The Service Department
THE SERVICE DEPARTMENT
Len Vucci
We welcome your technical questions or comments. We get an enormous amount of mail, but we attempt to answer as many letters as possible and we’ll publish those we think are of interest to our readers. We’ll also print some helpful hints and how-to’s reflecting frequently asked questions. Please limit your “Service Department” letters to technical subjects only and keep them as brief as possible. Send them to: “Service Department,” CYCLE WORLD, 1499 Monrovia Ave., Newport Beach, Calif. 92663.
HEADLIGHT TURN-OFF
In response to the February “Service Department” comments about adding headlight switches, this will provide some answers. There are currently two types of voltage regulators used on motorcycles: standard coil/relay type, usually adjustable, or solid-state type solid epoxy block, non-adjustable. The solid state units on bikes without light switches are designed to operate with this load. Removal of this load will raise the battery charging voltage to as much as 17 volts, which rapidly boils the electrolyte away (I proved this on my 1976 Gold Wing). To check charging voltage. simply remove the headlight/taillight fuses and. with the engine running at 2000-2500 rpm, measure the voltage across the battery terminals. If it exceeds 15 volts, a coil/relay regulator will require adjustment. A solid state unit should be loaded down with a dropping resistor.
I currently use a 10-ohm. 100-watt dropping resistor on my Gold Wing, available from Radio Shack, which is switched out when the lights are turned on. This seems to be the best way to go on the solid state units.
A final note: most of the new Hondas, CB400F through GL1000, are equipped with solid state regulators, so check it out first. Those big batteries are expensive!
E.R. “Butch” Chaffer
San Bruno, Calif.
AMAL CARB UPDATE
For CYCLE WORLD readers with Amal-equipped motorcycles, here is a worthwhile modification. After the first 10.000 miles, and on all pre-1975 Nortons and Triumphs, the installation of Amal up-date kits is advised. A redesign of early interior parts, the three piece combination of jet needle, needle jet, and jet holder provides greatly improved low speed running because of better taper design. Mileage is improved significantly for intown riding, and response is better. Installation of part number 622-235 will convert most grimaces into grins of satisfaction.
Another part that will improve performance on the English concentric is the Viton-tip float needle, which steadies idle significantly. The seat in the float bowl must be tapped up or down to regulate float level of the plastic float. About 1-2 mm below the gasket joint surface is a popular setting. Additionally, fuel height in the twin carburetors should be matched.
Jack Schally
CYCLESPÓRT MOTORS
St. Paul, Minn.
BMW BATTERY BOOST
With our state’s mandatory lights-on law, the battery on my BMW R/90 tends to get rather weak. I’d like to use a trickle charger to keep the battery up, especially during rainy periods when the bike is garaged. The owner’s manual states the cables must be disconnected before charging the battery. Does this also apply to a trickle charger?
R. Alldis Chehalis, Wash.
One of the members of our staff has used a trickle charger on his BM W after periods of inactivity. The cables were left connected, and no damage resulted.
Maximum rated output of the charger should be one ampere or less, and battery electrolyte level should be closely maintained.
KAWASAKI EXHAUST
I am presently facing a problem which many of your readers must also share, that is, what aftermarket exhaust system to buy for my 1974 Zl.
My pipes are rusted through and I’m up to my neck in ads claiming tremendous improvements in power, gas mileage, etc. I do extensive touring on my bike and I need a system that is quiet, allows access to the oil filter, retains side and center stands, and requires little or no modification to carburetion.
I am currently considering the 4-into-l system offered by Action Fours, which apparently meets the above criteria. I’d like your opinion of this system, and any suggestion you can offer for a system which best meets the above criteria.
P.B. Vasseur, D.V.M.
Los Angeles, Calif.
Your dilemma is indeed common, but you have an advantage over most in that you know exactly what you want.
CYCLE WORLD has tested only one accessory exhaust (Hooker 4-into-2) for the Zl. While offering a substantial gain in performance, that particular system fails to meet your other requirements. From direct experience, therefore, we cannot recommend one system over any other.
continued on page 114
continued from page 113
We do suggest you compare manufacturers claims, based on your own requirements and priorities, inspecting sample products where possible.
Required modifications in carburetion will vary between systems, and are usually minor; a needle position change and idle adjustment are typical.
Happy hunting!
YAMAHA XS750 TIPS
I really enjoyed your series on carbs. However, your article on the Mikuni CV (April) struck a responsive note. The setup and synchronization section states the idle mixture screws should be backed out Wi turns for openers and the limit caps replaced. The XS750D factory manual states these screws are set at 2]A turns with no adjustment.
It seems to me your procedure would result in a fairly lean idle mixture within the 180 degree adjustment of the limiter cap. Would you elaborate on this?
I would also like to pass on a few things I have done to my 1976 XS750D.
1. Cornering is much improved if higher tire pressure is used (28 front—33 rear).
2. By inserting a rubber bushing and grommet in the muffler attachment point on the right passenger footpeg, most of that annoying buzz between 3600-4200 rpm is eliminated. It seems to be mainly resonance in that big “blooie tube” of a muffler, and the original rear mount is a hard metal-to-metal attachment.
3. The top from a spray paint can makes a fine cover for the muffler outlet to eliminate condensation. Exact fit. believe it!
4. When mounting a Yamaha Silverbird fairing, be careful not to crank in full left steering lock with no weight on the bike. The tach cable is just a tad too short to allow this. The outer sheath sometimes pulls out of the crimped fitting at the cylinder head drive.
I have 2500 miles on my 750D now and really like it. I am really amazed that they could improve upon it, but the new 2D speaks for itself.
Dallas W. Hamlin W. Lawn, Pa.
A t the time the carb article was written, a factory manual was unavailable. Inspection of the pilot screws on two XS750D2 models showed a mean setting of IV2 turns, which was the figure given. As stated in the text, the original pilot screw settings should be retained in all cases.
Thanks much for the additional XS information.
