Sv650 Vs. Yz450f

[ricksr6]

Hey guys I am soon to be joining you on the race track. I was thinking about starting a project bike for the Lightweight class but wanted to get some opinions on it first. Do you think that a 450F motor in a R6 frame would be able to run with a SV650. I think it would do OK for smaller tracks but what do you guys think about the Straights, I haven't rode a dirt bike in about 4 years, and never really played with the Top Speed and what not. Any advice would be greatly appreciated!!

Rick
rick.engstrom@itron.com

[csbextreem]

SHIT... You could probably run that in open single, that would be kinda fun but I think you would get wooped on by the 125's.

HA

Go 125GP!

BTW, I don't ride one and I don't have the patience to tune them but holly molly! get pass by one of those guys in turn 2 at Seattle while your going as fast as you're comfortable going and YOU'LL be impressed too!!! :p

[timk]

The R6 chassis is too big and heavy for a 450 single, but if you put that engine in a 125 or 250 gp chassis you might have something. Cedric Smith put a Honda CRF450 engine in a 125 chassis a couple years ago and stomped the open single class with it -- the 125's were hopeless against it. He was able to run pretty well against SV's also, but I can't remember the lap times off the top of my head. You could check the results archives if you're interested to see how they compare.

[csbextreem]

[QUOTE=timk]The R6 chassis is too big and heavy for a 450 single, QUOTE]

Is that simply for rules and regs or just from a power to wheight thing. I am just curiouse if there are certain rules that need to be followed for that class for chassis size and what not??

[timk]

Sorry for the confusion. The rules would definitely allow it -- I was just offering my opinion that an R6 chassis wouldn't be the best choice for a frankensingle project because it was designed with a >100lb >100hp engine in mind.

[ricksr6]

Yeah the R6 frame would be a little overkill butt I have everything for a rolling chassy except the frame itself, could pick it up on ebay for around 200 and then use my Dirtbike motor. I hope to make it easy enough to swap in and out so I could go back and forth and use it on a dirt bike!!

[jeff191]

I don't think it would be worth the effort. You should put that motor into a Tigcraft minimono chassis (http://www.tigcraft.com) or a 125GP chassis.

It would be a slug compared to a 125....

For reference a 125GP bike weighs 160lbs. Yes, thats right. Its stunningly light. They put out 40hp in club racing form (50hp in world championship form).

Your frankensingle is going to weigh about 300lbs and put out about 45-55hp

So, its going to be a bunch slower than a 125GP, and its going to be slower in the corners (because its a lot heavier), and its going to have to brake earlier (because its a lot heavier).

Cedric Smith races an Honda CRF450 motored RS125 chassis in Portland. You should talk to him. It was a huge amount of work. His machine is spectacular. It weighs about 180lbs and puts out about 55hp at the rear wheel. It stomps open single and superbike SVs.

BTW - to the fellow that thinks 125GP bikes are too hard to tune... They are quite a bit more work than a streetbike but they aren't *that* bad and its worth it.

[ricksr6]

I don't htink the finished product of my frankensingle would be 300 pounds. The motor weight difference between the R6 and the 450F motors is probably 80lbs as I have had both out and carried them around!! Right there you looking at 270lbs from the stock R6 weight (365lbs). If you take into account the loss of all the wireing and battery, lights yada yada associated with race bikes, you would be looking at probably a 230 -250lb bike.

[jeff191]

Might be interesting... If you can get the bike light enough and the power output from the single high enough...

Just for reference:

All calculations below assume 160lb (in gear) rider

125GP: 40hp / (160lb bike + 160lb rider) = .125 hp/lb

Frankensingle: 50hp / (250lb bike + 160lb rider) = .122 hp/lb

Explosive Frankensingle: 55hp / (250lb bike + 160lb rider) = .134 hp/lb

Explosive Lightweight Frankensingle: 55hp / (230lb bike + 160lb rider) = .141 hp/lb

LW Superbike SV: 85hp / (375lb bike + 160lb rider) = .159 hp/lb

Cedrics RS125/CRF450 machine: 55hp / (180lb bike + 160lb rider) = .162 hp / lb

(Some of those superbike SV's are making over 90hp at the rear wheel btw...)

Maybe it could be interesting? Remember, your cornering speed and braking capability will be at a disadvantage to the 125GP bike because of your additional weight. But you'll get a much better launch and I assume that you will come off the corners better because of a wider powerband.

I think its all going to depend on how light the R6 chassis is. Take it apart and start weighing it...?

You might also want to work out gearing. You might have trouble fitting a large enough front sprocket / small enough rear sprocket to reach needed speeds on the straight. Also, the motocross gearing might be too widely spaced for roadracing use. Does the motor have 4speed or 5speed transmission?

You will also need to install a slipper clutch.

[ricksr6]

Thanks for all the input. I will start weighing all the extra part I have and adding it up slowly to see. I thought about the gearing as well, and speed is what I was concerned about. I also forgot that there will be some additional part to the frame even though there will be some parts that aren't used. I think it would be a steller bike to ride but as far as competing I don't know. I just thought it would be cool to be able to pull the dirt bike apart, put it in the street bike for a lightweight, then after the race put it back to the dirtbike for a bike to practice on and what not. The time to change it out would also play a factor depending on how you made it. Just an idea now, but may soon become my winter project!!