Advanced Bike Building Tips From Donnie Smith

Editor's Note: This is a chapter out of a recent Wolfgang book by Tim Remus. It's an amazing chapter. You get to see a Donnie Smith Bike from start to finish. I learned a lot. If you want more, there's info at the end on ordering the book or click on any Wolfgang banner to reach their library of tech books.–Wrench

When it comes to building beautiful, functional motorcycles, there are very few bike builders with the experience, class and attention to detail displayed by Donnie Smith and crew. Built for Larry Page from Richmond, Virginia, the bike seen here started as a hardtail frame from Frank at Motorcycle Works in Olathe, Kansas.

Built by Motorcycle Works in Olathe, Kansas, this very strong drop-seat style frame is the foundation for the whole project. The frame, and the sheet metal, determine the profile of the motorcycle. The front end is from Perse, and initially came a little too long for this particular project.

This particular frame is a long one , with 5 inches of stretch and a 42 degree rake angle. The rear section is wide enough to accommodate an Avon 300-35 rear tire and retain the 1-1/2 inch belt drive. The other end of the bike runs a slim 21-90/90, also from, Avon. Both tires mount to PM Contour wheels. The motor is a 124 inch Twin Cam from S&S connected to a Baker right-side-drive transmission. To avoid surprises later, the mock up is done with the real engine and transmission.

Power is provided by a 124 inch Twin Cam engine from S&S. Bolted on behind is a six-speed, right side drive dyna-style transmission from Baker.

As delivered, the frame comes with the rear tranny mount well supported….

Getting Started

Rob Roehl, longtime employee at Donnie’s shop and the man responsible for the mock up and fabrication of this bike, starts by building in a new battery box. This frame is designed to have the battery box located above the tranny mount. Rob and Donnie have decided however, to build in a nice neat, hidden battery box behind the mount. Building the box means cutting out the existing supports for the transmission mount, (note the before and after photos). As Rob explains, “With the supports out of the way, I can build a battery box, once I have that done I will box-in new supports for the transmission.”

…but Rob cuts out the supports for the mount in order to locate the battery just behind the mount.

Rob cut out the bottom tube and made the tray. Then he made small tabs, threaded and welded to the bottom of the frame, that the tray bolts to.

To make room for the new battery and tray, Rob cut one tube out of the bottom of the frame, “the tube we left in still provides lots of strength,” explains Rob. “And the boxing plates add strength too. On the bikes with a 145 inch engine I won’t cut out that other bottom tube, for reasons of strength.”

The cover will be part of the whole box, which will bolt in as a complete unit once it’s done.

Small threaded tabs are welded to the frame so the battery tray can bolt in from underneath.

Seat pan is finished, formed from 14 gauge cold rolled steel. Rob has already started working on the tunnel for the tank.

Form a Gas Tank from Scratch

Once the battery box is finished, Rob can move on to the biggest single piece of fabrication that will be done on this bike, the creation of the hand built gas tank.

“I’m trying something new with this tank,” explains Rob. “I made the tunnel first, and I’m going to work without a sketch. I will get the basic shape going and then refine it.” The shape is modeled after an old Sportster tank, what they used to call the Elvis tank. The first step is to cut out the top of the tank a little oversize. The tunnel is made from 14 gauge steel, though the rest of the tank is 16 gauge.

Rob made the runnel for the tank first, and will form the top panel to match his idea for the shape, and to match the length of the tunnel.

Rob used his bead roller to put a lip in the outer edge of the tank bottom.

As Rob explains, “by doing it this way I can do the mounts before the shell goes on. The bottom seam should be the last thing I do, and because I used an edge roller on the edge of the bottom, it has a lot of strength there, so there should be no movement or warpage when I weld up that seam.”

The mock up needs to be as complete as possible, including the location of all major electrical components and how the wires will be routed.

Rob designed the bike so the electronics mount under the seat. “I will run the plug wires up through the frame, and then down to the cylinders. The circuit breakers will mount on the same plate the ignition module mounts to, the wires can run down the frame tubes. Small tubes at the back of the frame support the fender, then I will probably fill in the areas between the fender and the frame (at the front of the rear fender).”

Metal Work, Shape the Tank Top

After cutting out a piece of 16 gauge cold rolled steel, Rob uses the power hammer to do the initial shaping. “Basically I’m stretching the metal,” explains Rob. Next, he moves to the English wheel, “I start with a pretty aggressive wheel, so it’s going to raise the crown pretty fast. The wheel will also smooth out the lumps from the power hammer.”

Most of the shaping for the tank top is done with the power hammer.

This is essentially a stretching operation, more crown means more time spent on that area with the power hammer.

These are the basic stretching dies Rob uses for projects like the tank top (shrinking dies are available as well).

The English wheel is another stretching operation, one done by squeezing the metal between two wheels. Rob patiently runs the tank top back and forth through the wheels to raise metal through the center of the tank. To raise the metal more the short way, Rob turns the top 90 degrees and begins a series of back and forth motions.

A variety of lower wheels are available, this mildly crowned roller is Rob’s choice for much of the early wheel work.

Next, he takes the top of the tank and shapes it by hand. Then it’s back to the English wheel with a flatter, lower wheel. “I want to get more shape the short way so I change to a less aggressive wheel. The first wheel was so aggressive it almost left grooves in the metal so I’m using the flatter wheel running the short way to get rid of that and add some shape, pretty soon I will pull it out and evaluate my shape.”

This close up shows the lip Rob put on the edge of the tank bottom, which adds strength to the edge and will prevent warpage when that seam is welded later.

It’s important to take frequent breaks to evaluate the shape as it progresses.

Sometimes there’s no better tool than a strong back and a pair of willing hands.

Rob often uses the slap hammer to roll and edge.

The leather face on he slap hammer means the tool leaves the metal unmarked.

“Now I want to create a little more shape at the edges with the slap hammer and the dolly. I’m just trying to add shape, I can deal with the puckers later. The slap hammer is nice because it doesn’t dent anything, and with the leather face, it doesn’t even mark the metal.”

Rob has the top formed, as well as the tunnel, the two are tack-welded together. Time now to make the side panels…

…which start as pieces of light board cut to size…

Once Rob is finished rolling out the top, he trims it pretty much to size and tack welds it to the tunnel, which is already fabricated. “I don’t finish weld till I’m right at the end,” explains Rob, “just a couple of little tacks will hold the top and tunnel together.”

…the panels are then cut out of 16 gauge steel, rolled out over a big piece of pipe for the initial shape and then run through the English wheel.

Tank Side Panels

For the side panels, Rob takes poster board, makes templates and then cuts the panels out of steel. To do the initial shaping, Rob rolls the panel over a piece of pipe, then does a bit of work with the ‘wheel. Not entirely happy with the shape, Rob rolls the edges with a hammer and dolly and then runs the panel through the wheel again.

With the help of a ruler, you can see how the side panel is crowned in both directions.

A body hammer and home-made anvil are used to roll the edges of the side panels.

Before welding the side panel to the top and bottom, Rob needs to trim it to size. “A lot of times I tape a panel to the other parts and then do the trimming, it means I don’t have to have so many hands. Once the trimming is done, I’m going to work on the side seam, tack weld it, then drop out the tunnel and work at finishing the seam. The bottom seam will be done last. The hardest part of making the side panels is getting them both the same.”

Note the way a putty knife is used to prevent one panel form sliding over or under the other, welder is set at 80 amps DC for the tack welding.

Tack Welding

“The most important thing to remember during the tacking process is to keep the joints butted together and not overlapped. I can close up the gaps later but if you overlap the joint you never get that out of it. The seam is so strong at that one point that you can’t hammer it or shape it.”

Rob does a bit of work on the seam as he moves along with the tack welding.

“At this point the bottom seam looks a little uneven but all that will pull in when I do the welding. Now I’m going to cut the tack welds and drop out the tunnel. Once I separate the top of the tank from the tunnel I can work both sides of the seam with hammer and dolly and slapper.”

Tack welds are spaced evenly…

In one area the seam is low, so Rob rolls the top of the tank over and raises the metal from the back side. “Once I’ve got the seam pretty even I can come in and fill in some of my tacks.”

This is the bull’s eye pick as described in the text, it’s kind of a pick and dolly all in one, good for raising small areas.

The true beauty of Rob’s plan is the ease with which he can get at the back side of the seam to correct a low spot before final welding begins.

There’s a little overlap at the front of the seam, Rob tries the bull’s eye pick, then a little work with a hammer working over a stationary dolly. “It raised the low part of the seam considerably. If it had been any worse than this I would have had to cut the tack welds.” The seam is looking pretty good now so Rob starts in on the final welding.

Rob does the final welding with 70 S2 rods, 1/16th inch diameter, “I pick the size of the rod by the gap I have to fill.”

In the hands of a craftsman, the tig welder leaves a very neat seam with a small heat-affected-zone. The final welding isn’t done all at once, because too much heat would likely cause warpage. Instead, it’s done in sections… …with time to work the seam, and let it cool, in between welding. …with time to work the seam, and let it cool, in between welding.

Though a heavier gauge of steel is harder to work, it also means Rob can use a sander on the seam without any danger of over-thinning the metal.

”I do an inch and a half of the seam, then stop, look at it, let it cool a little bit, and go back. I don’t find much advantage in doing a lot of work on the seam with a hammer and dolly as I go. This seam has a lot of strength because of the shape, and I have it fitting good right from the start, so I can just go over it with a small grinder later.

The test fit shows a very nicely curved tank with all the lines converging at the back.

After a little metal-finishing the tank hardly needs any filler.

With the side seam finished, Rob can weld the bottom, or tunnel, into the tank. As mentioned earlier, this seam is easier to weld without much warpage because both edges have a little shape right where they meet.

This boxed structure under the top tube will add strength to the frame and also form an external “bottom” to the gas tank.

The Boxed Structure

“I’m going to make this boxed structure under the top tube, which will help to stiffen the frame, and also give me a good place to put the front mount. In the rear I will use a regular T-mount.”

Once he’s happy with the fitment of the tank and the boxed structure, Rob marks the location of the front tank mount.

The box is made from 1/8th inch plate. As Rob explains, “The boxed section also makes a very nice ‘bottom’ for the gas tank and gives it a finished look. The fitment of the box and tank are critical. I always spend a good bit of time fine tuning the position of the boxed section and the tank.”

Now Rob tack welds the box to the top tube. Small panels still have to be added at the front of the box to close it in. Rob spends a lot of time ensuring that the tank and the inner box line up exactly at the front of the tank before starting the final welding of the boxed section. As is usual, he does the welds in short stitches. After two stitches he uses the slap hammer to adjust the position of the box slightly and then goes back to welding.

The bottom with the two mounts areas cut out and ready for mounts.

The boxed structure is finished and adjusted slightly to match the bottom of the tank, the tank itself is ready for mounts. Note, the rear mount is already cut out, the photos show Rob cutting out the bottom of the tank where the front mount will be installed. After the holes are cut Rob does a test fit then trims the holes with a mini-belt sander. “This is also the optimum time to eliminate all the pieces and grit from the tank,” explains Rob.

But first Rob trims the holes for a perfect fit with his mini belt sander.

Before welding, note the nice flush fit and the minimal gap between the tank and the mounts.

“I always weld the mounts in as one piece,” explains Rob, “and then cut the center out later. That way the tank doesn’t suck in and change dimension when I’m welding. I set the welder at about 125 amps, because these mounts are heavier, and then during the welding I concentrate the power on the heavier piece and feather it out into the sheet metal.” The welding is done in sections, Rob works on one corner first, then lets it cool and switches to the opposite corner.

Welding starts with a tack weld at each corner.

The center piece is cut out after all the welding is finished and the tank has had a chance to cool off.

Rob lets the tank cool for a good 15 minutes before cutting out the center sections of the mounts. Once the center sections are cut out, the rough edges need to be trimmed (with the mini-belt grinder again) so they’re flush with the sides of the tunnel. (These mount ‘kits’ are available from Donnie Smith)

…then the tank is dropped on again, and the frame part of the mount is screwed up into place and marked on the lower box structure.

Now Rob does a cut out for the mount.

It’s interesting to note the way Rob uses the big magnets to position the tank so the seams are easy to get at, and the way he uses a small block of steel as a rest for his hand. Note, the rubber pads, these regular Softail tank cushions are used on the frame all through the process so the tank floats and isn’t resting on the top tube.

The tank is carefully positioned on the mount as described in the text.

Now the tank is lifted off and the mount can be final-welded to the frame (rubber mounts are taken off for the final welding sequence).

With the frame mount screwed into place, Rob marks the boxed structure where it needs to be cut. “I’m just going to notch this with the cut-off wheel to match the thickness of the mount.” Now the frame mount is screwed into place with the tank in place also, and two small wooden wedges are pushed into place to hold the tank centered on the boxed structure.

Nearly finished, the flush-mount mounts. “These mounts are pretty heavy, we’ve never had a problem. The front mount is the most important, that’s where all the weight is.”

The frame mount is tack welded in place first, then the wedges are removed. Then the bolts are removed. What’s left is final welding (the rubber cushions are removed before final welding) and the installation of the rear mount for the tank. “We usually wrap the upper tube with foam, that way it won’t set up a buzz when the bike is running.

The custom exhausts pipes start as a pair of these machined collars and a piece of 1-3/4 inch mild steel tubing.

Hand Fabricated Exhaust Pipes

At the Donnie Smith shop, hand-fabricated exhaust pipes start as a set of port collars, as Rob explains, “Johnny (John Galvin) makes them in-house. He cuts them on the lathe and they fit tight. I start from the collars with 1-3/4 inch pipe, then I come out from the port an inch and a half before the pipes turn. I always try to frame the motor with the pipes, the actual layout varies from bike to bike in terms of the angle and the spread. I go from 1-3/4 to 2 inches, then to 2-1/4 inches. In terms of power and runability, that design works well for motors from 80 inches all the way to 124, it will work good on this too.”

“This is 16-gauge tubing, I mark it as shown and then cut it on the band saw. I used to buy the material from Headers by Ed. Different radiuses are available All are mandrel bent, which is important because the process doesn’t crush the pipes. Muffler shops can’t do this and keep the pipe round. Another supplier is SPD in California. Don’t go to a muffler shop and buy aluminized tubing, because it’s hard to weld and hard to chrome. Use good mild steel pipe.”

“I made this little cut gauge because when you cut tubing you have to be sure to cut on the centerline. otherwise it won’t match the pipe you come up against, the curve isn’t round.”

“You have to cut the curves on the centerline, (note the photo on the preceding page). When you cut them like this they stay round, I butt weld them with nothing inside the pipe. Sometimes I figure the layouts by just holding the U-bend up there to see how much angle I need.”

It’s important to clean any burrs off the edges of the pipes before welding.

“I get the head pipes going in the right direction, then I pick one or the other to be my guide pipe. And then I bend the other one around it. On this bike I’m starting with the rear pipe. Sometimes I pull a tape line to check the angle that I want the pipe to follow. The two pipes come out of the head about 8 inches. I try to get them the same length, but sometimes you can’t make them exactly equal.”

Rob starts with two short header pipes that bend inward to “frame the engine.”

Tape lines are used, as shown, to check the line created by the pipes.

“The rear pipe has a U-bend at the bottom that I cut, then a piece of straight, then a little wedge that I cut from another piece of U-bend. Then, using magnets to hold it in place, I slip on a piece of 2-1/4 inch pipe. The nice thing about the step-pipes is the fact that you can slip fit them when you’re doing the mock up. When I weld them up I only leave a quarter-inch extra on the inside.”

Rob tries to make the two pipes the same length, “but it isn’t always possible.”

Small little collars like that shown are often used to smooth the transition from one size pipe to the next.

“The key is cutting it straight and fitting them well. Ron Covell has an excellent video on working with tubing. (available from Wolfgang Publications). There’s really no limit to what you can do if you’re patient.”

The sections slide over one another, which makes the mock up fairly easy.

To make a nice straight cut on a piece of straight pipe, Rob wraps it in light board, then marks the edge as shown.

“To make a straight cut, I cut a 2 inch strip out of poster board, (note the photo) then wrap it around the pipe, that way you always get a straight cut, and if you’re butt welding these the two pieces have to meet really well. To shrink the end down where it meets a smaller pipe, I use an old piece of fork tube and a body hammer, and I just roll the edge, you can shrink it 1/8th inch or more. I roll the edge until it fits snug on the pipe that I’m sliding it over.”

The front pipe runs down at the same angle as the frame downtubes, before turning toward the back of the bike.

Neat cuts make for good butt joints which are easier to weld and easier to polish later.

Robs works the edge of a pipe over an old fork tube in order to reduce the ID for a better fit on the smaller pipe it slides over.

“Then I tack weld them and final weld them with tig. I suppose you can weld with gas or wire-feed but it makes life harder for the polisher.

The end of the mock up session. Both pipes are parallel to each other and to the lower leg of the ‘swingarm.’ “These have nice lines and they’re really not that hard to build.”

I try to use a center mount for good support. Because our little port-collar is flat and machined our pipes don’t move as much as the rolled factory-type pipes do, so we don’t have trouble with the pipes moving after they’re installed. I like to support the front pipe off the cam cover or someplace nearby, but you just can’t on this bike. I did make little brackets that tie the two pipes together, and then there’s the main support off the frame farther back.”

Did we mention the cheerleaders?

“For a heat shield I cut a piece of bigger pipe, and rip it the long way. Then John makes me a little bung or two, and I screw the shields to the bungs with button head Allens, it’s neater and stronger than the way they’re usually mounted with hose clamps.”

Small tabs can be cut out of mild steel, and welded to a pipe wherever a mount is needed. These two will allow the two pipes to be bolted together.

The main support mount comes off a vertical frame tube, ties the two pipes to the frame and to each other.

“You have to be real conscious of where the oil lines or cables are going to run. Usually I run the pipes six inches center to center, sometimes I go to four or maybe bigger for more gentle radiuses. The bigger the radius the harder it is to cut nice and straight. But when the bends are too tight it’s hard to cut and weld them without creating a corner and then that gets hot. We always make our own pipes, it’s part of our signature, the bikes are all hand built.”

“These pipes work pretty well, they cover some of the right side drive stuff, and they follow the line at the back of the ‘swingarm.’

The finished mock up. Even if you aren’t doing a lot of fabrication, the mock up must be complete to minimize trouble later during the actual assembly.

Molding and Final Assembly

Between the end of the mock-up and the beginning of the final assembly, a number of crucial operations take place. For each of these steps Donnie relies on a network of old and trusted allies.

Left side shows the belt drive and the Donnie Smith designed ignition switch housing.

Before final assembly, the whole thing must be blown apart, molded, primed and made readied for paint.

To eliminate all the visible welds, both on the frame and the custom fabricated sheet metal, Donnie calls on his brother Greg, who does the extensive molding work in his small home shop – after doing commercial body work all day long.

Master builder Donnie Smith with his latest creation. One more in a very long line of custom bikes that run as good as they look.

Once the surfaces are flat and ready for primer, everything moves to Paint Works, the paint shop where the Kandy Brandywine from House of Kolor is applied. For the tasteful application of gold leaf and graphics Donnie relies on another local legend, Lenni Schwartz from Krazy Kolors.

Oddly enough, once the paint is finished and the bike gets to Greg Gaspard’s hoist in Donnie’s shop for final assembly, the first thing on the agenda is the elimination of much of that carefully applied paint. As explained elsewhere, the paint on a custom bike is easily .025 inches thick, and in order to ensure the parts don’t loosen later after the paint squeezes out, and to get a good electrical ground, you have to cut out around all the areas where things are bolted to the frame.

Mounting the electrical components is easier as everything was mounted during the mock-up stage. All the wires, even plug wires, route through the frame.

If a components slides, like this caliper bracket, the whole area needs to be stripped of paint and then painted with a single coat of touch-up paint.

As Greg explains, “First I mark it out, then I cut through the paint and sometimes the filler underneath. Then I scrape that area clean with a razor knife.” Greg uses a variety of razor-knife styles to get at all the nooks and crannies on the frame. “Once I have the paint peeled off, I always paint the raw areas with touch up paint so it doesn’t show a white line at the edge and so the area doesn’t rust.”

Gotta clean all those holes.

Wiring

The wiring harness for all Donnie Smith bikes is crafted by hand. Greg, who does all the wiring on this bike, pointed out just a few of the little things he does to prevent trouble later. “The wiring for the headlight comes through the frame (like all the wiring) and then into the headlight bucket. I left the hole in the back of the headlight shell a little too big so the wires can move in the bucket as the fork is turned. And I will cut them so they aren’t any longer than necessary, I like to have the wires lay down nice and neat.”

Here you can see Greg cut the outline of the paint with the point of a razor knife…

…he then uses another flat blade to peel away the paint.

“I will probably have 120 hours putting this bike together,” explains Greg. “How well it goes together depends on how well it was mocked up. If the bike was fully mocked up with the actual engine and the actual belt drive we won’t have any trouble getting things to fit when it comes to the final assembly.”

Twin Cam engines use a substantial ignition harness, which makes hiding all the wires a bit of a challenge.

Greg often uses masking tape to protect the paint in any area where he’s working.

“It really helps to know where the wiring is going and where things like the ignition module are going to be mounted. On an Evo you only have three wires for the ignition, but on a TC you’re got like 18, which makes it much harder to hide the ignition harness.”

Small clamps like that shown are used throughout the bike to ensure neat routing of all the wires and cables.

“A lot of times we polish the little things, little pieces of hardware, during the assembly. It really adds a nice level of detail to the bike.”

Here we can see the belt drive installed (without the cover) and the license plate bracket.

At this point, the bike is nearly done, Greg still has some items to put on, like the carb and the throttle cables, which are made up by hand. And then there’s the battery and starter. Then it’s time to fire it up for the first time. “I usually put the tank on last,” explains Greg. We have a separate tank we can use to do the initial start up. That way I don’t have to take the tank off again if there’s something wrong or something I have to fix right away.

One week later, much is accomplished, like the rear wheel and drive-side rear brake, but there’s still much to do: carb, cables and a lot of wiring.

Details, details, details

As you look over the nearly finished bike, you see the little P-clamps everywhere you look, These are used to keep things out of the way and arranged neatly.

Sometimes called Pro-line, the teflon brake lines are really just a braided stainless line without the braided stainless.

Anywhere a collar or switch mounts to a handlebar with a set screw, Greg drills a little divot in the handlebar so the switch can’t rotate. As Greg explains, “In the case of the switches on the handlebars, if it rotates it might sheer the wires.”

The cool thing about these brake lines is the way they can be heated and bent into a shape that will remain after the line cools.

The plug wires Greg uses are small diameter wires from Accel. Small enough that they can be run up inside the frame. All the wiring is connected with small connectors. This is done to keep everything super neat. Even the three-wire plug on the back of the regulator is replaced with a smaller plug.

The same un-stainless line used for the brakes is used for the hydraulic clutch. Nearly all the lines run inside the frame tubes.

Here Greg does a test fit of the finished gas tank. The tank is one of the last things to go on for good, “we use another tank to start the motor the first few times.”

Finally, the bike is completely done. Because the owner, Larry Page, lives out of town, Donnie and crew take extra time to put some miles on the bike. As Donnie explains, “Larry lives a long way from here and we don’t want him to have any trouble once the bike gets there.

Left side of the finished bike, clean classy and ready to road test once the first Minnesota snowfall melts.

ADVANCED CUSTOM MOTORCYCLE ASSEMBLY AND FABRICATION BY WOLFGANG PUBLISHING–What started in the mid-‘90s when a few people decided to build “stock Softails” from aftermarket parts – because they couldn’t buy one at the dealer – has evolved into a full blown industry. Today, every small town has a Chopper or Custom bike shop and every cable TV channel has a Biker-Build-Off series. No longer content to build copies of stock motorcycles, today’s builder wants a motorcycle that’s longer, lower and sexier than anything approved by a factory design team.

Wolfgang Publications and Timothy Remus were there at the very beginning of the trend with their Ultimate V-Twin Motorcycle book. Today they’re back with their new book, Advanced Custom Motorcycle Assembly & Fabrication. Part catalog, part service manual and part inspiration, this new book offers help with Planning the project, getting the right look and actually assembling that custom bike you’ve dreamed about for years.

Three start-to-finish sequences show not just how the best bikes are bolted together, but how the unique one-off gas tanks are shaped and then covered with candy brandywine paint. With 144 pages and over 400 color photos, this book from Wolfgang Publications and Tim Remus offers the help you need to build your very own custom motorcycle. ISBN: 1-929133-23-5 (with this number you can order at any bookstore)$24.95.

–Jacki Mitchell
Wolfgang Publications
PO Box 223
Stillwater, MN 55082
ORDER LINE: 651-275-0194
OFFICE: 651-275-0198
SALES: 651-275-0143
FAX: 651-439-7052
www.wolfpub.com