Cr 500 supermoto/roadrace

Anyone in here try to set up this bike ??? Thanx,pj

 

Yes, do a search. IIRC, there is a cool thread about this.

 

Let me give you the readers digest version. It vibrates shit apart and you spend more time welding then racing. Also, it doesn't rev very high nor does it have alot of over rev. Two stroked MX bike engines are all the rage for road racing in theory but in reality the gearing, jetting and general characteristics of the motors make them the exact opposite.

A guy name RB on this board did a nice project of a RS250 with a rotax shifter kart 250cc single in it and that was a neat little thing. Right gearing, counter balancer, etc.

 

i built a cr500 roadracer in a nsr400 frame. had cbr front end and rear wheel. i had to use a wide ratio tranny in it and make my own front sprockets to get it fast enough for roadraceing. also had a 44 mm carb bored to 46. had the works into it. it vibrated so bad it was really hard to ride. six laps was the maximum. it broke the rear shock in half from vibration as well as the frame several times. it was fast and had great power, but was to much vibration. i have seen a guy at the local supermoto track riding a kx500. he seems to run well. just dont try to change the frame and ride it as a dirtbike first to make sure you can deal with the vibration. my two cents:up:

 

I'm wondering how it'd be in the 450 frame like the guys at servicehonda build. You could essentially build it into a road racer like the 450s around now.

 

Yep, done some research,not gonna do it !! Thanx 4 the responses!!

 

Good point, but why not use the cr500 frame?

 

Frame flex.

 

We raced one and gearing was always an issue. Couldn't fit a big enough sprocket on the front or a small enough sprocket on the rear to make it an effective tool. It was always out of gear even on the little tracks.

 

Well, nevermind then. :lol:

 

A friend of mine bought one that someone had put into an aluminum frame. The guy that did the work was a machinest and the installation was very well done.
It had been a while since I had ridden a steel framed 500 but the aluminum frame one vibrated horribly, much worse than I remember any other 500 vibrating. It even had a rubber mounted handlebar.
It wheelied like no bike I've ever ridden but my hands would probably be completely numb after about 2 laps.

Does the KX have a counter balancer? I know the Suzuki LT500 quad came with a counter balanced engine; that might be a better option from that standpoint.

 

Ours had a Biganski built motor in it and the steel frame. It vibrated so hard that it felt like your gloves were full of sand. Had a hell of a time holding onto that skinny little bike.

 

So the CR doesn't have a counter balancer? I've only taken our RS apart, but I thought all engines had one.

Did anyone ever get their crank balanced from a place like falicon? Wondering how well that'd work.

 

Definitely no counter balancer. Never had one balanced, but its a big single...its gonna vibrate.

 

Man...I can't imagine something like that without a counter balancer! Still a fun idea...

 

I tried a KX500 supermoto a few years ago.
Race 1- Barber: Piston, cylinder, crank, and cases all destroyed after a few laps..... But it was fast.
Race 2- Tally: Cracked piston, seized after 6 laps.
Race 3- Nashville: Tried to seize in practice, ruined the piston.
Race 4- Nashville: Finished strong.

I've been riding it off road since then with no problems.

That's one big piston, moving at a high rate of speed for a long time.

 

Did you jet it accordingly?

I've heard of people drilling out the pilot jet to keep the MX 2 stroke motors lubricated during extended off throttle runs, like under hard braking. As I understood it, this mainly what kills them in a road racing environment.

Just wondering.

I think I remember seeing you on that thing running around Tally, as a corner worker. It's been a few years since then.

 

Yes it was jetted correctly. I dont want to get into a jetting debate.

 

I wasn't doubting you, just curious what was done.

 

I doubt you, sorry. Then again, I don't know what oil you run, what gearing (for load) nor what ratio you were using either. BUT, I know once you get the combination correct, that KX500 should easily last 100 hours.

I know you don't know me from adam, but here's a pic:



bike had 100 hours on the top end when I converted it...And 180 when I sold it. Between the two, It never lost one point of compression. I checked it after every race/track weekend at multiple roadrace/kart events. Boy was it finicky about gearing and mainly oil. It'd get real hot without a large amount of oil. Come to find out, I was running nearly what all the kart guys were.

In it's first 100 hours of life, It was 60:1 motorex cross power, the last 80 it enjoyed Bel ray H1R at 20:1...obviously a lot different jetting, and you had to stay on top of it also.