Service
SERVICE
Len Vucci
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 vour “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.
CLUTCH THROES
I own a 1976 Yamaha XS500C with 8800 miles, and have had problems with the clutch since the initial break-in period. When starting out from a dead stop, the clutch grips with a jerk, the engine vibrates, and a crunch is heard from the engine area. The problem is worse when the engine is hot and I'm carrying a passenger.
I have lubricated the clutch cable, adjusted play at both the cable and push-rod. lubricated the “clutch-snake” and tried different types of oil. Nothing has helped. The clutch has been disassembled, but the plates looked as if they were new.
I have contacted nearly all the Danish Yamaha dealers, but to no avail. As I really like the bike, I would greatly appreciate your help.
Per B. Rasmussen Copenhagen. Denmark
If the push lever assembly (aka snake or worm) is in good condition, the trouble could be in the primary driven gear component (spring-cushioned primary gear). The cushion, integral with the clutch basket, uses six springs to absorb irregularities in clutch engagement.
If that is indeed the problem, the entire basket must be replaced as a unit, as it cannot be disassembled.
Also check the tension on the balancer and starter chain. If loose, they could contribute to excessive engine vibration.
I have a 1975 Honda G L 1000 that I am pleased with except for a clutch problem. None of the mechanics (they call themselves technicians) around here can offer any suggestions except to “tear it down for a look-see,” which translates into a monumental repair bill.
The clutch seems to slip at a point between initial engagement and full engagement. This happens when I leave a stoplight fast enough to keep the car behind me from imprinting my back with tire tread, but doesn't happen when I take off slowly. The clutch makes a sound like a very loud fine-toothed ratchet or a large zipper being moved rapidly. The bike vibrates in unison with this noise. Clutch operation is otherwise normal and there is no tendency to grab or creep. The clutch has been adjusted to specs. The transmission shifts smoothly and positively. I would appreciate any assistance you could render.
J. R. Coleman Texarkana. Tex.
The engineering department at American Honda provided an answer for us. The trouble stems from a laminated cushion disc—called the damper plate—in the clutch pack. It is composed of two outer metal discs, between which is sandwiched a series of shallow leaf springs, and it's used to smooth clutch engagement. In earlier GLs, the damper was installed toward the end of the clutch pack, and sometimes caused the symptoms you describe.
Correction of the problem necessitates removing the clutch pack and rearranging the plates so the damper is in the center. This can be performed without removing the engine, but requires a special tool (Honda # HC41303) to remove the clutch nut.
As an added note, only one of the two outer discs of the damper plate was sp lined on early models. Later dampers had both plates sp lined and were considerably stronger. The early plate is entirely adequate for normal use, but if you delight in entering your GL in stoplight Grands Prix, install the later plate for a margin of safety.
We should mention, too, that the Honda workshop manual for the G LI 000 is superb. It is clear; concise, and complete, and is an invaluable tool for the conscientious do-ityourself G L owner.
TRIAL SUSPENSION
Back in April of 1976, Messrs. Obermeyer and Nickelsen mentioned in their “Trials Notebook” that certain modifications to the TL 125 were successful in making it competitive. These modifications were applied to the exhaust, displacement, and suspension. There are anv number of companies anxious to supply exhaust systems and big-bore kits (Powroll springs immediately to mind), but suspension improvement seems a more difficult problem. I am aware that the suspension as supplied is inadequate for either serious trials work or general play bike use. but 1 do not know what to do about it. since most manufacturers seem to have ignored the lowly TL.
Robert A. Cudnev Aztec. N.M.
In front, use the damper rods from the Honda TL250. They'll have to be turned down where the plug fits into the fork leg, but the damping will be much improved. You might want to add air pressure, although that 's an option.
The rear shocks should be replaced by shocks from the TL250. They'll be a bit longer but will work fine. If you wish to pursue this further, with the experts, try the Budget Bogwheeler, P.O. Box 621, Longmont, Colo. 80501. The company has a complete line of trials equipment, and good advice, and works with the major companies so its trials shocks are among the best on the market.
FLICKERING FIRE
I own a 1976 Honda G L1000 which has been stricken with a very peculiar ignition problem. The engine runs roughly. After troubleshooting all the normal things, I found the symptoms but not the cause. The rough running is caused by irregular firing of the two left cylinders. I verified this using an inductive pickup timing light, which flickered on the two left cylinders but not on the right. The puzzler is that each of the two misfiring cylinders shares the coil, points, condensor, et al with a right-side cylinder, yet the right cylinders fire perfectly.
I've carefully checked the plug wires and caps, but they are in good shape. Swapping left and right spark plugs does not help either.
Besides performing the normal tuneup operations. I've cleaned the electrical connections and sprayed them with WD-40 to prevent corrosion.
The local Honda mechanic has drawn a blank on this one. and. after two months of experiencing this problem. I'm ready to dump the bike. I hope you can provide some help, as I’ve no patience left.
Joe Wieber St. Cloud. Minn.
This is a befuddling one, indeed. The engineering department at American Honda passed along some advice, however, which should elevate you from the depths of despair.
The problem is multi-faceted and stems from the construction of the 1975-'76 GL pistons. When the bike is supported by the side stand, which angles it to the left, oil seeps through the pistons' return holes, past the oil control and compression rings and into the cylinder. This is the cause of oil smoke from the exhaust when the bike is first started. The slightly greater accumulation of deposits in the two left cylinders makes them more likely to foul and misft re than the right pair.
A fouled plug is effectively a short circuit from the spark plug wire to ground. With dual-lead coils, used by most Tours, this provides a slightly hotter spark to the nonfouled cylinder, because the total plug gap has been effectively reduced. Since the fouled plug wire is at ground potential, your timing light will not trigger, even though the coil is producing high voltage.
continued on page 28
continued from page 26
Cleaning the electrical connections is a wise move. Poor electrical continuity, even with fully operational components, can reduce spark output significantly. Low spark intensity, if not the actual cause of your GL’sproblems, could easily be a contributing factor. The ballast resistor and capacitor connections are two critical areas to service.
Moreover, the ballast resistor, which is cooled by the fow of air into the airbox, can overheat if the airbox has been drilled for performance. If this has been done on your bike, spark output would be reduced, aggravating the misfiring problem.
As a final note, we have received several good reports concerning the new Nippon -denso Hot “U” spark plug. Its electrode design seems to prolong plug life, and makes it less susceptible to low-speed fouling than a conventional plug of the same heat range. Installing ND plugs and careful service of the electrics should eliminate the problem entirely.
EXHAUSTING PROBLEM
About a month ago I put an R.C. pipe on the 4-into-1 exhaust on my 1977 Honda CB750F2. I followed instructions and changed the carburetor main jets from #105 (stock) to #110. The bike accelerated excellently but I was getting a lean (light grey) reading on my plugs. So I went up one more size on the main to #115. Still good acceleration but still lean, but then I could hear a popping on deceleration.
I met a fellow biker who had the same set up as mine, but he was using #135 main jets with velocity stacks. So 1 bought some velocity stacks and installed #135 main jets. I’m still getting the popping on deceleration but I think I’ve lost some top end power in the process.
Could you please help me with this popping problem. I’ve gotten so many suggestions from so many people I don’t know' what to do.
Could it be my mid-range (needle jet) needs to be adjusted? Should I go back to the # 115 main and let the bike run lean? Any advice you could give me would be greatly appreciated as I’m at a dead end now.
Kevin Budd Brooklyn, N.Y.
We recommend reinstalling the stock aitcleaner as a first step. An alternative would be to mount individual foam filters on the> carbs. Engines live much longer when they breathe clean air.
Replace the #135 jets with the #110 pills, or, if foam filters are used, with the # 115s. This should get main jetting fairly close.
Raise each of the carb needles one notch; the carb article in the March issue of CYCLE WORLD will help there. This should bring proper color back to the plugs. During the majority of hard street riding, fuel is metered by the needle jet, rather than the main jet. The grey plug reading after such a main jet enlargement is, in this case, indicative of mid-range leaness.
Adjust the idle and ignition timing, and if possible, synchronize the carbs as our March issue describes.
Esing these settings, the plugs should look much better; and performance should he crisp. Some fine tuning might be necessary for peak performance, but at least you 'll be much closer at this point. [§1
