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Discussion Starter · #1 ·
Well here it goes.... I am an ME student at Clemson, and I've always been in love with two stroke power. I recently picked up a 2009 ninja 250 with 14k miles for $1600, not wrecked, and I plan on dropping a CR 500 motor in this. Looking at the frame, I think it can be done with proper planning. I picked up A 1986 CR 500 engine today that is in good shape and will start this project this coming semester after my fabrication skills have improved enough to undertake this project, and I have some cad work done on the cradle. The pipe will have to be custom made and wrapped directly forward and down to clear fairings and fit in general. No, I am not going to risk butchering the frame and not being able to ride it again, so I will be on the lookout for a salvage title frame to do all the Fab work on.. I think the most challenging thing to work on is running the electrics of the stock ninja separate from the CR ignition system and handling vibration, but I think it can be done. This won't be a highway bike, and I think I will be able to gear it for about 100 mph (I can't think of a good reason why I'd be going any fastert any where around here). Mostly this will be a pure acceleration and wheelie machine for back roads and such.. ;D I will start posting pics and progress reports when this gets underway.... Cheers
 

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Well all I can say is goodluck! I'm not sure what you want to change the gearing for since the lil 250R can already reach 100mph!
Make sure you take plenty of pics, this will be one to watch!
 

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This is gonna be sweet! Can't wait to follow along, and with a CR500, you should be able to go quite a bit over 100mph.... Even while still being able to do wheelies - a tuned pipe CR500 can have a wicked power kick. All the best, this is gonna rock!
 

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Discussion Starter · #6 ·
SO far I'm doing a little bit of design work in solid works, and getting the ball rolling on making the motor fresh for street use.. It's been in storage a while and the magnesium clutch cover corroded. I'm gonna have to find a new one :facepalm: I'll probably bead blast the exterior to remove all the old paint and that should do it. The piston and jug look in surprisingly good shape and the bottom end bearings feel ok, but I might just go ahead and replace them. Hanging the motor in the frame doesn't look like it will be a huge challenge with the parallel bars in the newer frame. So does anyone know much about electronics? I have about zilch electrical comprehension... :eek: I think I can run the lights off the battery but I'd like to find a way to keep the battery charged off the CR ignition... any Ideas? :popcorn: Could I use a rectifier, I think that's what its called, to change current from the ground wire? Honestly I think this will be the hardest part of the project...
 

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Discussion Starter · #8 ·
Titled frame, check.

Rebuilt CR 500 engine, check.

Potential problems a few... So i've been doing some research on the cr 500 engine and it seems that they are notorious for vibration. I've read stories of this beast cracking welds in fourwheeler projects, and in a NSR 250 project I saw, the builder said the vibration was simply unforgiving.


Part 3 - Project NSR 500

quote: "I got it out for a good ride today and it just does not seem very rideable. It vibrates extremely, extremely bad, and it just did not feel right in the turns. Even when going straight, it will not hold a steady speed, it wants to jerk and kick. It just does not run like it is supposed to be in there. The vibration is just unreal. It feels like I am holding the dang engine in my arms when it is running. Then all of that mass in the crank spinning must be affecting the handling, because it did not feel like it wanted to lean as easily. I think mostly the vibration is scaring me more than anything. I just hate to ride it very fast when it feels like every bolt in it will vibrate out in less than 2 minutes."

Ideas on vibration anyone? The frame I have is bent on the top bend where the fuel tank sits. I was thinking of possibly reinforcing this area and hanging the engine in a cradel held by a pin joint, and attaching the cradle to the bottom of the frame whith two large dampeners. Kinda like a clock pendulum held in place by shocks... I havn't got into vibrations all that much in my course load (next semester) so I guess I'll just have to see how it goes..
 

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jonvon, your doing all the research here, and I don't have time to go through that guys entire thread, but idea:

vibration comes from improper balance - sure, some motors are build with more vibration than others, but check into lightening the piston, possibly changing the timing, or changing the counter weight on the crank somehow... Build the engine first for less vibration.

THEN:

After test riding, pay particular attention to WHEN the vibration is worse - having a resonant frame is no good, and by altering the angle of engine, you can change the length of the engine mounts, and help to fight resonance, canceling out the vibes from each rotation....

Obviously, working in a counter rotating balancing shaft isn't an option - but another factor which plays into resonance...

Rubber dampners are a good idea, but should be used as fine tuning, not an absolute solution...
 
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