tank). tear down and blow out carb, new air filter , clean fuel tank, fresh fuel. remove spark arrester in muffler.-- all the usual stuff that fixes 75% of most problems.
  3. Primecut

    Primecut LawnSite Member
    Messages: 61

    Ok, thanks for the response. It just cuts down, no sputtering or smoke. New air filter. Relatively new spark plug. Will do the others. Thanks for the help.
  4. jasonnau

    jasonnau LawnSite Senior Member
    Messages: 454

    This may be a stupid answer, but, you know that the air intake in the back can easily get clogged with leaves when your blowing right. I have to turn my blower off every 15 minutes or so to pull the leaves off the back. Inbetween the motor and the part thats on your back.
  5. Primecut

    Primecut LawnSite Member
    Messages: 61

    Thanks Jason. Thats not it, but I'm familiar with what you're talking about. Also, does anybody know an online site that I can purchase the small springs that hold the blower to the frame. Thank you.
  6. sawman65

    sawman65 LawnSite Senior Member
    Messages: 754

    the next time it starts cutting out losen the gas cap and see if that helps i have had this problem before
  7. MuleCutter

    MuleCutter LawnSite Member
    Messages: 212

    this makes sense.... the cap vent might be partially clogged.
  8. Doug Z.

    Doug Z. LawnSite Member
    Messages: 93

    2 things to try. Clean the spark arrestor on the muffler. Take it off, and take a torch to the screen. That was what was happening with mine. The other thing that I was just told by my dealer, switch to the synthetic oil. He gave me 2 containers to try, but of course, this was at the end of the year, so I cant tell you the results for sure. But, try the spark arrestor first. When I did it though, I wound up breaking it, and had to replace the entire muffler. It sure made the differnace tough...
  9. mcambrose

    mcambrose LawnSite Senior Member
    Messages: 518

    My mechanic just recently had a couple of units with the same problem. He talked to the tech at Stihl and they told him they had some problems like this when the fuel lines became old and soft. When the gas level in the tank goes down, it causes the engine to pull harder to suck the gas out and the line collapses. They told him to pull the fuel line out of tank and see if it is really soft. If it is they said to change it out.
  10. fixer67

    fixer67 LawnSite Silver Member
    Messages: 2,098

    We just had a BR420 in the shop last week that was doing the same thing. It turned out to be an air leak. When the engine got hot the the metal expands
    causing the gas air mix to change. I am not saying you have an air leak but it may be worth checking.

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