Planet Minis

miamiGP

I race in SEMRA, the nsr50 falls in F1 (2s up to 50/ 4s up to100cc)I love riding this thing, but with very limited/expensive performance parts for the nsr, it was impossible to keep up with the crf50's bored to 95/98cc or whatever, I tried a metrakit but I don't feel comfortable on it, so I decided to try a derbi 50cc pro race series engine on my nsr frame.
what do you guys think?

shw911

must haul a$$

firepower354

Sweet. Anyone sleeve down and/or destroke a KX65, or are the real race 50's above that level?

miamiGP

That sounds like a good idea. the problem with the nsr engine is a very old design meant to last forever instead of to rip, it's also bulky and heavy, the kx65 is one of the dominant machines on F2 (2s up to 65/4s up to 125cc) I'm putting one of them togheter right now, if I like it, I may try one of those engines on another nsr as soon as budget allows me.

Luckystar64

Wow... That works! How hard was it to get in there? I have a Metrakit with a Pro50 motor in it, and the thing totally hauls living ass. I used to have a Pro76 top end on it-- and it was so strong on top--- it wanted to spin the tire in 5th and 6th gears if the power happened to come on while the bike was layed over in a turn! I dropped it down to a Pro50 with a 24mm carb instead of the 28mm that I was running. It's about 75 pecent as fast, and more controllable. It reminds me of a really good running SP72.

Speaking of an SP72... I just happened to have an SP sitting around in a crate with the upgraded crank no less. I've been waiting for GRC to release their GR5 and GR7 bikes. I was going to bolt it into that, but an NSR build would be cheaper. Let us know what it takes to get the motor into the NSR--- I've never heard of it being done before. ---L*64

miamiGP

the hardest part is to modify the swing arm to fit the engine on the same axle, I had to cut the tube between the swing arm legs, I also had to machine the 2 new ends to fit needle bearings.
I cut off the frame part that goes under the engine on the derbi senda and after a little of tube cutting and bending I welded it to the nsr frame, everything else is pretty simple.
my only concern is a little rubbing of the chain on the slider, will see how it does once I ride it with my weight on it.

Luckystar64

Oh Gawd... Sounds like alotta work. What didn't you like about the Metrakit? It took me awhile to feel comfortable on it too. I just kept riding it, and now I don't feel comfortable on anything else. I'm about to get custom fork springs, and a Penske shock for mine. I always seem to have some kind of BS problems with my bikes though. That's why I have two. Whem one is acting up, I pull out the other one. ---L*64

miamiGP

the seat is too high and forward, on my nsr I can tuck in behind the screen without a problem, on the metrakit the shield would hit my helmet about my nose area. I'm just 5'6", I think the metrakit is designed exclusively for little kids. when breakin I feel the wieght of my body is way higher than the clip on's making it very difficult to suport thay weight on the shoulders.

Luckystar64

Ha! Ha! I had that problem when I started riding the bike too. I feel terrific on it except for the fact that I can't quite get my head behind the screen either.

I did just get the 2 inch longer tail from the bigger bike-- The subframe and tail bolt right on. I'm thinking that the extra room will enable me to get just behind the windscreen. If this doesn't work, then I was going to try and make a screen that curves in a bit to let my head in.

Attached Images

Metrakit Racer 007.jpg (792.7 KB, 26 views)

miamiGP

I wish I feel comfortable on it, it looks absolutely awesome, makes me feel sorry about how the nsr looks but imho nothing handles like an nsr.

Luckystar64

You'd have to just keep riding it... I kept wanting to switch back and forth between the two bikes-- that won't get it. BTW, are you sure that you had the MK set up properly with the correct springs? I rode mine with the child springs, and it was basically unrideable. ---T