Service

SERVICE

Paul Dean

Ducaha or Yamati?

I have a 1997 Yamaha YZF1000. At about the 6000-mile point, I noticed that I was having to put about half a quart of oil in the engine every 300 to 400 miles. I had bought the extended warranty, so I took the bike to my local dealer, who disassembled the engine and found that the oil rings on the pistons had never seated. So they replaced all the pistons and rings and bored the cylinders. They also removed all the valves and reseated them. By the time they were finished, they had completed $3176 worth of work on the engine.

You’d think that this would have taken care of the oil-usage problem, but it didn’t. Not completely. I now have to add a half-quart of oil about every 2000 miles.

When I took the bike back to the dealership, they told me that it’s perfectly normal for a Ducati to go through half a quart of oil every couple of thousand miles-at which point I advised them that my bike is not a Ducati. So they called Yamaha’s tech department and were told that this level of oil consumption is considered normal.

I don’t agree. I did not buy this bike to keep an I.V of oil hooked up to it at all times. Also, I do notice a small puff of smoke coming from the exhaust when I start the engine after it is fully warmed. Can you please help? Bill Costa

Posted on America Online

While the need to add a half-quart of oil every 2000 miles might fall within Yamaha’s range of acceptability, I would not term it "normal,” especially for an engine that has just been rebuilt to remedy an oil-consumption problem.

I do think, however, that the smoke you notice during warm-engine start-up is a clue to your YZF’s oil usage. In all probability, that smoke is caused by oil that is getting into the combustion chambers by seeping past the valve seals and valve guides after the hot engine is shut off.

You said that the shop only reseated the valves rather than replacing them, so it’s unlikely that they installed new guides and seals. Those parts could be worn enough to be causing the oil-consumption problem. But even if that is not the case, the mechanic could have nicked the seals when removing or reinstalling them. Or, if he didn't ensure that each valve got reinstalled in the same guide and with the same seal that it had been mated with before disassembly, the resulting mismatch could

cause the aforementioned oil seepage.

Incidentally, if oil indeed is sneaking past the seals and guides, it will do so all the time. You only are aware of it when restarting the engine because the oil accumulates in the cylinders or on the heads of the valves and causes exhaust smoke when the motor is fired up.

Your biggest challenge will be getting the dealer to acknowledge that the oilconsumption problem is serious enough to justify repair under the terms of the extended warranty. You might even try contacting Yamaha s customer relations department yourself and getting a firsthand opinion. I can tell you how to fix the oil-usage problem, but 1 can 't tell you how to get the work done for free. That ’s an issue you ’ll have to resolve between you, your dealer and whoever underwrites your extended warranty.

¿Las llantas son robusto?

I live in Ecuador, the land of bumpy and twisty roads, and I have a question about tires. In any tire comparisons I have read, the testing has always been done with motorcycles in the sportbike class; hence, they are fairly light. What happens with the performance of those tires when they are used on heavyweight motorcycles (500-600 pounds) in the sport-touring class? Can these tires be safely used? Must you increase the tire pressures? Or should you stick with the recommended OEM tires? Forget about mileage; I’m talking about performance and safety. Jordi A. Fabara

Posted on America Online

If tire mileage is not one of your concerns, all you need to worry about is the amount of weight you place on each tire

and that you do not exceed its maximum recommended inflation pressure. All tires have load-capacity information molded into their sidewalls that informs you of the maximum weight that tire can handle at its highest recommended air pressure. A typical front sport tire-say, a 120/60VR17—will have a load rating somewhere in the area of 520 pounds at 42 psi of pressure. A typical rear-let’s use a 180/55VR17-will support around 800 pounds at 42 psi. An unladen 600pound sport-touring bike with a 50/50 front-to-rear weight bias will have 300 pounds of its weight on each wheel. So, you ’ll be able to carry a total of 720 additional pounds on the bike-up to 220 pounds on the front wheel and up to 500 on the rear. And those load ratings are valid for speeds up to 149 mph. Unless you find a way to ride faster than that

on Ecuador’s "bumpy and twisty roads,” using sportbike tires on your sport-touring motorcycle will cause no problems.

Teutonic gas hog

Last summer, I rode out west on my 1992 BMW K75RT that now has 30K on the clock. As I was coming down out of the mountains for the last time, I noticed that the engine wouldn’t idle, so I flipped on the fast-idle lever to keep it running at stop signs. At the next gas stop, I put twice as much fuel in it as I normally would, and from Wyoming to Minneapolis, my gas stops were more frequent than usual. The bike still runs great, with plenty of power and top end, etc. The dealer has had the bike since September and has tried everything, including calling in the national BMW representative who worked on the bike for two days. All the tests say that the bike is fine, but they can’t figure out why it’s running rich. Any info or direction you could offer would be greatly appreciated. Craig Geddes

Savage, Minnesota

If the hike has retained its usual acceleration and top-end performance, this would indicate that the fuel mixture is too rich only at idle or when the throttle is either barely open or closed altogether. Because the fuel mixture is regulated by the engine-control module (aka the “black box,’’ or main computer), logic suggests that the problem lies either in the ECM’s idle/low-speed programming or in one of the sensors that sends the ECM the data it needs to determine the correct mixture for that rpm range.

Normally, the test equipment BMW recommends for diagnosing the ECM should locate and identify this type of problem; but if neither the dealer nor the BMW rep have had success using the approved diagnostic techniques, perhaps something a little less scientific is called for-such as swapping the ECM for a new one or a used one of known quality, just to see if it remedies the rich-mixture problem. If it doesn’t, the next step would be to change the temperature sensor on the engine. When that sensor fails, it stops sending a signal to the ECM; the computer interprets the absence of a signal to mean that the engine is stone-cold, so it reacts by richening the idle/lowspeed fuel mixture.

I fully realize the ramifications—mostly financial-of such a trial-and-error diagnostic technique. But your K75 has been tied up for more than six months; desperate men make desperate moves.

Feed the starving

My friend is having trouble with a 1987 Yamaha FJ1200 he bought recently. The bike has 23,000 miles on it and was owned by a guy who took very good care of it. The problem is that after it has been running at 80-90 mph for anywhere between 30 and 50 miles, it runs out of gas.

It will start to cough and sputter and then just quit. As soon as he pulls over to the side of the road, he can choke it and the engine will try to start but won’t keep running for more than a fraction of a second. If he lets the bike sit for about 10 or 15 minutes, the engine will start right up and run just fine as long as he doesn’t ride faster than 50 or 60 mph.

So far, the owner has installed a new fuel petcock, and he has replaced the electric switch and the servo that turn the petcock onto the Reserve position. He’s also checked and cleaned all of the vent hoses. Any suggestions would be greatly appreciated. This is a really nice bike, but it just doesn’t want to run at speed.

Dewey Slough Posted on America Online

You said the owner of this FJ1200 had cleaned the vent hoses, but you didn 't specify which vent hoses—the ones on the carburetors or the one on the gas tank. All the symptoms you describe indicate that the gas-tank vent is at least

partially clogged.

As the fuel in the tank is consumed through normal running, air must be allowed to enter the tank to fill the space evacuated by the departed fuel. If this doesn’t happen, the pressure inside the tank gradually becomes significantly lower than the atmospheric pressure outside of it; that pressure imbalance eventually will become great enough to prevent fuel from flowing out of the tank and into the float bowls. In effect, the engine runs out of gas.

gas.

I think that the vent is just partially blocked because the engine quits only after the bike has been ridden at high speeds for

relatively long periods of time. At lower speeds, the vent seems to be allowing sufficient air to enter the tank to keep the inside and outside pressures reasonably even; but at higher speeds, fuel is consumed faster than air can enter through the vent, causing the engine to stop running until it is shut off long enough for the pressures to equalize.

Here’s the simplest and most conclusive way to determine if the fuel-tank vent is the culprit: Have vour friend ride the bike at high speed while a second ignition key is inserted into the gas-cap lock. When the engine begins to die, he should then flip open the gas cap, which immediately will allow air to rush into the tank. If the engine then starts running normally once again, he will know for certain that the gas-tank vent is the problem. His job then will be to determine precisely where the vent is clogged in the hose, in the system of

small orifices in the gas cap or anywhere in between.

Dyno fossils

I found a road test of one of my bikes (1990 Yamaha Radian) on the Net and saw that the dyno runs were done on a Kerker dyno. I’m interested in learning how the numbers from a Kerker dyno compare to the Dynojet numbers that seem to be most common these days.

Craig Sickler Posted on America Online

The dyno used in that 1990 Radian road test was in j'act a Dynojet. It wasn 't built by Kerker; it simply was owned and operated by that manufacturer of aftermarket exhaust systems, who often allowed magazines to use it for road-test and product-evaluation purposes. The dyno was sold when the Kerker operation was bought by SuperTrapp and moved from California to Ohio.

Even though 10 years have passed, the dyno numbers from that 1990 test should be fairly comparable to those obtained on a current-model Dynojet. The operative word here, though, is “fairly; ” Dynojet dynos have constantly been improved over the past decade, enough so to compromise the compatibility of old and new numbers. Matter of fact, even the numbers generated on two different modern dynos of the very same model may not be 100 percent compatible. That's why anyone conducting an R&D program won 't compare torque or horsepower figures that didn’t all come from the very same dyno.

So, go ahead and see how your Radian’s 1990 dyno results match up with today’s numbers. Just don’t expect the outcome to be much more than a fingerin-the-wind comparison. Ö

Got a mechanical or technical problem with your favorite ride? Can’t seem to find workable solutions in your area? Maybe we can help. If you think we can, either: 1) Mail your 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 ; or 3) e-mail it to CW1Dean@aol.com. Don’t write a 10-page essay, but do include enough information about the problem to permit a reasonable diagnosis. And please understand that due to the volume of inquiries we receive, we can’t guarantee a reply to every question.