stihl fs80 string trimmer lacks power

Discussion in 'Homeowner Assistance Forum' started by rknarr2, Aug 12, 2009.

  1. lawnmon

    lawnmon LawnSite Member
    Posts: 116

    Robert,

    There are NO valves in this engine, it's a 2 stroke.

    I know you don't want to hear this, but that carb needs replacing.

    joat
     
  2. rknarr2

    rknarr2 LawnSite Member
    Posts: 16

    I finally just took the weed eater to the stihl shop. I told him everything that I did and he was first surprised that what I did did not fix it then he asked me who did the work on it? I told him I did and that he thought it was still a gasoline problem. He asked me if I took any of the welch plugs off and pulled something out and cleaned it. I am thinking he is referring to the valve jet out of its seat. According to a stihl service manual that I bought recently, it says to use a 5 mm (approx. 3/16") dia. drift to press the valve jet out of its seat in the direction of the venturi (not sure what a venturi is) and wash it in white spirit. It might also be possible that i put in one of the gasket in wrong like the diaphram.
    Robert
     
  3. rknarr2

    rknarr2 LawnSite Member
    Posts: 16

    The stihl shop repair man told me that there were no valves as you stated in your reply and that the guy that suggested me to check float to make sure it was dry in the carburator. Well, the stihl shop man told me that my carburator does not have a float in the carburator it uses instead a diaphram. So, when I put in carburator kit it was part of it. I just hope that he can fix it without me having to pay for a new carburator but if he puts on a new carburator so be it. Thank you for all your support with my problem and in a week I should have my weedeater back and hopefully running correctly. Regards, Robert
     
  4. milike

    milike LawnSite Member
    from MI
    Posts: 169

    All the 'cost' of going through this thorough cleaning to 'save' an old carb...it would be cheaper and quicker to just spring for a new carb.
     
  5. twotone

    twotone LawnSite Member
    Posts: 43

    Do a compression check. A cracked piston ring could be the problem.
     
  6. hate2work

    hate2work LawnSite Member
    Posts: 91

    Welch plugs are small, aluminum domed discs that are pressed into place over the low speed acceleration ports for access to these ports at a later date by the mechanic.

    It's pretty rare to see an intake manifold cracked, but it does happen. Most often the replacement makes the machine run well again, as it no longer has an outside source of air.

    It sounds like you have what Stihl calls a BIS carb, or Balanced Idle System. We call them a BS carb, that should give you a clue about them.

    Once we determine the spark and compression are good, I will attemp to clean a carb one time. If it still will not pull fuel, a new carb is put on. A new carb is almost always a better fix. No comebacks and a better performing piece of equipment.

    Needle limiter caps are a pita and we are always removing them so an adjustment can be made. They are a product of the clean air laws, as they will not let you richen the carb too much.

    Robert, no offense, but if you don't even know what a venturi is, you really shouldn't be working on your carb. The 4137 series engine was a good one, we were still selling the FS-80 up until just last week when it became NLA.
     
  7. rknarr2

    rknarr2 LawnSite Member
    Posts: 16

    Got the weedeater back from Stihl shop. It was NOT the carbeuator like alot of you people thought. He showed me that an upper edge of the crank case had broken off and that its been like that for along time because of the roundness in the edge. He also showed me where the edge of
    the piston had a worn place on it.
    He told me it would cost me the following to fix it:
    Part Part Number Price
    Crank case 4137-020-2800 $67.60
    Piston 4137-030-2010 $63.55
    2 rings 4137-034-3000 2*$8.65 = $17.30
    piston pin 4137-034-1500 $ 8.95
    bearing 9512-003-1830 $ 9.00
    cylinder gasket 4137-029-2300 $ 2.00
    his labor (approximately 2 hours) $80.00
    Grand total $248.40
    + tax
     
  8. hate2work

    hate2work LawnSite Member
    Posts: 91

    Robert, this reminds me of trying to diagnose a problem over the phone. We're always getting people calling us, asking what the problem is < chuckle >

    Anyway, if you're going to have it repaired, have the dealer order the short block for this machine rather than all the individual parts. That's a much better way to go.

    If you have the BIS carb the part # for the short block is 4137-020-0201.

    If you have the adjustable carb, the part # is 4137-020-0202.

    The MSRP for each is $97.95. The labor should also be a little less if you went this way.

    Hope this helps :)
     
  9. rknarr2

    rknarr2 LawnSite Member
    Posts: 16

    That is a great idea to do a short block and it would cut the labor costs as well. I checked with my local stihl and was told that the short block $175 but I would also have
    to change out my old carb, S28D, which is around $60-$70 because it would not work with a short block.
    If I purchased individually, the stihl guy told me that I would need to add the following:
    Oil seal 9640 003 1195 $6.45
    Tube of sealant Dirko HT red(B) $14.99
    to this list previous mentioned in my last post:
    Part Part Number Price
    Crank case 4137-020-2800 $67.60
    Piston 4137-030-2010 $63.55
    2 rings 4137-034-3000 2*$8.65 = $17.30
    piston pin 4137-034-1500 $ 8.95
    bearing 9512-003-1830 $ 9.00
    cylinder gasket 4137-029-2300 $ 2.00
    his labor (approximately 2 hours) $80.00
    Grand total $248.40
    + tax
    However, I would not have to buy the following as stated by that other stihl shop:
    2 rings 4137-034-3000 2*$8.65 = $17.30
    piston pin 4137-034-1500 $ 8.95
    because these items are included with Piston 4137-030-2010 $63.55. Either that other
    stihl shop made an honest mistake or was going to try to charge me twice for the 2 rings and piston pin.

    This stihl shop gave me a total $182.74 parts + 2 hours labor ($48/hour)= $278.74+tax
    Thank you for the response.
     
  10. rknarr2

    rknarr2 LawnSite Member
    Posts: 16

    I made a mistake when I said in my previous post that I would also have to change out my old carb, S28D, which is around $60-$70 because it would not work with a short block.
    I would not have to buy a carb because I was given the part number for both blocks with BIS and Adjustable carb in the last previous response from hate2work. Sorry about that.
     

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