Hello Everybody, I've had these picture up for a couple weeks now, so
I guess I'd better add some text to let you know what you are looking at,
highlight the points of interest so to speak.
This is me with the finished product. The bike is 1974 Rokon MX 340 C, the "C" stands for Cobra. I'm told that there were between 60 and 70 of these bikes made, mine is Number 31, it has a cool plate with the "31" rivet to the frame, you can see it in the picture below, it's just in front of the gas tank. I have a close up of it that I post later.
The engine on this bike is not the Cobra engine, it is off of a RT 340. I thought it would be a good idea to start out my return to Motocross racing, after a 25 year plus absents, with milder tuned engine than the orginial Cobra engine. I took this option as a matter of self preservation. If I get really into racing, I'll rebuild the Cobra engine later.
The other major non-stock component is the swing arm, this is also off of an RT 340. I choose this option to comply with the AHRMA rule that states the rear suspension travel cannot exceed 4", even it the orginal model came with longer travel suspension. The Cobra swing arm has vertically mounted shocks that attach about midway between the rear axle and the swing arm pivot. I picked up a pair of Koni shocks that had the same part number as the orginal shocks, but over the years the spec's have changed. The bodies are now chrome, the orginal were black. Due to change is the top eye assembly the springs a different, larger diameter, so I had to get new springs too.
The seat was ripped so I had that recovered locally. I redid the the brake lines with stainless steel braided hose and cover them with clear tubing, not exactly period, although available at the time, but they work a lot better. I also got a pair of K&N bars and one of those 90 deg. twist grips at swap meet. Other than that I think the rest is stock Cobra parts. Oh yeah, I almost forgot the creative plumbing on the rear caliper is due to the new shock location on the swing arm.
I was hopeing to take the bike to the AHRMA Regional MX in Indy on June 26, but it doesn't look like things are going to work. The bike first outting will probably be Mid-Ohio Vintage Motorcycle Days. I had a great time putting the bike together, maybe I'll find another project at Mid-Ohio.