That Ď70s Bike: Rokon VMX Bike Build, Part 2
When we left off last month the Rokon RT2 project was coming along. It helps to have a solid base to build from, and this particular Rokon was definitely a good resto-racer candidate!
The forks were taken apart and cleaned. It was a simple enough task with the 8-inch travel Betor Forks, but cleanup took a while since what oil was left in them had long since turned to a puddle of muck. The left fork tube was also out of true, so we had Titan Racing (http://titanracingworld.com/) repair it in their press. The now straight forks were reassembled with new seals and filled with 15WT oil to 5.5 inches from the top of the tubes as a starting point for future tuning.
While the front end was apart, the steering head bearings were serviced and a new set of Renthal Vintage Bend handlebars from Vintage Parts 4U (http://www.vintageparts4u.com/) were installed.
Buchananís Spokes and Rim (http://www.buchananspokes.net/) provided a set of custom, stainless-steel spokes for the Rokon based on samples Iíd sent in. Turnaround time was quick. The new spokes fit perfectly and they even came with assembly lube! We now had a presentable, and strong, set of wheels. At some point Iíll lace up new rims, but for now the originals are just fine.
The Rokonís rims used sharp pins to keep the tire from slipping on the rim. I donít know if that method works well or not, so I removed the pins and went with normal rim locks instead.
DC Plastics (http://www.dcvmx.com/index.htm) provided perfect fitting reproduction Preston Petty fenders, along with number plates and plate graphics. Our Rokon was starting to look smart!
The front brake hose guide was made from a bicycle reflector bracket Ė it looks good and works perfectly. After this photo was taken, I adapted a Teflon inner sleeve to the guide to make it work better yet! The patriotic U.S flag stickers came from the local corner store.
The completed front end looks slick! Some things are weird though, like Rokonís decision not to use a normal axle nut but instead rely only on the fork pinch bolts to hold the axle in place. It doesnít seem too rigid, especially by modern standards. Iím guessing it was designed that way to speed tire changes and to give the front disc a chance to float a little, but it will be interesting to see how these forks actually work.
Mike Murphyís Rokon Renew (you can email Mike at firstname.lastname@example.org ) has the biggest selection of NOS Rokon parts going. He found a brand new Rokon MX gas tank, which is not only much better ergonomically but also looks a thousand times better!
Rokon Renew also supplied NOS Rokon 1976 bicentennial graphics. This bike was starting to look really cool now! In fact, the biggest slowdown to the build was becoming the steady stream of curious friends coming over to check the bike out! Along with the new gas tank and graphics, I also installed a new airbox to carburetor airboot, replacing the dried-out original that was questionable at best.
Everyone said to ditch the giant, restrictive and heavy stock muffler and install a modern aluminum silencer. Iíve seen lots of bikes at vintage races like that, but to me it looks awful. Instead I had Titan Racing modify an old DG steel body motocross muffler to fit neatly onto the stock expansion chamber and bolt to the stock pipe mounts without any cheesy looking ďone size fits allĒ brackets. While they were at it, they also blew a few dents out of the lower portion of the exhaust.
My original goal was to have the bike ready to race at the Gopher Dunes Sandstorm VMX race. As the deadline approached it became obvious that wasnít gonna happen. The bike runs fine now but little things keep popping up, like repairing a leaky gear reduction box seal. I also discovered the rear-tire-to-chain clearance was minimal after installing first a 120/90/18 tire, then a 110/100/18 and finally a scrawny 100/100/18 like I use on my 175 Can-Am. At least now Iíve got a couple spare tires for my 450 Ö Anyway, after adjusting the dish on the rear rim slightly to pull the wheel to the left a few thou the chain clearance was acceptable, but the chain and sprockets still needed to be replaced.
I had a Rokon trailer queen for Gopher Dunes, but at least the Can-Am was ready to race. I couldnít resist the urge to take a photo of my three http://www.off-road.com/ project bikes together. The 8.5-inch travel Rokon towers over the 4-inch travel Can-Am, and in fact it sits taller than my stock height 450 Suzuki. My backbone tells me the Rokon weighs about the same or slightly less than the 450 to lift onto a bike stand.
At the track the Rokon attracted a steady stream of attention, and with the help of Rokon Tom Canellos I answered about a zillion questions. It wasnít the prettiest bike in the vintage bike display, but it still looked great and was definitely the most unique motorcycle there! A few people have been pestering me to buy it, but sorry folks, itís not for sale. I built this bike to race and Iím sticking to that plan!
The other Rokon at Sandstorm was the í75 MX340 of Thomas Canellos. He literally flew around the track, running in the top-five until his Comet primary clutch blew apart. It was a bummer because we really hoped at least one Rokon would be on the podium!
Since weíre heading into the bicentennial anniversary of the War of 1812, I couldnít resist sharing this photo of Rokon Tom on his American-made Rokon and me on my Canadian-made Can-Am battling it out in Ďshort travelí moto-one at Gopher Dunes Sandstorm!
So hereís where we are now. Vintage Parts 4U is getting sprockets made for the Rokon as we speak. I need to address a few small issues; for example, the rear brake master cylinder, which has mysteriously decided to start leaking, need repair. The snow is almost ready to fly here, so Iíll keep picking away at little things over the winter and hopefully have the Rokon ready to race at our second-annual indoor vintage arenacross this winter.
Iíve got more go-fast stuff coming for the Can-Am project too, and the Suzuki RMX 450 project will be on a quest for power prior to getting converted over for ice racing this winter. Stay tuned, because thereís plenty of neat stuff coming up!