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.
BMW CLUTCH
My son has a 1975 600/6 BMW. Due to illness he is unable to ride it, so I ride it occasionally to keep it oiled up and the battery charged. I was amazed a few weeks ago while riding when I heard a loud screech and the bike came to a halt. On pulling the bike down we found the splines on the clutch plate and the input shaft stripped.
What would cause this? The bike has only 10,000 mi. on it and is supposed to be very durable, good for 50,000 mi. or more with no repairs, etc. 1 am very easy on the bike; I am 70 years old, so you can believe I am no hot rodder. I would appreciate any help or advice you could give me because these BMWs are expensive to repair.
Francis “Jesse” Owens Worcester, Mass.
We know of at least two other cases similar to yours; it appears some BMWs came off the assembly line with improperly
hardened splines on both clutch disc and shaft. If you are looking for a heavier duty clutch replacement, BMW lists an H.D.
disc in their parts books, part No. 21-21-1-236-332 for $56 list. Another source is Luftmeister, who make two very heavy duty clutch discs. One is their Turbo Clutch, part No. 1755, list price $89.50, built to handle the power from their 130 hp turbo motor; the other is the Street Competition model, part No. 1750, also $89.50. Luftmeister says these clutches will not slip when overheated, will work even if soaked with oil, and will not shear with hard use. Both clutches are guaranteed for the life of your bike. Luftmeister's address is 135 E. Stanley St., Compton, Calif 90220.
Z1 CAMS
Over the winter months I plan to install a 1075 kit in my 1975 Kawasaki Z-1. Other changes will be smoothbores or bored-out stockers, Gerex ignition, and headers. Can the stock cams be kept for good performance or will they restrict the air flow too much on the bigger engine? I don't want a peaky powerband.
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Steve Andrews
La Habra, Calif.
Whether the stock cams work or not will depend on the compression ratio you get from the pistons in your big bore kit. With anything up to 10:1 compression the stock Z-l cams will probably work pretty we 11+ you'll get a good strong mid-range and smooth power delivery, but power will flatten out as you approach redline. If the compression ratio is much higher than 10:1, however, pumping pressure will be very high with the stock cams and you'll have a serious detonation problem, especially with the awful gas now available at most pumps. If you want a little more power than the stock cams offer, nearly every manufacturer of big bike performance equipment offers an intermediate street grind for the Z-l. A friend of ours at Champion Kawasaki in Costa Mesa says he's had very good luck building fast, but tractable, Z-l street motors with the Engle K-12 cam.
COIL COMPATIBILITY
I recently installed a Dyna S electronic ignition system on my '76 Honda 550. I am planning to install Martek Blue Goose Coils and was wondering if the Dyna S will be damaged by the higher power coils.
Arthur J. Cook III
Fort Jackson, S.C.
The Dyna S system will work with any coil having at least 3 ohms of resistance in the primary circuit. Less resistance than that may allow a dangerous level of current flow and damage the Dyna S. The Blue Goose Coil offers a choice of three primary connecting lugs, a basic 3.4 ohm circuit, a 2.2 ohm circuit for use with inductive or CDI systems, and a I ohm connection for CDI only. The 2.2 and 1 ohm are intended only for special competition or drag racing applications where a fast buildup of coil heat and battery drain are not problems because of the short running time. In other words, the Blue Goose Coils should work fine with the Dyna S ignition system as long as the 3.4 ohm hookup is used.
THIRSTY HONDAMATIC
I purchased a 1980 Honda CM400-A (Hondamatic) two months ago. It now has 250 mi. on it. The gas mileage is terrible. At best, with very easy riding (I weigh 180), no more than 46 mpg. What can be done to increase this mileage to the 55 mpg it is supposed to be getting. It runs> like silk; I've had the dealership look it over twice. Nothing seems wrong. Please a^vise. _ . . ,,
Robert Arnold
New Orleans, La.
We haven't tested the 1980 version of the CM400-A, so we don't have our own mileage figures to give you. But when we tested the first Hawk Hondamatic back in Sept., 1977, the automatic Hawk was down nearly 4 mpg on its five-speed bretheren. Our 1980 and '81 Hawk sixspeed tests both netted 57 mpg, so we imagine good mileage for an '80 Hondamatic might be in the 50 to 55 mpg range.
However; when we test a bike for mileage we try to have about 1000 breakin miles on the motor. We then run the bike over a prescribed 100 mi. loop which includes every type of street riding condition; freeway, intown, etc. We also keep track of mileage on weekend trips, long road rides, etc. In other words, to get an accurate assessment of your Hawk's mileage capabilities you should have considerably more than 250 break-in miles on it, and you will probably want to base your mileage estimate on a longer total distance and a greater variety of riding conditions. Also, if you have traveled only 250 mi. in two months, you may be losing some oj your fuel to evaporation. If you put more miles on the bike and give it a chance to loosen up, you may still get that extra 5 or 6 mpg.
SUZUKI IDLE
My 1980 Suzuki GS750ET idles erratically; that is, it idles smoothly, but at ever-changing rpm. One day it will tick over at 1000 rpm, the next day it will race away at 2100 rpm. Correct idle speed is supposed to be 1 100 rpm, yet syncing the otherwise non-adjustable carbs and cleaning the air filter have no effect. The local dealer attributes this problem to the EPA armoring over the carb set screws and lean jetting—which is also purported to cause the off-idle flat spot and the four-grandwit h-no-oil-pressure-cold-start-blues of which all the tests complained. If I violate Big Brother's mandates and disinter the entombed carb set screws, can 1 solve these problems?
Chris Ossanna
Hopkins, Minn.
The inconsistent idle problem sounds like a sticking or maladjusted component in the choke system. You may have inadequate free play in the cable or the linkage to the enrichening tubes, so that one or more of the tubes are not returning fully to the off choke position. Check the adjustment. Another possibility is a bad control box on the CD I ignition, which could be giving you too much advance at certain times. If the choke setup is returning properly, check the advance sequence at different rpm to see if it complies with Suzuki specs. A third fault to check for is a possible cracked hose in the intake plumbing, causing a lean air leak that varies with the position of the hose.
It is remotely possible that one of the covered set screws is out of adjustment, but our friends at the Suzuki shop say they 've never had to touch the air screws, even on their racing bikes. If local laws allow, and you do the work yourself, going up a step richer on the pilot jets and shimming the main jet needles upward as done in our GS450 carb fix article (Jan. Cycle World 1981 ) should improve off-idle and overall throttle response.
KREEM CONNECTION
I, and undoubtedly hundreds of others, need an address as to where Kreem can be purchased, either over the counter or by mail. I have contacted accessory houses in the San Fernando Valley, W. Los Angeles, Anaheim, etc. Don't leave us hanging, furnish us with info as to where we can get some.
Albert Champion Sherman Oaks, Calif.
You can order Kreem direct from Flanders Co., 340 S. Fair Oaks Ave., Pasadena, Calif. 91105, (213) 681-2581. The retail price is $6.75 for a pint, $11.95 for a quart, and $34.95for a gallon.
GUZZLING TRIDENT
I bought a Triumph T160 Trident a few years back from a guy who said it wasn't fast enough for him. The Triumph proved fast enough for me but has an annoying habit of getting only 30 mpg on a good day. What is the problem with this motorcycle? The bike is stock as a stove: carbs, gearing, everything, and the plugs (Champion N3) are still as black as can be. What, if anything, can be done to make better mpg? It's a little embarrassing when I admit to the guy at the gas pumps with the Honda Civic that my gas mileage is worse than his.
Pete Lillo
Poughkeepsie, N.Y.
Unfortunately, there's nothing very unusual about your mileage figures. The Tridents quickly earned a reputation for heavy fuel consumption after their introduction so Triumph responded to owner complaints with a factory Economizer Kit. This consisted of U4 slides to replace the stock It3s and a set of longer, fatter needles. Check with your local dealer, as some shops still have these kits on their shelves. Our best source of Triumph tech and parts info, Big D Cycle in Dallas, no> longer stocks the complete kits with nee dies, but does have the 444 slides. Using these slides, they say, with 44105 needle jets to replace the stock 44106s, will boost mileage into the 40s, and just using the 44105 needle jets with the stock needles will help considerably.
Another Big D recommendation, if you'd like increased mileage, better power and a smoother idle on your Trident, is to modify the ignition advance unit. By welding up a hole in the back side of the advance plate, the fully retarded spark timing can be brought down from 24° BTDCto 12° BTDC, still using 38° as full advance. The stock 24° retard is simply too much advance for good idling and throttle response. Again, your local dealer or Triumph repair shop may be able to perform this recurving of your advance unit. If not, Big D will gladly do it for a charge of $11.00 if you send them the advance unit. Their address is: Big D Cycle, 3600 W. Davis, Dallas, Tex. 75211.
UNLEADED TWO-STROKE
Is it safe to run unleaded gas in a twostroke engine? I have asked this question of many people—the answers have been varied and vague.
Gene Norman
Santa Barbara, Calif.
The use of unleaded gas depends on the engine. You don't mention what type of bike you have, but generally the higher compression enduro and motocross bikes demand high octane leaded gasoline to prevent detonation. Lower compression, non-competition engines in street bikes, dual purpose bikes, etc. will normally run fine on unleaded gas, and even offer the added advantage of longer spark plug life because there is no lead to foul the electrode. Lead isn't needed for valve lubrication, of course, in two-strokes, so detonation is the main concern. For that reason, a premium unleaded gasoline will normally work as well as leaded fuel of the same octane rating.
If you are uncertain about the compression ratio of your engine or the risk of detonation, your best bet is always to cheek the owner's manual and follow the manufacturer's recommendation.
BREAKING THE BEAD
Do you have trouble breaking the bead on the new tubeless tires on cast wheels? So did I until I got this tip from a guy from Illinois I met in Canada.
(1) Let the air out of the tire. (2) Purchase a C clamp with a deep throat (!—Ed.). Usually you will need a clamp with at least 5 in., but I use a 6 in. clamp. (3) Put the clamp around the tire as near to the rim as possible. (4) Tighten the; clamp down until the bead breaks, which usually takes anywhere from one to five minutes. (5) Remove tire.
The advantages of this method are the low cost of the clamp, about $10, and its portability. It can be taken along on tour.
Ed Macnamara Arlington, Va.
CLIP STRENGTH
I recently installed a Goki air fork cap kit on my 1979 Yamaha XS750. Since I had not changed the fork oil before this, I assumed the fork caps threaded into the fork tubes, which is the only system I had seen before. Instead, the inner fork walls have a groove cut in them and a large Cclip on top of the fork caps holds them against the spring pressure. My question is, how strong is such a system? It seems the clip would be subjected to a large load in a small area. The Yamaha clip was just a piece of wire, hardly strong enough to be a good key chain.
While I'm writing, a tip for people who add wiring to their bikes: use wire with Teflon insulation (available from electronic supply houses) instead of the standard pvc or vinyl insulated primary electrical wire. The insulation is far more resistant to abrasion and won't melt even if it leans on a hot part like an exhaust header or cylinder head.
Thomas Mosteller Lansdale, Penn.
The snap ring spring retainer is a light, strong and simple method of holding the spring in place, and we've never heard of one falling out or breaking, even in hard dirt bike use. Proper installation is important, however, with spring clips that have been machine stamped. These usually have a rounded side and aflat side, looked at from the top or bottom. The rounded edge should face downward against the spring and the flat surface should face upward so it has a solid seating surface against the upper edge of the groove. It's also a good idea to hold the spring down and slide the clip in a circle once installed just to make sure it's seated.
Thanks for the tip on wiring.
