A really unique front end - Sportbike Forum: Sportbike Motorcycle Forums
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post #1 of 4 (permalink) Old 11-08-2002, 01:26 AM Thread Starter
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A really unique front end

This bike has a really strange and unique front end.
Can you identify the bike? I consider this trivia to be difficult, but I could be wrong again
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post #2 of 4 (permalink) Old 11-12-2002, 01:19 AM Thread Starter
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It seems I was right this time and this trivia proved to be quite difficult
Here is some help for you. The pictured motorcycle is almost the same as the rusty example above, but with a simplified version of the strange fork and it's just one year later than the previous bike.

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post #3 of 4 (permalink) Old 11-12-2002, 05:23 PM
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Hi Aris,

You were correct. This was a difficult one. It took me about 5 hours to find.

I learned a lot along the way so it was really worth it.

The motorcycle is Belgian. The company name is FN. The abbreviation stands for Fabrique Nationale. They made motorcycles between 1902-1965.

They were the first to introduce a four cylinder motorcyce in 1910. They also once held the land speed record (224.019 km per hour) in 1934.

Here is the model you referenced:

FN revamps the motorcycle production in 1947/48 with the instruction of the all to popular FN M.XIII. The origininal designs of the M.XIII dated back to 1940 before the German invasion. the model was available with a wide variety of configurations including 250,350 and 450 OHV and a 350 and 450 SV engine. The model was also available with a Precision sidecar. The first models were delivered with a patented Swiss front fork design and rubber suspension on the rear.

Link source: http://users.pandora.be/FN.oldtimers/fn_1945-65_.htm

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post #4 of 4 (permalink) Old 11-13-2002, 02:23 AM Thread Starter
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Andy you did it again, congratulations! I'm glad I could create a difficult one, even for you
FN is a marque with great history and they were the leaders in their time. There is a resemblance with BSA (Birmingham Small Arms) as both firms were producing guns and rifles and gained a lot of knowledge in metallurgy and their tooling provided great precision and tolerance accuracy to their products.
The FN rifles were very popular worldwide.

It seems they were a bit overambitious about the fork they installed on this bike, and they had to withdraw it soon after (see attached pic). I read about this bike in a magazine, Sammy Miller restored an example of this bike and let the writer ride it.
Although theoreticaly this front end would solve a few problems of the contemporary forks (girders mainly) it proved to be a bit problematic. Even on the perfectly restored bike, there was vagueness and the feel was really strange. It was very comfortable on the straights which was very useful with the roads they had back then, but once the bike was not upright the fork couldn't handle the cornering forces.
The condition was even worse in reality as there are a lot of bushes and shims in the linkages, and as a result play develops fast and 'vagueness' becomes, 'it goes where it wants'.
The later version is less compllicated with much fewer linkages but still it wasn't adequate and had to be replaced by a conventional fork later.
If you watch the pictures carefully you will see that there is a rubber rear suspension also which remained for all the models. At the time very few bikes had rear suspension, and the y were of the plunger type providing little comfort.
The rubber controlling the rear end can be seen under the saddle, where it is attached to the cantilever and swingarm.
Here you can see the same bike with a normal fork.

I'm glad you enjoyed it
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