Hot Cams Stage 1 Install in a Honda 400EX
The following is a general list of the steps taken to install a Hot Cams stage one cam in a Honda 400ex, most of the instructions are taken directly from the Hot Cams instruction sheet that comes with a Hot Cam, we have added some of our own experiences in with them. If you are unsure, ALWAYS refer back to your Hot Cams instruction sheet that came with your cam.

You need only to have basic knowledge of the workings of an engine to install a Hot Cams Stage 1 camshaft properly. With the Honda 400EX it is possible to install this camshaft without removing the engine from the frame

Break-in of this camshaft is VERY important and you should adhere to the procedure to the letter. A phosphate coating is used to assist with break-in, it will change color in the wear areas of the camshaft as it breaks-in. It is also very important to use plenty of engine assembly lubricant Hot Cams, Inc. recommends that you change the oil before the initial start-up of the engine after the assembly. These steps will help ensure that the camshaft breaks-in properly.

When installing the new camshaft, Hot Cams recommends that the rocker arms be replaced as well, as the old rocker arm pads will have worn in with the old camshaft, however, we have found that this step isn't always necessary. If you're unsure, replace them. If you have a trained eye, you should make your own decision. Maintaining the valve adjustment will be paramount to the durability and longevity of the camshaft, rocker arms, and valves. Following a regular maintenance schedule is always the best way to ensure durability and performance over the long run.

Before beginning this project, Hot Cams, Inc. recommends the purchase of a new cylinder head cover gasket and cam chain tensioner gasket, but these items are not included in the camshaft box. Cleanliness is always a good place to start. Make sure the ATV is cleaned thoroughly before you separate the head cover. It would be advisable to use an engine degreaser on the frame and the engine where particles may fall into the open engine. This will help ensure a clean engine during the assembly process and less of a chance of thread damage and/or dirt in the engine during reassembly. Note, we will not be removing the cam chain tensioner completley from the bike, therefore we do not need to replace its' gasket.

You will need the following tools to complete this project:

1. Flat Tip Screw Driver
2. A Pair of Channel Locks
3. A Hammer and a small piece of wood or a "dead blow" style plastic mallet
4. A #0 phillips head screw driver
5. A small "jewelers" flat tip screw driver
6. A set of metric allen wrenches or T-handle wrenches.
7. Needle nose pliers
8. 3/8 ratchet and extension
9. 1/4 ratchet and extension
10. 10mm Socket, preferably a 1/4 drive and a 3/8 drive
12. 8mm socket. - 1/4 drive
13. 12mm socket - 3/8 drive
14. 14mm Socket - 3/8 drive
15. 17mm Socket - 3/8 Drive
16. 24mm Socket - 3/8 drive
17. 14mm Box End Wrench
18. Anti-Seize Lubricant
19. Assembly lube (one tube)
20. In. Lb Torque Wrench (ft/lb will work as long as it goes to 5 lbs and will be accurate)
21. Shop rags
22. non-resudue leaving cleaning solution (carb cleaner or brake cleaner)

Start by removing the rear plastics/seat assembly, then remove each black side plastic piece by releasing 2 plastic retainers and removing a single allen bolt from the bottom rear.


Location of Clips and allen bolt (Allen bolt is far bottom)

remove the two clips located at the front of the gas tank cover plastics, then remove the gas cap, remove the cover and replace the gas cap.

Underneath each fender at the front front there are two 10mm nuts that hold the front plastics onto the frame bracket. Remove them from both sides and slide the front plastics forward, over the bumper and let it come to rest. There is no need to remove the front plastics completely. Don't let the plastics hang by the electrical wiring!!


Let the front plastics rest on the front bumper, there's no need to completely remove them.

Next, remove the two bolts located at the front of the gas tank and remove them. If the two metal inserts come out with the bolts, keep them together or easier re-assembly.


There are two bolts in this area, remove them both.

Next, remove the two straps near the rear of the gas tank and pull the breather line out of the handlebars. Next, MAKE SURE THE FUEL SELECTOR IS TURNED OFF. Located the fuel line coming from the petcock on the gas t tank (right behind the fuel selector) going to the carburetor, release the clip and remove it from the gas tank nipple.


Location of the tank to carb fuel line and removing the clip.

With the fuel line removed, you should be able to lift the gas tank from the frame. Set it aside in such a manner as to prevent putting pressure on the petcock, if the tank is empty you can set it on a flat surface gently. DON'T BREAK THE VALVE OFF OF THE GAS TANK!!

With the gas tank remove, you can see the under tank plastic protector, the air box snorkel, throttle cable tube etc. We found that it was easier to completely remove the air box from the bike than it was to wrestle the snorkel off of the air box. To remove the air box, unbolt the 12mm nut at the rear (near the seat latch catch), disconnect the transmission breather tank from the left side of the breather box, loosen the large clamp where the air box meets the carburetor, and pull the single retaining clip from the intake of the snorkel.


The single retaining clip that holds the snorkel to the frame.

You can now gently remove the air box assembly from the quad. With it removed, you can now remove the two 10mm bolts from either side of the Engine Over Tray..


The 10mm bolts holding the Engine Over Tray on.

Before you yank it off there, reach around front and remove the head cover vent hose from this plastic piece. It can now be removed from the quad.

You can now see the top of the engine. We will not be removing the throttle cable from the bike for this project, we will work around it.

NOW is the time to thoroughly clean the outside top of the engine. Be sure to clean off the Throttle cable too
As it will be directly above the open engine.

This will prevent dirt and debris from entering the engine once we remove the head cover. Be thorough and wipe it down.

Remove the spark plug wire and head cover vent tube and tappet covers.

At this point , we need to make sure and have the engine set to TDC, or Top Dead Center. This is accomplished by removing the flywheel access port from the right transmission case as well as the timing mark cover (These are the large and small inserts that require allen wrenches to remove. With a 17mm socket and breaker bar or “T” handled wrench, rotate the crankshaft in a counter clockwise (CCW) direction. Position the engine on top dead center (TDC) using the mark on the flywheel. Be sure to notice that the intake valve rocker arms were the last to move, this will ensure the engine of being on “true” TDC.

Next, we will remove the top engine mount bolt and spacers (seen in the picture above). This will take some doing as the engine will probably have settled a little in the frame. Start by loosening the 14mm nut from on right hand side of the engine, using the 14mm box end wrench to prevent the bolt from turning. leave the nut on the last few threads. Next, use your dead-blow mallet (or hammer and wood.. DO NOT USE HAMMER WITHOUT A SOFTER MATERIAL BETWEEN THE HAMMER AND THE NUT). to gently persuade the bolt to move by tapping on the nut..once the bolt is out far enough to get your channel lock pliers BEHIND the head of the bolt, you can tap the jaws of the pliers with your mallet to remove the bolt all of the way. Do not grab the bolt by the head with the channel locks. The two engine spacers are different sizes. Note that the left hand one is smaller for re-installation.

After this, you can begin removing the head cover bolts. As a general rule, anything that has to be torqued back down should be removed in a crisscross or star shaped pattern to prevent warpage. Don't forget about the 12mm bolt in the center of the head cover! It’s possible that the cylinder head cover bolts will be corroded into place. If the bolts do not come loose easily, using a long punch and hammer, sharply rap on the top of the bolts to loosen the corrosion on the threads of the bolts


The Head Cover bolts should be removed using a crisscross or star pattern to prevent head cover warpage.
(Tappet covers removed to reveal the rocker arms - these are for setting the valve lash)

Also note that the long bolt removed from the right-hand side FRONT may be discolored. This is due to the heat generated by the exhaust and it's close proximity. This bolt should be put back in the same hole during re-assembly.

The head cover should now come free fairly easily. If some persuasion is needed, gently tap on the head cover with a dead blow hammer. Not much force should be needed. Take great care when removing the head cover not to loose the two positioning dowels that are in the head itself. They may come out with the head cover. Locate both of them and remove them for now.

The gasket located between the head and the head cover is metal, with some patience you can gently remove it from the head without warping it and it can be re-used. Don't be surprised if oil begins to pool in the front left section of the head and then drips from the engine. Have something handy to catch the oil.

With the head cover removed, you can now see the cam and valve springs. Note the positioning of the cam lobes (they should be pointed downward), and the positioning of the cam chain sprocket carrier bolts (they should be top and bottom and in line with the center of the camshaft), this will help during the installation of your new Hot Cams camshaft. Note also the location of the sealed bearing on the right end of the camshaft and the direction in which it is facing (seal to the outside).

Loosen the bolts that hold the camshaft sprocket. Remove the lower camshaft sprocket bolt first, it will be necessary to rotate the crankshaft. Rotate the crankshaft back to “true” TDC.

Loose the cam chain tensioner. Remove the screw that covers the end of the tensioner block, turn the flat blade screw slot clockwise, this will retract the tensioner block shaft, it will lock in the retracted position. . Remove the top camshaft sprocket bolt. Pull the sprocket off the camshaft but maintain upward tension, do not allow the chain to sag, it is possible for the chain to “slip” on the bottom sprocket of the crankshaft and change the cam timing. Remove the camshaft bearings. Remove the camshaft. Place the handle of a screwdriver or other object that fits threw the hole in the cam chain sprocket (you can also use a zip tie between the chan and the accelerator cable for tension) to prevent excessive droop of the chain. Remove the decompression plunger and it’s spring from the cylinder head. The plunger and spring are located on the cam chain side of the engine.






We use a small piece of welding wire from a MIG welder with a small "L" bent into one end to remove the spring.



Here, you can see the difference between the two cams. To the naked eye, you couldn't tell the difference, if it weren't for the decompression mechanism on the OEM cam (right). Also note how the dowel part of the cam that fits into the sealed bearing is different. The decompression mechanism DOES NOT get transferred to the new cam as it is not needed.




Put assembly lube on the camshaft and in the supports in the cylinder head. Be Generous!
Liberally apply it to all wear points of the camshaft and rocker arms and bearings.



Install the camshaft in the cylinder head as to represent the “true” TDC positioning and install the camshaft sprocket and chain. Install the bearings. We have found that it's easiest to have one person position the cam-side bearing on the cam WHILE it is going in place - this is the only disadvantage of NOT removing the entire cam chain tensioner assembly. Install the top sprocket bolt fully but leave it loose. Twist the flat blade screwdriver slot in the cam chain tensioner CCW ¼ turn and remove the screwdriver, install the plug in the end of the cam chain tensioner block. Turn the crankshaft in a CW direction for the lower sprocket bolt to be installed, tighten it fully. Rotate the engine back to TDC and tighten the top sprocket bolt fully.


Clean the cylinder head cover gasket surfaces of the head and cover using a clean rag and a non-residue leaving cleaner (Berryman’s B12 cleaner sprayed onto a clean rag will work). Install the cylinder head cover locating dowels and new gasket. Install the cylinder head cover being sure to get all the sub-rocker arms in the correct places.


Use anti-seize compound on the threads AND THE SHANK of the head cover bolts and torque them down to 86 in/lbs or 7.2 ft/lbs and the center bolt to 120 in/lbs or 10 ft/lbs.

Slowly rotate the engine 2 revolutions and feel carefully for any unexpected binding. If any is felt, check the cam timing before going any further. Rotate the crankshaft to open the exhaust valves to their furthest openings (this ensures that the cam lobes for the intakes are on their base circles) and set the intake valves’ clearances to .005” (inch). Rotate the crankshaft to get the intake valves at their furthest openings and set the exhaust valves’ clearances to .006” (inch). Install the tappet covers. Install the spark plug. Install the engine breather tube to fitting on the top of the cylinder head cover. Install the timing hole cover and the crankshaft cover.

Install the top engine mount, over tray (position the breather tube under the tray, throttle cable over the tray and fuel hose through the opening in the rubber flap), intake snorkel, you may have to remove the air box hold down bolt in the back of the air box and remove the intake runner to the carburetor and the breather box on the side of the intake runner. Install the tank, front fender , and seat/rear fender assembly. Change the oil.

Upon initial start up it is very important you DO NOT let the engine idle. The engine must run for at least 20 minutes at 3000 rpm or better, constantly changing the rpm level (a nice light test ride is best to keep the engine cool). Only light engine loads are to be used. No excessive rpm or lugging. Let the engine cool completely. Restart and continue riding for an additional 40 minutes using the same criteria. Let the engine cool completely. Check your valve clearances, reset if necessary.

You are now free to explore the new limits your machine has in store for you, enjoy your new Hot Cams High Performance Camshaft.