Service

SERVICE

Hot-rod RD125

I own a 1975 RD125B and I have currently been trying to update the suspension components (other than OEM), such as tires and shocks. Could you give me some ideas as to where I can find small, high-performance tires (front 2.75-18, rear 3.00-18)? As for shocks, I need a source that can supply dimensions and spring rates, for I have yet to see my bike mentioned in a manufacturer’s listing.

By any chance is there anything on my RD that is compatible with the TA125 production racer? The engine cases and some other components look dead-on compared with those on my bike.

Joe Schuster Cincinnati, Ohio

M38 Michelins in a sport compound and suitable sizes are available through Moto-Race (RO. Box 861, Wilbraham, MA 01095; [413] 7346211). The front fork, disc and wheel assembly from an RD200 can be used on the smaller RD, and Works Performance (8730 Shirley Ave., Northridge, CA 91324; [213] 701-1010) can supply rear shocks if you give them the required eye-to-eye measurement.

Some TA 125 chassis parts could certainly be adapted to turn your RD into a café racer; the TA was, after all, built from the RDI 25 and RD200 parts bin. This is undoubtedly less true with engine parts, however, as the TA 125 's level of tune rules out street use. If you check the classified ads in Cycle News, you might be able to find a complete TA parts bike for very little money.

Handlebar weight sources

In the May, 1986, Service column, we discussed the possibility of adding weights to handlebars as a method of reducing the vibration that reaches the handgrips, but we couldn 't recommend any sources for such weights. Since then, we've received serveral recommendations from readers:

From M&M Honda, of Albuquerque, New Mexico: Handlebar weights are available as Honda Part

Number 08138-44502. These are very cheap at a suggested retail of $2.68 each.

From Stan Chiras, RSC Performance, 1740 Cobb Parkway, Marietta, Georgia 30062; (404) 953-6851: We sell two different bar-end weights—one constructed of rubber/ steel and the other of aluminum. They sell for $ 12.95 per set.

Exhausts and jetting

I own a 1983 GPz550 Kawasaki. My problem is that the mufflers rust after only about 12,000 miles. With 27,000 miles on the meter, I have used up two sets of exhausts.

A mechanic friend suggests replacing the stock exhaust with a 4into-1. But I have read some reports that changing to a 4-into-l may require rejetting the carburetor. Since the GPz carb jets are not readily available here in Malaysia I am reluctant to switch.

Is it true that I need to rejet? Can I use a Marshall or Kerker exhaust without rejetting and yet retain the same performance?

T. A. Lim

Kuala Lumpur, Malaysia

In our experience, recent Kerker exhausts have not required carburetor rejetting as long as only the exhaust is changed and the airbox is left stock.

We have no direct experience with the Marshall exhaust, so we can't say for certain it will behave similarly. In any case, the need for such rejetting is actually greater with a U.S.-model motorcycle than with one sold in Malaysia. U.S models have their

carburetion set up to deliver mixtures that allow the engine to meet our emissions laws, mixtures that are often marginally too lean for good running to begin with. So we'd expect your Malaysian GPz and a 4-into-l pipe to be a happy combination.

Cooler Turbo

I ride a 1982 Yamaha 650 Turbo.

This bike generates a lot of heat, and, therefore, I am considering replacing the stock oil cooler with a bigger one. Would a bigger cooler cause my bike to lose oil pressure and thus burn up the turbocharger? Talbert Reese Memphis, Tennessee

No. It might take a few seconds longer to build up oil pressure when you first start the engine, and even that 's assuming that all the oil drains from the cooler on shutdown. But once the cooler is full of oil, its larger volume will have no effect on oil pressure, and no effect on normal operation. 13