ARC Factory Tour

Inside The Factory’s Factory

Factory bikes have the coolest components, but who makes those amazing parts? In some cases, it is the manufacturer’s development team, but in other cases the race shops farm out the work, and one of the top men doing that work is Bob Barnett of ARC, the company that invented and manufactures the ARC folding lever. Bob has made factory pieces for most of the supercross/motocross race teams, and we recently spent a day with Bob at his SoCal shop to pick his brain and look over some of his current and past creations.

Linkage

Bob worked with the factory Suzuki effort when Ricky Carmichael came aboard. In perfecting the RM250’s handling for supercross, Bob would get a call each Sunday from Roger DeCoster with new specifications. Bob would then spend the next four days programming, tooling, machining, honing, shot-peening, and anodizing the pieces in time to get them to FedEx by Thursday. The team would get them on Friday and put them on the bike for Saturday’s racing. Bob thinks he had about six hectic weeks like that during the 2005 race season.

Offset Steering Stem Race Cutting Fixture

Bob’s early production of offset races was a long, difficult process. As Bob tells it, “Roger [DeCoster] came to me and he said, ‘We need some offset bearing races,’ and I didn’t know how to make ’em. So I thought about it, and I go, ‘The only way you can do ’em is if you put something exactly on center and have it twist a quarter or a half degree.’ So I made this incredibly accurate fixture, which is probably accurate within two-tenths of a thousandth. That’s 0.0002 of an inch; that’s how accurate this is. And it would take me about two hours to indicate it into the lathe to do the final operation.” Bob’s fixture can cut the offset at either a half or a quarter degree off center and only works for the motorcycle frame it was designed around since steering tubes can vary in length.

Offset Steering Stem Races

Bob’s later offset races were made with a wire EDM machine, a sort of high-precision, slow-speed band saw that uses a wire to dissolve the surface by stripping away the metal at the molecular level. Even then, because the angles needed for these races push the wire EDM’s limits, “I have to take a little drum sander and with my magnifying goggles I do, like, bodywork on it because it has a high spot. So I have to first dress the high spot, and then I have to crosshatch it without hurting the surrounding area to get it so it’s all exactly the same height; otherwise you’re gonna have a lump when you’re steering the thing.”

Offset Triple Clamps

Bob helped dial in James Stewart’s SR250 two-stroke’s handling when Stewart moved up to the premier class. “They knew they wanted to do different offsets just for testing purposes to see what worked better for different conditions. And it would take six to eight weeks to get the drawings generated from Japan, and I go, ‘Guys, just give me the part and the stock drawing, and I’ll figure it out. I’ll stretch it where it needs to be stretched, and I’ll compress it where it needs to be compressed, and I’ll keep the ribs and everything else as the same style of construction, but I’ll make the holes where the forks go in a different location, just what you’re after.’ Therefore I was able to take an existing drawing and an existing part and in two days I’m on the machine making parts for them, whereas if KHI waited to do their normal course of business, it would have been three months before the drawings were made, and then approved, and then they could approve the parts that I was going to make.”

Prototype Factory Item

This is a current item in development for one of the top US factory race teams. We can’t tell you what it is, we can’t tell you what it improves, and we can’t tell you who it’s for, but by the time you read this it’s likely on a factory bike (or three) chasing championships.

Fork Lugs

Broc Helper snapped the front brake caliper mount from his fork lug when a branch or stick wedged between it at the ground during a national. The team called Bob for some beefed-up lugs. With the factory blueprints, he made seven sets of stronger axle lugs out of billet 7075 aluminum. It took eight days, but there was a weekend break between events, so the team had the tougher lugs on the bike for the next race.

Fuel Petcock

When Carmichael went to the Suzuki RM-Z450, the team was having trouble with boiling fuel. They’d wrap the fuel line with heat-resistant insulation, but as the gas passed by the cam tower it still overheated. Bob designed them a new tank petcock for a better location at the rear of the tank to help prevent boiling fuel.

Start Device

Teams often change the fork guard to reposition the start device for different types of dirt. Bob created this two-position device to make the race day go smoother for the Kawasaki factory squad.

Flex Tester

In response to potential production product customers who feel ARC’s Memlon (plastic) levers flex, “I went up to Ryan Villopoto’s factory Kawasaki with my digital fish scale from Bass Pro Shops and measured it. It took 9 pounds of energy to pull in the clutch. So I made the levers have 12 pounds of strength. So if someone says they can feel flex—everything has flex. Push on the window of your house. It has flex, but it still does the job. The levers, yeah, they have flex if you sit there and wrench on them, but that’s not how you ride a motorcycle. Under the conditions that you ride a motorcycle, the levers don’t flex.” Regarding the contact patch for this measuring device, “The puller part is a block that I ground back on one side to simulate a one finger pull, and it’s full width on the other to simulate a two-finger pull, to see if it made any difference on where or how you pulled the lever. It didn’t make any difference.”

Cable Pull Position/Feel

“To accommodate the different riders’ preferences, I made the special levers per the team’s requirements, but then I don’t drill where the cable goes in the lever for the ratio because each rider wants a different feel. Some guys want it like a light switch, some guys want it really progressive, some guys want it to engage really far out, some guys have smaller hands and they need it to engage closer to the handlebar.” Bob also tunes the ratio, designated by the cable end position in millimeters. The larger the number, the more progressive the clutch engagement will be. The smaller the number, the more sharply the power will be transferred to the rear wheel. Factory riders get to pick whatever they want, and Bob carried this choice over to his production levers where customers can pick from a few different ratios. More progressive engagement (the higher numbers) is a huge benefit for getting good starts and what Bob recommends for four-stroke racebikes. For modern bikes, the stock ratio measurements are between 26 to 27mm except for the Suzuki 450, which is 29mm. ARC’s “standard” production lever is set at 27mm. To describe how a rider looking for holeshots would like going with a higher ratio number than stock, Bob says, “They would love it. They would get starts like you wouldn’t believe because it’s like an air-cooled Volkswagen in San Francisco taking off from a stoplight. It’s just smooth, progressive engagement. No burning rubber, no spinning the tire. It lays all the power to the ground because it’s a slow, progressive engagement.”

Production And Soon-To-Be

ARC’s metal folding lever has been on the market since 2000, the Memlon (bendable, shape-memory) plastic lever has been for sale since 2012, and sometime around the summer of 2015 ARC will release its new front-brake assembly that allows for adjustment of position on the bar (more so than a stock brake), reach, progressiveness (with swappable leverage inserts), power (with piston size choice when ordering), and distance from the bar.

Want More?

To check out what ARC has available for sale, to read its warranty, and to see video footage of the levers surviving crashes, go to arclevers.com.