How to mess up your valve adjustment
There are two main ways that the Ninja 250 valve adjustment gets screwed up:
Wrong feeler gauge size
Some people make the mistake of using standard (inch) .10 gauges in the mistaken notion that that's what is called for. One quick way to tell if the gauges you are using are the proper ones is if the gauge is as thin as a piece of paper. If it's as thick as a dime, that's the wrong size.
Measuring the gap when the cam lobes are actuating the valves
What happens is that you align the timing mark on the crank, and then take the measurement, or try, and don't realise that the cam lobe is currently pushing the rocker arm down onto the valve. There is no clearance at this point. You need to turn the engine one more full turn until the mark lines up again, and the cam lobe isn't touching the rocker arm.
Basically, the engine is in the proper position when the exhaust (front wheel side) cam lobe is pointing toward the triple clamps, and the intake (rear wheel side) cam lobe is pointing towards the rear seat. That's when you can take the measurement on that cylinder.
Remember, you need to rotate the engine again when you are lining up the other cylinder. You can't do both cylinders without rotating the engine at least once.
Split this job into two parts
Do all the prep work getting to the valves in the evening, then let the bike sit overnight (let the valve cover rest in place to keep big things, like mice, out of there). Then in the morning, do the adjustments and button everything up and go for a ride.
This splits the task in half, and keeps you from doing it after working a full week OR getting up really early before a planned ride. It's mostly just a bit of wasted time that you can use to your advantage.
- Make sure you know which ones are the exhaust and which the intake valves and the specs for each. Hint: The exhaust valves are the ones closest to the exhaust header; there are four of them. The intake valves are closest to the airbox; there are four of these, too.
- Don't drop one of the spark plug gaskets in the engine. In the pictures those gaskets just sit there all nice and pretty. They have been known to stick to the valve cover then fall off, or find other ways of getting into the engine. Be careful.
- You have to unbolt and remove the left-hand coil, but it isn't necessary to drill the spot weld and remove the bracket. The cover is no harder to get out with the bracket left in place than with the bracket removed.
- Consider this "optional, but not necessary". Removing the bracket will make a tiny bit more room for your hands to get in and the valve cover to come out, but a lot of experienced 250 mechanics say to skip it. Should you decide to remove it, one admin insists that a long screwdriver and a bit of rocking back and forth gets it done, while another says he almost pulled the bike over on top of him doing that. And remember, it isn't really necessary.
Moving the radiator
- After you've taken out the radiator bolts and the coil bolts, it's even better to also "back out" the large long bolt that goes through the front of the engine. It's the one that goes through the two brackets (one on each side) that the radiator bolts to. If you back out that long bolt (it's the last one really holding the bracket) then you can move the bracket and the right side of the radiator further from the head and get more room to work.
- The exhaust valves can be done without the Kawasaki tool, though it's very hard without moving the radiator. You don't need to drain the radiator, just move it.
- If you take the outlet hose off the bottom of the radiator, it's much easier to push the radiator forward to give yourself room to look at what you're doing on the exhaust valves. Of course, this means you'll be draining the coolant and will either have to pour it back in or change it.
Kawasaki valve tool
For an explanation of the Kawasaki valve tool, see here. Lots of people have no trouble doing their valves without it, but there are others who can't imagine not using it.
- If you want to use a special tool, get the Kawasaki one. Other sets, specifically the Motion Pro one that's designed for use on multiple kinds of bikes, won't fit.
- If you want to try the adjustment without the tool, get a 1/4" drive, 9mm, 6-point, deep well socket. Use it to make the actual adjustment, without a ratchet but with an eyeglass-type screwdriver through the middle. That way you can turn the nut and use the screwdriver to hold the screw. At the beginning and end, when you're just breaking the nut loose or torquing it back down to spec, you can use your socket with a 1/4" drive ratchet. You might twist the screw a little, but when you're loosening it doesn't matter, and at the end you should have enough leeway that the gap is still in spec. Double check afterwards, though, to make sure.
- You might want to find some longer feeler gauges (about 5~6" long). The short ones can be used, but keep them together as a set; that will effectively lengthen them, as well as prevent single blades from falling down the cam chain well.
- The reason for the longer gauges is that the space is pretty cramped when you're actually "in there" getting it done. The longer gauges eliminate the need to have a hand actually buried in the top end while trying to get the gauge in as well. The longer ones aren't totally necessary, but they make it a little easier to get done.
- Instead of buying feeler gauges with bent tips, you can just bend the last inch on straight ones and they'll work fine.
- Don't drop your feeler gauge into the engine. You have two choices: Make a leash for it and tie it to your wrist/belt/earring
- or have a long magnetic pickup standing by. Alternatively: 1. Don't take the gauge out of your set. 2. Take off the feelers you need and loop zip ties through the holes; if you do happen to drop one, it's not going far.
- For telling how much pressure should be on a feeler gauge, the old school technique was to feel a little drag on the feeler gauge... it was described as about what you'd feel when pulling a sheet of paper out from under a magazine or two. Slight drag. New way of thought is that ANY adjustment, within spec, is good enough (and it is for street riders). So, just make sure the gauge for the middle spec goes in fine, but the next thicker one doesn't go at all.
- Finding the correct amount of gap with a feeler gauge is easier if you use a "go-no go", or "stepped" gauge. The stepped feeler gauges have the smaller clearance on the first inch of the blade and the next higher clearance on the upper part. This makes it easy to see where you are with just one gauge instead of flipping back and forth between two different ones. Like this:
- Note: This photo is just a demonstration. This gauge is not the right one for the EX250.
- You could buy two sets of feeler gauges. Then you can just pull out one from each set (still attached to the whole set). One you dub "go" and the other "no-go". It costs about $6 more than one set, and you don't have to keep flipping through them.
- Leave the feeler gauge between the valve and rocker when tightening the locknut to prevent the gap from changing.
- Sears' automotive valve clearance gauge set is sufficient for the job, assuming you want to adjust your valves to the looser end of spec (as most do). The three thinnest gauges are 0.005, 0.006 and 0.007 inches, marked handily in both metric and SAE. 0.005/0.006 is a usable "go/no-go" pair for the maximum specified intake valve clearance, and 0.006/0.007 is usable for the maximum exhaust valve clearance. This set also has the handy feature of having one tip of the gauges bent up at 45 degrees from the rest of the gauge. Considering you can use either end of the gauge to check clearance, this is very handy, particularly for the rightmost intake and exhaust valves. Stupid cam chain...
- Sears also has another set that has more precision for metrics. This set has .102, .127, and .153mm feelers, which are more precise than the SAE feelers and work well for the Kawasaki tappet clearances. A little bit of confusion is created by the fact that on the back of the package the sizes are rounded to .10mm, .13, and .15, or something like that.
Leaking coolant pipe
- After several valve adjustments, you could start to see a leak from the coolant pipe (the metal piece connected to the cylinder head). What does the coolant pipe leak have to do with the valve adjustment? You may rub the pipe a little each time you take off the cylinder head cover, as you try to wedge the cover out toward the right side of the bike. Putting the cover back rubs it a bit more. The rubbing might be enough to move the pipe ever so slightly side to side. This could be enough to allow a worn out O-ring to start leaking.
- The O-ring alone is about $3 at Ron Ayers, or you can get one at a local hardware store. However, there is one that you can have for “free”. The oil filter comes with a small O-ring, which (at least in Fram filters, and should be in all of them) is the same size as the coolant pipe's O-ring. Since most people don't replace the small O-ring at every oil change, you can use one for this application, if needed.