Bobbing Fenders and Fly Screen


NBR founder
Original author is D9

WARNING - do not read or view this post further if you are offended or upset by the sight of scooters, messy *****-filled garages, the mundane trappings of suburbia, or eccentric Bonneville owners with sharp tools.

Below are some pics taken while bobbing fenders & Flyscreen. No pics of rear fender, but it was done the same way as the front.

Tools are what you see - nothing special. The narrow-handled extension on the Dremel really allowed delicacy during the cutting maneuvers - highly recommend it. BTW, don't even THINK about getting anywhere near a Dremel without total eye protection - full goggles.

The cutting wheels used are the fiberglass reinforced type, approx 1". The wheel used to bob the Flyscreen was slightly larger, about 1 1/4" diameter.

Also recommend high quality 1/4" masking tape from any automotive paint supplier - it really helps to have a re-positional tape that allows smooth curve contouring, makes it easier to get the shapes smooth.

No marking or drawing was required; instead all "lines" were formed and refined with the tape - which also served as an essential high contrast visual guide while cutting. For the symmetry-challenged, one could easily make a simple paper template and use that as a tape guide. I did use a piece of tape or two, applied horizontally, to check for symmetry. Once the tape was giving me exactly the curve I wanted, it was pressed firmly in place.

The cutting "line" is on one edge of the tape, depending on where you want your curve to begin and end.

After positioning and repositioning, eyeballing, checking, and finally burnishing down the tape, safety goggles on, cutting wheel mounted securely, I started in with the dremel at highest rpm setting, moving very slowly, back and forth about an inch at a time, until a reasonably consistent groove was slotted all the way across the fender, then kept making smooth, light, back and forth passes until the wheel started to cut through. Care is required as the wheel begins to cut all the way through, as it tends to grab edges and jump. As seen in the photos, two hands are used at all times to cut and brace the tool.

After cut-through was complete, I used fine metal files to smooth the path, remove any ragged metal, and contour edges and just worked until I was satisfied with it and the edge felt reasonably close to the painted factory edge. With medium or dark colored fenders, it helps to
put a white piece of paper behind the fender to help fine-tune the curve, as the paper will help you to see any roughness or unevenness.

I purchased a small bottle of touch-up color at a local auto parts store - not a perfect match, but I'm only intending to brush about a scant 1/32" on the edge of the fender. I used PPG DX330 as surface prep/area degreaser prior to painting.

Taped the mask line for the touch up, shook the bottle, and brushed away, let dry for an hour, brushed on another coat, done.

To bob the inboard edge (engine side) of the front fender, I first removed the four bolts securing the fender to the fork, removed the fender, turned it around, bolted two of the four fork bolts back in place, pushed a piece of wood between the tire and the underside of the fender to help reduce excess movement and vibration, then proceeded again to cutting with the Dremel. Certainly could have done something different to hold the fender, but this worked well, and it was all right there, so that's what I did. I did let most of the air out of the front tire to allow easier removal and replacement of the bolts that secure the fender to the fork.

I seriously considered removing the chrome fender stays, but decided to leave them on for now - plenty of material left if I decide to take off more later.

Flyscreen was handled the same way - on the bike, with care. After cutting, rather than filing, I sanded down and smoothed the edge with wet 220 grit automotive sandpaper on a rubber block - once again, just slowly working it to a smooth, even edge that feels good to the fingers. Probably should gently wet sand again with some 400 grit prior to painting, although the edge pretty much disappears as the Flyscreen is made of black plastic.

Overall, the changes are subtle but pleasing to me. The bobbed Flyscreen IMHO is an especially nice mod - I don't have a good pic of it yet. Overall I'd say the bike looks slightly leaner and cleaner, somehow lighter on it's feet - or rather, tires.

I'd highly recommend practicing a bit on a piece of 1/16" steel, whether or not you've worked with a Dremel previously, to get a feel for material resistance and feed rate while using the cutting wheel. And again - wear full coverage eye protection - the Dremel really throws off a lot of debris at an impressive velocity.


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NBR founder
I got a bit more involved in the planning phase this time since the front fender stays were to be removed and the tip of the front fender needed to gracefully extend past the point where the bracket holes on the fender had been. Those parameters determined to some extent how the curve would be shaped, but there was still some fine-tuning to do, so I decided this time to make a couple of paper templates to use as a rough shaping guide.

The front fender, measured across the contour of its width, is about 6" wide, and what was needed was a shape - maybe a half oval - that smoothly blended into the edges of the fender. So the night before, after drawing and experimenting with several ovals and ovoid shapes and bisecting and manipulating curves (my tool of choice at this phase wasn't a dremel, but a Mac) I ended up with a couple of approximate half ovals that might work. Printed them out, cut the half ovals out of paper, went out in the garage and just held them in place on the fender, and was able to get a better idea of what looked good. This gave a good jumping off point the following morning.

Still, we ended up doing quite a bit of taping, standing back and just looking, adjusting, stepping back again, adjusting again, walking around the bike and viewing it from all sides and from different angles, including sitting on the bike, leaning over the headlight and looking down - just considering how the curves worked or didn't work, what the relationship of the fender shapes would be to the rest of the shapes on the bike, to the forks, to the frame down-tubes behind the fender, how highlights and shadows would change. We briefly considered bobbing the inboard (engine side) of the font fender to just parallel with the down tube, but for some reason it just didn't look quite right, nor did it look right to do a symmetrical, equidistant bob (same fender length out from fender bolts) - it looked too severe. We pretty much just experimented until the right shapes materialized - so while the template helped, much adjustment took place anyway, and for the rear fender as well.

After all was said and done, Lox ended up with a unique and noticeably different look than what I ended up with on my bike.

My advice to other DIY'ers after having done this twice is - take your time and enjoy the process of designing the fender shapes you want to end up with on your bike, and don't hesitate to get a second set of eyes on it before you start cutting. Good luck!