Service
SERVICE
We welcome your technical questions and comments, and will publish those we think are of interest to our readers. Because of the volume of mail received, we cannot return any personal replies. Please limit your “Service” letters to technical subjects only, and keep them as brief as possible. Send them to: “service, ’’CYCLE WORLD, 1499 Monrovia Ave., Newport Beach, Calif. 92663.
FRONT SHUDDER
I have a 1979 GS850 Suzuki. It is a fantastic bike and handles great. The only problem is that at between 32 and 40 mph the front end shakes badly. The bike has no fairing and is equipped with stock tires. The only thing my dealer did was change the psi in the front forks. However, this did not help. Any suggestions?
Morris D. Hammack Whitehouse, Texas
Several things can cause a bike to shake between 30 and 40 mph, not the least of which is a general tendency in many of the relatively wide Japanese Fours to do exactly what you describe. The problem is often most noticeable when the rider backs off the throttle (slowing down to 35 mph as you enter a town, for instance). In the GS850, however, front end shake is uncommon and indicates that something is probably wrong.
Your best chance of tracking down the problem is to run through the following steps and see if you can find any irregularities:
1. Make sure your tire pressure is correct; 28front and 32 rearfor the 850. A n amazing number of handling problems begin with the assumption that tire pressure is set correctly. Also check the tires for out-of-roundness, cupping or other odd wear patterns, and improperly seated beads. Worn tires are a common cause of low-speed shimmy.
2. Spin the front and rear wheels to check for wheel runout; should be no more than 2mm on the GS.
3. Check your suspension adjustment to ensure that the rear settings for preload/ damping are matched to the correct psi in the front forks, as recommended in your owner's manual.
4. With the bike on its centerstand and someone pushing on the rear seat to raise the front tire off the ground, grab the front forks near the bottom and try pushing them fore and aft, checking for play in the steering head bearings. The 850 has tapered roller bearings in the steering head, and while these are less prone to defection than ball types, it's possible that they haven't been torqued properly. If you find any play at the bearings, have your dealer tighten the steering head shaft to the correct torque.
5. Check the bike for wheel alignment. On shaft drive bikes alignment problems are rare, but the 850 does have an adjustment that allows for offset of the swing arm. The 850 shop manual outlines the swing arm alignment procedure.
If all this fails to eliminate your front end shake ( we are assuming the bike hasn 7 been
bent or crashed, of course), U.S. Suzuki welcomes a call or a letter to help you straighten out the problem.
LOADING THE KZ400
I own a 1976 KZ400-D3, and I’m planning on touring a little. My problem is how to get my bike ready for two riders, tent, sleeping bags and change of clothes. Total weight is about 340 lb. Will my shocks and forks take it? Can my engine and oil take the heat? Also, I need a new exhaust system. Should I go headers or stock? Any little hints before I go would be well taken.
Terry Allen
Leonidas, Mich.
The KZ400 has a rated load capacity of only 265 lb, so 340 lb. is pushing it a bit. For product liability purposes, however, manufacturers often provide conservative figures on vehicle loading, which gives you some latitude. But going 75 lb. over the limit may cause a few problems that demand attention.
If there is no way to reduce the load by lightening up on camping equipment, extra clothes, etc., the next best move is to distribute the burden carefully. A tank bag will hold a surprising amount of gear and remove weight from a luggage rack or saddlebags—and the already overloaded rear suspension and tire. Shifting weight closer to the bike's c.g. also improves handling, which can deteriorate markedly on an overloaded light/middleweight motorcycle. Keep weight at the rear as low and far forward as possible. A high, heavy load on a luggage rack can rapidly amplify a small speed wobble into a genuine tank-slapper, as well as making the bike a handful at low speeds and on soft road surfaces.
Shocks will be less a problem than your springs, because too low a spring rate will allow bottoming on potholes and dips in the road. This in turn feeds impact loads into the frame and tires. The frame can probably take it, but a blown rear tire on a fast downhill, two-up, can cause a bad moment or two. The 80 lb./in. stock rear springs should be replaced with either 90 or 100 lb. / in. coils, or by progressive springs within that range. The fork springs, which are dual rated at 29/40 lb./ in., can be shimmed with washers for a slight increase in preload, or replaced with springs of a higher rate. With the suspension fixed to prevent bottoming, a larger rear tire, such as a 4.00 x 18 will provide higher load capacity and an added safety margin over the stock 3.50 x 18. For touring double Kawasaki recommends tire pressures of 25 psi front, 36 rear. Engine and oil temperature vary widely with weather and terrain; long climbs in summer heat can go hard on the 400, or any bike, and only an oil temp gauge will confirm or allay your fears. For normal speeds and moderate climbing, however, the KZ has a strong, reliable engine and oil temperature should be no problem. For hot weather, go with a good grade 20 W50. If it's time for a new exhaust system, a 2into-1 header will probably be cheaper than the stock pipes and mufflers, and will also trim 10 to 20 lbs. off that unwanted 75 lb. overweight. Some header systems, however, can be annoyingly loud and resonant on a long ride, so check out the sound level before you buy and make sure it's something you can live with.
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TWITCHY SUZUKI
I purchased a new ’79 Suzuki GS1000N about three months ago and now have about 3000 miles on it. It’s a fine bike but not perfect because it has three annoying things that were not mentioned in any of the five test reports I’ve read on the bike.
First it sounds as though there is gear whine at 60 to 70 mph in fifth gear. The dealer says it’s the # 630 O-ring chain. Do these chains make this kind of noise?
Second, the bike twitches and wiggles on freeway rain grooves. Is that normal? And last and worse it wallows in turns that are bumpy and undulating. I have experimented with the suspension system by trying various fork pressures and rear damping but that didn’t help. The GS 1000 had such rave handling reviews it makes one wonder if they were riding the same bike.
Also a friend of mine has a ’78 GS1000 and it’s faster. What specifically was changed in the power train between ’78 and ’79? What can be eaily changed to get a little more out of the GS.
Great magazine.
John Dietrich Newport Beach. Calif.
It is always difficult to troubleshoot problems about handling when the whole picture isn't presented. For all we know, you might be a 300 lb. giant, in which case your Suzuki would handle quite differently from most others.
There are certain things to which the Suzuki GS1000 is particularly sensitive. The type and condition of the tires can affect the handling quite drastically. When the stock IRC tires become worn on the center of the tread, and this can happen within 3000 miles, the machine will be more prone to wallowing in bends, a characteristic that no amount of suspension adjusting will
change. The only solution is to replace the tires.
Without extensive personal testing with different tire makes there’s little you can do about the twitchiness you’re experiencing on rain grooves. A general recommendation from the tire companies is to avoid ribbed front tires or highly angular tires such as a Dunlop K-81 to minimize rain groove wiggle. If it’s any consolation, it’s the road engineers who are at fault for cutting rain grooves in line with car tires and not the motorcycle.
The manufacturers look for tires which are least affected by rain grooves while retaining good road behavior on other surfaces.
It is also possible that the rear shocks have deteriorated, the only recourse being to replace them. However, before doing so, return the machine to the manufacturer's specification regarding suspension settings and tire pressures (and replacing the possibly worn rear tire) and try borrowing a set of shocks which you know are okay for fitting and comparison.
The only difference in the power train between the ’78 and ’79 GSJ000 models was a tightening up in the tolerances for the carburetor jets. Suzuki had to conform to the EPA regulations for the '78 model year when they used lean jetting, but for ’79 the same basic jetting was used. The ’79 jet part numbers have an A suffix that denotes the narrower specifications. So there shouldn 7 be any performance difference between the '78 and '79 models. Perhaps your machine needs a tune up.
The GS1000 uses a gear primary drive. Some may whine more than others because of variations in manufacturing tolerances. There’s nothing wrong. The chain contributes noise, and the large 630 chain is noisier than a smaller 530, but the o-ring design doesn 7 increase noise.
Triumph Ignition
Could you please tell me if it is possible to use auto coils on my 1976 Bonneville and, if so, the proper way to hook them up?
Also, does anyone, besides Triumph, make an electronic ignition? Have looked high and low for one with no luck. (Triumph dealer says it will take 10 or 11^ months to order complete unit from factory.) M. Key worth
LaPorte, Ind.
Auto coils will work fine on the Bonneville, though you mav have to make your own brackets and mount them lower than the stock units, which ft neatly into the cutouts under the tank. The '76 Bonneville has traditional English positive ground wiring, so the positive, or “Bat. ”, terminal on any coil made for negative earth systems will have to be connected to the contact points lead, and the negative, or “Dist.”, terminal to the hot wire jrom the ignition switch. The>
high tension lead, of course, goes to the plug.
Piranha and Boyer both make electronic ignition systems for the Triumph Twins. The Piranha uses the stock mechanical advance, stock coils, and is triggered bv an L.E.D. eye-and-window mechanism. List price is $99.95. The Boyer features electronic advance, but requires the use of two six-volt coils, not included, and sells for $119.95. Both are available through Big D Cycles, 3600 W. Davis St., Dallas Texas 75211. Lucas also makes an electronic ignition, called the “Rita 76“ for your bike, which may be the unit your dealer has backordered. This kit includes coils, pickup and rotor, and eliminates the points assembly and automatic advance unit. Price on the Lucas system is $160.00, through GP Cycle Works, 4721 Telegraph Avenue, Oakland, Calif. 94609. We checked, and they have them in stock. The new Triumph electronic ignition for 1980 is a negative ground .system, not readily adaptable to use on earlier models.
GOLD WING GLITCH
Perhaps you could give me some good news about the hesitation I am experiencing with a 1978 Honda GL1000. It runs like a dream on the highway, but at any speed below 50 mph or so, it won’t hold a steady speed without sounding (and feeling) like it’s starving for a little more gas. Unless there is a load on the engine or it is accelerating, it just loves to hesitate. I have tried hotter plugs with no improvement. And the dealer has checked that the carbs are synchronized. I really like this bike but it’s almost a chore to drive it slowly. One more clue is that when the engine does reach the white zone on the temperature gauge the hesitation all but vanishes. The problem is that as long as the bike isn’t standing still the engine runs nice and cool, below the white portion of the gauge but still well within the limits of the normal zone.
Mike Campagna
Buffalo, New York
It’s possible your problem is caused by a carburetor float level that’s too low or by a jet that’s plugged up, but the chances are that the primary main jet is just a little too
small to give best performance. The '78 Gold Wing was the first emission controlled GL and its carbs are different from earlier and later carbs. Jet sizes are smaller on the '78 model and the conditions you describe sound exactly as though the primary main jet is too lean. At speeds above 50 mph or under a load, the secondary main jet takes over on fuel supply, eliminating the problem, but under that speed it's handled by the primary main jet. The 1978 GL used a #60 primary main jet, #120 secondary main jet and had a 21mm float level. The 1977 GL used a #62 primary and #125 secondary. We suspect a #62 primary main jet in each curb would solve your problems. Because your motorcycle is emission controlled, it's against federal law for your dealer to change this jet, but it's not illegal for you to do it yourself.
GS CAM CHAIN
In your Feb. 1980 issue you tested the Suzuki GS550ET. On page 96 it talks about the automatic cam chain tensioner, which it says can get all goofed up at high rpms. I own a 1979 GS750E and was wondering if my automatic tensioner is the same way.
The article also gives some ways to remedy the situation, and I was wondering if the same procedures would correct mine if it has the same problem.
If my tensioner is the same, could I send it to Kazuo Yoshima at Ontario Moto Tech to be modified? If so, could you give me the complete address I need to send it there. I would also like to know if you have any idea how much the modification would cost.
I would appreciate any help you can give and I’d like to thank you for your cooperation on my previous letters.
Greg Mosser Fortuna, N.D.
The '79 GS750E has a cam chain tensioner which works on the same principal as that on the GS550. The 750 unit has caused fewer problems than the 550’s, but if revved high enough is capable of developing the same troublesome chain backlash when the throttles are suddenly closed. If the 9500 rpm redline is observed, there is no cause for worry, but for competition or very hard running, the same modification recommendedfor the 550 is good insurance. Given the entire cam chain tensioner assembly, Ontario Moto Tech will make the necessary>
changes for $50. Their address is: 6850 Vineland Ave., Unit 16, N. Hollywood, Calif. 91605.
XS SNATCH
Every Yamaha XS750 (mine’s a ’77 2D model) comes standard with severe driveline snatch at low speeds—a condition that frustrates all attempts at being Mr. Smooth Cruiser around town. I'm certain the CV carbs are to blame for this behavior, but I’m not aware of a fix. Can you help? It’s the only real flaw in an otherwise outstanding machine, thus I’m prepared to spare no expense (new carbs/whatever) to eliminate it.
Don Kellog Hamburg, Mich.
A good part of the driveline snatch in the XS750 comes from the combined slack of the HyVo primary chain, gearbox and driveshaft gears. The CV carbs, however, provide the on/off throttle response that keeps the driveline surging back and forth.
If you are willing to go for a set of new carbs, a company called Specialists Two provides a bolt-on set of three 34mm Mikunis, complete with cables, for $220.00. The part number is 1013, and the company is located at 102 E. Prospect Avenue, Burbank, Calif. 91502.
The stock XS750 carbs have needles with three-position clips, so a small amount of their touchiness can be eliminated by insuring that the needles are raised into the highest position, fattening the mid-range for more even response.
WHICH OIL?
I’ve got a problem with oil and I am sure ' there are a lot of people with the same question to ask.
The question is not with the brand of oil but with weight. I have a Yamaha XS1100SF and the factory says the correct oil is 20W-40 for summer and 10W-30 in winter. But the place where I got the bike says to use 20W-50 because we are in a warm area. The bike is stock except for an oil cooler, oil temperature gauge and oil pressure gauge. The pressure runs from 15 psi at idle up to 60 psi at 4000 rpm and the temperature never gets above 120° in winter driving in San Jose.
Who is right about the weight of oil? Can the 20W-50 do any harm? What is the best temperature range for the oil? I also have the same question about the shaft drive. Service manual says hypoid 80W-90 all season. The local motorcycle shop says to use 90W-140 hypoid. Who is right? What should I use and why?
Lynn D Free San Jose, Calif.
Yamaha recommends that you use a 20W-40 if you're running the bike in ambient temperatures over 41°. But if you use the bike often in temperatures tower than>
that and occasionally up to 60°, use a 10W30.
Since it’s likely that the temperatures will only rarely drop below 41° in San Jose it’s hardly necessary to go to a lighter oil than 20W-40. For all practical purposes, a 20 W50 oil will perform virtually the same as a 20W-40—it simply has a wider performance range. The same goes for the hvpoid oil in the shaft drive. A 90-140 weight oil contains additives that improve the load capacity of the 90-weight oil at high temperatures, so there is no real reason why you should not use it unless the manufacturer specifically says so.
If your oil temperature never gets above 120° in the winter, it’s too cold. At that temperature the water collecting in the oil doesn't get warm enough to evaporate. It would be a good idea to wrap up the oil cooler to keep it from cooling the oil below 160°. Cooler oil is not necessarily best. A good operating temperature for oil on your motorcycle is around 200°.
FUEL CORRECTION
Reading your article “Yamaha XS1 1 Special” (Dec. "79) brought a question to mind.
I just bought a 1980 XS11 Special and enjoy this superb bike. But reading your specifications list. I notice that you show the recommended fuel as unleaded. My owners manual says regular is recommended. With this kind of bike, I want to do what’s best for maintenance and economy. Which gas would you recommend? John H. Cox North Lauderdale, Fla.
You are right. No one knows how we slipped the un onto leaded, but both the owners manual dnd the factory spec sheet recommend leaded regular. Unfortunately, gas lines and empty pumps frequently mandate the use of whatever fuel is still flowing, which is most often unleaded. Leaded fuel, aside from providing anti-knock qualities, helps to lubricate the valves. The effect is cumulative, however, and an occasional tank of unleaded will do no harm to the XS11. Leaded premium, of course, will also work fine and provides the next best alternative to regular, cost being its only disadvantage.
MORE GRIP CALLED FOR
I’m having trouble leaning into corners with the stock tires on my XL500S Honda. It appears that the tires aren’t treaded for this, being a dual purpose cycle. I’ve varied tire pressure, too. I’ve tried to find a rear tire that will stick and the front 23 inch.er is unchangeable, so far. Any ideas to keep me out of the trees?
George Thomas Eagle River, Alaska
You don't say whether your cornering problems are on road or off road, but if it 's off road, you can improve matters. The XL>
uses the dual purpose Claw Action tires from Bridgestone. There’s also an enduro and a motocross Claw A ction tire in a size to fit your bike that will improve off road traction. Another tire company, IRC will soon have a conventional knobby tire available in the 23 in. size for the front of your bike, too. If it ’s pavement problems you ’re referring to, it’s not so easy. There are no 23 in. street tires available and switching to a 21 in. front wheel isn’t the best solution because your bike is designed for the greater trail provided by the 23 incher. If the rear end of your motorcycle was lowered by installing shorter shocks, you could have a 21 in. front wheel laced to your hub and that way you could use street tires on both ends of your bike now that Goodyear is making a 21 in. street tire that’s standard equipment on the Harley-Davidson Wide Glide. Avon also sells a 3.00-21 tire, called the Speedmaster.
UNDER TIRED
My 1979 Honda CX500 (standard model) has a rated load capacity of 330 lb. The Custom is rated at 430 lb. The only difference I can find is in the tire size. If I increase my rear tire size from the present 3.75-18 to a higher capacity 4.25-18 will it effectively increase load capacity?
Jeffrey Purtee
Tempe,
Arizona
Yes, but be careful. Honda lists a maximum load figure that the company figures is safe for the motorcycle. If you carry a greater load than 330 lb. and have a handling problem, Honda certainly isn’t responsible. Also, the larger tire on Honda’s Custom is a 16 in. that has a smaller circumference than the 18 in. Going to a larger 18 in. rear tire not only will raise the gearing so your motorcycle will have slower acceleration, but it will tend to raise the back of the motorcycle slightly and that will increase the rake of the forks and decrease trail, which decreases stability. The CX500 is a terrific motorcycle, we’ve had one around here for a year now and still like it, but it isn’t the greatest for hauling loads. Too much weight on the back wheel can cause handling problems on the CX. We’d recommend holding the rear tire size to a 4.00-18. It won’t detract from the handling, will have a greater load capacity, depending on the tire, and will have a very small effect on gearing. As far as the load capacity goes, a CX500 could probably handle a load of nearly 400 lb., but we’d rqthernot ride ours with that large a load.
