Service

SERVICE

Paul Dean

Y2K-bike

I have a 1985 BMW K100. It is fuel-injected, so it has a computer-controlled engine-management system. Should I have any concern that a Y2K bug might be present in the engine-management computer? Dennis Bogusky Temperance, Michigan Fear not, Dennis; your BMW won't grind to a halt at the stroke of midnight this coming December 31. The much discussed Y2K problem applies only to computers that contain calendar-year data in two-digit form. This includes, unfortunately, virtually all the PCs, laptops, mainframes and other computers that pretty much run everything on this planet, but engine control unit (ECU) computers on fuel-injected motorcycles are not among them. Actually, the "black box" that runs your bike engine-management system is not much of a computer by today's standards. It's really just a very simple processor that receives input from sen-

sors that monitor engine rpm, throttle position, ambient air temperature, en gine temperature, intake air volume, etc. Using that information, the com puter then optimizes fuel mixture-and on some bikes, ignition timing-for any

given set of operating conditions ac cording to a predetermined "map." But in performing that task, the pro cessor has absolutely no need for day, month and year data, so it is not pro grammed with that information.

Liquid magic

I have a 1995 Suzuki Katana 600 and was wondering what would happen if I put Prolong (a super-lubricant oil additive) in my engine. I’ve heard that it will “eat” my clutch, but I’ve also heard that it will reduce engine noise, make shifting easier, improve starting and add 3 horsepower. I’ll pretty much do anything to get more power, so I’d like to know if this stuff is safe for use in bikes. In case you need to know, I use Suzuki 20w50 oil in the engine. Danny Adams

Lakeland, Florida

Well, let’s see: A clutch’s efficiency is based on how much friction it can generate, and Prolong supposedly is a friction-reducing additive. Do you detect a message in there anywhere?

Try looking at it this way: Bike manufacturers spend millions of R&D dollars on their high-performance models in an attempt to squeeze out just a few more horsepower; if merely dumping a can of additive in an engine would produce all of the wonderful results you have “heard,” especially the part about adding horsepower, don’t you think that at least one of them would recommend its use? Besides, is your engine noisy? Is it hard to start? Does it shift poorly? If so, leave those repairs to a real mechanic, not to one supposedly living in a can.

The dogs of wear

I just bought a 1997 Suzuki RF900 that has 13,000 miles on it. The bike runs really well except when I shift quickly into second gear or accelerate real hard in second. The bike then kind of skips or stutters and jumps back and forth. It doesn’t do this in any other gear, and it only does it when I’m accelerating wide-open. My local dealer says it needs a whole new transmission, but a guy I sometimes ride with gave the bike a test ride and he says the clutch is bad. Who is right?

Robin Richards Clarksville, Tennessee

Your dealer was in the right ballpark, but he was sitting in the wrong section. Based on your description of the symptoms, I’d say that either the second-gear shift fork is bent or the engagement dogs on second gear are badly rounded-off—or both. Repairs would require the replacement of two gears and one shift fork, not the entire >

six-speed transmission, which consists of 12 gears, two shafts and three shift forks. Some of those other components might he worn enough to warrant replacement while the gearbox is apart, but not all of them.

This kind of transmission damage is not uncommon, and it generally stems from poor gear-changing techniques. The worst offenders are full-throttle power shifts, particularly if they are done sloppily, and downshifts during which the rider simply mashes on the lever without matching engine speed to road speed. Take the bike back to the dealer and explain the problem based on what you read here; if he still insists that the entire transmission needs to be replaced, find another dealer. Or, look up one of the top Suzuki roadracers in your area and explain the problem to him. Chances are good that he ’ll either refer you to someone who is capable of repairing the transmission competently or maybe even offer to do it himself.

Lash for cash

I recently purchased a 1985 Yamaha FJ600 that has under 20,000 miles on it. I bought it from the original owner, who told me that he had never had the valves adjusted. I’ve ridden the bike about 50 miles using various rates of acceleration and have had no problem.

I have a feeling I should get the valves adjusted because...well, just because. But I don’t want to plunk down $300$400 to have it done if it doesn’t need it. Is there any risk of damage if I don’t have it done? And how do I know when it is time to have the valves adjusted?

Ray Hecht Dallas, Texas

The only sure way to know when the valves need adjusting is to pull off the cam cover and actually measure their clearance, one by one. Unless you do that, you ’re just guessing. But if you follow the manufacturer’s recommended intervals for checking valve clearance, at least it ’s an educated guess.

Many people think that if a valve isn’t making any noise, it doesn’t need adjusting. That’s dead-wrong. A valve that has too much clearance may make an audible ticking sound, but one that is too tight generally makes no unusual sound whatsoever. In many cases, a too-tight valve actually is quieter than a properly adjusted one, especially if it has zero clearance. And even a valve with excessive clearance often doesn’t

make enough clatter to signal the need for adjustment.

An excessively loose valve will eventually hammer its valve seat into submission and damage the end of the valve stem, and a zero-clearance valve will cause a compression leak; and if an exhaust valve loses all of its clearance, a small amount of the still-burning exhaust gas will seep between the valve and its seat during every combustion cycle, eventually overheating and deforming the head of the valve.

Don’t take that risk: Get the valves adjusted. Yamaha recommends checking valve clearance every 8000 miles on an FJ600, and your bike has now gone 2V2 times that far.

One last thing: If it was a dealer who told you that a valve adjustment on an FJ600 would run you $300-$400, don’t go back there. That job should only cost between $125 and $150, possibly as much as $175 in some high-income areas. Any more than that and you re getting ripped off.

Agua non combustus

I have a ’92 Honda CBR600F2 that sat unused for three months. When I cranked the engine after that period, it started right up. I couldn’t ride it that day because of the weather, so I tried firing it up again when the weather cleared two days later, and it wouldn’t start. It would backfire but it wouldn’t run. I bought the bike from a dealer about five months ago, and it only has 4000 miles on it. Please respond if you have any helpful suggestions.

Kris Hynum Utica, Mississippi

The most likely explanation for this problem is that your Honda now has water in the float bowls that wasn 't there when you started the bike the first time. While the bike was sitting unused, condensation caused moisture to accumulate in the bottom of the gas tank, and running the engine allowed some of that moisture to flow from the tank into the float bowls.

Drain the tank and all four float bowls, and put fresh gas in the tank; the engine then should start and run normally. The next time you park the bike for a long period, put fuel stabilizer in the tank, fill the tank to the brim with gas, turn off the fuel petcock and drain the float bowls. That way, the engine will fire right up when you decide to end the bike ’s hibernation. □