View Full Version : CRF450R Motor in a 2000 RS250 chasis...

04-18-2003, 02:35 PM
I know someone has used a CR500 2-stroke motor and it worked. Has anyone used a 4-stroke dirt bike motor? I am thinking of using the XR650R motor but it seams to weigh a bit more than the CRF450R however in stock trim the XR only puts out 5 more horse power. Anyway looking for some advice, tips, or links if anyone has any.


04-18-2003, 04:25 PM
why would you want to put a slow 4 stroke piece of shite engine like that in an all ready beutiful and really fast rs250? I can see if you want to install a 500 two stroke single cylinder honda cr motor because that would be fast. Also 4 stroke = less hp and way different ride than the already perfect rs 250. Waste of alot of money but if your a rich man then I say what the hell blow your money away.

04-18-2003, 06:16 PM
That particular motor "CRF450R" IS a fast motor, no premix, WAY less rebuilds, more torque, plenty of kit parts available in the U.S. and at a resonable price. The cost of parts in the U.S. for this bike is the reason I am considering a 4-stroke motor. If I put in a 316kit the cost of it here is about $3,000. and that is for pipes, carb work, motor work, crate, shipping, etc... now once it is time for a rebuild I am stuck with the same problem I have now, "expensive parts". I can pick up the CRF450R motor for about $3,000 with pipe and the rest of the kit parts maybe $4,000 total, BUT parts are cheap and usually in stock at any shop, there is no ordering, paying high prices, or finding a particular part. I still get to enjoy the RS but with a longer shelf life, not to mention MORE horse power.

04-19-2003, 05:16 AM
well i think it would be a great bike,if you manage it.Keep us informed if you go ahead with the plan.The only problem i could see is that those four strokes singles are quite tall.

micah apriliaforum com
04-19-2003, 07:52 AM
I am willing to do the conversion for you if you do not want to do it yourself.....it will cost some $$$ but sounds like a great idea. The 450 Honda motor is not free of issues however....they burn more oil that your 250 does probably...and for less rebuilds, I would not be so confident. (anything with that little piston skirt is gonna consume some parts and that is a very high performance engine)...it is an awesome motor to ride....so is the 650 but you are correct that it is heavy....lots a torque though.

04-19-2003, 01:20 PM
What kind of ball park figure are you talking? I have an engineer, a wielder, and a good mechanic friend that are willing to do the figures and the install of the motor. I realize this is no easy job and if I didn't know the people I know I would not even try this. My cost for this project is going to be very minimal, parts & supplies.

<img src=http://www.ezboard.com/intl/aenglish/images/emoticons/ohwell.gif ALT=":\">

04-19-2003, 06:27 PM
I considered converting my RGV to a supermono streetbike, which would have been the shyt, but later lost interest. The mono's aren't any faster, but they'll give you a lot better range of power & torque, and less rebuilds (depends on which motor and how much you mod it). There are quite a few motor options out there, just depends how much you want to spend...

The Rotax would probably put out the most power, but that wouldn't be cheap.

04-19-2003, 06:32 PM
Honda RS/XR Supermono (http://www.users.bigpond.com/nmilne)

Here's a link that'll give you an idea of some of the issues that you might encounter with the older xr motor, and the install in general...

04-20-2003, 02:18 AM
60 hp RS250 blow the 45hp CR450 away , they lose compresion and power after 5k miles

as far as super mono they are a hard to start , hard to kick start or bump start a a 650cc with racing compresion ,they vibrate and sound shatter eydedrums , not streetable like you think--any attempt to muffle it and lose 10hp , they put a electric start but it make it heavier and defeats the perpose

04-22-2003, 05:13 PM
Does anyone have the website for the guy that put the CR500 motor in the Aprilia RS250? I have found some links to CR500 kit motors and some of them have reached as high as 90hp not to mention the weight saving of the 2-stroke single...

I would appreciate it if someone could pass on the link.

Oh by the way Ed this the guy in Hawaii. I will probably be ordering some parts here in the next few months.


04-25-2003, 12:27 AM
its too easy to do as long as pipe fits .. dante on macdizzy board fitted YZ490 into RGV frame

i think 90 is hogwash , i saw 65 to 70 claimed on the rear wheel which is more than enough to get you highsided in tighter corners

i remember a radically moded kX500 raced in 250 class and it had very abrupt short power -- once tuned they lose the low end and still cant rev too high so you end up with a monster with narrow band , crank it leaned over in first gear and hope not to spit you off

04-25-2003, 03:53 AM
I have seen a couple of RS 500 convesrions using
the Suzuki RG500 gamma engine (two stroke) - ovet 110 bhp, 150kg weight, and almost 160mph top speed - now thats the kind of engine you want to be putting in:
(www.isk.kth.se/~isk_joan/...S500.html) (http://www.isk.kth.se/~isk_joan/Aprilia_RS500.html))

04-25-2003, 03:54 AM
this is the right one:

www.isk.kth.se/~isk_joan/..._RS500.htm (http://www.isk.kth.se/~isk_joan/Aprilia_RS500.htm)

Cannon Fodder MOO
04-26-2003, 12:10 AM
I haven't even picked up my RS and I'm dreaming already :p

...nahh too much hassle :x

04-28-2003, 03:51 AM
my $0.02

if i had a twin brother who could ride the same as me & he had a RS500 (conversion) & i had my RS250, i would kick his arce in anything other than a str8 line...

the RG 500 engine is peaky, unreliable & to fit one into a rgv/rs frame invloves a scenario where u pratically have to drop the engine everytime u wanna change the plugs... (ok OTT but certainly the heads....)

04-29-2003, 04:37 AM
4 stroke in an RS frame ???...... oh dear lord, what has become of this forum?? i go away for a couple of weeks and 4 strokers take over!, the CR500 might fit ok, but the 4 strokes got all that cams an' stuff over the barrel and might b a tad on the high side, heavy little suckers them big 4-singles too, i dont rekon the power characteristics suite the chassis either and you'd run out of legs at say...160kph??, gearing might be an issue. sorry Adam but i rekon the rg500 motor is so far superior to the rgv250 in every way, even the 400 version is more streetable than the rgv will ever be.(my opinion only mate :D ), the rg500 donk still is a luvely piece of kit, even now.