Timing is Everything
A million awesome points to any one who reads our blog often enough to remember this motor. And to anyone who doesn't, score a million awesome points just for being here today. Plus a million more for going back and reading this post about thread repair and/or telling your friends about us.
If you're just tuning in, the remnants of blue silicone are from the previous owner's attempt contain a leak caused by a stripped thread in one of the cam covers. The last time this motor appeared on our blog, we had just finished repairing the thread and were on our way to drop this motor back into the machine it came from and cross this project off our ever-expanding to-do list. But as any true ATV enthusiasts and/or gear heads know, not everything is always so simple.
After making the two hour trek to reunite the motor with his owner, we were ecstatic when the bike finally started. It was a relief to hear the rumbling of the motor and the loud bwah as we watched it take off. After ten minutes, and just as we were ready to climb back into an air conditioned truck and head home, it stopped. Flash forward a few months and now we have the whole bike in our garage. A 2006 KFX 400.
Since the motor hasn't started since then, we are basically starting from scratch. So from the ground up (or from the valve cover down), we'll be writing a series of posts to help out anyone encountering a similar problem. We'll write about the order we use for troubleshooting and document any issues and what we did about it along the way.
Because the motor hasn't started since that day (we should add that the owner replaced the entire carburetor), our first thought was that the timing may be off. But before we got to checking it, we had to get comfortable.We removed the fuel tank, fenders, and upper motor mount. It's not usually necessary to remove the fenders completely or to remove the motor mount, but with two of us trying to work in a small space, it makes everything else easier. I also went ahead and used my lift to raise the whole bike a few feet. If you have access to a lift, I highly recommend it. When I was searching for a lift, I couldn't find any that I liked. I ended up custom building one and it works great. Once we were all set up, I removed the valve cover for what felt like the millionth time. With the valve cover removed, I needed to turn the engine over to top dead center. To do this I took out the timing plug and the crank shaft nut access plug. (Try saying that three times fast!) Forgive the photo above, we'll just have to imagine that I removed the plugs and that my wife isn't distracted by things like butterflies. To make turning the engine over easier I also removed the spark plug. (That must have been one interesting butterfly because we're missing a photo here too.) Then, using a ratchet and socket, I turned the crank over while watching the timing plug hole for the mark to come up. On the KFX, the timing mark is a vertical line next to the letter T. With that mark in the hole the cams should be lined up as follows: The intake cam (the one in the rear) should have the number 3 arrow pointing up and the number 2 arrow pointing to the front of the engine and running parallel to the top of the head. At top dead center, the exhaust cam should have the number 3 pointing to the rear, with the number 2 pointing up, and the number 1 pointing forward. Both the number 3 and the number 1 should be parallel to the top of the head. It sounds confusing, but it's really not. Below is a photo of how the cams should look when they are at top dead center. As long as what you see matches the photo and your timing mark is lined up correctly, you should be good to go. Once you are sure that your cams are lined up right, the next thing you should do is count the number of pins on the timing chain. You can see in the photo above that there are 15 pins spanning from the number 3 on the intake cam to the number 2 on the exhaust cam. Lucky us, our timing was right on the money. But what kind of maintenance blog would we be if I did not show you how to adjust the timing if it was off? Don't worry, we won't make you answer that. If your timing was off, or if you are putting in new cams and/or timing chain, have to pull the head and/or jug off, or had to adjust the valves, you will need to adjust your timing. Fortunately, that's relatively simple. The first thing you will want to do is remove the timing chain adjuster. To do this I took out the large bolt that holds the spring and then removed the two smaller outer bolts. Then I removed the timing chain hold down followed by the cam covers. When you're removing the cam covers, be cautious and remember what bolts go where. There are two different sizes and while the short one will work in the long hole, it will strip out if you try to torque it. Then I just pulled the cams out of the head. I always tie up the chain just to keep it from falling down in the engine. The KFX has a bolt in place to keep the chain from falling down, but I like to use the wire. It takes two seconds and I don't ever have to mess with fishing for the chain. Once you are done doing what ever you were working on to begin with, just place the cams back in their designated areas. What was that? You didn't pay attention to which was the intake cam and which was the exhaust cam? Luckily, they are marked for you. Just like the cam covers, the cam shafts are each marked with IN for intake and EX for exhaust. Just remember that the intake goes toward the rear of the bike while the exhaust goes toward the front. On the KFX, the intake cam is at the rear (carb side of the head) and the exhaust cam is at the front (exhaust pipe side) To install the cam shaft, pull up on the chain and place the intake cam shaft first. I try to pull tight on the chain get the cam as close to top dead center as possible. After that I install the exhaust cam, again, trying to get everything lined up correctly. If you follow the simple diagrams of how the lines on the cam goes then you cannot get them wrong. Once the cams were in place and the marks were right I put the cam covers back on and installed the chain adjuster. Just like when we adjusted the timing on our 600 Grizzly, you'll need to reset the timing chain adjuster. Even though this KFX motor is very different from the Grizzly, the adjusters reset the exact same way. Just pull the tap back with your index finger and push the bolt all the way in. With the adjuster back in place, you can move on to replacing the timing chain hold down and the cam covers. I never torque the cam covers right away. I usually just snug them up. That way, I can turn the engine over by hand a few times to make sure the timing stays in check. Once I was sure everything was good, I torqued the cam cover bolts to 45 inlb then to 89 inlb. I've noticed that KFX 400’s tend to have an issue with the valve clearance, so while I was tore down this far and the engine was already at top dead center, I figured I'd check that too. Checking valve clearance literally takes less than a minute and if you've had the cams off, it's worth it to make sure nothing shifted and changed the clearance. For the KFX 400, the clearance for our valves should be within 0.1 mm to 0.2 mm for the intake valve and 0.2 mm to 0.3 mm for the exhaust valve. Thankfully ours was within spec and we were able to pack up and get some dinner. This time. If you have a KFX 400, you're in for a real treat. We didn't just check the timing then put everything back for the fun of it. Oh no, this guy's got some issues and we'll be delving even farther into this motor in the next few weeks. Have you ever worked on an ATV and checked everything you could think of and still could not get it to run? What was your worst timing experience? Anyone out there distracted by butterflies?