Unsafe Tricks Performed By Some Custom Bike Builders - Tech Matters

Dumb and Dumber
One afternoon, associate editor Cherney and I were discussing some of the finer points of motorcycle design when I mentioned something called a "five-finger rake." For those of you unfamiliar with the term, a five-finger rake refers to the old chopper builder's trick of slicing away a portion of the steering head where it joins the frame then bending it upward to increase the rake. Rather than resort to anything as sophisticated as a tape measure, protractor or frame-alignment jig, backyard customizers would just pry up the steering head until they could insert some number of their fingers into the gap. A five-finger job was pretty extreme, especially since a lot of guys used nothing more than Kentucky Windage to align everything before stitching it all back together. To say the bulk of them were crudely done and dangerous to ride is like saying the war in Iraq hasn't quite gone like we planned.

Cherney commented that the five-finger method was one of the dumbest things he'd ever heard of, and I'd have to agree. However, as I began to recount some of the dumb things custom builders used to do, as opposed to some of the silly things they do now, I realized it was only one of many.

Consider the infamous slug. Slugs were pieces of threaded pipe, typically 2, 4 or 6 inches long, that were used to increase the length of a fork tube with as little effort as possible. The concept was as simplistic as the execution. Essentially, the fork cap was removed, the slug inserted in its place, and just like that, you had an extended fork. You could then slide the tubes down in the triple clamp for that boss custom look.

The only hair in the soup was that while the lower portion of the steering stem had a firm grip on the fork tube, the top clamp had only a loose hold on the slug. This left the majority of the fork's length unsupported. When the inevitable fork-tube flex occurred, the threaded, unsupported joint between the slug and fork tube acted as a hinge. As you can imagine, the end result was both predictable and unpleasant. Once that fork snapped, and quite a few of them did, the rider was at the mercy of the fates. If he got lucky, he might ride it out or at least get to count the holes in the ambulance's roof liner on his way to the emergency room. If not

Another dumb idea was the rediscovery of the plunger-style frame in the late '60s. The plunger frame was a detour on the road between the rigid frame of the pre-WWII era and the twin shock swingarm frame that replaced it. In the plunger design, there is no pivoting rear fork. Instead, spring boxes are positioned in stirrups welded to the rear frame loop. The rear axle is carried in an eyelet mounted in the middle of the spring box. This arrangement allows the rear wheel to move a limited distance in each direction, which provides some rear suspension. The manufacturers liked the plunger design because it could be readily-read that as cheaply-adapted to existing stocks of rigid frames.

The problem was that the plunger was a flawed design right from the start. First, the basic design destroyed what had been the rigid frame's strong point, namely freedom from flex. Second, it allowed the rear wheel to twist sideways as it rose and fell. And third, because the rear wheel traveled in a straight line rather than in an arc, as it does with a swinging arm, the chain tension varied greatly at the limits of its travel. After a few short years the OEM manufacturers discarded the plunger idea in favor of the far superior swingarm. Why some customizers thought the plunger idea was worth re-exploring a few decades later has always mystified me.

The aptly named "suicide" clutch never made a whole lot of sense to me either. As a kid, I owned an old tank shift Harley, and being an avid old bike fan, I've ridden plenty of hand-shifted bikes since.

As conceived, a foot clutch wasn't a terrible idea. Unlike an automobile's clutch pedal, a motorcycle-style foot clutch normally uses some sort of friction device to keep the pedal positioned where you want it. This makes it easy to control and allows you to hold it partially engaged if need be when creeping along in heavy traffic. Old-time racers removed the friction damper from the clutch pedal so it'd spring up when they released it to allow for faster starts. Why anyone thought that was a good thing for street use puzzles me, especially when it's generally used with a hand-operated "jockey" shift located behind the rider.

So many dumb ideas, so little space, and I've used it all up without even scratching the surface. But fear not, I'm sure we'll be addressing this topic again.