cr500 motor in 400ex chassis

[panteramatt]

Ok, Im going to get a complete 400ex roller and want to know how difficult it would be to fit a cr500 or kx 500 motor in it. I need to know:

Will the sprockets line up
Where can I get a pipe
Will a cr500 pipe fit
What about the silencer
What year motor is the best
What to do about a radiator
will I need to trim the rear fenders

[frosti108]

well 1st off im pretty sure youll have to balance the crank or something like that... theres so many more problems with this than i think your aware of...

all im saying is, i dont think its as easy as it looks

[DamageInc]

Well, I don't know anyone who has done this swap, so I can't help with your question much, but I can tell you that you are going to get a bunch of responses from people who will tell you that the vibration will crack your frame or some crap like that. Most of them have probably never even ridden a CR or KX500, much less done any kind of a swap. Ask them how it works in the CR500 without cracking the frame? Just make sure you use rubber motor mounts, and if you can live with the vibration, so can your EX. Just use loctite on all of your fasteners, lol.

I think one of the biggest problems will be adding a radiator without having it look too cobbled up and homemade. Isn't there a company that fits CR250 motors in these? Maybe you can see how they do it for the radiator. Also, keeping the front end on the ground will be nearly impossible unless you add a longer swingarm. :)

[frosti108]

just come to your senses already and buy a quadzilla lt500 :D

[BIGBLOCKBILL]

I've seen several 250Rs with CR500 motors in magazines.It looks like a fairly simple swap. I think a company used to make swap parts for this setup.Maybe do an internet search for old Dirt Wheels or ATV Action magazines for a TRX500R.

[TCracin440ex]

ok....this conversion is not a very bright idea because that motor vibrates so much that it will break anything u bolt it to besides a dirtbike...buddy of mine did put his cr 500 motor in his 250r chassis and he broke 2 frames due to the power of the motor...and vibration....id do a crf 450 conversion before a cr500


far as seeing the cr 500 motor in a mag. macracinginc built that trx500r...but they used a 250r bottomend and a cr 500 topend.

and even if you do pull it off it will vibrate the teeth out of your head

[44oEX]

the carb will hit right where the upper shock mount is. my friend tryed it.

[pairanutz]

the vibrations are horrible for anything other than hillclimbing or drag racing
2 buds of mine have this set up -one in a 400 frame and one in a 250r frame-both cr500
in 400 frame the stock pipe fits fine-when you install cylinder and pipe at the same time-silincer has to have mounts made
the sprockets line up if you weld the motor mounts in correctly
carb just use a universal k&n or uni filter
radiator -suzuki lt fits best -mount between stem and frame -where the 400 oil tank was
hope this helps have fun

[frosti108]

i heard theres something you can do to stop the vibration tho. somethin like you gotta balance the crank or the rod or something...

[pairanutz]

the reason cr500s vibrate and 250r motors dont is the trx250r motor has a counter balancer-dirt bike motors dont -why ??
one way to help cut down vibrations is find old a-arms cut up and use the end with the bushings as motor mounts -helps some
you also ned to cut up your rear fender or make the rear fender a flip top -to clear kick starter

[DuneAholic310R]

I have a Cr500 motor in a zilla frame and the vibrations arent as bad as everyone is saying I had the crank sent out to Crankworks and had it balanced... and w/ a anti vibe stem and siliconed handle bars its not bad at all

[DamageInc]

I have a question for all of you folks that say the vibrations will break it apart: how does the CR500 stay together then? Do they use some magical different metal in the frame than what a quad uses?

If you've ever ridden a CR500, then you know that they vibrate a lot, but no different than if you put it in a four-wheeler instead of a two. It's just part of having a 500 single two-stroker, and just something you have to live with if you want that type of power.

[UglyMotha™]

Originally posted by DamageInc
I have a question for all of you folks that say the vibrations will break it apart: how does the CR500 stay together then? Do they use some magical different metal in the frame than what a quad uses?

If you've ever ridden a CR500, then you know that they vibrate a lot, but no different than if you put it in a four-wheeler instead of a two. It's just part of having a 500 single two-stroker, and just something you have to live with if you want that type of power.




well you just made it obvious that you have no clue what your talking about a cr500 dirtbike vibrates nothing like it would in a quad frame, you are talking two different worlds most majority of dirtbike motors will vibrate badly in a quad frame, this is due to the fact that dirtbike engines don't use counterbalancers cause of the way there designed the front forks of a dirtbike absorb vibration unlike a quad which doesn't have front forks there is now way to absorb the vibration that is why a quad motor has the counterblancer, the trx250r motor isn't just a 250r motor thrown in a quad frame the 250r has counterbalancer which decreases vibrations, so no you can't use the phrase a cr500 vibrates just cause that the nature of the beast, because it's not true, it's just not designed for that aplication

[440exnacsracer]

honestly, i dont see why you couldnt try. it has been done, and i believe that if you used alot of rubber for bushings (would have to be hand/custom made by you), i know it could be done. by gusseting the frame to make it stronger and finding a radiator and making brackets for the radiator and motor, you would have a start. i think a 250r frame would be the best bet though, with the radiator mounts already there. if you really have enough money, you could look at newer, taller frames such as the raptor or even predator. it would be very easy to find a broken predator frame and repair it with the rath racing gusset kit. you would then be able to clear the top shock mount with the carburetor and have plenty of room to deal with the exhaust. the narrower frame would also help with vibration. good luck and i think it would make one heck of a quad!!

[DamageInc]

Originally posted by UglyMotha™
well you just made it obvious that you have no clue what your talking about a cr500 dirtbike vibrates nothing like it would in a quad frame, you are talking two different worlds most majority of dirtbike motors will vibrate badly in a quad frame, this is due to the fact that dirtbike engines don't use counterbalancers cause of the way there designed the front forks of a dirtbike absorb vibration unlike a quad which doesn't have front forks there is now way to absorb the vibration that is why a quad motor has the counterblancer, the trx250r motor isn't just a 250r motor thrown in a quad frame the 250r has counterbalancer which decreases vibrations, so no you can't use the phrase a cr500 vibrates just cause that the nature of the beast, because it's not true, it's just not designed for that aplication

And you believe that because someone told you that, or because you are an engineer? Yeah, that's what I thought. Don't believe everything you hear. The forks on a bike might make the vibration a little less noticeable to the rider, but the vibes still have to travel through the frame. The primary reason why counterbalancers are used in quads is because of the way they are ridden. Quads are mostly trail ridden, often all day long. A dirt bike is usually ridden for short periods of time and on a racetrack. The vibrations are simply less acceptable for quad use, as well as more noticeable.

Have you ever ridden an LT500 and a CR500? The LT's use a counter-balanced motor, but they still vibrate a lot, just like the CR does. It IS the nature of the beast, counter-balancer or no counter-balancer, forks or A-arms.

[UglyMotha™]

Originally posted by DamageInc
And you believe that because someone told you that, or because you are an engineer? Yeah, that's what I thought. Don't believe everything you hear.



you do a great job of sticking your foot in your mouth :o



deffinantly no point in arguing with ya there, bucko :rolleyes:

[86atc250r]

There are a lot of myths out there on "why". Most of them have no basis what-so-ever.

It has nothing to do with forks.

It has nothing to do with 2 wheels vs 4

It has nothing to do with how many "axes" or "contact points" a bike has vs a quad.

The answer is really very simple.

A motorcycle frame is very compact and strong when compared to a quad frame - that's it, mystery solved. No black magic forks - no mysterious contact points - no strange things happening with one axis vs another.

Plain and simple strength issue. Think about how a motorcycle's handlebars connect to the chassis - thru a very bulky triple tree setup attached to a very strong steering head section of frame. Now compare that to a quad, who has a long steering stem made from thin, small diameter hollow tube, and is unsupported for several inches before it reaches the bars (essentially a vibration amplifier)

Lets now turn our attention to the engine cradle section -- a motorcycle's engine cradle is usually only large enough for the engine itself & has heavy tubing up the front toward the steering head - where a quad engine cradle is very open and airy, with small diameter tube as a perimiter.

It all seems very simple and clear to me - I'm not sure why so much effort's been put into these various myths, maybe just perpetuating info from magazine articles?

FWIW, yes, I've built a CR500 powered 400ex. Yes, I did quite a bit of work to strengthening the chassis and engine mounts. No, it's not a simple drop in installation and there are many problems to be solved.

Although the project is currently unfinished, it is rideable - whether I'll finish it or not is still up in the air. The new 450 class of quads put out much "better" (read that useable) power than does a CR500 engine & a 450 with relatively light modifications will compete with a CR500 with relatively light mods so I'm not sure at this point if it's worth persuing.

Vibration with a CR500 in a 400EX chassis --- reasonable if done correctly. You will feel it mostly at higher RPMs in the footpegs and bars. If you do things right, it should be manageable. Does it have more noticible vibration in a quad chassis than the bike chassis -- yes.

[DamageInc]

Do you have any pics of your project? I'm mostly curious about how you mounted the radiator.

[86atc250r]

I don't have any pics on me -- pics of my radiator setup won't do you a whole lot of good since I've got a temporary Cannondale radiator installed and some temporary tabs and brackets in place for testing. So the radiator setup is definitely not what it will have permanently.

Really, the radiator mounting is one of the easiser parts, all you have to do is weld a couple brackets in place to hold it

[440exnacsracer]

you had enough room to fit the radiator and motor, with carb clearing the top shock tower? must be a tight squeeze in a ex frame, i just think it would be a little easier in a taller, longer frame, like i said before, such as the predators and raptors.:confused:

[86atc250r]

If you correctly locate the swingarm pivot it will free up a decent amount of clearance for the carb to clear the left hand frame tube and upper shock area. You'll still have to fabricate an air intake boot though

Not the easiest swap, but do-able....