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.
UNLEADED IRREGULAR
About six years ago I read an article in the American Motorcyclist Association publication concerning unleaded gasoline in air cooled motorcycles. It warned that in spite of owner’s manuals giving their OK to use unleaded, the lead-free gas should never be used in air cooled engines because it burns hotter than leaded and air cooled engines can’t cool themselves enough to prevent heat-related damage.
I recently wrote to the AMA to see if this advice has changed. The man who wrote back said he wasn’t aware of the article and had no info on the subject. Do you have any information on this matter?
Pete Riehm Indio, Calif.
We haven’t seen the article either, but if it warned against using unleaded gas because of heat problems, the subject may have been detonation. Unleaded doesn’t burn any hotter than leaded gasoline, but the lower oc-
tane rating of most unleaded fuels can cause preignition and detonation in some engines, particularly high compression engines designed before the switch to predominantly unleaded gas. Detonation, or pinging, can be very hard on an engine and cause it to build
up hot spots in the pistons or cylinder head and generally run at a higher temperature. Some of the normal cures for this problem have been to retard ignition timing slightly, add extra, or thicker, cylinder base gaskets for lower compression, and to keep revs up and avoid lugging the engine while riding.
Another advantage of leaded gas is that it lubricates the valve seats, reduces seat wear and thereby lessens the possibility of valve leakage and burned valves and seats. However, most modern motorcycle engines use valves and seats of very hard, high quality material and burned valves are a rarity, even when unleaded fuel is used exclusively. In fact the valve trains on some Japanese Fours actually work better with unleaded fuel because lead deposits on the valves can interfere with proper seating.
Manufacturers can build air cooled engines to run at any of a wide range of temperatures, depending on the size and placement of cooling fins and the routing of air flow through the engine, so few stock motorcycle engines ever suffer any form of heat damage. The majority of modern motorcycles were designed to burn unleaded fuel and will run fine on a steady diet of the stuff. Again, possible detonation is the only real problem with low octane unleaded gas. If your bike doesn’t ping during low rpm rollons, there’s no problem. If it does, switch to a higher octane fuel (leaded premium, if you can find any), or try a mixture of unleaded premium and leaded regular. If that doesn’t work you may have to retard the timing or reduce compression ratio, as mentioned before. Simply keeping revs up when accelerating away from a stop, or downshifting to keep rpm up during hard roll-ons will do much to eliminate destructive detonation.
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HUNGRY RUST
I have a 1978 Yamaha 750 Triple which has been averaging about one set of exhaust pipes per year. The local dealer says that it’s using them to excess. Every winter I run the bike until it’s hot, then stuff rags into the pipes and cover the bike—it isn’t garaged all winter. Any hints? A friend said that excessive heat may be causing them to burn out. Would an oil cooler help?
Ken Griffith Champaign, 111.
You may be getting some condensation after shutting the bike off, and the rags are preventing the insides of the mufflers from drying out. Our advice is to take the bike for a good ride to dry out any leftover moisture, then ride the bike back to your garage and remove the air cleaner. Hold the engine at 3000 rpm for about half a minute while you spray a mist of WD-40 into the carbs through the airbox. Spray enough WD-40 to produce plenty of blue oil smoke from the mufflers. This will coat the inside of the pipes and keep the rust down. Keep the ends of the pipes covered with your bike cover so no rain or snow gets into the pipes, but don’t stuff the ends with rags.
It’s unlikely that excessive heat is causing the problem, and an oil cooler, in any case, would have little effect on exhaust temperature.
BASKET CRANK
I just bought a 1974 Kawasaki Z1 for $475 and it came in about 500 parts. The crankshaft is slightly rusted and pitted and so are the camshafts. What is the most up to date interchangeable crankshaft I can buy from my dealer?
Rick Allen Mobile, Ala.
Your best choice is probably the 1978 crank, part no. 13031-1006. This crankshaft has a larger flywheel than your old one and is slightly better balanced. The 7 979 crank has a heavier duty center pin than the 78, but the cam drive sprocket is larger and you would have to change both camshaft sprockets to use it. Unless you are building a full race motor, the 78 crank will be more than strong enough. List price on the 1000 crank is $453, however, so you may want to rebuild the rusted and pitted crank you now have.
LTD/GPz
I recently purchased a 1981 Kawasaki 1000LTD and love everything about it except the riding position. After studying photos of the raved-about 1 lOOGPz with its European riding position, I was wondering how difficult and expensive it might be to convert my footpegs and controls to the rearsets used on the GPz.
To further relieve my back pain, would you recommend the GPz or KZ1000J handlebars? I realize 1 will probably have to replace the angled brake levers.
Thomas J. Kurland Bridgeton, Mo.
We have no official parts-swapping data from Kawasaki, but after measuring the frame brackets on both the GPz and the I000LTD it appears that both the right and left footpeg bracket assemblies, complete with brake lever, pegs, and shift linkage will bolt directly onto the LTD frame. The same should be true for the KZ1000J. Unfortunately, we can’t give you any price On the footpeg < hange because the part numbers and pri :e list on the GPz are not yet available.
In changing I andlebars you will be left with some ver long throttle and clutch cables and fror ' brake hose to reroute and tuck out of th ? way, unless you replace> them with items off the GPz or J-model. Also, changing the levers alone is not enough; the master cylinder and clutch lever mounts on the handlebars are cast specifically for the LTD’s high bend, so you may not be able to snug the clamps up tight against the new bars. A happy alternative would be swapping parts with someone who wants to turn his standard model into an LTD.
Whether you prefer the KZ1000J or the GPz handlebars is a matter of comfort and personal taste, but the GPz bars are not ats outrageously low or far forward bend, having just a little more rise than the popular Superbike bend, and they should be comfortable enough on the LTD if you cam get levers, cables and controls to fit.
LOW VOLTAGE HONDA
I bought a new 1978 Honda CB750. The bike is a flawless machine except for one problem, the electrical system. There are no electrical accessories added to the bike so I can’t understand the problem. At any RPM above 2500 everything seems to work fine. Below 2500 rpm the electrical system doesn’t put out enough juice to operate the turn signals or sound the horn. I checked the system with a voltmeter and it seems at idle the bike will produce only 10.5 volts and at 5000 rpm only 12.0 volts. I installed a new Die-Hard battery and have tried to adjust the voltage regulator. There wasn’,t any noticeable difference before or after the adjustment. The voltage output did not change. Your help would be appreciated.
Chuck Bellis»
Orlando, Fla.
So as not to 'overlook the obvious, it would be a good idea to check the battery again before doing further work on your electrical system. The symptoms you describe could be caused by a battery which, while new, may not have been sufficiently charged before it was sold. Put the battery on a trickle charger for a day, then check each cell with a battery hydrometer and make sure they are all up to an even chargé. If everything is okay, the voltage regulator is probably the next suspect. Home (and shop) adjustments on voltage regulators produce notoriously poor results, as the points never quite seat properly for good. contact. The easiest check here is to borrow a working regulator and plug it in to youv bike. You should be getting about 14.5 volts across the battery at 5000 rpm, with an 0.5 drop when the regulator switches over to its low-speed circuit. On your bike 2200 rpm is the break even point, below which no charging is taking place and you should be getting only a battery voltage reading. (Your prescent 10.5 volt reading means the battery is already discharged more than it should be.)
If none of that helps, you could have a gounded winding in one of the three phases of your alternator, a bad rectifier, poor connections on your wiring leads, or a bad ground on the rectifier.
ARMORED TIRES
I recently bought a new motorcycle and would like to keep it looking like new. I have been using Armor-All on the seat and rubber parts. 1 would like to apply it to the tires but don’t know if it would be safe on the tread area of the tires.
Paul D. Brundage No. Bennington, Vt.
Armor-All and other protectants are fine on your sidewalls, but keep them away from any tread surface that can possibly touch pavement. This goes for all other tire dressings, waxes, polishes, etc. These can do nothing but reduce traction, especially on the critical, leaned-over edge of the tire contact patch, and will put you on your elbow very quickly. We know several people who have ridden display bikes home from motorcycle shows and found this to be true.
SUNKEN TREASURE
While I had the skid plate removed to facilitate changing the motor oil in my Yamaha XT500 I decided to take the ignition cover off to check on the Martek electronic ignition unit. When I removed the cover about 1 oz. of water sloshed out. The Martek tirgger unit was encrusted with white mineral deposits and the magnets were completely covered, yet this unit never faltered.
Apparently each time I washed the bike water entered through the ignition wire grommet. Martek claims the unit is not affected by moisture; well, this one ran partially submerged more than a few times. This was the first time I’ve removed the ignition cover in seven months.
Fred Smith Abilene, Kan.
