Can someone please explain the difference between a /2, /5, /6, /7 (is there a /8?), and what exactly is an “oil-head” and a “k” bike? And what are these Earle forks that everyone speaks so reverently about?
OK, this is off the top of my head, so it may contain some errors.
2 = second version of some of the Earles fork bikes. The designation is often used incorrectly for all Earles fork twins. Not all were designated /2. Updated normal 500cc bikes beginning ca. 1960 were designated /2. The Earles fork is a swinging arm design, superior for sidecar rigs and off road applications, very plush riding, but a little heavy steering as a solo setup. They do not nosedive under braking, in fact they tend to rise in the front as the bike comes to a stop under heavy braking. These machines have very stout frames with sidecar bosses built in. The fork has adjustable geometry to accomodate the sidehack. The bikes were produced from 1955 – 1969. They came in normal and high performance versions of the horizontally opposed twin displacing either 500 or 600 cc. R50 and R60 designated normal performance. R50S, R69 and R69S are high performance models, the R69S making 42 HP and exceeding 110 mph. Despite the nomenclature, R69 models still displaced 600 cc, go figure…. 1969 models were shipped with either the Earles or a telescopic fork the same fork as the /5 series built from 1970-73. They were designated “US”. So an R69 US was a high perfomance 600 cc with a telescopic fork. There is also a 250 cc bike, this was a vertical single cylinder engine, uncommon in the US due to its lack of performance.
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I recently finished going through the process of reviving a 1973 R75/5. One of the challenges I faced was that of missing keys. Sure, the ignition nail key was there, but the keys for the seat lock and the steering head lock were missing. I needed to remove the lock for the fork in order to complete frame painting, and really wanted matching keys for both the seat and fork locks if at all possible. This precluded me from simply drilling it out. I was pretty sure that the locks were original to the frame, and that the keys should be the same for each.
So, here is what worked for me…
First, go to your local dealer and buy a few correct key blanks.
Remove the seat lock mechanism, and detach the lock housing. Don’t lose the small screw that holds the lock to the striker mechanism.
Take the blanks to a competent locksmith and ask them if they can make an impression cut key. Keep looking for someone who will give it a try. Now, just so you know, I was advised that they might damage the lock mechanism while making a key in this manner. If they (or you) are uncomfortable making an impression-cut key, the lock may be disassembled and the tumblers opened up for their key making efforts, but it is critical that they get the pins back together in the same order to have the fork lock work with this key.
OK, we’ll assume that you have a key that works with the seat lock cylinder. You will try it in the fork lock and, surprise, it won’t work!! Here’s what to do:
Look at the key that you have. You should see four valleys in the key blank, which were cut by the locksmith. You will also notice that they are evenly spaced along the key, and also that there is room on the end closest to the handle of the key for another cut to be made. Starting at the end of the key furthest from the handle, we’ll refer to these as cuts #1, #2, #3 and #4. The trick is that the seat lock uses four tumblers, and the fork lock uses five. You will need to cut the last one, #5, yourself.
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