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.

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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.

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Using an EZ-Out and Properly Installing a Heli-Coil

Found myself with a free afternoon in the shop today and put some more time in on the Suzuki 4LS hub to Norton Roadholder fork conversion. After pulling all the parts out of the kerosene tank from soaking all week, I started to fix up the fork legs.

The one leg had a broken off stud in the fender mount boss that looked like it’d been there for a while. Rusted in pretty good and a nice jagged break indicating it took a lot of force to snap. Usually that means it’s stuck pretty good. The other leg had a brake stop boss that needed to come off. Got both done today but I’ll save the latter for another article. As the new setup will use these fender mount bosses as brake stay mounts, I thought setting them up for a larger stud (1/4″ – 20) and installing steel thread inserts would be wise.

This article will show you how to remove a broken fastener from a blind hole using what is commonly known as an “EZ-Out” or screw extractor. It will also show how to properly install a helical thread repair insert, or Heli-Coil which is the primary manufacturer of these style inserts. I used a milling machine to do the drilling and tapping for the thread repair, but this certainly isn’t necessary. Since I have one, I’m gonna use it where it helps me. You could just as easily do it with a hand drill in a vice (with a little care) or better yet, in a drill press. Drilling and tapping in a fixed setup like a drill press or milling machine ensures the holes are drilled square and the tap starts correctly.

I’ve heard plenty of people say that helical insert thread repairs are no good or don’t last. Bullshit. When installed correctly (I suspect many that say they don’t work are ham-fisters) they will be stronger and last longer than the original threads. Many manufacturing applications use them as standard equipment, not just for repairs but for new products.

There are sleeve style inserts for thread repairs too. They have strengths and weaknesses just like helical inserts. Some fixes may lend themselves to one or the other, but that’s a subject for another day. Both will perform beyond adequately when installed with care.

I had a great day listening to old blues and gospel music with the early spring sun shining in my workshop window. Just me and an interesting project. Hope you find this helpful.


The first step is to grind or file down the broken screw so you have a nice flat surface to start with. Be careful not to gouge up the surrounding area too much. After it's ground flat, you can center punch the broken screw so the drill will not skip off.

Carefully drill a hole in the center of the broken screw. The largest hole you can drill without going into the surrounding material is best. This serves two purposes: 1) Allows use of a larger screw extractor that can take more force 2) Thins the screw you're attempting to remove, exerting less force on the hole in which it's stuck.

After choosing the extractor that fits the hole you just drilled, place it in the hole and smack it forcefully with a hammer so that it bites into the screw. Be careful not to shift the extractor or put any lateral force on it after you've "set" it into the screw. You can see in the picture how the sharp edges on the extractor bite into the screw and are twisted counter-clockwise such that it grips better as it is turned outward.

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4LS to Roadholder Fork (part 1)

My friend JW is building a traditional British cafe racer from parts he’s been collecting for some time. He has a Norton slimline featherbed frame, a Roadholder fork, and Ariel pre-unit motor and a beautiful hand-shaped aluminum tank. He suggested that documenting the conversion of a Suzuki 4LS brake (four leading shoe) to an early Brit fork might make for a good read. I agree. Let’s do it!

This hub and brake setup is pretty sought-after for its significant stopping power and that it’s not a modern disk. I think they’re worth upwards of a grand, so I’m measuring three times for every cut. Modification is necessary because this hub is over and inch-and-a-half wider than the forks it’s going be used with.

My plan is to remove material from both the brake plate axle supports and the inside fork bosses to make it fit. The original brake stay boss needs to be removed from the fork leg and straps will have to be made to anchor the brake plates to the fender mount bosses on the fork legs. The speedo drive mechanism and associated features on the brake plate will have to be removed and welded in. A new axle will also have to be made once I get the hub fitted up nicely. I’ve decided to no attempt any lightening of this brake/hub (it’s HEAVY) as I don’t really see any opportunity for significant lightening. The internal aluminum webbing could be drilled but how much weight would a few slugs of aluminum save when compared to the four thick iron liners and various steel linkage parts? Not worth it to me. For now, JW agrees. But he’s one to tinker (and do it well) so we’ll see what he does with it after I give it back to him.

First order of business last night was to measure the fork and hub to get the final numbers for use in trimming down this hub.

Using layout dye on my metal bench top to measure the width of the fork at the bosses.

Using a square to ensure leg bosses are perpendicular to the table surface. I then scribed the table at the back of the square on each side and measured the distance between the marks.

The final numbers tell the tale. Having a metal bench top is great for notes and measurements.

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Chris’s Norton mill goes together

Sunday night I met Chris aka Goodwill down at the shop to put his Norton Commando motor together. While he has never built a motor before he has a pretty good mechanical knowledge and I get the pleasure of working with him 5 days a week to answer all his questions. He’s been coming down to the shop on Sundays and tuesdays for a few months quietly working away. Ive been pretty busy with my other projects so I haven’t been paying much attention to what he’s been doing. All his busy work of cleaning bolts, fixing threads, and sorting what goes where paid off on sunday.

He will be running one of those fancy superblend bearings on the drive side an a ball on the timing side to control the crank end float.

Chris heating up the cases to accept the bearing race

Crank has been built up and the rods polished by Classic Cycles in frenchtown NJ, you could comb you beard in the reflection of these things. We put the bearing in the “bearing shrinker” aka shop fridge for a while and sorted a few things out. After sufficient shrinking time Chris fired up the heat gun and heated the cases to install the bearing. It dropped in for install with no hamfistery needed.After that, we used sufficient force to assemble the case halves for a dry run on the end float of the crank and camshaft. 2 or 3 tries later we had the float within acceptable limits on both and were ready to jizz them together.We fitted the halves back together one last time and torqued the bolts to: just tight enough in/lbs, checked it one more time and had a Beer. PERFECT SUNDAY