Probably a question for Ash. . .

[Tom]

Would it be possible to fit an XR650R engine in a CR or CRF alloy frame? (99 - 02 model or similar).

I'm negotiating for an XR engine on the cheap, just wanted to teach myself how to rebuild and modify and engine without killing the one i have. . . and then the idea hit me. . . CRF650R monster track bike :D.

Don't care about road registering or anything like that, just something to play with in the garage over the chrissy break and smash around the track next year.

Possible? or just ridiculous? :-k

[Wobbly]

Funny you should mention that Tom, but I've been having similar thoughts but with a different motor. I did consider the XR lump, but to be honest you are going to struggle. The 650 motor is just physically big, to an extent end to end, but to a greater extent vertically, because of the SOHC & rocker design and long stroke. This means that the rocker cover protrudes quite significantly into the petrol tank area and maybe even to the cross bracing behind the steering head (if any - there is in the frame I'm looking at).

I have considered the 650 motor in another dirt bike frame (ala crf) as well as in the supermono chassis that I put a XR600 motor into (which was considerably easier due to the short nature of the engine as it didn't include the swingarm pivot in the case design). When looking to see what will fit, what you basically need to do is line up the motor around the central axis of the frame and then work out your countershaft location, given any restrictions such as a shared swingarm pivot assembly. You then work out how best to mount the motor, either machining existing engine cases or (preferably) the frame, or by looking at running an outrigger bearing on the countershaft to support a different sprocket location (which may require some welding of the shaft itself).

Then you need to look at engine angle and what supporting mounting needs to be in place. When using a dry sump motor you want to make sure that engine inclination doesn't cause too much oil to be carried in the sump due to the oil pickup location, otherwise you need to change where the pump scavenges from, but generally this shouldn't be an issue unless dealing with large changines in engine position. Then once you have your motor basically located, cut off any other engine mounting points that are presently in place and weld up new ones or, alternatively, make up some brackets of sort to apply the appropriate offset.

Of course there are normally about 1 million other things you need to do, mainly finicky little things, but that's generally the gist of it...

[Wobbly]

Here are some pics of stuffing something where it aint supposed to be...

http://members.iinet.com.au/~nmilne/supermono/bikeTopmount2_fullsize.jpg

http://members.iinet.com.au/~nmilne/supermono/bikeFullframe1_fullsize.jpg

http://members.iinet.com.au/~nmilne/supermono/bikeFramemotor_fullsize.jpg

[Tom]

Hmmm, didn't think about the dry sump bit. Trying to fit an oil tank as well as the engine might be a bit of a stretch.

[Wobbly]

There are many options - it just takes some ingenuity, a plasma cutter and a lot of welding :lol2:

[Wobbly]

I made up an oil tank to sit under the carbs and a header tank to fill from, above the level of the oil cooler...

http://members.iinet.com.au/~nmilne/supermono/bikeOilTank_fullsize.jpg

http://members.iinet.com.au/~nmilne/supermono/bikeOilRes_fullsize.jpg

[Flash]

I was going to say height will be a big issue as they are real tall and obviously 2 stroke aren't.

[Sibbo]

WOW, I do like the idea of the trianglated front engine mounts run off the main frame.

The beg issue of putting a 500 (yes, its not a xr650) into a cr250 frame is the fron engine mounts are further forward on the 500. This results in a bit of cutting or fancy designed new engine mounts.

[Wobbly]

Meh, I wasn't all that keen on them because of the lack of torsional stiffness ... the engine cases and rocket mount should provide enough, but still...

[Sibbo]

Would make for quick engine changes.

[Tom]

General consensus seems to be possible but very difficult. Perhaps i'll just rebuild the engine for fun and then sell it. . . or put it in a go kart :lol:

Did you guys see that video of the guy with a GSXR1100 engine in a Go Kart? Maybe an off road version of that?

[Sibbo]

put a turbo on it and see how many psi it takes to kill it, then back it off a bit and put it on the good engine.

[Tom]

You're a thinker Sibbo. . . I like it :up:

[Flash]

I have seen a few turbo's on xr's and I have advised on 1 also. They work well because of the low state of tune and already being bullet proof

[megahead]

I've seen in a roadbike mag a yr or to ago a gsxr1300'busa engined r1 swingarmed front end megabuggy it was the SHIT!!! and the owner had plans to turbo it . NUTSSSS!!!! i WANT ONE
wish i had some pics its in an old amcn i think