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Any tips appreciated have a crf 250 2010 bike and want top put cr250 2001 engine in what air box to use etc cheers

Tip #1 put a 500 in it.

i see its your first post so welcome and enjoy

FINCHMAN wrote:Any tips appreciated have a crf 250 2010 bike and want top put cr250 2001 engine in what air box to use etc cheers

2001 CR250 air boot works good, but I would scrap the CRF conversion and find a 2002-2007 CR250 2-stroke to convert instead, they are just easier to convert. The CRF's are nice if done good though.

i dont expect it to be easy just abit worried about getting the engine in the correct position what spacers etc and does the clutch casing touch the frame the fabrication would be done by a friend just need pointing in the right direction Thanks

FINCHMAN wrote:i dont expect it to be easy just abit worried about getting the engine in the correct position what spacers etc and does the clutch casing touch the frame the fabrication would be done by a friend just need pointing in the right direction Thanks

I'm pretty sure you can use 2002-2007 CR125 swing arm bushings and spacers for your conversion, don't hold me to that.
54mm in the LH side
59mm on the RH side
Chain and sprockets line up perfect.
That is what I did for mine, and if I'm not mistaken all CR's and CRF's have the same size and width swing arm from 2002-2011. You will most likely have to file the weld under the engine case if you only extend the "U" rather than replace the engine rails..........Just search CR500AF builds on this site, you will find lots of info, good luck!!

Thanks for your help much appreciated!

FINCHMAN wrote:Any tips appreciated have a crf 250 2010 bike and want top put cr250 2001 engine in what air box to use etc cheers

Sounds like a lot of trouble for a 1% ( if that) return.

Put that 2001 motor in a 1993 steel frame.

I just started the same "hybrid" myself. Right now, I'm building the
engine (2000 CR250), and I plan to use a 2010-11 frame.

After looking at pictures of other conversions, I want to "adapt"
a 2000-01 cradle to the CRF frame. This would allow the correct
cylinder angle and provide clearance for the clutch cover and the
other bolts without grinding. One drawback I have already
indentified, is the pipe will need to be modified to clear the
front wheel with the forks compressed if I stick with the stock
offset.

The conversions I have seen so far all have the engine tilted
back in order to conform to the CRF cradle (and probably to
clear the wheel). In addition to looking silly, it raises the CG.

There is still a lot of CAD work to merge the two and still maintain
the OE look.

Not sure what to use for the airbox on the gen 5. I have stock
CRF box sides with a billet front plate and a 2001 CR250 filter
plate and boot on my gen 4 (2008).

Anyway, that's the direction I'm taking - just food for thought.

Put that 2001 motor in a 1993 steel frame.

Already got one of those.

dogger

just been looking at doing the same thing as yourself i have a 2000 bike and was thinking of cutting the cradle off it including the y and mating it on to the crf frame as it also has the engine mounts on already but i never thought of the pipe clearance on the front wheel ive been told that the 2000 -2001 airbox boot will mate upto the airbox we will see i'll let u kno how i get on

i'll let u kno how i get on

Sounds good, I'll do the same.

dogger