Service
SERVICE
PAUL DEAN
Cut me some slack
Q I have a question about chain adjustment on my Yamaha XT225. I bought the bike new in 2006 but found the gearing too low for the street, so I recently installed a one-tooth-larger front sprocket. Afterward, when I was adjusting the chain, the axle would shift and pull the chain tighter than spec when I’d torque the axle nut. I tried starting with the chain looser than spec but still could not end up with a tight axle nut and proper chain slack. I tried holding the wheel in place with a nylon ratchet strap but to no avail. I also backed the rear wheel against the wall of my garage, but when I tightened the nut, the wheel moved back and pushed the bike away from the wall. A friend suggested pinching the adjusters with vice grips to keep them from moving; lo and behold, it worked, and I finally got the correct chain slack. Why does this happen and what can I do (besides using vice grips) to keep it from happening again? The
next time the chain needs an adjustment, I might just sell the bike. Larry Betts Posted on www.cycleworld.com
Don’t take out a want-adjust yet. If the big, flat washer under the axle nut is missing, or if the outer surface of the XT’s cam-style chain adjuster is not exactly parallel to the backside of the nut, tightening the nut would tend to drive the adjuster one way or the other, despite your efforts to prevent it from doing so. I’ve encountered this problem on a few bikes over the years, and I’ve always been able to overcome it one way or another.
If the aforementioned big washer is not under the nut, for instance, replace it; it’s an important medium that helps prevent the condition you describe. But if the washer is still in place, try rotating the wrench in the opposite direction of wheel movement-that is, if the wheel wants to move backward, position the wrench on the nut so you’re always pulling it to the front when tightening, and vice versa. The XT225 has a rod-oper-
ated mechanical rear brake, so you can also deter wheel movement if you or a friend hold firm, steady pressure on the brake pedal while tightening the axle. Because the 225’s axle nut is on the right side, it’s relatively easy to do this yourself by pulling the wrench forward while keeping a foot on the brake pedal.
Quite a few off-road riders use another method if the rear wheel tries to move rearward when tightening the axle nut. They wedge something between the top run of the chain and the rear sprocket-often something a little soft, like a hammer handle, sometimes something as hard as a ratchet extension-and roll the bike backward until the wheel won’t turn any farther. Then they use the previously described method of holding the wheel in place with the rear brake while tightening the nut; with all those deterrents at work, it’s highly unlikely that the wheel could move. This is not a method I personally like, since it can put undue stress on the chain, but it seems to get the job done.
Carpe piston
QWe are having problems with a 1981 Suzuki RM250 we bought for my son to race in vintage motocross. The guy we bought it from said it needed a new piston and rings, which he gave us and we installed. The bike ran for a half-hour, then the engine locked up.
We dismantled it and found the piston badly scored. We replaced the piston, ring and wristpin, but after a half-hour or so it did the same thing. This has happened three times now, all with new pistons. We know the ring gap is good, the timing is correct, it has a new carb that is jetted like the original setup, but the engine is getting hot enough to seize the piston, which scores in the front, opposite the carb. We’ve used Klotz oil, then switched to Maxima Castor 927.
We have checked for a vacuum leak and found none. We would really appreciate any help. Darla Carter
Posted on America Online
A You mentioned ring gap, but what about piston-to-cylinder clearance? It should be between .025and .030-inch, measuring the piston front-torear at the lower part of its skirt. Every time you replaced the piston, did you clean up the cylinder walls and hone them to have a nice crosshatch pattern? Those are necessary steps to give the piston and rings a smooth, adequately oiled surface to slide against.
You also say that you have checked for a vacuum leak, but where? You probably are referring to locations on the outside of the engine, such as the joint between carb and intake manifold or between manifold and cylinder. But another likely source of leakage is the crankshaft seal on the ignition-rotor side of the engine. Your RM is more than a quarter-century old, and who knows if or when that seal has ever been replaced? If it is leaking even slightly, it would allow air to be drawn into the crankcase during the intake stroke, causing a lean-mixture condition that could easily result in piston seizure.
Two-strokes are rather sensitive to such matters, especially older ones that have survived several owners and questionable maintenance over the years.
This is why most people who buy an old two-stroke with the intention of riding it hard or in competition generally do a complete engine teardown to determine its condition. Otherwise, they’re likely to spend more time troubleshooting and repairing than riding.
Yaw come back, hear?
Q I have a Kawasaki Eliminator 125 with only 7000 miles on it that looks like brand-new. When I test rode it before buying, the front end seemed to yaw side-to-side as if out of alignment. It needed tires, so I had new ones put on and computer balanced, but the bike still did the side-to-side sway ing. Someone told me to bleed the air from the top of the fork tubes, but that didn't help. Other people said I should add 5 psi of air to each fork with a bi cycle pump, and someone else told me to raise the front end off the ground and loosen the triple-clamp bolts to align the fork; but it's winter here and I haven't yet tried either of those. The bike does not appear to have been in an accident, and the original owner took immaculate care of it. Can you offer any help or sug gestions? Will Howerter Wind Gap, Pennsylvania
A Sure can: The steering-head bear ings are either misadjusted or badly worn. If the bearings have been adjusted so they are too tight, it would cause symp
toms much like those you describe. If a bike is ridden very far in that condition (7000 miles could do it), the bearing races will develop little indentations right where the ball-bearings ride when the bike is going straight, causing symptoms that are exactly what you describe. Those indenta tions act like detents that make the fork resist turning when you put any kind of steering pressure on the handgrips, so you have to apply more pressure; the fork then moves too far, so you have to overcome the detents in the other direction. These fork movements usually are so subtle that you might not be ftilly aware of them; but the end result is that you ride down the
road in a never-ending series of tiny steering over-correc tions, first one way and then the other, which make the bike weave side-to-side. You can check the condi tion of the bearings by raising the front end off the ground, grabbing the lower fork legs and slowly swiveling the fork back-and-forth from one steering stop to the other. If you feel any roughness or "lumpiness" whatsoever in that movement, the steeringhead bearings are detented and must be replaced. If you feel no roughness, aim the front wheel straight ahead and then rotate the fork one way or the other about halfway to its steering stop; from that point, let go of the fork and it should fall the rest of the way either on its own or with almost no assistance from you. If it does not, the bearings are adjusted too tightly.
The task of installing or adjusting steering-head bearings is a bit too in volved to describe here, so you have two options: either take the bike to a competent shop or mechanic to have that work done, or, if you would rather do it yourself, purchase an Eliminator service manual and follow the instruc tions therein.
Foul play
Q Just for fun, I bought an old Montesa enduro bike, a 1978 360. It's in good shape and runs like a bear except that if the engine gets hot or the bike tips over, it refuses to start and sometimes fouls the sparkplug. The cyl inder head has two sparkplug holes and one was unused, so at the recommenda tion of a friend, I installed a second plug that is a few heat ranges hotter. Now, when the engine decides it won't start, I switch the plug wire over to the hotter plug, and the bike starts up with a couple of kicks. Then I rev it a few times before shutting it off and putting the wire back on the regular plug before restarting again. That seems to fix the problem, except another friend claims that leaving the hot plug in the head could damage the engine. I don't understand how that could happen, since the plug isn't con nected while I'm riding, but I thought I'd better get some expert advice. Kevin Conover Flint, Michigan
A Your second friend is correct: Leaving the hot sparkplug in the head could result in engine damage, most likely a holed piston, a piston seizure or both. If the second plug were only one heat range hotter than the recommended one (Champion N2C, NGK B8ES or an equivalent), the risk would not be so great; but a "few" ranges hotter is asking for trouble.
A hot plug has a greater resistance to fouling because the porcelain insula tor that surrounds its center electrode is longer than the insulator on a colder plug. A longer insulator retains more heat of combustion, giving it a greater abil ity to burn off deposits that can foul the plug. But it also creates a hot spot in the combustion chamber that can lead to pre ignition, a condition that, left unchecked, can melt a hole in the top of the piston and cause a seizure. If an engine is not designed or tuned to run with a hot plug, it should not be fitted with one. Combustion is what heats the insula tor, not the spark that jumps across the gap. So when a sparkplug-any spark plug-is threaded into a cylinder head, its insulator will retain the same amount of combustion heat regardless of whether or not a plug wire is attached. In fact, you could render an excessively hot spark plug inoperative by smashing its ground electrode into the center electrode or by cutting the ground electrode off alto gether, and the insulator would still have the same potentially damaging effect on the engine. Here’s a better idea: Carry the hot sparkplug with you. When your Montesa won’t start, swap the standard plug for the hot one, start the engine, then, once the motor is running cleanly, swap them back. It’s a little bit more work than just moving the plug wire, but it’ll likely save you a lot more money.
Filter filler
QI have a 1994 Harley-Davidson 1200 Sportster with about 19,000 miles on the odometer. When changing the oil and filter over the last few years, the oil-pressure light takes a long time (about 3 minutes) to turn off after I start the engine. I can hear the valves ticking loudly until the oil pressure light goes off, then everything works normally until I change the oil and filter again. I use synthetic 20w-50 oil and change it annually, but I only ride about 1500 miles per year. Why is the oil taking longer than usual to reach the right pressure, and am I causing any damage to the engine or valves? Can the oil pump or valves be the problem? Benedetto Marrone
Posted on America Online
A During startup after an oil and filter change, it always takes a little time for the filter to fill with oil. This is the case with most engines, but especially so with Harley-Davidson Big Twins and Sportsters, which have roller-bearing lower ends fed by comparatively lowpressure oiling systems. Until the filter is completely full, which can take a while at idle, your engine does not have oil pressure, so its hydraulic lifters are not pressurized, allowing excess valve lash that causes the ticking sound you hear.
As soon as the pressure builds, the tappets pump up again, reducing the valve clearance to zero and making the noise go away. So long as you do not ride the bike or rev the engine during this filling period, no damage will occur.
You can enable the oiling system to reach normal pressure more quickly by putting as much oil as possible in a new filter before installing it. This is a common practice among car and bike mechanics, especially those who work with race engines. In fact, with filters that mount vertically, it’s possible to fill the filter to the brim before installation so the system achieves full pressure almost immediately. Harleys mount their filters horizontally, however, making it difficult to install a full filter without spilling some; but with a little practice, you can get the filter at least three-quarters full and still reduce spillage to a manageable level.
You weren’t specific, but you hinted that the engine now takes more time to establish oil pressure than it did in the past. If that is so, there could be numerous explanations. Are you using the very same brand and weight of oil as before? Ditto for the oil filter, as the internal construction of filters can vary slightly from one brand to another, which could account for the longer delay. Did you previously change oil during the warm summer months and are now doing it in the winter, when the oil is cold and flows more slowly? Your engine seems to run just fine once the oil pressure builds, so I have to assume (since you didn’t state otherwise) that the lag in oil pressure buildup only occurs after a filter change.
My advice? Don’t worry.
Bag o' donuts
Q Here’s a quick question: What is the best way to store unmounted tires? I am thinking of laying in a supply before prices get out of hand and want to keep them fresh for a year or three.
Craig Rogers
Cedaredge, Colorado
Here’s a quick answer: Tightly wrap each tire in one of those big green plastic trash bags and store it in a cool-or at least not a hot-place. The bag does a good job of protecting the tires from the harmful effects of ozone and ultra-violet light, and absence the of heat prevents the oils in the rubber from being slowly cooked away. I know of a couple of big-time car-race teams that socked away tires for a couple of years using this method and claimed they performed
just as well as fresh rubber when they finally hit the track.
Stop yer whining
Q I have a 1991 Ducati 900SS with 15,000 miles on it that I bought new, and I have taken extremely good care of it. It has had an oil change every 1000 to 1500 miles, first with Ducati’s recommended Agip, then later on with Amsoil full synthetic. It has never had any problems except that the transmission, a six-speed, whines in fifth gear; none of the other gears make any noise. It sounds like a worn bearing and has been doing this for several thousand miles. The noise doesn’t seem to be getting worse, but I know that transmission failures could lock up the rear wheel at the worst time. I also know that removing and tearing down the engine/trans is expensive.
The trans has never been abused (power shifted or clutchless shifting). Have you heard of this problem? BC Foster
Posted on America Online
A No, 1 have not. But just in case I missed something (a distinct possibility), I consulted with one of the country’s top Ducati experts, Jeff Nash of Advanced Motorsports in Texas. His reaction was, “Good Lord, no. Transmissions are one of the least problematic areas of Ducatis, including those 900SS models.” More than likely, the noise in your 900’s transmission is the result of the way the teeth of the fifth-gear pair mesh with one another. Though the gears are manufactured to very tight tolerances, the teeth of a mating pair occasionally end up meshing just a bit too tightly, and that can result in a high-pitched whining noise. This usually does not cause gear failure, but it can be annoying.
Such a whine can also be caused by certain wear patterns on the gear teeth. Some of those patterns are not troublesome, though others are. If the wear is no more than tiny chatter marks on the teeth, no problems should result. But if the wear has lead to pitting of the teeth, that could cause the affected teeth to break off and possibly wedge between other gears. That could cause the rear-wheel lockup-the “worst time” scenario-you mention.
Unfortunately, without an expensive engine teardown, there is no way to know if the condition of the affected gears is terminal. Considering the stellar track record of Ducati transmissions, the chances of the gears failing are rather small, and the chances are smaller yet that the failure would result in rear-wheel lockup. But as always, there are no iron-clad guarantees. □
Got a mechanical or technical problem with your beloved ride? Can’t seem to find workable solutions in your area? Or are you eager to learn about a certain aspect of motorcycle design and technology? Maybe we can help. If you think we can, either: 1) Mail a written inquiry, along with your full name, address and phone number, to Cycle World Service, 1499 Monrovia Ave., Newport Beach, CA 92663; 2) fax it to Paul Dean at 949/631-0651; 3) e-mail it to CW1Dean@aol.com; or 4) log onto www. cycleworld.com, click on the “Contact Us” button, select “CW Service” and enter your question. Don’t write a 10-page essay, but if you’re looking for help in solving a problem, do include enough information to permit a reasonable diagnosis. And please understand that due to the enormous volume of inquiries we receive, we cannot guarantee a reply to every question.
