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Original Article:
450 Super Single Project

Please discuss the Motorcycle.com article 450 Super Single Project in our Motorcycle Forums below. Use the reply button to let others know your comments or feedback on the article. Constructive criticism is always appreciated, along with your thoughts and personal opinions on the bikes and products we have tested.
 

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One of the coolest things about these bikes is the use of a stock frame. That means lots of legroom for those of us that knees that don't quite work as well as they used to.

Want a street legal version? Start with a KTM or Husqvarna.
 

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"In the engine compartment would reside the 450cc dirtbike motor that can be tuned to produce nearly 60 hp with about $1000 worth of work."

And costs about $3,000.00 to fix when it blows up like a hand grenade.

Affordable? Only if you're rich to begin with...

Now a CR500 powered road racer, that'd be cool. Just ask Sean Alexander...
 

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"In the engine compartment would reside the 450cc dirtbike motor that can be tuned to produce nearly 60 hp with about $1000 worth of work."

And costs about $3,000.00 to fix when it blows up like a hand grenade.

Affordable? Only if you're rich to begin with...

Now a CR500 powered road racer, that'd be cool. Just ask Sean Alexander...
Rotax/Ktm/Husky are easily within this range and don't think for a minute that Honda/Yam/Kaw/Suz can't do that. Your replacement motor parts for such a bike would not be your biggest investment. Suspension is the costly part.

This is a way to get kids and club racers into "spec" racing for people with budgets. It's a good idea. I would support such efforts.
 

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What's the point? 125cc and 250cc road racers are going to be cheaper..
I think motoGP has shown that. There are already plenty of bikes in the 40-60 hpr range anyway, aprilia RS250s, EX500, ninja 250s?

Trying to make a spec class based on half a dozen customized dirt bikes seems a bit silly.

Why not just go out and by 125 gp bikes?
 

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One of the coolest things about these bikes is the use of a stock frame. That means lots of legroom for those of us that knees that don't quite work as well as they used to.
Uh? I think your sadly confused... the frame has nothing to do with legroom. See... you sit on the seat and put your feet on those peg things. It's the distance between the two that determines how much you have to bend your legs ;)

If you notice the pegs and seat are about the same on those as a 2-stroke GP bike.

Just suck it up and do some stretches :) My 70 year old father has ridden some of my practice sessions on my 125GP bike and he races a RS250 himself :)
 

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Why not just go out and by 125 gp bikes?
Uh, 'cuz these aren't 125GP bikes? I dunno - you tell me.

Mo' racin' is Mo' Betta'.

At least in my book.
 

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Uh, 'cuz these aren't 125GP bikes? I dunno - you tell me.
Mo' racin' is Mo' Betta'.
At least in my book.
Just worries me they bill them as entry level bikes. I just hate to see racing become even more expensive than it already is and if you compare running a 450 MX bike with running a 250 2-stroke MX bike the costs are much higher for the 4-stroke.. I image road racing will only be worse.

I don't see why these custom bikes that aren't even readily available should be billed as the next spec racing entry level class. We have so many racing classes as it is, do we need one more? What do these offer than a 2-stroke GP bike doesn't ? I guess they're a bit cheaper new if they're only $10k, that's the only thing I can think of slightly cheaper new...

Maybe it's just me anyone else think of a reason?
 

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euro monos

Interesting.... in italy supermono racing is alive and kicking and most bikes have switched form big singles to light 450's 4-str MX motors anyway. main difference is that people stick those motors inside italian supersport frames like aprilia's RS250-125 and cagiva's mito 125.
Sounds good but as it's a pretty open formula, tuning at high level = expensive. titanium rods, heavilly modified heads, etc. carbon fibre everything.

only way to keep costs down would be tight limits on tuning and mods, something that is often hard to check.

BTW, pukka gp 250-125 are damn expensive, last time I checked the privateer honda 250 racer was something like 30K euros. At world championship GP level, leasing (not buying) a bike for one season goes up to 100-200K!

Still, roland is onto something.
-Yossef-
 

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Interesting.... in italy supermono racing is alive and kicking and most bikes have switched form big singles to light 450's 4-str MX motors anyway. main difference is that people stick those motors inside italian supersport frames like aprilia's RS250-125 and cagiva's mito 125.
Sounds good but as it's a pretty open formula, tuning at high level = expensive. titanium rods, heavilly modified heads, etc. carbon fibre everything.

only way to keep costs down would be tight limits on tuning and mods, something that is often hard to check.

BTW, pukka gp 250-125 are damn expensive, last time I checked the privateer honda 250 racer was something like 30K euros. At world championship GP level, leasing (not buying) a bike for one season goes up to 100-200K!

Still, roland is onto something.
-Yossef-
Wouldn't it be easy to require dyno runs of the top 5 positions and anyone out of spec would be disqualified? Hp limits seem to be the key in this. Run only 450cc 4-strokes and use something like AMA superstock rules for mods. Then suspension is the factor- not who's spending the most on the motors.
 

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Uh? I think your sadly confused... the frame has nothing to do with legroom. See... you sit on the seat and put your feet on those peg things. It's the distance between the two that determines how much you have to bend your legs ;)

If you notice the pegs and seat are about the same on those as a 2-stroke GP bike.

Just suck it up and do some stretches :) My 70 year old father has ridden some of my practice sessions on my 125GP bike and he races a RS250 himself :)
Hmm. Maybe I'm mistaken, but it looks like they're using the stock subframe, too. That's a bit more legrom than the usual GP bike.

Aaaaaah. We shall see. Or maybe I'll just build one myself.
 

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They could.....

"In the engine compartment would reside the 450cc dirtbike motor that can be tuned to produce nearly 60 hp with about $1000 worth of work."

And costs about $3,000.00 to fix when it blows up like a hand grenade.

Affordable? Only if you're rich to begin with...

Now a CR500 powered road racer, that'd be cool. Just ask Sean Alexander...
.... just allow the 250 2-strokes to compete against the 450 4 poppers like they do in MX.

Heh heh. Never happen. Too humiliating to the 4 strokes.

2 stroke MX..... accept no substitute.
 

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Wouldn't it be easy to require dyno runs of the top 5 positions and anyone out of spec would be disqualified? Hp limits seem to be the key in this. Run only 450cc 4-strokes and use something like AMA superstock rules for mods. Then suspension is the factor- not who's spending the most on the motors.
Pretty much the whole point of a spec class, isn't it? It's for cheap and even racing. They even have weight limits for bike and rider, which should be in every racing class. That then opens up racing to people that have the most skill, and not who is just a jockey.
 

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BTW, pukka gp 250-125 are damn expensive, last time I checked the privateer honda 250 racer was something like 30K euros. At world championship GP level, leasing (not buying) a bike for one season goes up to 100-200K!
Hmmm I bought a 1995 Honda RS125 GP bike for $2700 put another $2k into freshing and tuning the engine and it's quite competitive. I regularly race against a ~2002 Aprilia RSW125 and it keeps up with it just fine (and usually I beat it) Luckly the 125 bikes haven't changed much over the last 10 years at least at the club level. Sure you can spend $50k on engine work but in the end you'll gain maybe 4 hpr which will be an advantage but not an impossible one. Elena Myers kicked my ass though with her $100k engine but several people beat her with what I believe are much cheaper engines.

I race for around $400 per month (2-day race weekend with WSMC) total cost, including engine rebuilds, gas, hotels, tires, and entry fees.

From what I've heard that's very cheap racing.
 

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good for you :)

I was obviously talking new 2007 prices for the RS250. have no doubt that an 1995 RS125 is a great ride, would love to have one actually but at national or international level it's hard to believe it'll cut it. The last Aprilias RS250, RSA 125 and KTM's have raised the bar very high in the last couple of seasons in GP. Honda has officially declared that it had stopped development of two strokes 125 and 250 for GP.
I am having my share of cheap racing on a heavily modified vintage CB500 Four that I built in the garage with less than 2000 $ of special parts and my racing costs are about the same as yours. fun fun fun for pennies.
-Yossef-
 

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A stock Yamaha 450 has a recommended by Yamaha in the owners manual 30 hour top end rebuild time. How long do you think a modified/abused 450 would last then?

Yes I do know people that race 450 motorcross/ATVs. And yes it is very expensive to rebuild the motors, much more than a 2 stroke.
 

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I was obviously talking new 2007 prices for the RS250. have no doubt that an 1995 RS125 is a great ride, would love to have one actually but at national or international level it's hard to believe it'll cut it. The last Aprilias RS250, RSA 125 and KTM's have raised the bar very high in the last couple of seasons in GP. Honda has officially declared that it had stopped development of two strokes 125 and 250 for GP.
I am having my share of cheap racing on a heavily modified vintage CB500 Four that I built in the garage with less than 2000 $ of special parts and my racing costs are about the same as yours. fun fun fun for pennies.
-Yossef-
You might be surprised a 1995 honda 125 can be quite competitive on the national level. I have raced with the USGPRU and power wise the bike is right up there. If you look at the changes from 1995 to present on the RS125 they didn't change much at all engine is all still the same, they changed the bolt pattern of the cylinder head, and they changed the carb and the styling but that's it really.

While at the world level the honda 125's aren't competitive at the moment (though two or three years ago one won) on the national level they are. I believe they're at the top of there game in the british 125 championship, a highly competitive series.

Really there are only three options when buying a 125 GP bike - Aprilia RSW125, Honda RS125 and Yamaha TZ125. That's the order most people see them as as well from fastest to slowest but they're really all so close it just takes a bit of port work and a new head to change everything. From what I've heard the KTM's are way fast but you can't buy one.

And like I said I regularly race against a professionally setup Aprilia RSW125 and don't have a problem.

So basically I feel 125 racing is going to be cheaper than this 4-stroke dirt bike engine racing. More fun (slightly better power to weight) and the bikes new and used are all readily available with people already racing them.
 
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