I will tell you how to do them :D
1. You need a MKW ISO...(DO NOT PUT A @#$%ing link here.)
2. Open it with wiiscrubber and click on data, and race, then kart.
3. You should see bunch of random names. It WILL be confusing so make sure you know that the LAST 2 digits are gonna be the character's name.
(la_bike-fk are gonna be one of funky's bike because of the FK)
4. Find a bike, for example, daisy mach bike. Find ma-bike-ds(you might have to guess for some bikes are called because they are so confusing) and open it with szs modifier.
5. Go back to wiiscrubber and chose a medium(can be large or small but medium is the best) kart because daisy is in the medium weight class.
6. Sprinter works best with mach bike so choose me_kart_ds.(It took me a while to figure out that was Sprinter

)
7. Open Sprinter on szs modifier and click on the plus you see when the screen opens up. Click on the other plus that pops up and you should see kart_model.brres.
8. Click on it and right click export and save it somewhere.
9. Go to daisy mach bike on szs modifier and do the same but and click import.
10. Import the file you just saved earlier.
11. You are done! Put this in the my stuff folder and Enjoy!!!!
Names as seen on teh iso! Thanks to Mario and Sonic Guy.
bds = Baby Daisy
bk = Dry Bowser
blg = Baby Luigi
bmr = Baby Mario
bpc = Baby Peach
ca = Birdo
dd = Diddy Kong
dk = Donkey Kong
ds = Daisy
ds3 = Daisy (Biker Outfit)
fk = Funky Kong
jr = Bowser Jr.
ka = Dry Bones
kk = Toadette
ko = Toad
kp = Bowser
kt = King Boo
lg = Luigi
mr = Mario
nk = Koopa Troopa
pc = Peach
pc3 = Peach (Biker Outfit)
rs = Rosalina
rs3 = Rosalina (Biker Outfit)
wl = Waluigi
wr = Wario
ys = Yoshi
la_bike = Flame Runner
la_kart = Offroader
lb_bike = Wario Bike
lb_kart = Flame Flyer
lc_bike = Shooting Star
lc_kart = Piranha Prowler
ld_bike = Spear
ld_kart = Jetsetter
ldf_bike = Standard Bike L
ldf_kart = Standard Kart L
ldf_bike_blue = Standard Bike L (Battle Mode + Blue Team)
ldf_bike_red = Standard Bike L (Battle Mode + Red Team)
ldf_kart_blue = Standard Kart L (Battle Mode + Blue Team)
ldf_kart_red = Standard Kart L (Battle Mode + Red Team)
le_bike = Phantom
le_kart = Honeycoupe
ma_bike = Mach Bike
ma_kart = Classic Dragster
mb_bike = Sugarscoot
mb_kart = Wild Wing
mc_bike = Zip Zip
mc_kart = Super Blooper
md_bike = Sneakster
md_kart = Daytripper
mdf_bike = Standard Bike M
mbf_kart = Standard Kart M
mdf_bike_blue = Standard Bike M (Battle Mode + Blue Team)
mdf_bike_red = Standard Bike M (Battle Mode + Red Team)
mdf_kart_blue = Standard Kart M (Battle Mode + Blue Team)
mdf_kart_red = Standard Kart M (Battle Mode + Red Team)
me_bike = Dolphin Dasher
me_kart = Sprinter
sa_bike = Bullet Bike
sa_kart = Booster Seat
sb_bike = Bit Bike
sb_kart = Mini Beast
sc_bike = Quacker
sc_kart = Cheep Charger
sd_bike = Magikruiser
sd_kart = Tiny Titan
sdf_bike = Standard Bike S
sdf_kart = Standard Kart S
sdf_bike_blue = Standard Bike S (Battle Mode + Blue Team)
sdf_bike_red = Standard Bike S (Battle Mode + Red Team)
sdf_kart_blue = Standard Kart S (Battle Mode + Blue Team)
sdf_kart_red = Standard Kart S (Battle Mode + Red Team)
se_bike = Jet Bubble
se_kart = Blue Falcon
*Not all combinations will work well*
-video coming soon-