There are thousands of YouTube videos of motorcycle restorations and custom builds on the internet, but I challenge you to find one quite like this doozy from The Junk Man. The video shows Jon Rhodig, a motorcycle repairer from Nebraska, taking two barn-find Kawasaki F9s and turning them into one period-correct motocross hot-rod.
What’s really special about this build is the attention to detail and the sheer bulk of information Rhodig provides. The video above is a mash-up of his five-episode Barn Fresh Restoration series.
The Kawasaki F9 is a 350 cc rotary-valve motocross bike from 1973 which Rhodig says was a “lackadaisical enduro” out of the box. Rather than build a factory-stock restoration, Rhodig took the approach that a budget-conscious amateur racer might have taken in the early 70s, and attempted to turn his F9 into a replica of the F81M and F21M 238 Green Streak racers of the same era. One of his two donor bikes already had an aftermarket expansion chamber fitted, which inspired the different approach.
By the end, Rhodig has himself a beast of a vintage MX bike that can contend with the best machines at most vintage events. The aftermarket part list includes plastic fenders from mid-70s KXs, KX high-bend aluminum handlebars, and a petcock from a Harley-Davidson Sportster.
There are also, of course, a lot of internal engine mods. For example, the cylinder has been ported and port matched. Rhodig did use the Bassani after-market expansion chamber on the final build and added a hand-build carburetor cover screen that mimics the one from the F81M. Unfortunately, the kick-starter broke late in the build and so you can’t hear it running in this video.
The oil tank has been retained even though the two-stroke motor is now fed with pre-mix. Rhodig says the F5 Speed Kit manual advocates this approach because the oil pump lubricates the main bearing. The intake feed line is blocked, and the cable disconnected so that only a small amount of oil is being used to lubricate the main bearing at idle-speed rate.
Like every other lunatic who loves playing with vintage, small-displacement motorbikes Rhodig can’t stop thinking of ways to tinker, tamper, and alter the bike even now it’s finished.
This is a real, usable, vintage motocross bike that Rhodig plans to run at his local track and the sheer volume of work and expertise that has been poured into it makes this video worth the watch.