Kohler 18 to 20 hp

Discussion in 'Mechanic and Repair' started by maacla, Apr 3, 2002.

  1. maacla

    maacla LawnSite Member
    Posts: 10

    I bought a used Lazer Z last fall. It has the 18hp engine. I have read that it can be raised to 20hp by removing the throttle stop screw and changing the governor spring setting. Well I cannot see how this will achieve this. Removing the stop screw seems to allow higher rpm's but I could have achieved this by putting the governor spring in the next hole. Also I noticed that specs on both engines are rated at 3600 rpm. If the rpm is set at 3600 then how could the hp be raised? Mike
     
  2. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    By raising the rpm's you may make the mower run faster but the hp rating and torque will drop. It will just seem like it's more powerfull. The most realistic way of getting 2 more hp is to put a 20 hp unit on it. There are other things you can do to a standard engine to increase hp like increasing the bore and or stroke, raise compression,hotter camshaft ect. You will have much more money in it than it's worth. For about $1500.00 you can make a 5 hp briggs turn out 11 to 13 hp @ 8500 rpm's. But you wouldn't want it on a mower.
     
  3. Remo Sid

    Remo Sid LawnSite Member
    from USA
    Posts: 55

    By raising the rpm,s, will make the hp rating drop???
     
  4. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    By looking at the hp and torque curve provided by Kohler for thier engines you'll see that the torque drops off quickly. The highest hp rating is at 3600 rpm's. So raising the rpm's higher will reduce the effective hp. And drastically reduce the torque.
    http://www.kohlerengines.com/ads-cgi/viewer.pl/pdf/pro18v.pdf
     
  5. Richard Martin

    Richard Martin LawnSite Fanatic
    Posts: 14,700

    There was a thread here on Lawnsite that explained how to raise the hp from 18 to 20 and it didn't involve raising rpms. I think it had something to do with the carb since both engines are nearly identical.
     
  6. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    I stand corrected. I checked the bore and stroke of the 18 and 20 hp command engines. They are identical. The bore is increased on the 22's. So like Mr. Martin said it may be the carburation. So I need to do more research on the subject. The compression rating is the same also.
     
  7. Remo Sid

    Remo Sid LawnSite Member
    from USA
    Posts: 55

    khouse....before I get into this torque-hp thing I would like to ask you a question. Does the number 5252 mean anything to you?
     
  8. maacla

    maacla LawnSite Member
    Posts: 10

    I know that the 18 and 20 are the same engine, from posts in the past. I'm just not sure how to tell if mine was upgraded to the 20. That is what i'm looking for. Mike
     
  9. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    I talked to Hank @ Kohler tech services about this issue. He said that he could specifically tell me the difference it I gave him the spec #'s of the 18 and 20 commands. I told him I didn't have them and he said that there are some slight changes in the head and combustion chamber. He thought that there may be a slight difference in the camshafts also - but wasn't sure. He said by putting a 20 carb on an 18 would give it more power - but not 2 hp. I guess one would have to look up and see if indeed the cams are different. That's what I found out.
     

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