KX450/500 Supersingle Build-up. Questions abound?

I'm warning you. That motor won't last long.
That's an extremely large piston, moving very fast.
Stick to the small tracks.
I tried it in 2004 with a KX500, 3 blown motors in 4 weekends.
It was a fun ride. Good luck.

 

Summit Shenny is the main target of building this. i had a retarded idea to look into having a 6speed transmission made for this thing in a fit of boredom last week, but i'd rather just go almost buy somebody's used 07' R6 trackbike for what that'll cost, or i'll just build a godamn TSS RS500 or something rather than waste that money. we'll see how next year goes... if i really wanna go racing i'll just get a 600 and keep this for fun. i'm not pressed to go big track racing with this guy in 1 class only. its more of an exercise in doing something unique and fun and 2 stroke. thanks for the concern tho, i'm sure i'll let you guys know if/when it blows and i go tumbling off into the stratosphere.

annnnnndddd... this also remind me that i totally forgot to call Tryce like a jackass. thanks for the bump.

oh and a ton of shit coming this week from TJ (who is awesome). only things left to buy really are brake lines, tires, and fairings now... then its off to get the swingarm fux'd with and engine mounts, rad mounts, steering damper mounts, and gauge cluster holder made up. coming along.

 

It's alright...I forgot you were going to call and what about!!!

 

its probably not important for a while anyways don't worry about it haha. it'd be cool if you'd sit here and lavish us with tales of yore and how this motor ISN'T going to blow up though... that would be swell. tell a fable.

 

There is not a more demanding race for a motor than the european beach races. Full throttle, power robbing sand straights MILES long...the king of these races were for years the 70-80hp 500 2 strokes. Some roadrace is not going to phase these things if setup properly.
That was one of the things that drew me into the 2 strokes...disproving all the "wives tales".
Have fun!

 

The power robbing sand actually stops these motors from over revving.
I now have a very healthy cr500 that I ride off road. Riding in the sand WOT doesn't concern me, but I would never put that motor on a road course.

I don't remember what front sprocket I had (the biggest that would fit) but the rear was a 38t. Stretched the rod after two laps at Barber the piston hit head and killed the cylinder, crank, and cases.

Just my $.02

 

i'll keep it in mind of course. if it blows once in a season or needs a rebuild every 2 years like suggested, its so cheap i'm willing to forgive it (as long as it doesn't seize and subsequently throw me into oblivion and break all my shit). if its 75% like in your case... i shall rethink its usage and purpose (which would also include taking the entire front end off and replacing it with stock R6 stuff and putting those nice goodies on something else). it won't be topped out on Shenny i don't think, or... JUST getting there by the time you have to let off, so maybe i'll be just fine, the straights aren't very long. Main is another story... it'd probably be sitting at 120mph for a good while, which would potentially concern me as i go to close the throttle coming to T1. we'll see.

i too have watched a MILLION beach and grasslands runs on youtube of dude's just WOT for like miles and miles topped out, over and over. just makes me wonder about your engine builder maybe? porting? tune? mixture? were you monitoring temps real well? 100% not accusing, just genuinely curious. i feel like a lot of 2T problems can be backed off before they occur, if they look like they're going to occur... at least with respects to temp indicators. even tho that sucks cause it would probably mean pitting in early in the session, fiddling with things, trying to make it back out before your session is over, missing some of the time you paid for... BUT, better than blowing up no?

 

Whatever...you obviously have never seen a beach race or what the demands are...as far as your experience, sounds like poor setup to me.

 

I'd say the Baja 1000 puts a pretty high demand on motors.

 

I would agree!!!

 

You have obviously never road raced a 500.

I've seen the beach races and Baja, bikes get destroyed. I still say that's not as stressful as big road courses.

 

I'm not saying it won't work. Just be prepaired to spend the money.


Dr. Rob Tuluie CR500
http://www.motorbyte.com/mmm/pages/bikebuilders/tulda12_96.htm

...this past season and raced the Tul-da at a couple CRA meets at Brainerd International Raceway. BIR has an extremely long and fast front straight and first turn. Racers must hold their bikes wide open up the mile-long straight and through Turn One, and the Tul-da did not like it. It siezed three or four times. Tuluie is still considering ways to fix this problem.

 

so what do you think was the culprit of your seizures? (heh heh)

 

I don't know. I got tired of spending the money, and switched to sv650.

Possibly, Closed throttle (no oil) and high rpm deceleration.

I seized one piston, cracked one piston, and streached a rod on the other. It was never the same problem.

 

interesting. OEM rod and piston setup? i'm planning on a lighter and stronger version of both, maybe that might go a long way as far as stress from rotational weight of a larger single. maybe not and i'd just be breaking more expensive shit.

did you analyze or have somebody analyze the markings on the pistons/cylinder walls? I know that Gorr has some crazy SAE papers where he shows pictures of like a dozen different kinds of failures, and the wear/scorching/carbon buildup etc... and explains what was most likely the causes in each... too rich, too lean, oil mixture, bad gaskets, etc... they were interesting reads.

 

I just PM'd you all my KX knowledge, hope it helps.

 

its interesting stuff to know. thanks. did you run an airbox on yours or open pod? i'm trying to grasp just how big of a difference it will make as far as tuning and consistant jetting between open and boxed. i assume more constant air pressures/temps will be better in that regard, but i dunno. i'd have to custom make something up i guess.

 

so then... a bunch of stuff came, a bunch of stuff in the mail. basically i now have every "part" except fairings, brake lines, and tires either here, or on the way.



TJ at Riders Discount came bearing gifts. rad dude. still another package to come from him, but it felt like channukah and xmas and a birthday all wrapped up into one.

Renthal clipons and grips, Renthal sprockets, Ohlins side mount damper, Brembo RCS, CRG SS clutch, Motion Pro overflow tank, RJL brake pads, DID ERV3 chain, gas tank came, some seat foam, brake caliper spacers, rear brake rotor...

Steering stem, rearsets, and adapters are in the mail this week from Geoff at GP Tech being mega awesome.

Gixxer radiator came in, gonna need to do a bunch of welding on it for mounting, and for mounting the damper, gonna have to weld up a bend in the outlet for the water pump so it points more towards the rad. This radiator seems kinda wide to me, but maybe its just cause there's no fairings yet. I guess we'll find out whether it fits inside or not.





Supermoto Engineering axle sliders coming... let's see what else... i dunno... Motion Pro OEM type throttle. too bad they don't make adjustable Revolver Kits for pull-type only throttles. oh well.





Then I took a trip up to see Kenny at MRP... made me up some trick captive spacers for my front forks/wheel. 1 day turnaround, after i sat waiting a month for another shop to not even look at it yet and all they had to do was take measurements. i know who i shall be going to for my racing bike needs from now on. class act. i was super impressed with the customer service.



and so here we sit... saving up for a month or so for the fairings... then after that comes in, it'll be time to take the frame and swingarm up to my buddy for engine mount fabbing, swingarm bracing, radiator and damper mounts, and subframe bracing.



then the engine will go out, get exhaust pipe made hopefully at the same time. come back, assemble, button up last minute shit like safety wire and installing the sensors for the dash, get the jetting dialed in... then powdercoating and vinyl wrap, and done.

so much to do, but coming along i guess. hopefully Feb/March i can get this thing rollin. then still suit, boots again, new gloves, tire warmers, blah blah blah blah...

 

I think on GP bikes the pilot jet is extra large to prevent this very thing from happening.

Best of luck Sweatypants. If it's like any of the 500's I've ridden, it's gonna vibrate your fillings out.

 

This what I have done for the 1/2 mile and Mile ovals. The MJ would stay the same but I will richen the pilot for the off throttle settings. JMO