Thumper Club Forum
Club House => Chatter => Topic started by: andy230 on February 21, 2007, 11:27:18 AM
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you know the supermono class has a new subdivision for the coming season.
Got me thinking re the recent post from hondamichael:
Current rules are
single cylinder, of maximum 1300cc (was 800cc last year)
minimum weight of 95Kg
Aircooled or water cooled.
The new class is a 250 thumper. Minimum weight limit of only 75Kg. I'm not sure if there will be any this season, but its an interesting prospect. Assuming you had a *very* trick and light chassis, what would you build into it??
Could you (or rather, "one"), build a 75 kilo bike, with a 250 thumper? Would presumably be expensive to get it light (wheels, forks, ally tanks etc)
A 250 crosser in an aprillia RS50 chassis?
a
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Guess you would have to become a bit of a home expert on lost foam moulding - allowing CF tank seat etc - probably also have to be stressed parts too.
250 Crosser lump sounds good, BSA C15 does not.
R
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hm this could be done like that one here
basically a monkeybike fitted with 12" wheels and a 470cc husaberg engine single cylinder 4 stroke
just swap it for a 250 engine
http://www.sns1.de/web/mb/cars.nsf/1bfe03883765ddefc12569d60070f089/11d3f17b98711371c1256e2a00550f62
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250 Crosser lump sounds good, BSA C15 does not.
Ha!! :) True!!
The monkey bike is excluded (but nuts!) as "supermoto type machines are not permitted"... sadly!
a
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75kilo ..250cc.... easy job ... carbon frame with build in tank , carbon wheels, carbon brakes , the rest magnesium (levers and footrests and thinks like that) is lighter then alloy ...so has anybody half a million for me to build a prototype ..for the final one i need a bit more money
just kidding but it says minimum weight 75 kilo my honda cbf has a dry weight of 139 kilo ...and loads of things on it you wont need on a supermono the exhaust alone should nearly safe 8 kilo if you would fit a all alloy system on it , the footrestassebly for rider and pillon is one big part alloy but also weights so just bold on some rear sets from a bit less alloy and you could safe another 5 kilo , the alloy wheels if changed to some wired alloys , everything electrical not needed for a supermono should add up to another weight loss of (do i need a starter, the engine has no kick start is bumb start allowed?) another 20 kilo if the bumb start is allowed (there might be a possibility of fitting a kickstart the hole is there in the engine but closed , so i`m already at under 100 kilo
with a smaller alloy tank it should be possible to get to 95 kilo , then get rid of all the plastic parts which are not needed and cut the rear end behind the place for the rider and i think we are at around 80 kilo
ok the engine has only 20bhp but thats due to emmisions originally in brasilia it has 25 bhp (without kat) so it should be a easy job to get out near 40 bhp with other carb and improved cams , do we need a balancer then we could get rid of it and the engine would be lighter too ups we are already under the 75 kilo
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75kilo ..250cc.... easy job ...
my honda cbf has a dry weight of 139 kilo ...
... ups we are already under the 75 kilo
Hey michael-
Hmmm. Maybe its a good starting point...
But the quoted wet weight for the SRX is 176kg. I've taken everything off (well, not the "unnecessary" brackets but I will eventually put it back on the road), and its still at 149 kilos (need to reweigh now actually, may be more :-( )
With all respect, I think you're being a little optimistic with shedding weight. Tho yes you can take the starter off, everyone bump starts. And yeah, ditch the heavy wheels, replace with superskinny carbon ones. But the thing is you're also going to have to (presumably) lighten/ uprate the forks, swingarm, etc...
Would be an interesting project tho!
Anyone got a sporty donor 250?? I like the idea of a 50 or 125 chassis.
a
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ok i might be a bit optimistic, but a 125 frame should be the better idea , because i`m not sure if a 50cc frame is stable enough to withstand the power,
but my typ of engine would be a good starting point to get power out of it
aircooled, dohc, 249ccm
water has also weight and a watercooler has to be bigger then a oil cooler, the oilcooler at my bike has only 2 fins and i suppose honda has only added the oil cooler to make absolutley sure it doesnt overheat in slow city traffic or long distances , so in the supermono series you wont need it
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I guess the Cagiva Mito RC would be a good starting point...
Mind it costs loads to stripthe weight really back on a bike - there again I am carrying over 15Kg excess.. so maybe we need to look at radical surgery for the rider too?
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One of my projects for this season is to build a 250 mono.
What I have planned is to put a cbx250 (35hp@10,000 rpm) in to a cb250 road frame with as much unused stuff as possible removed, Other items will be replaced with alloy etc. (spending as little as poss. as part of the project) using std. cbx wheels (very light) & ending up with a skeletal frame that should be strong enough to handle the motor but light enough to handle well. I have most of the components already lying around here so it's just a case of getting started.
Will keep the projects section posted.........
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So - as if as suggested this will be a class for this year but no one will enter - I just need to get my Dad's old C15 out and I could clean up a national championship in my first season...?
R
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One of my projects for this season is to build a 250 mono.
What I have planned is to put a cbx250 (35hp@10,000 rpm) in to a cb250 road frame
Hooraaay!! Sounds good John! Whats a CBX250? Got any pics?
That should be a good project. Do you know of any others on the grid this year? Keep us posted matey
cheers
a
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what wrong with this little thumper. just pop a 250 in it... wow factor and cheap as well.
http://www.scootersales.com.au/News-17-mediarelease.aspx
you may even be able to dump some kilo's to compensate for the engine
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sorry, didnt notice it only refers to the 50cc version. The 125 is also on the market.I reckon a 250 would be a perfect town bike.
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Seems you can claim an Egli frame?
http://tinyurl.com/396y5g
R
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i like the madass design , but in 2004 they have made a protoype of a madass 500!
http://www.t5net.de/messebilder/intermot2004/images/intermot2004_041_jpg.jpg
sadly it never made it into production
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MMMmmmmm ! 500 Enfield lump with 5 speed box !
Different !
Jethro