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Replacing 450 Topend - what parts?

Discussion in 'General Tech' started by PitRacer, Apr 27, 2011.

  1. PitRacer

    PitRacer PR Founding Father

    Location:
    Medina, Ohio
    When replacing a topend under normal maintenance for a 450 what all do you normally replace along with it assuming valves are ok? Obviously piston/rings and all gaskets but what else? Timing Chain? Flux Capacitor?
     
  2. Scotty810

    Scotty810 PR Addict

    Location:
    Dayton, Ohio
    When you say piston/rings, I assume you include the pin and clips? Gunna change the powerband while you're in there?
     
  3. hershey

    hershey PR Elite

    Location:
    Ozone Layer
    Racing Number:
    01
    I just did my first one. I replaced the piston, rings,pin and clips. I checked the valves and only had two out of five that needed shimmed. I also checked the valves for seal. It didn't leak bad but I had a valve job done for $55 anyway. Everything else looked great. Check with a Zuk dealer service dept you trust to see if there are any issues they know of to look for or replace when apart.

    BTW it was the first time I opened the motor since I bought it 3 seasons ago !
     
  4. MX955

    MX955 PitRacer Pro

    Location:
    Waterford,Pa.
    Racing Number:
    955
    Yes,do the timing chain also.I usually put a new spark plug in my bike after a top end also...
     
  5. C Hudak

    C Hudak PR Addict

    Location:
    Lordstown, OH
    Racing Number:
    2
    I allways put intake valves, all four valve springs, and all four seals. Along with new piston, rings, pin, clips, gaskets, and spark plug. Allthough every top end I've done in the last four seasons (each having one season of racing/riding), has checked in spec. I go through the top end just for piece of mind. Its about $350.00 for a brand new season. A little more than a 2str, for alot more performance, in my opinion.
     
  6. C Hudak

    C Hudak PR Addict

    Location:
    Lordstown, OH
    Racing Number:
    2
    doing the top end through the bottom end.

    phone pics 12410 019.jpg The hard way to change the piston, when the crank won't let the piston spin out of the cases.
    Not my bike by the way. Just helping someone out.
    Goodtimes, Goodtimes!
     
  7. C Hudak

    C Hudak PR Addict

    Location:
    Lordstown, OH
    Racing Number:
    2
    By the way, that piston and ring still checked in specs. I went ahead and replaced it for him anyways.
     
  8. MarctheSharc

    MarctheSharc PR Founding Father

    That ones going to be more than $350.....
     
  9. hershey

    hershey PR Elite

    Location:
    Ozone Layer
    Racing Number:
    01
    valves,springs and seals ????? Wow all that was in spec on my bike after three seasons, must be a Honda your working on !!! Lol .....
     
  10. talonrunner18

    talonrunner18 PR Addict

    Location:
    Medina
    Need to send your cylinder to be re-coated at least every two seasons. Worn cylinder will cause rings to go bad quick. Always change valve seals. You dont need to replace your valves unless they are out of spec. They wear with valve seats so if they are shimmed correct they are good. As for the piston pin, you need to look at the end of the connecting rod, the bearing surface is softer than the pin so the pin doesn't wear. No real need to replace cam chain, I've never heard of cam chain failure except on 400ex, LTZ 400 and KTM RFS. But if you have 4 or 5 seasons its not a bad idea.
     

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