BannedCR500Riders.com

Does anyone have any info in this type of conversion? I have the frame from both bikes and was thinking of moving the Y up on the CRF then replacing the lower frame rails with the 2001 Cr250 frame rails. Would this work or are the frame bends way to different? Any input from someone who has tried this would be much apreciated.

My 500 conversion is still going strong and now I wana upgrade the old 2001 cr250 but dont wana dump money into an older technology chassis.

i started one u will need to do some weird bend on the lower tube to get it to clear on the clutch side or just put it in and have it with the wrong cylinder angle and sprocket alligenment like service honda does if u set the motor like it should be it needs a downward bend just out of the pocket i didnt like it so i just put the 98 250 motor in a 2003 cr 250 frame i really dont think their is a better bike that i have ever rode than that and the motor fits right in just adjust the front mount a tad and put a good air boot on it i used a 2001 lined up nice ond alot better seal than the newer boot

Have you seen this one?


http://www.bannedcr500riders.com/board/ ... hp?t=11757

I started a gen5 with a cr250 engine

Wow, nice looking work! That will be one sweet 250 setup.

Nice looking welds too!

What are you hoping to gain over a stock Gen 3 250?

The Gen5 factor.

Or to be one of the first. More SH competition.

Good looking mounts, btw.

What did you use to extend the cradle when you moved the Y up? Looks really good.

Not looking to gain anything noticeablly more than a gen3 frame. But I do like the idea that the 07 crf250 frame is skinnier and lighter feeling while riding. I couldn't find a gen 3 250 for a reasonable price. Then I came across the 07 crf250 for $1300. With nothing majorly wrong with the bike. I'm planning on riding it as is then when I get sick of the 4 stroke sell the motor and drop in the 01 250

cj250f wrote:What did you use to extend the cradle when you moved the Y up? Looks really good.

I used aluminium bar.

I'm working on a similar idea using an 09 CRF250R frame and a 00 CR250
engine. I'm still looking at all the options for the frame but to keep the
weight down, I lean toward using the cradle from a gen 2 CR250 frame
instead of a billet cradle. The stock CRF cradle doesn't provide the
needed clearance for the right side case cover which is what jarnott71
was talking about in his post.

The cradle, airbox mod and pipe fitment should be the extent of the major
changes. No reshaping the brake pedal, no problems with fuel tank to head
clearance, no shock spring divot in the center case and the CR250 uses a
single return radiator hose like the CRF.

I know I said in an earlier post, I had planned to go the gen 5 route, but that
frame has too many geometry problems, so I am switching to the tried and
true gen 4. Since the A-kit suspension is only sold as a front and back set,
I will have a trick works Showa short body shock for sale in the near future
for any gen 5 guys that have an extra $3000 burning a hole in their
pocket

dogger

Thats exactly what I was thinking... use the gen 2 250 cradle, im hoping that after fitting into the crf frame I can use the existing motor mount tabs on the gen 2 frame rails. Ill probly start the build in two weeks or so. Anyone in need of an 07 Crf250 engine, carb and electrical?

You're starting on your frame before I am, I'm still building the engine.
Keep us posted on the cradle compatibility with the gen 4. At first look,
It appears to be a good match. And as you said, Everything but the
hanger plates will already be correct. You'll need to find a place for
the ignition module. Since you're using a pre-HPSD frame, you can
mount it on the steering tube behind the front number plate just
like an OE CR. I'll be mounting mine between the radiators like on
the stealies.

dogger

Did a quick comparison of the engine cradle frame rails and the 01 250 frame is a different size than the 07 crf250 frame rails. Its enough of a difference to not be able to do what I was thinking.

Gen 2 rails are retangular, gen 3,4 rails are square, gen 5 funny shaped.

The front mounts by the pipe would be the main difference over a normal CR500 conversion. The lower mounts interchange from a 01 CR250 motor bolt pattern and a CR5 pattern. CS position not taken into account.

Thanks for the info. I still want to use the 00-01 cradle shape so I'm going to
try to replicate the 00-01 cradle using the correct 08/09 compatible tubing.

I'll have to find a competant shop to do the bends. With Aluminum, they may
have to use something like hydroforming to prevent kinks. Looks like the cost
of this project just went up.

dogger

started on the project. Got the CRF250 down to the frame and did the first fit of the 01 250 engine. This conversion will require alot more mods than the Gen2 500 conversion. I will post some pics when i get a chance

Cut out the Y and did some test fits. The engine still needs have the front rotated down, but I need to clearance and finish the area buy the R/H foot peg. Also trying to decide on what to do for extending the frame rails. I was thinking about trying to make the Y out of flat sheet like a post I have seen before or figure out how to extend the frame rails and reuse the stock Y. I cant find anyone localy that has 1" square stock with the corners rounded like the frame..... Anyone have some that they are willing to sell?

if u get the motor to sit right u will need th replace the hole cradel if u clearance the stock cradel you wont have even half the tube left

Bummer..... Is getting the engine straight more of a visual thing or does it affect other things besides CS sprocket. I'm waiting on a new pipe so that I can mock it up and see how it fits with the engine sitting as is.

I mounted my engine using two parameters....

Where the end of the pipe ended up.... ( The important one)

Where the C/S sprocket ended up after positioning for the pipe.

Rolling the engine too much places the C/S too low, and will create lots of chain slider wear.

Rolling the engine not enough aims the pipe at the rear brake caliper.

Your trying to find a happy medium in between...





I did not replace my cradle, just ground it a bit to roll the 500cc motor to fit.

I would think the 250 cc motor would fit as well.

Thanks. I was thinking along the same lines. Once I get my pipe I will mount the engine where ever I get the best pipe fitment. Still need the 1" extensions for the frame if anyone has some they are willing to sell. I can't find anyone in Hawaii that sells it... Besides the square edged stuff which I refuse to use.

it dont fit as well the 250 motor is differant than the 500 motor so start grinding and see how much tube u have left when u get done again good luck not replacing the cradel oh and just so u know 2005 and up cr 250 has the same shock linkage nuckel swingarm forks wheels only differant valving so what u are getting out of all the work is differant plastic and frame spares you could put your motor in a 2005 cr 250 frame and have a badass bike in a couple hrs and have some $ left to get some hookers or somthing lol good luck with the build it can be done to do it right is going to take some fancey tube work or just throw it in sh styel and have a pos when u get done

Thanks, I am aware of the parts interchangability.

Having owned various years of CR250's I can definately say that the 07CRF250 feels much lighter, skinnier, and smother feeling than my 06 CR250 that I had, but maybe thats just personal preference. I got the 07crf250 basicaly for free after selling the motor, exhaust, carb and ignition from it. I am confident I will be able to finish this project and the final product wont be a piece of shit thrown together like SH "as you say".

Hopefully!!!!

CS position affects rear suspension performance. Dogger315 was schooling me last week about the angle the motor is clocked, specifically the angle the piston travels up and down at and the resulting gyroscoping affect on handling.

IMO how the motor is clocked is the most overlooked aspect of AF.