Kx500 motor in a streetbike chassis?

[PaulBWatertownCT]

(reposted from introductions area in hopes of a reply)

Hi all,
I have had many, many bikes over the past 25 years but have always had the itch for a 2 stroke streetbike. I am considering buying a KX500 and transplanting the engine into a 2008/2009 Ninja 250R. I have been doing some extensive research and believe the motor will easily fit into the 250R frame with some custom motor mounts for the front of the engine. Some larger rubber and steel braided lines would be my only other mods.

I would appreciate any feedback on thoughts regarding driveability, vibration, or other thoughts and ideas. My purpose is to have some fun and ride something fast, different, and a complete sleeper. I figure I can buy a new or almost new 2008 Ninja 250r for about $3500 and I have seen some excellent condition 2000 or newer KX500s for around $2500. For $6000 plus some garage time and a custom pipe, it sounds like a solid plan.

My current bikes include: 2005 KTM 300 MXC, 2002 KTM 200 MXC, 2002 Aprilia 1000.

Past bikes are too numerous to list but started with a 1975 Yamaha GT80 and run through 2007 Ducati S2R1000. Favorites include 1986 GSXR1100, 1996 TL1000s, 1993 GTS1000, 1997 CBR1100xx.

Let me know your thoughts (and I do know it would be cheaper and less hastle to buy a new supersport bike but that's not the point).

Thanks,
Paul B.

[Polar-Bus]

Sounds like a cool project, I am thinking your only nagging issue to combat will be excessive vibration....

KX500 vibrate quite a bit. When I ride my 500 on hard surfaced logging roads for extended periods of time my feet start to tingle fron footpeg vibration.

[jfabmotorsports.com]

KX500 vibrate quite a bit. When I ride my 500 on hard surfaced logging roads for extended periods of time my feet start to tingle fron footpeg vibration.

Look on the brite side....It can't vibrate more than a Harley. I also had a Suzuki Intruder, an '86, that you had to reach up and touch the mirror if you wanted to see behind you. Besides Chiks dig it!   

[gwcrim]

I've put a lot of miles on a Sportster and THEY vibrate.  There is a big difference between the vibrations though.  The Sportster is more mellow.  The KX500 is MUCH more buzzy.  Change the chassis though and who knows.............

I think you're idea is wicked.  I wish I had the fabrication equipment to build something like that.  I'd love to put an RZ350 engine in a 250 Ninja chassis.

[KXcam22]

Paul,
  You might be happier with a RZ350 or TZ250 frame.  They are both stiffer, handle better and will handle the wheelie shock better than the ninza 250, which is not really a bike designed to house serious hp and handle cornering G's.  I saw a pic once on a KX500 engine in a 250 apprillia frame.  Very nice.  You can get rid of much of the vibratio with some crank truing - a must for the street.  Fun project. Plan ahead on a hidden frame mounted reservoir tank to hold 2cycle oil. An old injection oil tank or rad overflow tank from another bike works well. Cam.

[kneedrager428]

ALso if you really want a trick little bike, Find an old FZR400. These can be built cheaply, handle Awesome and with a YZF 600 4cyl they are around 330 wet. I cant imagine what it would weigh with a 500 in it but it should be spectacular!

[jfabmotorsports.com]

Or....Super single!

http://www.rolandsands.com/images.html#

[BDI]

I think if I was to do it I would have to put the engine in something more technologically advanced then a 250 ninja. The idea is very cool.

[SMPKX500]

I also was thinking of the K5 250r swap. Would it really be worth it?

[KXcam22]

It would be a fun swap. Like BDI, I don't think the 250 is the right frame to use.  Better off with a more performance oriented bike. Cam.

[BDI]

A newer aluminum framed kawasaki 600 might be the way to go.I know one might think it would be to heavy but all the weight of the bike is the engine. With the engine out of the bike I can lift the whole thing very easily. The bikes are way lighter then you would ever think once the engine is removed.

[KXcam22]

The new bikes are super light. I can lift the rear of my CBR900RR easily with one hand on the swingarm.  Cam.

[PaulBWatertownCT]

Thanks to everyone that has replied with your thoughts and comments.

My take aways are this:
I feel the 2008/2009 Ninja 250r chassis is modern enough for the type of riding I'm looking to do. (I have my Aprilia 1000 for long rides or two up). Also, seems better to start with a brand new or one year old bike for the low cost to acquire.

Sounds like I will need to fabricate a frame cradle for the bike, as some concerns have been raised about how the stock frame might handle landing a hard wheelie (I'd like to think I'm smooth, but not always

Sounds like I will also have to get the crank balanced and some bar end inserts or urethane mounts for the handle bars.

I has also considered a Banshee 350 twin, however space becomes a concern fitting both the engine and the pipes, and the KX motor looks much easier to fit in.

Some had suggested a 4cyl motor, been there done that.

Thanks again,
Paul

[BDI]

I went and looked at the bike you are talking about and it does look like a cool little bike. When you said ninja 250 this was the first thing that poped in my head. You should go for it, what about registration and insurance. If you do it you should do a whole post about the build from begining to end with pictures. We need more of that around here.

[kaw rider]

Brian
I think a good running K5 would give a 600 a run for there money. Look at the 600 torque curve.