Service

SERVICE

Paul Dean

Six-cylinder gas hog

I recently bought a 1981 Honda CBX and have only been able to get 12 mpg with it. I know that it’s old and has six cylinders, but should 1 expect better mileage than that? I purchased it to economize, what with the rising price of fuel, but I thought it would get more than 12 mpg. A friend looked at the bike and said it appears that some engine work might have been done on it, and another friend said it might be a California model because of the big pump on the exhaust. Did I get taken advantage of and should I ask for my $1400 back? Please help.

George Dillaway Posted on America Online

I am afraid, Sir, that you and your friends are terribly confused. There is no such thing as a California-model CBX, 1981 or otherwise, and no CBX of any year was equipped with a “big pump ” on the exhaust. I suspect that you own a CBX that has been fitted with an aftermarket turbocharger-which is, in effect, a big pump, driven by the exhaust, that pressurizes the intake tract to force a greater volume of fuel-air mixture into the engine than it would receive through normal intake vacuum. I also suspect, then, that said turbocharger is not functioning properly, which would have a serious negative effect on the bike ’s fuel mileage and overall performance. If the turbo’s bearings have failed, for example, that would prevent the turbine from spinning; instead, the multi-vaned turbine wheel would be stationary; presenting a significant restriction in the intake tract. And although the length and volume of the intake system are tuned for efficiency when the turbo is functioning, it’s highly inefficient for normal aspiration.

Under no circumstances-other than top-speed runs at Bonneville, perhaps, or long trips on the autobahn at full throttle-should a CBX get as little as 12 miles to the gallon. The mileage obtained during various road tests of CBXs in the late Seventies and early Eighties varied somewhat but generally ranged from the mid-20s to the high 30s.

I suggest you take your CBX to a qualified mechanic, preferably one at a Honda dealership, for a thorough inspection at the very least. If the bike indeed is turbocharged, and if the turbo is not functioning, the repairs could be too expensive to justify on a bike of that age. What ’s more, according to the Kelley Blue Book, an average 1981 CBX ought to sell for somewhere around $3400. The $1400 price you paid for yours indicates that the seller either was completely ignorant of the bike ’s actual value or was fully aware of its substandard running condition and knew that it had a problematic turbocharger.

My suggestion, all things considered, is that if you can get your money back, do so. And if you decide to buy another motorcycle to economize on fuel, for God ’s sake, don’t choose a large-displacement, high-performance machine, especially one with six cylinders to feed. Look instead for something smaller with fewer cylinders that was designed as a more practical means of two-wheel transportation.

Can’t stand the Heet?

My 1999 Kawasaki ZRX1100, which has just 5200 miles on it, is suffering from some kind of engine problem. It runs erratically at idle, choking and sputtering, almost to the point of dying. At 3500 rpm and above, however, it runs fine, with no loss of power or anything; but under that engine speed, it runs terribly and white smoke comes out of the exhaust, which possibly could be from the fuel conditioner

and the Heet gas-line anti-freeze I added to the fuel. A dealer told me the problem could be that the battery is too low on juice. Is that possible or is something else wrong? Jason Peters

Plainville, Illinois

If you got the engine running by using the electric starter, the battery voltage isn’t low enough to make the engine run poorly at low rpm. A number of other conditions could cause the the symptoms you describe, but without being able to inspect the bike personally, I can’t offer a very accurate analysis. I suggest you try completely draining the gas tank and carburetors, then installing fresh gas. I don’t know what brand of stabilizer you put in the gas or how much of it you used, and neither do I know the effect of combining that stabilizer with Heet fuel-system anti-freeze. I suspect that the problem lies in your ZRX’s carburetors; perhaps the pilot jets are plugged or the carbs have gotten way out of synchronization, or maybe the cold-start enricheners are not closing completely when the choke is turned off. Whatever the cause, you ’ll never adequately diagnose the problem until you run some fresh, unadulterated fuel through the system. If that doesn’t remedy the problem, you ’ll have to remove, clean and thoroughly inspect the carbs, then resynchronize them after reinstallation, as well as adjust the cold-start enricheners to ensure that they are not bleeding excess fuel into the intake tract when turned off.

Gixxer fixer

I have a 1998 Suzuki GSX-R600 with a full Yoshimura race exhaust and a K&N air filter, and all the jetting is from Factory as follows: main jets for cylinders 1 and 4 are #145; for cylinders 2 and 3 are #142.5; pilot jets are #15; all needles are 3 positions from top; floats are 8mm high; and all mixture screws are out 2XA turns. My question is, why does my bike still have a hard hesitation when I turn the twistgrip to full throttle, and why does it surge badly at steady throttle around 4200 to 4850 rpm? This sucks when just cruising around town or doing slow wheelies.

Nick Thornhill Daytona Beach, Florida

Even in stock form, the 199 7-2000 GSX R600s were notorious for their shortage of bottom-end power, their tendency to hesitate when the throttle was snapped open at low revs, a noticeable dip in the torque curve between 4000 and 6000 rpm and their propensity to surge in that rpm range. They ran crisply and absolutely wailed from that point up to redline, enough so to give a lot of 750s all they could handle, but they were underwhelming at lower revs. Suzuki engineers worked hard to develop stock intake and exhaust tuning that would reduce these traits to a tolerable level, but if the bike is fitted with an exhaust that significantly changes the system ’s back pressure, the balance of the OE tuning is altered enough to exaggerate those flat spots and hesitations. Since your pipe is a “full-race” model, it’s a highly unrestricted system that likely delivers a solid increase in peak power, but the reduced back pressure it provides is detrimental to lower-rpm running.

FEEDBACK LOOP

In your “Lashing out” response (December, 2004), you said that H-D Sportsters have used hydraulic lifters since 1957. Both the K-model (the predecessor to the Sportster) and all Ironhead Sportsters had solid lifters with screws in the top of the roller tappets for lash adjustment. Harley did not put hydraulic tappets in Sportsters until the Evolution version came out late in 1985.1 enjoy reading Service and find it very informative, but you were way off on this one.

Russ Sharbaugh Naples, Florida

Yo, Paulie, hydraulic tappets on an Ironhead Shortster? For shame. Leo Payne just turned over. Leif Rubber Yeehaw Junction, Florida

I don’t think Leo merely “turned over” in his grave; he probably was spinning at more than 5000 rpm in reaction to my faux pas. Sportsters indeed were not fitted with hydraulic lifters until the 1986 model year, a fact that I clearly understand; I once owned a ’59 XLCH and adjusted its valves several times. But I apparently lost my mind when writing that inquiry by stating that all Sportsters have hydraulic lifters. My apologies to you two, the late Mr. Payne and all of the many other readers who have informed me of my blun der.

Now, Leif, let ’s talk about Yeehaw Junction, which is an actual town just south of Orlando. I gotta ask: When your city s founders named the place, what the hell were they thinking?

There are a couple of courses of action you might take. You didn / state which Factory jet kit you 've installed (there are three for your Gixxer-a Standard Dropin Kit, a Ti Pro Kit and the 1.7 Race Kit), so I have to assume that you used the Standard Kit. If so, tiy experimenting with the jetting: Raise the needles another notch or two and turn the pilot-mixture screws out another V4 or P2 turn. If that doesn’t deliver acceptable results, you may have to switch to the Ti Pro Kit, which requires a small amount of curb machining but is likely to yield better allaround performance. You might also consider installing one of Factory’s Ignition Advance Kits, which changes the spark curve in ways that will help the surging and hesitation-although it might not get rid of them altogether. □

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 “Letters to the Editor” button 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.