250R motor into a 450R frame - Ideas ?

[Langbolt]

I picked up a 450R frame to see what all would be involved to setup a 250R motor. my thoughts would be to have all 450R component as they're readily available as opposed to 250R stuff slowly diminishing.

Here's a pic with the motor in place.

What to do with the rear shock cross brace....it's right in the way of the carb.

I was thinking of using a tube to pass through it that the carb could connect to on one side and the air filter tube on the other.

Anyone have any Ideas for a good solution ?

[Langbolt]

Side view

[hawaiiysr]

not much of a detailed picture but its what i have saved on my computer. this is not mine. just a picture i came accross online and saved.

http://thumbnails31.imagebam.com/18399/06cf7d183984723.jpg (http://www.imagebam.com/image/06cf7d183984723)

[headache]

looks like you are definetly going to have to notch the frame there. i would do what you are thinking and clamp a tube on the carb and the filter on the tube. good luck on your project!

[Langbolt]

Yeah I saw that one....and this one too!

It looks do-able.....I'm thinking of lowing the Swing arm pivot location to lower the motor....and creating an Upper shock mount like my Laeger frame....I'm thinking that's the best path to take.

[Honda5]

Is there a big need to have the pivot thru the motor? It looks as if you could make better clearance and a better engine angle if you moved it front and the back down.

[Rossi 46]

Came across this on ebay. He has alredy done the same conversion. Might be of interest to you.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=220994329029#ht_980wt_1185

[deathman53]

did you try a 400ex carb-airbox tube? my atc450r had the same issue, the guy that built it, made a custom airbox that used a 400ex tube to solve the problem.

[hartwill]

It looks like it should be quite a bit closer just by lifting the front of the motor but I would guess some fabricating to the area would be your best bet.

[mx Eli]

could try fabing a upper shock mount that is supported from the bottom instead of having the tub go across the top of it

[Langbolt]

Thanks MX Eli....I was toying with that Idea....but I think the Tension load instead of compression (like the stock mount) would require some seriously strong brackets and tubes....but with that method it would make clearing the Carb a piece of cake.

Remove the old Cross tube.....Install a NEW one below the Intake tube and bracket the Rear Shock mount to that.

Any other good Ideas out there ?

:D

[250x_kyle]

if you built a simple jig for the shock location you could probably slightly notch the upper frame rails a tad higher then stock back frame rail. if that was the case you could tubular gusset it like the older houser aarms and build a new shock mount. would probably gain your about 3/4 to an inch of clearence. could probably encorperate the sub frame tabs into the gussets. sorry if this doesnt make sense lack of sleep is kicking in. i will try to hagardly draw up what i mean in paint unless someone has a 450r frame in a dwg format.

[Langbolt]

This is what I was thinking might work....

[laeger400]

This what I done on my crf 400ex geo frame for clearance. I did go with a crf450 rear link also but the 400ex 450r frames are similar in design.

http://i1109.photobucket.com/albums/h426/jdub160/LSR%20CRF%20450%20PROJECT/7251e6a5.jpg

http://i1109.photobucket.com/albums/h426/jdub160/LSR%20CRF%20450%20PROJECT/4758f019.jpg


Thanks Jerry

[Langbolt]

Thanks for posting the pics Jerry,

I have all 3 frames now - 250R, 400EX & 450R....And yes the 400EX & 450R are very similar....most of the differences are in the front A-Arm mounts....the rear of the frames are very close.

Did you have to modify your Plastics to clear the new Shock mount ???

Or was there plenty of room ?

:D

[laeger400]

It fits. It's close but it's just Ike any other chassis that has a crf450 or cr500 setup.

[250x_kyle]

Originally posted by Langbolt
This is what I was thinking might work....

very similar to what i was thinking. but a touch different. the 450r frame has a little sharper roll to if if im remembering correctly.

[madmaxmodquad]

looks like you can flip the carb mount to angle it up more unless that interferes with the tank and seat