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Kawasaki 23hp to 25hp conversion

Discussion in 'Mechanic and Repair' started by Accu-cut Lawn Care, Jan 2, 2007.

  1. Accu-cut Lawn Care

    Accu-cut Lawn Care LawnSite Bronze Member
    Posts: 1,206

    I own an 03 Hustler z with a 23 hp kawasaki engine. It currently has about 1100 hrs on it and still runs great. My question is... When it comes time to rebuild the engine, is it possible to convert it to 25hp? I know that the displacement of the 23 and the 25 are the same...is it differences in the head assembly and carb that make more hp? Any info would be appreciated.
     
  2. LCPullman

    LCPullman LawnSite Senior Member
    Posts: 589

    The carburetors are going to be different. It may be as simple as changing the main jets and idle mixture, but then there may be more involved, I'm not completely sure.

    The cylinder heads, intake manifolds, valves and camshaft all have the same part numbers. So its probably entirely a carburetor difference.

    If you care to take the time to do this, you could go to http://www.buykawpower.com/kmcb2c/M...2B&pageToGet=3&historyDepth=0&parentID=266149 and compare the part numbers for the two engines FH680V and FH721V. But that will take quite a while.
     
  3. pugs

    pugs LawnSite Gold Member
    Posts: 3,018

    If its time to rebuild the engine, pull the 23 off, stick a new 25 on.
     
  4. carcrz

    carcrz LawnSite Silver Member
    Posts: 2,085

    Is there anything else that would need to be changed when switching to a 25 hp motor? Or can you just bolt it in & mow.
     
  5. Accu-cut Lawn Care

    Accu-cut Lawn Care LawnSite Bronze Member
    Posts: 1,206

    It's not time to rebuild it. The engine has good compression and runs very well. If it is simply a carb replacement, I think it would be worth the money to replace it to give me some more mulching power when crabgrass season hits.
     
  6. pugs

    pugs LawnSite Gold Member
    Posts: 3,018

    Go back and read your original post.
     
  7. Accu-cut Lawn Care

    Accu-cut Lawn Care LawnSite Bronze Member
    Posts: 1,206

    I was under the impression that head components and such would need to be replaced as well. If changing the carb is all that needs to be done, I would consider doing it now.
     
  8. Accu-cut Lawn Care

    Accu-cut Lawn Care LawnSite Bronze Member
    Posts: 1,206

    I wonder if restrorob has any comments regarding this conversion?
     
  9. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Posts: 1,164

    The only difference between the 23 and the 25 that I am aware of is the carb.
    The jets will be different in the 25 and also the throttle shaft opens further on a 25 hp carb. The only exception to the jetting is for higher elevations commonly between 3000-6000ft. Since Kawi has never made a short block your only option is to rebuild or replace, if you are not doing the work yourself I would not rebuild. Hope this helps.
     
  10. Accu-cut Lawn Care

    Accu-cut Lawn Care LawnSite Bronze Member
    Posts: 1,206

    I don't really understand your post. The engine does not need to be rebuilt and I do not need a shortblock...I simply want know if replacing the carb with a 25hp version will give me more power.
     

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