Help with project bike

[carbondaddy]

Recently I picked up a 2003 KTM 400 MX with a blown motor. The idea is to build a long track/higher Hp bike to compliment my stock 2011 KX 450/short track. I have a few ideas for the motor such as a suzuki sv 650, kawasaki 650 ninja twin, ducati 749 or 848, aprilia 750 v-twin etc. I could also do a cr500 or kx500 with a big bore, or just rebuild the stocker with a big bore. I haven't ruled out NOS and turbocharger yet. So anyone else have any ideas? Anyone have the appropriate motor laying around or know where let me know.
Craig

 

[Rush44]

Seems like the biggest obstacle to big bore bikes is keeping the motor weight down. I remember several big motor bikes getting a lot of hype over the HP gains, but once they hit the snow the big motors turned the bike into a tank that doesn't corner or bob through the trees well.

 

[Ausm7499]

I would strike the street bike motors off your list, they are too heavy. That 03 RFS engine is a good one that has a lot of big bore options and good reliability but could get expensive. A CR500 transplant would probably be your cheapest option if you can find an engine.

 

[snowhawkaddict]

2 Stroke Oneski Phazer crowd pleaser!

I have a project also but my frame is a steel twin spar so if it ever happens it can be cut and widened to fit a TL1000, LC8, SV650, or just upgraded to KX500, 540, 600, etc.

The Banshee 350 parallel twin engines are everywhere kick start and chain drive to boot. Clearance of your frames backbone would be no harder than Shane's YZ, he was a diehard snow biker and I have no doubt it was on his to do list to convert before he ran out of time.

http://www.youtube.com/watch?v=xzewahjsZ1E

http://www.enduro360.com/2012/04/30/news/r-i-p-shane-donaca/

Travis scrapped this for submarine duty, too much ski ballast!
http://www.youtube.com/watch?v=ifKyrXeLdnQ



http://www.youtube.com/watch?v=3t8MeE8Ik4Y
http://www.snowestonline.com/forum/showpost.php?p=3114616&postcount=3

 

[KAWGRN]

I would strike the street bike motors off your list, they are too heavy. That 03 RFS engine is a good one that has a lot of big bore options and good reliability but could get expensive. A CR500 transplant would probably be your cheapest option if you can find an engine.

I wonder if an M-8 motor would have enough torque to run without a transmission and turn some sort or slipper single ratio clutch like a rekluse single speed??Or a light weight yamaha phazer fan,,they made like 75hp with a pipe?

 

[carbondaddy]

I know there was a GSXR 750 powered bike, and it was heavy. The sv650 motor weighs 95 lbs. and I weighed the box of engine parts that came with my bike and it comes to 80 lbs. Not that much more. The sv 650 makes about 72 HP and could easily get 85 out of it. I could rebuild and big bore my RFS for about 2000.00 and get about 65 to 70 hp. The sv 650 will easily handle a 30 shot of NOS all day long. I've thought about putting an 800 Rotax in it, but just think the clutches and belt would be too problematic. The secondary would be right where your feet are and you would have to enclose everything so they would run hot. An 800 rotax with clutches is right around 100 lbs. and the exhaust would be an issue. Just some thoughts.

 

[KAWGRN]

I remember the old Rotax singles that came in the ATKs they were flat tracked at over 80-90 hp air cooled nowater weight ! Still see them Ice racing in the midwest!

 

[blackandyellow]

A boosted thumper would be your best bet as far as power to weight. Even those big street bike motors will lose power at elevation with out loosing any of there weight.

Im sure you have already seen this video before, but since its summer and some of us have nothing better to do lets watch it again.

http://www.youtube.com/watch?v=He_LNBg8nDQ

 

[eskimojoe77]

Polaris Outlaw 525 engine

The polaris outlaw 450 or 525 4-wheeler engine is an option, 5 speed with a reverse gear. It is the same engine as the KTM 525 bikes. I have cylinder off of one on my 2003 Ktm 525sx (same parts). You can find these engines on ebay all the time and parts too, only a whole lot cheaper than KTM parts (exact same parts).

 

[backcountrysnowbikes]

Street bike motor. is way to heavy go big bore 2 stroke kx500 you can get 75hp. out of it at a fraction of the weight.

the 750 had the HP but sure felt heavy in the snow.

92 mph in a 400ft grass drag sure was fun

 

[funjunkie]

What about a ducati 900 air cooled engine. Out of a 90's monster or 900 d. They are fairly lite and make good power.

 

[carbondaddy]

ya, I'm kinda leaning towards a big 2 stroke. Looked at a couple websites on conversions, should work out good. Just have to find a good motor. Anybody got any leads?

 

[mtn-doo]

Call A.J. at Service Powersports in Indiana. 1-219-932-3588. He will hook you up with a new KX500 or CR500, ported and tuned to your wishes. New motors, not re-builds. Light weight and 80hp. Very aggressive motors, twice the torque as a 450F and explosive HP. Will make an awesome boondocker.

 

[jheitzman]

project

How heavy is a 700 Honda out of a quad?

 

[4Z]

80 hp out of a CR/KX 500 make The most sense to me. I have seen more KX transmissions go bad than Honda though.

 

[jheitzman]

honda

Was thinking electronic shift Honda trans and then build a "fatboy" snowbike with a 13-15" track and custom ski... But how would it handle? Just a crazy thought maybe...

 

[snowhawkaddict]

Like a Hawk running on one jug!

Or that still has the factory setup holding it back.
http://www.youtube.com/watch?v=jJewbFZHI34


Honda TRX700 is similar as XR650R only larger and electric start, same for Yamaha XT/TT - Raptor 660/700.

 

[snowhawkaddict]

Freeway shoulder sightings.

80 hp out of a CR/KX 500 make The most sense to me. I have seen more KX transmissions go bad than Honda though.

Your biased but since you sold the CR your going to have to let the new owner know to keep an on it. Failure is out of neglect in most cases, gearbox oil changed frequently never gets a chance to dirty. 12yrs at #1 in Baja wer'nt because Larry R., and Danny H. were out for a stroll.

I'm not a Kawasaki diehard, and used to covet the RED bikes, but it I kinda roll my eyes each time Honda pats themselves on the back for not having much factory competition. Bet any of the other Japanese Mfr's could be right with them in a year or two especially K since the 450 edges out the others in hp.

KTM will outdo Honda in the desert but It looks they are focused on the larger goal of SX, Husqvarna will surprise them in both arenas.