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.
RD DROPOFF
I purchased a 1973 Yamaha RD 250 last spring and have had trouble with it all summer. The bike runs well until dropped into sixth gear. Once in sixth, there is no power at all and it acts doggy. The only way I can gain any speed is to drop it back into fifth gear. I have had the carbs adjusted twice by a Yamaha dealer but I still come up with the same problem. Bike season is coming soon and I don't want to deal with it again this year. Any suggestions?
Duane Mears Durand. Mich.
If the engine isn't missing or displaying other high-rpm running ills in the tower five gears, you may have an overall power loss that prevents the engine from pulling top gear. Assuming you've tried new plugs and points and set the timing correctly, a compression check is in order. With the engine warm, you should be able to kick a compression gauge up to 125 — 150 psi with roughly
equal readings in both cylinders. If it's any
lower than that, the engine needs rings. A Iso check your sprockets and make sure a previous owner hasn 7 geared the bike too high. It should have a 15-tooth countershaft sprocket and 40 teeth at the rear wheel. With the bike on its centerstand, check for dragging front or rear brakes, which can have a serious effect on the top end of smalldisplacement performance.
A clogged air cleaner can cause the same
symptoms, because the engine will run slightly rich and lose power at the top end. Carboned-up muffler baffles will also cause power loss. Yamaha recommends a new air cleaner element every 3000 miles, and blowing dust out of the element with compressed air whenever necessary. The baffles should be decarbonized every 2000 nales: either cleaned in solvent or heated with a blowtorch and tapped gently to remove carbon particles.
Other suggestions: make sure you don't have a blockedpetcock or other impediment to fuel flow, check the curb and manifold connections for air leaks, and make sure your plug wires are in good condition. Even a slipping clutch can cause the sensation of power loss without the rider being aware of the problem, because rpm may increase only slightly for a given naming speed. Smaller two-strokes need all the horsepower they were designed for to pull top gear on the highway, so tuning problems and lost power from engine wear will show up in a big way as wind resistance increases with speed. >
HAWK LOAD
In your January 1980 issue you tested the Honda 400 Hawk. You state that the load capacity is 417 lb., but your test of larger bikes such as the 750F show the load capacity is only 385 lb. Please advise whether the 417 figure is correct and just what the load capacity actually means.
1 am interested in buying a new bike and enjoy touring. Would the Hawk be a fit motorcycle for this purpose? My weight is only 140 lb. and I am not comfortable on large bikes. Also. I like the mountain roads and curves and you rate the Hawk as excellent in this area.
Larry Phillips Winston-Salem, N.C.
Our test on the Honda 750F lists its toad capacity at 445 lbs., or 28 lb. higher than that of the Hawk, which is still not a great difference considering the relative size and displacement of the two hikes. Fhe reason for this apparent discrepancy is that larger, heavier bikes often have tires (and other structural parts) whose load capacity is not as great in proportion to the weight of the hike as similar sized tires and components would be on a much smaller machine. In other words, the 750F starts out 142 lb., or about 26percent, heavier than the Hawk, so the tires have to support that weight plus the added carrying capacity people expect from a large bike. Given similar sized tires, gross vehicle weight rating isn't as different as weight.
In our road tests we figure load capacity by subtracting the test weight from the gvwr listed by the manufacturer.
With its six-speed transmission, 57 mpg, and fine handling the Hawk makes an excellent sport touring bike, its slightly hard seat being the only drawback.
HAWK CAM
1 just purchased a 1980 CB400T Honda and would like some information regarding two areas. First, way back in the June 1979 CW there was a Project Hawk article that tested a mild cam that would give a slight performance boost without modification to the valve train. I have two questions; what is the cam number (and Mega Cycle’s address), and will the modifiedfor-emissions 1980 cylinder head/piston crown still allow installation of the cam without major modifications? Secondly, I would like to install a stronger headlight, but am unsure whether the 170W alternator could still provide proper charging to the battery with, say, a 65/50W headlight.
My Hawk is going to be my daily transportation w ith occasional entrances on the local tracks for some production and endurance racing, so I’ve been reading the Project Hawk article to pick up what info> was available. Unfortunately there was a lot missing in regard to the Mega Cycle cam, which seemed like the best (ie.: lift, part number. Mega Cycle’s address.)
Gary Johnston
Ottawa. Ontario
The earn mentioned in the project Hawk article is the Mega Cycle 36X1, available from Mega Cycle Cams, 90 Mitchell Blvd., San Rafael, Calif 94903. They tel! us the 36X1 cam will not work on the 1980 Hawk unless valve relief pockets are machined into the stock pistons because of the smaller valve-to-piston clearance on the '80 engine. Mega Cycle is a H isco dealer, however, and will soon have high-performance H isco pistons available for the Hawk in both 10:1 and 12:1 compression ratios, compatible with their high-lift cams.
The larger headlight you suggest, a 65/ 50 \V, should work on the Hawk without causing problems. The Hawk has a permanent magnet system with improved output over the old excited field type, and with normal running lights breaks even at idle, rather than 1800 rpm or so. If high beam blows the headlight fuse, you can safely go up one amp on the fuse rating. Stock high beam on the Hawk is rated at 50 W, and the
charging system handles that toad with no problem, so the low beam of a 65/50 W will not increase the demand. A lot of short trip riding on high beam, however, could cause a gradual battery drain, so if your riding habits include that sort of thing you may want to monitor the battery condition for a few weeks. If the battery runs down, an addon headlight switch can help by cutting the headlight during warm-up and other times when it's not needed.
SHINY PIPES
In regard to the letter of Mr. John Nichols of Baltimore. Md.. in your March issue regarding discoloring pipes. 1 have some tips that have worked well for me on Honda and Kawasaki Fours on which I have installed chrome aftermarket exhaust systems.
First, make sure that the ignition timing is spot on. Next, increase the main jet in the carburetor a size or two and raise the mid-range needle a notch if possible. Before installing the header pipes, pack the mouth of each pipe w ith an ounce or so of a heavy wheel bearing grease. Before starting the bike, place an electric fan in front
of the bike to insure a constant flow of cooling air to the engine. Start the bike and let it run for twenty minutes or so. The bike will smoke excessively during this time so be sure the garage is well vented or have the bike outside. Once the bike has burned the grease out of the pipes you can begin to jet the engine properly for power.
This method of installation creates a lot of smoke, but the chrome remains shiny and doesn't turn blue.
Charles M. McDaniel Gastonia. N.C.
SEI GEARS
1 hope you can help me. 1 have an almost new Benelli 750 Sei with a blow n transmission. Can you tell me.where 1 might be able to locate parts? The dealer I bought it from here in northern California is no longer in business.
Mike Williams Brownsville. Calif.
Gearbox f ailure was a common problem with the Sei on engines up to #6775, after which improvements were made. To take advantage of the redesign, the entire late model gear assembly has to he transplanted, as parts are not interchangeable. The new gear set fits right into the old cases, however. The parts are available from Cosmopolitan Motors at Jacksonville Rd. & Meadowbrook Ave. in Hatboro, Penn. 19040. Their phone number is (215)-672-9100.
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COOPER CONFLICT
I am writing hoping you can give a helping hand. 1 am in the U.S. Navy and would like some information concerning (don't get scared now) a Cooper 250 Islo 5V. I've checked with Harley-Davidson. Yamaha. Honda, and Suzuki but have been unable to find a place to get parts or information on the contraption.
A friend gave it to me before he went overseas, and he didn't know where to get parts either.
The thing runs great and it's fast, but before I run into any trouble 1 would appreciate it if you could help me locate a source of parts and some literature on it.
SM2 Alfred Gallegos USS Mauna Kea (AE22) FPO San Francisco 96601
We're sending along a couple of articles we dug up on the Cooper Islo. For parts, try the following people: Ammex, 20872 Currier Rd., Walnut, Calif. 91789, ph. (714) 598-1985.
XS750 DWELL
I own a late 1977 Yamaha 750 (XS7502D) and would like some information on tuning. What would the point dwell be for the points on this model? By knowing this, it would be considerably easier to tune the bike because I wouldn't have to use a feeler gauge.
Gary J. Stebbins Felton. Calif.
Dwell angle for the XS750 is 195°. Yamaha, however, recommends use of a gap gauge rather than a dwell meter. With one coil firing each cylinder (rather than the usual four, six, or eight on cars) there is plenty of saturation time for each coil and dwell angle is not critical. Gap, on the other hand, is important because irregularities in the points or cam can give you a normal dwell reading when the points are gapped too wide or not wide enough. Too large a gap can cause the points to float, and too small a> gap can cause arcing or pitting, and possibly fail to fire the coil.
If vou prefer to use a dwell meter, you will do better to establish a dwell angle for your own particular engine rather than use <4 general recommendation. To do this, install a new set of points, set them at the minimum and maximum recommended gaps (12 and 16 thousandths) and take a dwell reading from each. Use the angle halfway between the two for your standard setting. This will prevent errors caused by trying to fudge angle readings from the four or six cylinder scales found on most dwell meters. For timing purposes, your bike is essentially a Single, and it is possible to lose accuracy using a dwell meter calibrated for an automotive Four, which is another reason Yamaha hesitates to provide dwell listings in their tune-up specs.
SIDECAR PARTS, STRESS
I am doing the preliminary planning for an odd sidecar project and need a little help finding the right people to ask questions of.
(1) 1 need information on toothed fiber belts (I need to transfer the power of a lOOOcc Z1 about 36 in. or so), where to buy them and what size would do the iob.
(2) I’ve been told that motorcycle wire wheels are not designed to take the side loads that hard cornering of a sidecar would impose. Is this true? If so, are there companies that replace, make different hubs, etc.? If you know of a company or companies that specialize in sidecar pieces please forward their addresses to me.
Gordon Chism
Seaside, Ore.
For belt drive info try: Phase 3 of America, Inc., 7628 Jackson St, Paramount. Calif. 90723 or Drag Specialties Corp., 5401 Smetana Dr., Minnetonka, Minn. 55343 or Chopper Engineering, Box 99A, Rd. #2, Cochranville, Penn. 19330.
W ire wheels can be made to take sidecar loads without different hubs or a changed lacing pattern, but heavier spokes are needed to handle the side loads, particularly on the rear wheel. One step better than heavy spokes, sidecar builders tell us, is a good set of cast wheels.
Help on the bits and pieces for your project can be found at Doug Bingham's Side Strider, 15834 Arminta St., Unit 25, Van Nuys, Calif. 91406: Motorvation Engineering, 18421 Hart St., Reseda, Calif. 91335, or Sidecar Restorations, 115 So. 20th St., St. Louis, Mo. 63103. Two sidecar organizations who can provide good information and newsletters are: The United Sidecar Association, 1621 Palomino Lane, Kingwood, Tex. 77339, and The Third IY heel, Inc., P.O. Box 1111, Minneapolis, Minn. 55440.
GS NON-WOBBLE
I have a 1978 GS1000 Suzuki and have experienced handling problems similar to those described in your May column.
While riding to Laconia last year. 1 suddenly started to feel a front shudder between 30 and 40 mph when backing off 4he throttle. Triggered by small, rippling bumps, the shudder would build to a fullfiedged tank slapper if I did not stop it by applving steady pressure to the handlebars. Shocked and surprised. 1 headed for the nearest Suzuki dealer who told me. “They all do it.” Unconvinced. I asked another Suzuki dealer that I met at the race. “The rear w heel is out of alignment,” he said with authority, “it’s the only thing that will make a Suzuki wobble.” That looked okay to me. so while riding home I stopped at yet another Suzuki dealer. “Can’t fix a wobble,” he said, pointing to a /5 BMW. “You should see that thing wobble.”
W hen I got back home I had my own dealer check it out. He found that the head .yaces were loose and needed tightening. Result? No more wobble, superbike handling restored.
I have also found that the GS1000 is very sensitive to variations in tire pressure. More front tire pressure, even 2 psi.. makes the bike easier to steer around town, but tjie bike becomes difficult on rain grooves and road seams. The best setting seems to l%e recommended by the factory.
Art Gottschalk New York. N.Y.
CB550 MILEAGE
I own a 1977 Honda 550F which, even on the highway, gets no more than 38 mpg.
1*do not ride hard and get this mileage even .after a tuneup. Would a less restrictive air filter help much? If so, would it be necessary to rejet the carburetors? Would any tvpe of electronic ignition help'? Any suggestions you could offer me would be greatly appreciated.
Leopold Loder. Jr.
Clifton, N.J.
The late 550s do suffer from restrictive air filtration. You can get a boost in mileage by replacing the 550 filter element with a ÇB500 Four filter, which has about 30 percent more area. It also helps to reroute the breather hose that comes off ' the top of the rocker cover and also the crankcase gas recirculator hose to either a catch tank or an open breather hose. A n open breather hose should vent behind the rear tire; you can i+suallv run it under the seat and along the rear fender. Both these lines, in their stock kookup at the airbo.x, tend to mist oil onto the filter element, causing further restriction. The crankcase gas recirculator> normally vents into a foam-and-metal separation baffle at the bottom of the airbo.x, and this too should be removed.
Do a test run on the hike before changing jets. It should run okay w ithout a jetting change, but if it feels lean or the plugs and exhaust pipes show signs of lean running you can go up one size on the main and pilot jets.
An electronic ignition may cause a slight improvement in gas mileage, mainly because it will hold spot-on timing, while the stock points can wear themselves out of proper adjustment between tune-ups. A 550owning associate reports good tuck with the Martek unit.
XS11 TANK AND CRANK
1 am the very proud owner of a 1979 XS1 1 Special with low bars, a Don Vesco Rabid Transit fairing with lowers, a Kerker header and low cruiser seat. Next month I hope to order the Vesco matching seat. I am trying to get as much of a European cafe look as possible.
1 have two problems maybe you can help me with. 1 am looking for a roadrace tank for my bike, something around 6 gal. Do you know anyone who offers or could make one for me? Second, when the temperature gets down around 20° the motor turns over fine, but when it starts to fire the starterjust spins. When it’s colder than 20° this can be a real headache. Several other people 1 have talked to say their Elevens do the same thing.
Jerry Harris
Columbus, Ohio
Target Products, 2724 14. Main St., Alhambra, Calif 91801 sells a 6-gal. fiberglass tank w hich they say can be adapted for use on the XSIT Cost is $150. If you would rather have a tank fabricated for the XS, Hyper-Cycle at a 15828 Arminta, Unit 11, Van Nuys, Calif 91406, phone (213) 7872868, can make one to order for your hike. They tell us they've made several tanks for the XS11, one as large as II gal. in the style of the old BMW touring tanks. Cost range is $150 to $225, depending on the size and complexity of the tank. Another alternative, used by endurance racers, is to buy a second XS11 tank and have a single, larger; tank welded together by a reputable shop, using an extended top or bottom from the stock tanks.
Your starter problem is the result of using an oil of too high a viscosity for the ambient temperature. A heavier weight oil will cause the rollers in the starter clutch to skid on the thick oil film and act as roller bearings, rather than wedging against the shaft and spinning the engine. Yamaha recommends a 5 W -20 or a l()W -30 motor oil to prevent the problem when temperatures drop to around 20°.
PAD SQUEAL
The problem with my 1978 Yamaha is that the front brake squeals under moderate pressure. The brake pads have plenty of wear left. I have tried both sanding and reversing the pads without success. Do you know what causes the squeal and can you suggest a solution?
Don Davis
Sunnyvale. Calif.
The squeal is most often caused by highfrequency vibration between the steel backing plates on the brake pads and the caliper piston and body. Some of the vibration can be eliminated by sanding the pads, as you have already done, to remove surface glaze, or by filing a beveled edge into the leading and trailing ends of the friction material. If the brakes still squeal (which they often will), the backs of the pads should be lubricated where they come into contact with the caliper. This will damp the noise-producing vibration. The Snap-On Tool Co. sells a high-temp lubricant called Never-Seize, and Bel-Rav markets a similar product called Molylube, both of which work well on brake pads. We've also had good luck with Permatex Disc Brake Quiet, a spray which tries to form a rubbery coating on the backing plate. Ordinary mineral lubricants, such as chassis grease, should be avoided because they can melt at high braking temperatures and run onto the disc or friction *surface.
On some disc brakes a glaze can form on the pads from repeated low-speed stops, particularly when most riding is done intown. A few hard brake applications from higher speed will often clean up the surf ace and stop the squeal.
If all else fails, replacement pads with different friction material or having the disc(s) drilled mav help. A ftermarket racing pads with high metallic content are generally quieter under moderate-to-hard use,
. though some tend to be noisier for braking at low speeds. Drilled discs, an expensive .option, generally eliminate squealing altogether, and offer better braking in the >rain. ®
