Piston Install on a 2004-2005 TRX450R

 

Tools Needed:

  1. 1/4" Metric sockets and ratchet.
  2. 3/8” Metric Sockets and ratchet.
  3. 3/8” Torque wrench.
  4. #2 Phillips head screwdriver.
  5. Small flat blade screwdriver.
  6. Slip-joint pliers
  7. Spark plug socket.
  8. Allen head sockets.
  9. Metric end wrenches.
  10. Dead blow or rubber hammer.
  11. Needle nose pliers.
  12. Feeler gauges.
  13. File.
  14. Ring gap filer (optional, you can use a regular file but the ring gap filer is much easier to use and more accurate).  Check out Summit Racing #SME-906000 for $88…a wise investment.
  15. Bore Gauge (optional).  Check out Fowler Xtender-E Electronic Bore Gauge #74-646-401 for $195.  You can look at thetoolwarehouse.net.

 

Materials Needed:

  1. Container to catch coolant in.
  2. Zip ties (12” or longer).
  3. Paper towels.
  4. 600 grit wet sand paper.
  5. White out / finger nail polish / paint (to mark ends of oil ring).
  6. Motor oil of your choice.
  7. Coolant of your choice.
  8. Moly paste.
  9. Loctite.
  10. Container to mix motor oil / moly 50/50 solution in.
  11. Hot Cams shim kit if you plan to check the valve specs or a local dealer stocking shims.
  12. 12251-HP1-671 Gasket, cylinder head.
  13. 12191-HP1-671 Gasket, cylinder.
  14. 91373-733-003 O-Ring (45.5X2.5) (Optional—re-use old one, thermostat housing o-ring).
  15. 12391-HP1-670 Gasket, Head Cover (Optional—re-use old one).
  16. 91305-KF0-003 O-Ring (27X2.0) (Optional—re-use old one, crankshaft hole cap o-ring).

 

 

I would highly recommend you do not perform this install without the factory Honda Repair manual 61HP101.

 

NOTE: If there is more then one bolt holding anything on that you are removing follow this procedure.  Example: There are 3 bolts holding the valve cover on, put your socket on bolt #1 and break it loose, then bolt #2, then bolt #3, then remove bolt #1, then #2, and finally #3.  DO NOT remove #1 before you break #2 and #3 loose.  If there are 4 bolts follow the same procedure using a crisscross pattern.  The same goes for tightening, install all 3 bolts and hand tighten, then cut the torque spec in half and start with #1, then #2, finally #3.  Then reset your torque wrench to the full amount and repeat.  Use this procedure anytime there is more then 1 bolt…it may take a little longer but not in comparison to a broken bolt or stripped threads.  If you have any questions regarding this process please email me.

 

Read through the entire document before starting…ask on any of the boards or email me if you have any questions.

 

1)      Remove the seat, rear plastic, and finally the front plastic.

***Plastic removed***

2)      Remove the gas tank.

a)      Ensure the gas is turned off.

b)      Remove the screw holding the petcock and remove the lever and fuel mark plate.

c)      Remove the hose from the bottom of the tank to the carburetor, remove the 2 bolts securing the tank, the two tank straps, and lift the tank off.

3)      Remove the PROTECTOR, TANK HEAT (LOWER) (the plastic piece below the tank).

*** PROTECTOR, TANK HEAT (LOWER)***

4)      Remove the Carburetor:

a)      Drain gas from carburetor.

b)      Disconnect carburetor wiring from plugs.

c)      Disconnect Insulator (rubber boot) from the head by removing hose clamp.

d)      Disconnect carburetor from Insulator (rubber boot) going to air box by removing clamp.

e)      Disconnect rubber hose going to Vacuum T.

***Carburetor plugs***

Leave the control cables (hot stat/throttle) connected and lay the carb on the front of the R by the headlights.

 

5)      Drain Coolant:

a)      Place a drain container on the right side under the motor.

b)      Remove the radiator cap.

c)      Remove the drain bolt.

***Remove this bolt to drain coolant***

 

6)      Remove the thermostat housing and the thermostat.  Note the small hole on the top side of the t-stat…it needs to be placed back on the top when you reinstall. 

7)      Unplug ECT Sensor.

8)      Disconnect water pump bypass hose from head.

***Remove these 3 bolts to remove the t-stat cover then unplug ECT Sensor***

 

***T-stat removed***

 

9)      Remove the Spark Plug boot and the Spark Plug.

10)  Remove the 3 bolts holding the valve cover on and remove the valve cover.

11)  Remove the Crankshaft Hole Cap to set the motor to Top Dead Center (TDC).  TDC is achieved when the two marks align and the lobes of the cam point to the rear of the quad.  ***Note: There are 2 TDCs on a 4-stroke***

***Remove this bolt to align the marks to TDC***

 

***Lobes of cam point to rear of quad***

 

You have a couple of options here…you can remove the cam sprocket and the chain, or you can do what I did and remove the tensioner…it is up to you and personally I do not think one is easier then the other.

 

12)  Remove the single bolt in the end of the cam chain tensioner and then remove the two bolts holding the cam chain tensioner to the cylinder.

 

***Remove these two bolts***

 

13) Remove the tensioner completely and the cam chain will be loose.

14) Remove the four bolts holding the cam assembly.

***Remove these 4 bolts***

 

15)  Steadily lift of the cam assembly taking care not to drop any of the shims into the motor.  The assembly is positioned with bosses just work it back and forth gently and lift up at the same time and it will come off.  If any of the shims come off make sure you place them back on the correct valve.

***Here are the shims***

 

 

16) Remove the cam chain from the sprocket and tie a LONG zip tie around the chain.  About 12” will work.

 

 ***Zip tie on chain***

 

17)  Remove the upper engine hanger nuts, bolts, and plates from both sides of the quad.

18)  Remove the 2 cylinder head bolts (lower) from the left side of the engine.

***Remove these two bolts***

 

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