Stihl FS100RX trimmer leaking gas into air filter.

Discussion in 'Mechanic and Repair' started by G.M.Landscaping, Jun 2, 2012.

  1. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Posts: 1,164

    The "pressure" your referring to is what the EPA calls evaporative emissions. The fact that your tank is holding these is good since it's one of the things manufactures have to control. They need to have low permeation tanks, lines and caps. Pressure testing tanks is part of new test procedure.
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  2. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,142

    I don't notice this on Echo.......so i guess this big pressure build up is why the PB420 is so very very easy to flood on starting???
     
  3. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Posts: 1,164

    If your referring to the BR420, these are non-primer carbs. I never pull more then twice on choke, actually never more then two tries on choke for any brand and model. Then full throttle off choke till they fire up which is usually one pull.
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  4. ed2hess

    ed2hess LawnSite Fanatic
    Posts: 13,142

    YOu are right ....never ever ever use the choke after the initial start in the morning. I am trying to find explanation of why this machine is so likely to flood. I think I now know....to pass epa they keep all that vapor caught in the tank. Then when you pull the rope all hell breaks loose when that big rush of gas under pressure hits that carb. So my idea was to vent that tank with a echo breather that will let fumes pass out of it. Think that will make it less touchy?
     
  5. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Posts: 1,164

    The vent is a one way valve, and that one way is air into the tank not out. If air passes that duck bill valve inside then so will gas(leak) I pressure test them, should hold 1-2psi for a full minute.
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