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WR/YZ250F Custom Bike Build Engine Question

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I was looking into new2012 KTM EXC 350f $9800

Then I went to the 2012 WR250f $6500 I have been riding for almost 34 years Just want to do some enduro style riding . I want a light bike with power. I was then looking at the GASGAS EC250 4t..they use the WR250f motor in there bike,still $8500.

My Question is will the WR250f engine fit into the YZ250f frame

I had Ideas of just building the bike I want...

I haven't bought a bike or frame I can buy any year frame and motor.. I know 03-06 are one style and wr aluminum frame 07-11 wr

Just wanted to find out if anyone has tried this?

I'm thinking if I just spent my 5k on a custom build I might be getting a bike I really want . I was going to get the new Wr then remove the Rims and tires for some aftermarket rims and alum hubs, then use the open cartridge forks, then upgrade the triple trees and add steering damper,FMF exht....etc I didnt want a complete bike laying next to me when I was done!

Basicly putting a WR250F Engine in a YZ250f bike looking for the 208 lbs dry weight.

Thanks RoscoeJ (John) :bonk: Let me hear what your thinking ..

Edited by RoscoeJ

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The WR and YZ 250F's were identical in '01 and '02 and have nearly identical frames on later models (up to '09). The only difference in where the subframe attaches to the frame on the lower left side. This change was made to accomidate the quick-access airbox on the '03 and later WR. The engine on the YZ and WR is identical and many parts interchange between '01-'11 WR's and '01-'09 YZ's. The change to aluminum frame was made on the YZ in 2006 and the WR in 2007 but the motor mount location remained the same. The 2010 and later YZ cylinder head was changed to reposition the mounting point for the head stay. The forks (and triple clamps) were upgraded to from 46mm 48mm in 2005 on the YZ's and WR's but the WR forks remained the old style open cartridge type. The 48mm twin-chamber YZ forks will bolt right into the '05 and later WR triple clamps. The '06 and later triple clamps on the YZ's and WR's have removable bar clamps. Wheels, axles, brake rotors and calipers, sprockets, brake pads, and triple clamps (with the matching forks) will intercange on all '01-'07 YZ's and WR's. In '08 (or '09?) the rear axle diameter and rear sprocket was changed.

I recently purchased a 2005 YZ250F for $700 and plan on installing a WR250F transmission, flywheel-magneto, and rear wheel from a 2002 WR250F parts bike I picked up. I also plan on using a Hot-Cranks stroker crank with an Athena big bore kit to get the bike to 306cc. This bike, when it's done will weigh about 218 lbs and be a great ride for the type of riding you have in mind.

The great thing about the YZ/WR250F from 2001-2009 is the huge aftermarket for parts and the ease in which parts can be interchanged.

I plan on spending about $3500 on this project and I'll essentially have a brand new bike.

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I cant thank you enough for your post,not many arround with this knowledge.Please keep me in your projects loop or IM me with pics and your progress ,I would like to see some pics! Where did you find your yz for $700? did it have a bad engine? Thanks Again!

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If you do a search there was a very in depth and lengthy thread about a guy on here that installed a WR motor in a YZ frame and custom made tranny with gears from both. Came out extremely nice. He used the wiring harness of the WR but removed half of the wires because they weren't necessary.

On the info that grimjim had mentioned there are a lot of things the WR was a year behind the YZ. I know in 04 the WR forks were 46mm and the YZ was 48mm. Ran into that problem myself and found out the hard way. Good luck on your adventure and please post picks and info on your project as you go.

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Every bit of engine internals will interchange on all 250F YZ's and WR's from 2001 to 2011. The head casting is different on the '10 and later YZ's but all of the internals are the same. It's just a simple matter of parts swapping to build what you want.

The only sticking point is with electric start WR's ('03 and later). The crank is different on the left side but you can still use a YZ crank if you can live without the e-start. You can use the YZ mag cover, flywheel, and stator, or you can convert your e-start WR to the '01-'02 WR non-e-start by using the '01-'02 mag cover, flywheel, and stator. The '01-'02 YZ's and WR's used identical cranks.

The other hang up is the WR's quick access airbox on '03 and later bikes. The WR's subframe-seat-fender can be adapted to the YZ fairly easy (a little welding is required) but puting the WR airbox in the YZ is quite a pain-in-the-arse (but it can be done).

The YZ/WR 250F is really a great platform for making a custom bike because of their were so few changes in the bike since its introduction and the use of many identical parts between the YZ and WR. Something not even remotely possible with a Honda CRF-R or CRF-X.

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On the info that grimjim had mentioned there are a lot of things the WR was a year behind the YZ. I know in 04 the WR forks were 46mm and the YZ was 48mm. Ran into that problem myself and found out the hard way. Good luck on your adventure and please post picks and info on your project as you go.

The 48mm fork was introduced on all models in 2005. The open-chamber-rubber-bumper 46mm fork was used on all YZ and WR models in 2004. I can't account for the difficulty you may of had, but as they came out of the crate, 46mm in 2004 for all bikes and 48mm in 2005.

There was (and still is) a significant difference internally between the 48mm fork used on the WR's vs. the YZ's. The 48mm WR forks are still the old open-cartridge style and not the twin-chamber type as on the YZ. Yamaha did do away with the rubber-bumper bottoming device and switched back to a hydraulic lock collar when they made the witch from the 46mm to the 48mm WR forks in 2005.

There were also major internal differences made with the YZ fork between 2005 and 2006. Internally, the 2005 48mm YZ fork was a freak one-year-only design that should really should be avoided if you plan on revalving your forks. But for the most part, all 2006 and later 48mm YZ forks are the same internally.

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How I found out the difference was I ordered triple clamps for an 04 YZ for my 04 WR and the fork clamps on top were larger. I looked it up on here and sure enough in 04 the YZ had 48mm and WR had 46mm.

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How I found out the difference was I ordered triple clamps for an 04 YZ for my 04 WR and the fork clamps on top were larger. I looked it up on here and sure enough in 04 the YZ had 48mm and WR had 46mm.

I can't say for certain but I think the change was to the upper tube on the '04 YZ's. Yamaha's had issues with the triple clamps not providing enough clamping force to the fork tubes on '98-'03 YZ's and WR's allowing the forks to twist in the clamps every time the bars hit the ground. I had this problem on my '99 WR400 and replaced the triple clamps to fix this. When I bought my '03 WR450 I used the triple clamps from my '99 WR with no problem. I remember Yamaha changing the top triple clamp in 2004 to fix this twisting problem but they only changed the diameter of the top portion of the upper tubes (and only on the YZ's).

I do know the lower tube (the chrome plated steel tube) was 46mm on all '96-'04 YZ's and WR's. The years ('04 and '05) where Yamaha changed the upper tube diameters @ the top triple clamp but it doesn't reflect any change to the lower tubes. These changes in dimentions to the top of the upper tube didn't affect anything but top triple clamp fitment. Internally, all '96 to '04 YZ and WR were essentially the same with 46mm lower tubes and open cartridges. There was a change internally in '99 when Yamaha did away with the hydraulic lock collar on the damper rod and replaced ir with a rubber-bumper (carried over on the WR's untill '04) and again in '03 when the diameter of the damper rod piston was increased and then later reduced to the older size in 2005(?).

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If I did not need the electric start I would start with a Yz 09 would be the best year. The 10 and later had a lot of changes to the frame and it may be more diffcult getting a bigger gas tank. I would put 3rd, 4th,and 5th from a 07 wr or later. A wr gas tank from a 07 or later get the forks revalved. If you want working lights just for a enduro tech inspection 8 doubble A will drive a Led headlight made from a 20 bulb led flashlight from harbor freight for $6.00, and a Rocky mtn tail ight for $ 29.00, or you can buy a after market stator for power but not enough for night riding. I know I have done all this and have been racing enduros for 28 year and around 400 enduros or so I lost count.

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Ok, Iwas wrong about the 48mm forks on 2004 YZ's They were one year only forks using the open cartridge damper assembly. They have nothing in common with any 48mm fork from 2005 on. They were basically the the old '96-'98 style with 48mm tubes.

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How About the EXCEL rims, what year and what bikes did they put them on? WR/YZ250F ?

I like your saying Jim !

--------------------------------------------------------------------------------

There should be a licencing requirement to buy tools, just like applying for a concealed weapons permit.

I always said there should be a licence requirement for spray foam ...lol

I have found a 06 yz250f

Edited by RoscoeJ

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How About the EXCEL rims, what year and what bikes did they put them on? WR/YZ250F ?

I like your saying Jim !

--------------------------------------------------------------------------------

There should be a licencing requirement to buy tools, just like applying for a concealed weapons permit.

I always said there should be a licence requirement for spray foam ...lol

I have found a 06 yz250f

If I remember correctly, Excel rims were OEM on 2003 and 2004 YZ's and WR's (the WR250's may have had DID, can't remember) I believe Yamaha went back to the crappy DID rim in 2005 for the WR250's and have used them through 2011. The WR450's have had Excel rims since 2003. All of the YZ's (not certain on the 125) have had Excel rims since 2003.

Another interesting difference is the YZ's had Titanium footpegs in 2005 and 2006. The WR's did not. They are no longer available from Yamaha. A magnet will not stick to the Ti footpegs. A magnet will stick to the later stainless footpegs.

I've seen horrible things done with spray foam, like a 4 foot hose attached to a can of spray foam and stuck up the tailpipe of someones truck.......I know nothing about that.

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Thanks for that jim ,I didnt konw that about the excel rims , any info on the installation of a hydraulic clutch,on the WR or YZ.

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Thanks for that jim ,I didnt konw that about the excel rims , any info on the installation of a hydraulic clutch,on the WR or YZ.

Only one I know of is the one made by Magura. Nice piece of hardware, but you'l have to pack a KTM clutch lever with you.

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I seem to recall there is one piece that I need to ground that stator in the conversion from 2001 to an aluminum frame....can someone help me out here?

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Hey guys, i got a question. I got a 2007 yz250f im convertion to spuermotard, my buddy and i had completely rebuilt. had an 01 wr transmission lying around so we figured we'd throw it in while we had the bike completely apart. then found it was not compatible at all. my question is what year wr gears would be best to use. i was looking at ordering OEM 2007 wr 4th and 5th and putting them on the yz  main and drive axle. Id appreciate the help/opinions. 

 

if it helps. here are the links to where id order from. i was also comparing part numbers to be sure.

yz- http://www.boats.net/parts/search/Yamaha/Motorcycle/2007/YZ250F%20-%20YZ250FW/TRANSMISSION/parts.html

 

wr- http://www.boats.net/parts/search/Yamaha/Motorcycle/2007/WR250F%20-%20WR250FW/TRANSMISSION/parts.html

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There's an option mentioned around on this thread, and I've done this:

I installed an 03 WR tranny into my 03 YZ.  Just got a good bottom end off a WR and went to town on it.

Light weight, 5 speed Wide Ratio, 215 lbs and it'll show you 65mph in a heartbeat.  Only prob I've had is not having lights.  I've been caught out late a couple of times.... not good.  So I got a WR just for the lights to ride in winter when it gets dark early.

 

The guys who ride behind me come up and ask if its a 450, and the guys who ride it come back with a big wide smile!  If you're used to riding the close ratio, you gotta be careful when you catch 3rd gear because it will literally leap forward if you short shift it under power.

Edited by ronbuell

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