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His work is incredible to say the least. Unfortunately that little laydown streamliner has been banned. There is a rule stating a bike has to be able to lean 20 deg. each way. It obviously can't meet that rule. Jack has a way of taking rules to their limits.
His work is incredible to say the least. Unfortunately that little laydown streamliner has been banned. There is a rule stating a bike has to be able to lean 20 deg. each way. It obviously can't meet that rule. Jack has a way of taking rules to their limits.
A buddy of mine, who builds racecars, says all the time..."It's not about what the rules say you can or can't do, It's about what the rules DON'T say you can or can't do"
I'm really excited to watch this build! I've thought about buying a mid 90s CB250 or a GN250 for a cafe project for a while now! I must ofcourse finish my bobber first but I'm really keen to see how yours turns out so I can have some ideas for mine. My main attraction to these lovely 250s is the awesome gas mileage you get! Post lots of pics and keep us updated!
I am in France !
All I can get from you guys is knowledge and your sympathy for outsiders ...
18" rear wheel sounds good, I'll see if I can find some.
The appeal of the 17" wheel was its total compatibility with the bike as it was fitted to the TU-X wich replaced the GN (rear wheel size and tank / seat combo being the only evolutions)
Tires I have been able to find (of the same brand and same model front and rear) were 50cc motard tires (michelin and S rating for speed wich is 115 or so mph)
I thought Ducati's fairing are the narrowest of the bigger bikes but maybe I need to wrap someting from scratch.
The tricky bit I foresee is the back of the bike as a lot of drag is created by the "vacuum" left by the driver.
But first, time for some clip on bars !
Maybe I will ask the admins to move this post to the builds as the start is really part of it ?
OK, bigger front fitted yesterday 15*41 is now 16*41.
I was going for 16*39 but the rear sprocket is a mismatch.
I need to ream the 4 holes to a bigger size.
BUT the bike is now slower !
7mph shaved off top speed !
I was kinda' expecting that since the only aero mod was lowering the windscreen but still ...
Next mod after the rear sprocket is gonna be replacing the 3" indicators and clip on bars.
Is your goal to hit the ton on this 250 with or without fairings?
I'd imagine that it would be a rather important thing to think about, not than I'm any expert in such aerodynamics and such....
Photos? Videos?
Keep it up! Because if you can pull this off it would be much inspiration to many
Your in France!
You can get stuff we can't get in USA. (or only with a lot of difficulty)
Find 1990's sport 125 fairing, Suzuki RG, Yamaha RD, Honda and Kawasaki all made 'restricted' 125's for British market and unrestricted in the rest of Europe
There's also the Aprillia 50/80/125 fairings, plus, 'race' plastics for any of the older 125 GP bikes
You need rear-sets before you go any further, you already have clip-on bars?
:
if your running the bike at WOT you should make a proper exhaust with an open reverse cone megga. Loud as hell, but will perform nicely. also open carb with a velocity stack. of course, the bike wont run as well when your not at wide open throttle, but it will maybe make another horsepower at wot.
also when you do the top speed runs, I would run tire pressure a couple of psi above what you usually run; less rolling resistance.
dropping the bike an inch or two front and rear means that much less of the bike will need to cut through the air.
consider making some spoke covers out of sheets of plastic. in a cross wind the bike will veer, but the additional aerodynamics are good for at least 10mph Id say.
The target of the ton is without engine mods for a start so fairings are definitely on the cards.
Unfortunately (?) the fairings available on standard bike I don't really like, they are too "shinny" for my liking.
I'd like to go for some full fairings as seen in racing in the '50's that were banned shortly after their introduction, that looks like speed enhancement to me !
That's assuming the same aerodynamics and no fairings.
Lowering, narrow high pressure tyres and a fairing need a lot less power
How fast did NSU go with a 50cc moped engine in the 1950's?.
Think it was around 113mph with 6~7 bhp?
Its how you part the air as you hit it but more importantly its how you close the hole in the air as you pass through it. Drag is the killer. Less drag equals more speed. Mueller went 121.700 in 1956.
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