There can be many reasons to remove and replace your cams. Perhaps you are checking valve clearances and have discovered a valve is ‘tightening’ (the clearance is less than the minimum specification) or you have just gotten a set of high performance cams (be sure to check the clearances after the new cams are in!)
Hot Cams Camshafts
Most people find cams and setting the timing to be a scary subject and it is the reason many guys that ride a two stroke shy away from a four stroke. It ‘takes too long to get the timing right and set up all those extra parts in four stroke’. The truth is, with a little care and forethought, installing cams, setting the clearances and timing the cams is typically a 15 minute job. Twenty minutes if the radio station stinks.
Like most jobs, there are basic procedural things that are the same no matter what you do.
- Clean the bike
- Have the correct tools. A small torque wrench, a strong magnet pencil like tool, feeler gauges, a length (a few feet is plenty) of solid core wire and some clean shop rags or paper towels and a tool that can remove the crank and timing plug on your bike. Along with the basic assortment of wrenches, ratchet and extensions and sockets (6pt is ideal).
- Read your owners/service manual. You will be tested on the material in it!!
- Good lighting
Mechanics (surgical gloves) while not critical, I find they do make the job more pleasant.
Motion Pro Feeler Gauges
Now you have done the hard part. Remove the seat, shrouds, fuel tank. Remove the connector to the spark plug. Tuck it up and out of the way. Clean the valve cover and the areas around the timing plug cover and the center cap over the crank on the stator side of the bike.
Peer down inside the spark plug cavity and ensure it looks clean. If it is not clean, clean it out. Spray some mild solvent (brake parts cleaner or electrical parts cleaner) in there; expect the excess to run out that tiny hole you have wondered about on the side of the head. Now remove the spark plug.
Many bikes the interior space in the engine is so small they run dry sumps. But when the engine is off and the bike been sitting, the sump can be filled with oil, sometimes ABOVE the center cap on the stator cover, so you will want to either, drain the oil or lean the bike against a solid wall to have the oil run toward the clutch side. Remove the center cover slowly. Assuming the previous owner did not over tighten it, a quarter turn and it should spin out. Just a cap with an oring. When you are done and reinstall it, spin it in with just your fingers than typically, a quarter turn with the tool. You do not crush the oring. You are just snugging things up and the oring rubber friction will keep it from coming loose. Repeat this procedure with the timing cap above on the stator cover. Next, remove the bolts holding the valve cover on. Remove the valve cover. It might be stuck. DO NOT hit it with a hammer. Just try to grab it and pull. If a corner lifts away, just work from that point. Chances are the rubber (reusable) gasket will be stuck to the head, mostly at the ‘half moons’. If it is stuck to the head, you can probably leave it there, if one of the half moons is free, you’ll need to remove the entire gasket. On re-assembly the half moons is the one place that you use case sealant , aka ’ThreeBond’ though each manufacturer sells it with their own name (YamaBond, HondaBond, SuzukiBond) Same stuff. If you removed the gasket, peel away the sealant on it. Clean the valve cover. Put them aside where you will not disturb them.
Now you can see the cams! Whirly bits! A chain. Now you need to get to TDC. There are two TDC in a four stroke engine, an exhaust TDC and a compression TDC. You want the compression TDC. Easy enough to find. Insert your ratchet in to the hole in the center of the stator. Rotate clockwise (nearly all engines rotate clockwise when viewed from the stator side, your manual should mention this-do not rotate the engine backward, if you go too far rotate the crank twice to get the cams to where you want them) Watch the lobes of the cams. When the exhaust lode (front cam) points toward 10 O’clock, the intake lobe (back cam) will be point to 2 O’clock. Now look in the inspection port on the top of the stator cover. You should see the timing mark. Also, from your diligent reading of the manual, you should see the marks on the cam sprockets lining up just as the book showed. You can also count cam chain pins between cam sprockets. Usually, there are marks on the top of each sprocket and just count the number of pins and write it down. Count two or three times. Your manual may mention this specification, it may not. It is possible a person prior to you moved the cams by a pin to vary the timing. Think. Congrats! Now stuff a clean shop rag or wad of paper towels in the tunnel the cam chain is in. This is to prevent you from dropping a part down there and face the misery of turning an easy job into a real PITA. Next, take the piece of wire you have and tie it to the chain, typically just in front of the exhaust cam. Lightly tie the other end someplace. This is to prevent you from dropping the chain down into the bottom of the engine. Clean off the head of any residual ThreeBond, if the gasket had to be removed. Clean is good, dirty is bad.
Time to remove the cam chain tensioner. Your manual will explain the correct method. Some have a bolt and behind the bolt, a spring. Then remove the tensioner. Some are more difficult and use a wind up spring. These require you to insert a screwdriver and typically rotate it clockwise a few turns until tight. Then pull on the cam chain, (you can tighten your wire to keep the tension on the chain) and insert the cam chain tensioner holder, often little more than a little ‘T’ shaped tool. Remove the tensioner, clean it and set aside.
ThumperTalk Manual Cam Chain Tensioner
Now, remove the cam caps. Depending on the engine, you may have to do it in a crisscross pattern, a little bit (like a quarter turn) until all are loose enough to come out with just your rubber gloved fingers. Do not remove the bolts, just fully loosen them. Some engines, the bolts are different lengths and taking them out completely just confuses things. Lift off the cam caps. Careful now, some engines have ‘C’ clips on the bearings used to locate the bearing, the can stick to the cap, stick to the bearing and if you did not put the rag in the cam chain tunnel, will fall into the depths of that tunnel, ruining your day. Now you can remove the cams. They might be suck, a little wiggling and they will pop out. Remove the intake cam first then the exhaust cam.
If you were doing a valve adjustment, you can temporarily install the cams without the chain on to confirm you have the right shim in, then take the cams out and continue the installation process. You would do this just in case you made a mistake and installed the wrong shim or a shim did not sit properly. The magnet pencil tool is hand for pulling shims off of the valve retainer.
To reinstall, is pretty much a reversal of the disassembly process with a few changes. First, make sure the cam chain is taught. If you’ve been careless and let it fall down into the engine at all, it can bunch up at the crank, in which case, you just rotate the engine back and forth a little free it up. This is the only tome back and forth rotation is allowed. Once the cams begin to go back in, the crank must not be disturbed! Set the crank so the proper mark is lined up in the viewing hole in the stator cover per your manual. Insert the exhaust cam and put the chain on it, while gently rotating the cam counter clockwise just barely enough to remove any slack from the section of chain that goes from the cam down to the crank. Check the marks on the cam; they should be in the right spot. If not, move the chain a tooth and recheck. With practice, you can do this first time as you will just know where you have to start to be where you want to be to finish. Re-confirm the crank is still lined up and that the exhaust cam is right. Install the intake cam. I find it easiest to simply poke my finger in the hole where the tensioner was to apply tension to the chain and then check the crank is in alignment with the mark, the exhaust and intake cams are on their respective marks and the pin count matches. If all is good, install the tensioner. Now either remove the ‘T’ tool and let the tensioner unwind or insert the spring and install the cover bolt. Re-confirm the cam timing looks good.
Install the cam caps and ‘C’ clips if used. CAREFULLY tighten the caps per the manual. Reconfirm the cam timing looks good. Remove the wire used to hold the chain. Remove the wad of paper towels or shop rag from the cam chain tunnel. Rotate the engine through two complete revolutions and re-confirm the marks line up and the pin count is correct. This is very important as this the number one reason guys have problems. Cam timing is off by a tooth.
Almost done! If the valve cover gasket was removed, you will have to apply some ThreeBond to the half moon of the head or the gasket, I always apply it to the head. A 1/16” or less bead at most is all you want and just in the crescent center. Put the gasket on, put the valve cover on and tighten it down CAREFULLY!!! Screw the two caps on the stator cover. Do not crank down, finger turn until the oring bottom and then just another ¼ turn is all it needs. Like a spin on oil filter on your car.
Sparkplug in; connect the plug, fuel tank, seat, shrouds.
Done! It took me 5X longer to write than it takes to do. Your first time, assuming your bike is cleaned and no bolts buggered up, a cam swap might take you 90 minutes. With experience, that can become 20 minutes.
- Read the Owners/Service Manual – Photocopy the pages for reference in the garage so the manual stays pristine (other than drool).
- Confirm you are right every step.
- Recheck your work.
- DO NOT over tighten a bolt. In 99% of the bolts on your bike, loose is better than too tight.
- Read the Owners/Service Manual. You will be tested.
Have a question? Post it to the comment section below and I'll do my best to help you.