4LS to Roadholder Fork (part 4)

A couple weeks back I got another chance to work on this fork conversion. I just never got around to putting the pics up. Things have been hectic lately.

When we left off, we were modifying the fork to work with the original Suzuki axle for this hub. The answer to the bonus question from last round? I’d bushed one fork leg but not yet bored it to allow access to the fork damper retaining screw. Bill Becker was the first to point this out, just minutes after the article was posted. If anyone has an nit-picky eye for detail (and style), it’s him.

This time I modified the axle and related hardware to finish this job.

Here we go.

I was able to mount the fork leg to the milling machine table vertically with just enough room to get the boring head setup. However, there was no way to keep the leg secure enough with it acting as such a long lever and having limited contact where mounted. I then decided to mount an extra vice we had in the welding area to the table with a large angle plate. This allowed me to hang the leg off the side of the table so it could be clamped closer to the work area.

Big old vise mounted to an even bigger angle plate. This setup worked pretty well, even if I did scar up the fork leg a bit. Nothing a little sanding and polishing won't fix.

Leg after bushing has been bored to match existing bore in axle boss. Now you can get the damper retaining screw!

There needs to be a means to secure the axle while tightening down the axle nut. I don’t want to rely on the pinch strength of the boss on the other leg as it seems lame and likely to stress the leg. It also leads to incorrect installation as the last step of securing the wheel is to tighten the pinch (after axle nut is torqued) so that the legs are parallel and not pinched together. I decide to make a small diameter hole in the axle for insertion of a screwdriver or rod to keep it from turning. Old Harley Hydraglide forks use this setup and it works. In our case there is no axle protruding so I made the hole so that it lines up with the damper retaining screw hole under the leg. Hidden. Functional. I did realize afterward that while I intended to drill the larger end, I messed up and did the smaller end. Dammit.

Axle secured in a v-block. Located under the quill using a "wiggler" for drilling.

Axle drilled. Hole is perfectly centered. Drilling on a milling machine is so much easier.

Whole setup assembled. Note the access hole for securing the axle.

I turned down the axle nut to leave room for a lock washer and made up a thick flat washer to spread the clamping force over the original fork material and the new reducing bushing I installed. The washer has a flat ground in it to engage the lower fork casting so it doesn't rotate when tightening.

That’s it for this session. I have to drop some parts off for chrome and polish the lower legs then we can assemble this and ship it home.


4LS to Roadholder Fork (part 3)

Managed to squeeze in one more session last night before heading out for vacation in DR Friday in the wee hours. You know I’ll be thinking about this project next to the pool with a drink in my hand. Can’t turn it off. Ever.

I walked into the shop last night at 8:30p after a 15hr day traveling and working. I was on the lathe making chips by 8:33p.

This is the original Suzuki axle that belongs to the hub/brake. Research showed that most folks used the Norton axle for this modification. Well, I don’t have one. Plus, the Suzuki axle already has the correct dimensions for the bearings, which is an important fit. At the end of last session, with Young Dan and Mika’s input, we came up with a plan to turn down the pinched section of the axle to match the right right fork leg. We also decided to bore and bush the left leg to match the smaller axle diameter and face it off so the brake plate and heavy washer and main nut will have a large uniform engagement area to better handle the increased braking loads and resist deformation.

I didn’t have a suitable piece of steel to make the bushing so I used a piece of bronze bushing stock I found in my scrap bin. I never throw metal away. I’m the type of weirdo that will pick nuts and washers up off the street and pocket them for later deposit in the junk barrel. Don’t laugh. I almost always come up with a suitable piece of material.

Step by step below in pics, as usual. Only had a cell phone last night, so pics are crappy.

Bonus question for the observant: One of the fork legs requires one more machining operation. Be the first to name it and we’ll send you sweatshirt next time we make a batch.

Adios, mi amigos.


Pinch-side fork leg before modification. Note the crack. I don't think it's in a critical area considering most of the load is borne nearer the pinch boss.

Locating the fork leg in the milling table vise is a hassle and takes time to get right. I decided to try a new approach. I made an arbor/fixture out of aluminum such that one side fit the collet and the other a slip-fit in the fork axle boss. Chuck the arbor, install the fork leg and locate the table and vise to the suspended leg. Tighten down and check that the arbor travels freely when you raise and lower the quill. Worked like a charm! Had to set the leg three times last night for various steps and this took a minute each time.

Suspended fork leg on the fixture/arbor made for this purpose.

Boring the axle boss on the mill. This old girl is in such great shape the automatic down-feed and shut-off still work flawlessly. These features are usually broken on old manual mills. I wanted the bushing to have sufficient wall thickness to that it would not deform when pressed in. I also wanted a uniform hole for the press-fit. Otherwise I would not have modified the fork leg.

Continue reading

4LS to Roadholder Fork (part 2)

I’m on a roll here! Three shop sessions in a single week. Feast or famine.

I’ve been thinking this project over in my head every day and considering things I may have overlooked or misunderstood in earlier sessions. That’s the way I work. Constantly confirming observations and reassessing approach. I catch a lot of mistakes and omissions this way. Last night I tested a few initial assumptions with some layout blocks and squares. First, that the protrusion of the fork axle bosses was equal on both sides. It wasn’t. Second, that the hub and brake plates were symmetrical. They are despite different casting features on the speedo drive side. Lastly, that material must be removed symmetrically from fork leg pairs and brake plate pairs. Not true. An artificial constraint. Really, only the total amount of material removed the combination of brake plate and fork on each side must be same (less any symmetry difference in the legs) in order to leave the hub centered in the fork.

This last realization allowed me to save more material around the speedo drive boss and leave it in working condition. There was room to cut the fork back further on the speedo side allowing me to cut back less on the corresponding brake plate. An important finding.

So I got busy after getting home from NYC at 8pm. Getting up for work at 5:30a, traveling to the city to work all day, then driving back to Philadelphia makes for a long day. Didn’t stop me from heading directly to the shop though.

After removing another .110″ from the speedo-side fork leg, I next set about figuring a way to fixture the brake plates in the lathe or mill for final material removal. I preferred to use the lathe if possible as it’d be much easier to ensure the faced surface was perpendicular to the axis of the axle. There was no way to grip the brake plates with my 10″ swing lathe (due to no suitable protrusions, not diameter) so I decided to make an arbor out of some steel round stock, turned down to a press fit in the brake plate sleeve. This worked great. When done, I just pressed the arbor out on the hydraulic press. I also faced off the arbor so that I could use the depth mic to quickly and accurately measure material removed from the brake plates while still fixtured.

It all worked out and I got much more done than expected. The modifications are complete and the hub/brake setup slipped between the fork legs perfectly!

Next step is to modify the axle and fasteners to fit this Suzuki axle to the Norton fork. We came up with a plan late last night. Details in coming installments. After that, design and creation of brake stay straps and a fork brace to run between the fender bosses. Then finally, to polish and paint it all up for a proper appearance on JW’s fine Brit racer.


The mouting arbor pressed into place on the brake plate. Fit is .001" interference. The arbor is shouldered. The plate indicated true once mounted in the lathe chuck.

The machined arbor face used to measure material removed. Using a depth micrometer dropped from the boss (in red) a reading can be taken quickly and accurately.

Removing material on the lathe. Note the steel insert feature on the brake plate.

Continue reading

Square pegs in round holes

Just when I was about to button up the ’64 panhead last week after rewiring and a bunch of other improvements I found the seat pivot boss to be stripped. Dammit. Decided to go to 3/8″ bolt from 5/16 as the tab is not really thick enough for a thread repair and tapping welded areas varies from troublesome to impossible. The original pivot pin is hardened and ground and made out of that incredibly tough metal that Harley used to employ as a matter of course. Carbide wouldn’t put a scratch in it. No way to bore out the original pin.

So I made one out of 660 bronze. Sorry once again, purists. Functional over stock every time, where the latter isn’t available and I’d like to actually ride somewhere.

So the only bronze stock I have is square. No way to hold it in the three-jaw chuck on the lathe. Guess I’ll break out the four-jaw. It’d been a while. Then I figured I take a couple snaps and show how to center a part in the four-jaw chuck. Here it is. . .

A three-jaw chuck is designed to close concentrically on any round or six-sided piece with a single adjuster screw. It is the type most commonly found on lathes and has a million uses. Sometimes though, you have do do offset or square work. The four-jaw chuck has four independently controlled jaws that must each be set when aligning a part as desired.

Here is a chuck I got pretty cheap and rebuilt it. It's been around the block a few times, but who hasn't?

The first step is loosely place your piece in the chuck and get it visually centered by whatever means you like. You can eyeball it, rotate it by hand slowly, use the guide lines on the chuck face or anything else you can come up with. Once the piece is where you like it, snug each jaw, but not too tight as you’ll be making further adjustments.

Square bar loosely in chuck.

Continue reading

They Stopped Making These . . .

Hmmmm. How to make this part fit that part. . . I don’t think smashing it closed and bolting it down will do.

So as I’m leaving to go for a ride a couple weeks ago the kicker on the red & black pan gets stuck in the bottom position and no longer turns the motor. There were no noises or other indications that the shaft had broken, but it did. A number of years ago I fixed this shaft when the threaded boss for the internal gear sheared off. That one was my fault. Sometimes I’m still a gorillla-fist and tighten things too much. I machined off the end and tapped it for a retainer screw and made a thick retainer washer. This fix lasted about five years. Not bad.

At that time I was too stubborn to buy a new shaft as I thought they were too expensive at almost a $100. Well, now you can’t get one at all for any price. I searched pretty thoroughly. Seems they stopped making them. The shaft for this particular kicker has an oversized boss where the arm attaches for increased strength. The arm has an extended length compared to stock, too. The attachment point on this one measures at .788″ where a stock one is closer to .600″. That’s a big difference to cover by fashioning some kind of shims but I imagine it could be done.

I ordered a replacement shaft of stock dimension from the local shop (Riverside Cycles in Phila) and figured I’d come up with an idea for how to make it work shortly. It came to me later that day: Cut the old shaft in two, keeping the oversize arm attachment portion. Cut a perfectly good brand new shaft in two, keeping the internal gear and shaft portion. Weld them together. What makes this job tricky is that the shaft material is extremely hard, tempered and precision ground. You can’t weld at the shaft as you’d have no way to grind it back down to original dims. It’d also probably be weak. I decided to cut them off just behind the arm attachment point, taper them down to a “V” shape to allow deep welds and then clean up the welds back to original size.

Guess there’s no way you can claim to know how to weld if you don’t trust your own work. This application will be good test. You can imagine that there are major forces exerted at the repair point including flex and torsion. I don’t claim to be a welder but I have welded a ton of parts for my bikes and a few others’ that have held up just fine. I know the machine I have very well and can generally be confident in my work. I also have fucked up a bunch of stuff. . . and like to think I learned from it. We’ll see with this one.

I was pleased with how this came out in that at least it looks decent enough. I’ll see if it holds in real life. This kicker is used to start a 93ci shovel/panhead motor with 9:1 compression. Not huge, but no 350 Honda either. I’ll keep you posted.

Let’s get to it. Pics and steps after the jump . . .

Continue reading