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***
19) Remove the 4 cylinder nuts and washers by loosening them in a crisscross pattern in several steps (remember the first paragraph?). Take care not to drop any nuts or washers into the crankcase (area where the cam chain is)…you can stuff paper towels in there just in case. NOTE: ensure the 2 dowels are in place.
***Remove these 4 nuts and washers taking care not do drop them into the crankcase***
20) Remove the cylinder head from the cylinder. Do not use a screwdriver, I was able to gently rock mine front/back and side/side to remove. If yours is really stuck, try gently hitting it with a dead blow/rubber hammer…gently.
***Head removed***
21) Remove the cylinder by removing the final bolt on the left side of the engine and gently lifting the cylinder off the piston.
***Remove this bolt to remove the cylinder***
22) Immediately stuff the crankcase with paper towels to avoid anything falling in.
23) Use a pair of needle nose pliers and remove the circlip or piston clip from the piston. I used a properly sized socket to push the pin out of the connecting rod. Then remove the piston from the rod.
***Cylinder removed…NOTE the paper towels***
***Piston removed***
24) Time to start cleaning…clean all gasket surfaces for each part.
25) Inspect Cylinder for taper and out-of-round at three levels in an X and Y axis. Take the maximum reading to determine the taper and out-of-round. With the cylinder out measure with a bore gauge 1” below the top, in the middle, and 1” above the bottom.
Service Limits (pg 10-5)
Taper: 0.05 mm (0.002 in)
Out-of-round: 0.05 mm (0.002 in)
If your cylinder is out-of-round it will need to be repaired or replaced.
***Take 6 measurements total on the X and Y axis 1” below top, middle, and 1” above the bottom of the cylinder***
26) Time to gap the rings…Insert the piston ring into the bottom of the cylinder squarely using the top of the piston. Use a feeler gauge to check the ring gap. After removing the piston place the correct feeler gauge in the gap between the ends of the ring, slide the gauge out of the cylinder and you should feel a slight drag on the gauge. You should have received ring gap specifications from the piston manufacturer and if you did not then get them.
***Ring inserted squarely with piston***
***Piston removed…now you can check the gap***
27) If your rings need filing you can either purchase a ring filer from Summit Racing, Jegs, Snap-On, etc. Or you can try the old fashioned way and use a file. Only file in one direction and make sure you do not leave any burs on the rings. You may have to use some 600 grit sand paper to smooth it all out again. Keep the ends of the rings square.
***Manually gapping rings***
28) Now, take a look at your piston and if it has valve relief’s you will want to sand the edges of the relief’s with 600 grit wet sand paper. You are trying to take the sharp points off from the casting. Then go over the entire top of the piston with the wet sandpaper.
***Basically sand all these areas to remove sharpness and the go over the hole top***
29) Determine installation of the piston direction or which way points to the front of the quad. Some pistons will be marked with an “N” for intake and it goes toward the intake side of the head. Pistons without the “N” and has valve relief’s the larger relief’s go toward the intake side of the head. The intake side of the head is the back side facing the rear of the quad or facing the air filter.
30) Install the rings in this fashion…note if the rings have any letters on them they go facing up. Make sure the oil ring does not overlap…you can put white out, fingernail polish, paint, whatever on the ends to make it easier to see. The ring placement is provided by Tony Tice a very experienced engine builder/racer/contributor/all around great guy!
“Right-side-up is with the lettering on the ring up…
Positioning of the ring end gaps is a good thing to know too. There are two schools for end gap placement. Looking down on the piston from the seated position on the machine, I put the bottom oil rail end gap at 10, the top oil rail end gap at 2, the spreader end gap at 12, and the top ring end gap at 6. This does several things for the ring that gets all the pressure: 1) it puts the ring gap on the cool side of the engine. 2) since the gap is away from the exhaust side of the engine, this evacuates the engine better. 3) when the piston is moving up from BDC, the piston is pushed toward the rear of the cylinder bore, this closes the ring gap and makes for better cylinder sealing while pushing out the exhaust. Since there is no pressure from the combustion process this is somewhat important with low tension rings.
The second school is to place the end gaps at 10, 2, 4 and 8. While this certainly has a more organized look, it doesn't work as well with low tension ring set-ups.”
31) Piston Installation: now, this is where my method differs from the norm but I think it is much easier to do and to ensure you have not rolled a ring.
a) Install new gasket on the crankcase
b) Re-install cam tensioner and tighten bolts securely (may need new gasket).
c) Lube the cylinder liberally with motor oil.
d) Lube the rod and piston pin with a molybdenum and oil mix.
e) Take the piston and install the circlip in the left side of the piston.
f) Slide the piston pin half way in.
g) Turn the cylinder upside down and insert the piston. Make sure you are putting the intake side of the piston in the correct place in the cylinder. I used my hands to compress the rings but you can purchase a ring compressor to aid in the installation but I do not think it is necessary using this method. Slide the piston in far enough the piston rod will touch the bottom of the cylinder preventing it from going in any further (this is why you only slide it in half way).
h) Look from the bottom of the cylinder to determine if any rings have been rolled. You are looking for anything out of place; rings can come out of the ring grooves. If anything is out of the norm…start over!
i) Look from the top of the cylinder to determine if any rings have been rolled.
j) Holding the piston in place so it can not move carry the cylinder out to your quad and install it. You will need a second person to route the cam chain up through the cylinder. Sliding the cylinder down the studs until the bottom of the piston reaches the rod have the second person help you hold the cylinder and place the rod into the bottom of the piston and slide the piston pin through the rod.
h) Install right side circlip in piston.
l) Push cylinder all the way down on crankcase making sure it is all the way down and even.
32) Re-Install the cylinder bolt and hand tighten.
33) Re-Install the cam chain guide (white plastic piece) by aligning the guide end with the groove in the crankcase and the bosses with the groves in the cylinder.
***Cylinder re-installed***
34) Install the two dowel pins and a new gasket.
35) Route the cam chain through the cylinder head and install the cylinder head.
36) Apply engine oil to the threads and seating surfaces of the cylinder head nuts and install them with the washers.
***Oil threads and where the washer fits***
37) Tighten the four nuts in a crisscross pattern in several steps. Torque is 40 lbf/ft of torque, start with 10, do all four in a crisscross pattern, then 20 do all four in crisscross, 30, and finally arriving at 40.
***Final torque of 40 lbf/ft reached***
38) Tighten the two cylinder head bolts and the one cylinder bolt alternately. There is not torque spec given but they should be snug.
39) Install engine hanger plates with bolts, engine hanger bolt (from the left side), spacers and nut. Note: Marked with an L and R for left and right.
Torque fasteners in this order:
Hanger plate bolt: 20 lbf/ft
Engine hanger nut: 30 lbf/ft.
40) Install cam tower (Torque to 10 lbf/ft) and put chain back on sprocket. You have to take the tower in at a bit of an angle to get the sprocket on the chain. It will be easier if the second person puts a small flat bladed screwdriver into the adjuster and turns it clockwise to allow slack in the chain. Make sure you are still at TDC and line up the timing marks on the cam sprocket and the cam tower. If the marks do not line up you are off a tooth on the sprocket, release the tension and move the chain a tooth, keep doing this until the marks line up.
***Insert flat head and turn clockwise to release tension***
***One of the cam gear marks (there is another on the right side)***
***Alignment mark on the cam assembly (there is another one on the left side)***
41) Mix your Molybdenum and motor oil in a 50/50 solution and apply to the top off the shims, lobes on the cam, rocker arm and lifters. I used Moly Paste, my Honda dealer did not have anything else, but it worked great.
***All lubed up…good time to check your valves too***
42) Install ECT sensor, radiator cap and drain bolt.
43) Install Thermostat with the hole facing UP.
44) Install Thermostat cover tightening bolts securely (remember the first paragraph).
45) Now begin reassembling your 450R and do not forget to put coolant and motor oil in before starting!
Torque Specifications for Re-assembly:
Head cover torque: 7 lbf-ft.
Spark Plug: 17 lbf-ft.
Crankshaft Hole Cap: 11 lbf-ft.
***Oil and moly solution I used***
The End!!!
