18hp briggs vanguard twin smoking

Discussion in 'Mechanic and Repair' started by brucec32, Sep 25, 2006.

  1. brucec32

    brucec32 LawnSite Platinum Member
    Posts: 4,403

    I have a 8 year old (hours unknown) toro 44" with the briggs 18hp vanguard engine. I bought it used about 3 years ago and it has run strong until recently.

    It is now putting out black smoke when running and loses power when you turn on the pto. I have cleaned the fuel lines and carb but no change. The engine races some when running but generally it is just weak. The initial trouble started when mowing a tough tall lawn a few months back. The mower stalled then, and barely ran when restarted, but when I tried it the next day it ran decent, and I admit I used it on a few lawns while it was smoking, out of necessity during a busy time. But now it is really just unusable.

    The mower is old enough I'm not interested in a new engine or really spending much on repairs. But if it's something simple I'd hate to sell it for parts.

    Any ideas from the engine experts on what problem this is? Just worn out?
     
  2. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    Sounds like possibly the float needle valve is not closing all the way (bad) causing a high fuel level and rich run situation. But before you go that direction make sure the choke butterfly is opening all the way, Could be just a cable adjustment.
     
  3. brucec32

    brucec32 LawnSite Platinum Member
    Posts: 4,403

    Thanks, I already checked the choke operation and it's fine. I'll give the float area another going over.

    What kind of smoke would I be seeing if the rings were simply worn on the cylinders?
     
  4. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    Oil smoke is blue in color, If it's a fuel problem the plugs will be dry black and sooty looking, Rings or burning oil the plugs will be black carbon-ed and wet looking.
     
  5. brucec32

    brucec32 LawnSite Platinum Member
    Posts: 4,403

    After figuring out that the cost for the dealer to diagnose it, plus transportation costs to/from (100 mi total) I decided to chance just replacing the carburator with a new one for $90. in the hopes of a quick, cheap fix. Unfortunately, the mower still runs very weak and has black smoke coming out. One plug was wet, the other dry but a little sooty.

    I'm just about to give up, it's just a back up anyway. Any other ideas to check?
     
  6. FIXDISS

    FIXDISS LawnSite Senior Member
    Posts: 445

    Rob. What about a bent pushrod since he said problem started when overloaded in high grass ??
     
  7. FIXDISS

    FIXDISS LawnSite Senior Member
    Posts: 445

    Before you can it for parts,pull valve covers off each side and check for bent push rod or a rocker arm that has jumped off. If it has low power and smoking black smoke this could be your problem. Just a hunch.
     
  8. Bill Kapaun

    Bill Kapaun LawnSite Senior Member
    Posts: 923

    Have you tried new plugs? maybe just swap the plugs to make sure the problem is the cylinder and not the plug.

    My guess (if not plugs) would be a bad coil/HT wire.
     
  9. brucec32

    brucec32 LawnSite Platinum Member
    Posts: 4,403

    Yeah, new plugs, air cleaner and foam wrap, even a new carb. Checked the push rods and rocker arms and they seem ok. I even detached one plug to see if either cylinder was not running, but both run, just weak and with black smoke, stuttering some. It gets weaker as it runs

    It did strike me as being some sort of ignition related problem too. I may just put it aside and fiddle with it next winter. It's eating up time I don't have right now.
     

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