Q: I recently switched to a larger tire in front, which caused my front end to be slightly higher than the rear. I have a set of Progressive Suspension springs up front. When I installed the springs, I had to cut the stock spacers down to Progressive’s specified length. Can I take a little more off the spacers to lower my front end, or will that compromise the handling?

Donna
New York

A: If you’re trying to compensate for a slightly taller front tire, lowering the front of your motorcycle by shortening the fork spring preload spacers is a good approach. The reduction in spring preload will lower the front ride height and will reduce the overall stiffness in the front suspension.

I recommend cutting the spacers down .25" at a time until you achieve the front ride height you’re looking for. Once you have the height you want, test ride the motorcycle. As I said, this modification will slightly soften the front suspension, so if excessive front-end dive or bottoming occurs, you’ll want to increase the spacer length to boost the stiffness. Basically, you’re looking for a reasonable compromise between ride comfort and ride height.

I recommend using a Schedule 40 PVC irrigation pipe as spacer material if you need to make new spacers. Use the size (.5", .75", 1", or 1.25") that’s closest to matching the outer diameter of your stock spacers or fork springs. Also, be sure to use the appropriate size washers between the spacers and springs, as well as between the spacers and fork caps.

Scott Hodgson
Progressive Suspension

Q: I have an ’02 Yamaha RS Warrior, and I tend to ride long distances in hot climates. I’d like to help my air-cooled engine by using a synthetic oil called Duralube, which has heat-dissipating properties. My question is, can this high-viscosity oil negatively affect my hydraulic clutch?

John Serrano
California

A: Oil choice is always a hot-button question, so I’m going to avoid the usual “My oil is better than your oil” diatribe. And I’ll start by clarifying one thing: you don’t have a hydraulic clutch — you have a wet mechanical clutch that’s hydraulically actuated.

Motorcycle clutches come in two varieties: wet, where the clutch plates are bathed in oil, and dry, where they’re exposed to the air. These clutches are actuated either with a cable (mechanical actuation) or with a hydraulic system consisting of a master cylinder at the lever, a high-pressure hose, and a slave cylinder at the clutch. This system works just like a brake system, using a hydraulic fluid (usually brake fluid) to transmit the force and movement to operate the clutch. So, the oil you’re asking about has nothing to do with the hydraulic part of your clutch. But it has a lot to do with how your clutch transmits the engine’s torque to the transmission.

One other clarification: synthetic oils have greater film strength and a more consistent viscosity with temperature changes, and they’re more stable over time. However, synthetics usually have a lower viscosity than petroleum-based oils.

I’d recommend using a synthetic oil in nearly all cases, but only a synthetic that has been specifically tested and recommended by the manufacturer for motorcycle use. Auto-mobiles don’t use wet clutches, and it’s possible (but not likely) that an automobile oil may not be compatible with a wet clutch and could cause slipping or sticking. Look at brands like Motul, Bel Rey, and Castrol, or OEM products formulated specifically for bikes. You’ll probably experience smoother shifting, easier cold starting, and, as you correctly suspected, cooler engine temps.

Doug Meyer

Editor’s Note: Doug Meyer recently left Muzzys Performance Products, moving on to messing with fast airplanes. Doug spent 40 years working on everything from 700-hp Can Am sports cars to 500-hp turbocharged dragbikes, and has held 16 Bonneville motorcycle land speed records.

A: The engine oil and the hydraulic fluid used in the clutch release mechanism do not come into contact with each other. So, an additive like Duralube wouldn’t affect the hydraulic clutch in any way. The engine oil is another matter; some additives may cause the clutch to slip as they do share the same oil. If you don’t want to experiment, stay with the Yamalube product designed for your motorcycle.

Nigel Patrick
Patrick Racing

A: Motorcycles that share their engine oil with the transmission and clutch are sensitive to oil types. In cases like this, it’s very important that the oil be formulated for use in motorcycles.

Oil companies that specialize in motorcycle engine oil are keenly aware of wet clutches. These oils are formulated to fully protect engine internals without working against, or creating, a slipping clutch. Of course, while synthetic oils and blends come highly recommended, it’s just as important that the oil be designed for motorcycle use. Buying an automotive-type oil off the shelf at a local auto parts store is usually a bad choice.

Robert Popiel
Aprilia

Editor’s Note: We checked with Duralube to get an official statement regarding use of the product in motorcycles. Here’s the company’s response: “Duralube Engine Oil Treatment is only suggested to be used in motorcycles that DO NOT utilize a wet clutch.” RB