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Who This Article is For This article was written for the growing backyard mechanic that does most of their own motorcycle maintenance work, but lacks experience with more involved & complex engine internals work. It's more of a generic "how to" and doesn't address all the different variations from bike to bike. If you're someone that wants to do this sort of work, but lacks the confidence & first-hand experience, this is a good primer on what to expect and some of the key things to pay attention to. We all started somewhere! ##### There can be many reasons to remove and replace your cams. Perhaps you're 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 2 stroke shy away from a 4 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. 20 if the radio station stinks. Like most jobs, there are basic procedural things that are the same no matter what you do: 1. Clean the bike thoroughly and use compressed air to remove any remaining depress in the nooks & crannies. You don't want any dirt falling into the top of the head when the valve cover is removed. 2. Gather the correct supplies & tools: Small torque wrench. Strong pencil-shaped magnet. Feeler gauges. Solid core wire (a few feet is plenty). Clean shop rags or paper towels. Nitrile gloves. Related Article: Real Men Don't Wear Shop Gloves! Crank removal tool & timing plug. Basic assortment of wrenches, ratchet, extensions and sockets (6pt is ideal). Good lighting! 3. Read your owners/service manual. If you don't have one, invest in one. I say invest because it will pay you back over and over in terms of savings on dealer maintenance & repairs and a more enjoyable ownership experience. Motion Pro Feeler Gauges Cam Removal Now that you've done the hard part, remove the seat, shrouds and fuel tank. Remove the connector to the spark plug and tuck it out of the way. Before you remove the valve cover, again, be sure that the entire area surround it is clean and free of anything that can fall into the head. Also clean 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 you can't see, assume it's dirty. Use compressed air to blow out any loose debris. Then spray some mild solvent (brake parts cleaner or electrical parts cleaner) into the cavity. Expect the excess to run out of the tiny hole you've wondered about on the side of the head. Hit it one more time with compressed air and you are ready to remove the spark plug. With many bikes, interior space in the engine is so small they run dry sumps. But when the engine is off and the bike has been sitting, the sump can be filled with oil, sometimes ABOVE the center cap on the stator cover. Because of this you'll want to either drain the oil or lean the bike against a wall so that the oil runs toward the clutch side. Remove the center cover s l o w l y. Assuming the previous owner didn't over tighten it, 1/4 turn and it should spin out. It's just a cap with an o-ring. When you're done and reinstall it, spin it in with just your fingers, then typically a 1/4 turn with the tool. Don't crush the o-ring, snug is enough. The friction from the o-ring will keep it from coming loose. Repeat this procedure with the timing cap above on the stator cover. Next, remove the valve cover bolts and remove the cover. If it's stuck, don't hit it with a hammer. Just work it off with your hands. If a corner lifts, just work from that point. Chances are the rubber gasket (reusable) will be stuck to the head, mostly at the ‘half moons’. If it's stuck to the head, you can probably leave it there. If any one of the half moons is free, remove the entire gasket. On reassembly, the half moons is the one place that you use case sealant (ThreeBond, Yamabond, HondaBond, all pretty much the same stuff). If you removed the rubber gasket, peel away any residual sealant on it.. Clean the valve cover and put it along with its fasteners aside. Now you can see the whirly bits; cams & chain! Time to set your engine to top dead center (TDC). There are two TDC in a 4 stroke engine: an exhaust stroke TDC and a compression stroke TDC. You want the compression TDC. Easy enough to find! Insert your ratchet into the hole in the center of the stator and rotate clockwise. Nearly all engines rotate clockwise when viewed from the stator side. Do not rotate the engine backward (your repair manual should mention this). If you go to far, rotate the crank twice to get the cams 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 illustrates. You can also count cam chain pins between cam sprockets. Usually, there are marks on the top of each sprocket; just count the number of pins and write it down. Count two or three times. Your manual may or may not mention this specification. If the bike is used, it's possible a prior owner moved the cams by a pin to vary the timing. Now stuff a clean shop rag or wad of paper towels into the tunnel that the cam chain is in. If you accidentally drop something into this tunnel, your easy job just become a real PITA. You've been warned! Next, take a length of wire and tie it to the cam chain, typically just in front of the exhaust cam. Secure the other end without tension on the cam chain; it's just there to keep the chain from dropping into the bottom of the engine. Time to remove the cam chain tensioner. Your manual will explain the correct method for your application. Some have a bolt and behind the bolt, a spring. Some are more difficult than others, namely those that use a windup 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 this in a crisscross pattern, turning each bolt a small amount (1/4 turn or less) until each are loose enough to thread out with your fingers. But don't remove the bolts just yet, just fully loosen them. On some engines, the cam cap 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 them. They can stick to the cap or bearing and if you didn't put the towel in the cam chain tunnel, they can fall into the bottom of the engine and run your day. Now you can remove the cams. They might feel stuck, bit a little wiggling and they will pop out. Remove the intake cam first. If you were doing a valve adjustment, you can temporarily install the cams without the cam chain to confirm you have the right shim, then take the cams out to 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 magnetic pencil tool is handy for pulling shims off of the valve retainer. Cam Installation Installation 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 into the engine at all, it can bunch up at the crank. If that happens, rotate the engine back/forth a little to free it up. This is the only time back/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 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 cam chain and pull out the wad of paper towels or shop rag stuffed into 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 is cam timing that is off by a tooth. Almost done! If the valve cover gasket was removed from the head you'll have to apply sealer to the half moon of the head or the gasket. I always apply it to the head and a 1/16" bead is the most you'll need. More is not better here. Install the valve cover gasket onto the head, install the valve cover and tight it down carefully per the specs in your manual. Screw the two caps on the stator cover. Again, finger tight + 1/4 turn is all it needs. Spark plug installed, wire connect and you're ready to button 'er up with the fuel tank and body work. All Done! In all reality, it took me 5X longer to write this than to do the actual job. 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. Key Points: 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. 👍 @William1