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2001 WR250F w/ 2003-up crankshaft stator/flywheel/cover question

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So I got a wr250f that ran very poorly and smoked like bingo night for 300 bucks. Since it was a redneck who owned it, it was no surprise that the oil filter was clogged to the point of collapsing on itself. I beat the metal shavings out of the oil filter into a bucket and took the bucket to the scrap yard to pay for the parts for a complete rebuild which I just completed yesterday, aside from the stator, flywheel, CDI, and cover. (?)

When I search thumpertalk for the answer to this question there are quite ambiguous answers, so I thought I could clear it up for myself and future searchers on the issue.

The 2003 crankshaft that I put in the 2001 wr250f is beefed up and the taper is different, so you have to fit a 2003-up stator and flywheel to it, including the new CDI. When I laid the 2003-up stator cover gasket onto the left case halve, it clearly has a different bolt pattern. Can I use the 2001 stator cover or do I need to tear the engine back down and get a 2003-up left case half just so the 2003-up stator cover will fit?

Thanks in advance.

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You have a problem. When the electric starter was added on the '03+ WR's they changed the crank, cases, flywheel, and stator. The '03+ WR's have the stator mounted in the mag cover. All others, the stator is mounted on the case half.

So, your '03 crank will bolt into the cases but there is no combination of parts (cover, stator,or flywheel) that will fit.

You can switch cases, but the cases are only available from Yamaha as a set, they aren't sold individually (unless you buy a used half). If you were to go that route then you have the issue of what to do about the electric starter.

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Jim got it right. I don't see any way around tearing back down for a re-do. The 01 WR has more in common with the 01 02 YZ than an 03 WR.

If you have a shop close by that can rebuild the crank, you can order an 01 left crank half and have then swap parts for you, which seems like a good alternative. Another alternative is remove the crank and ebay it as installed but never run, and get a new 01 WR crank from Hot Rods. Steve Beavers is good to deal with there. Good luck.

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If you have a shop close by that can rebuild the crank, you can order an 01 left crank half and have then swap parts for you, which seems like a good alternative.

That's not going to work either, The crank-pin on the '03 crank is 2mm bigger.

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Oooops. Good catch there Jim. You tried that??

Working on a zombie bike. See my post on the YZ306WR

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I searched for 30 minutes trying to find the link where someone said they had done it and only mentioned they had to replace the cover. I'd really like to move up from the weak 2001-2002 crankshafts and was wondering if I got the left side 2003 case half would it mate directly to the right 2003, and is it possible to leave out the starter? microfiche can only tell you so much.

At this point I am a little frustrated and wouldn't mind taking the gamble on the 2001-2002 crankshafts. The part numbers are updated for the assembly but I cannot find a lick of information on what was changed. I am thinking not much considering that none of the big dogs seem to be making a crank anymore for 01-02 besides OEM. If you know where I could get a crank, let me know!

EDIT: http://www.thumpertalk.com/forum/archive/index.php/t-889686.html found the link I was talking about. I'm gonna try to contact them so we can clear it up for me unless you guys know how he got it to work or can decipher how he managed to get a 2003 crank working in the 2001 with so little work...

Edited by 86bg

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I searched for 30 minutes trying to find the link where someone said they had done it and only mentioned they had to replace the cover. I'd really like to move up from the weak 2001-2002 crankshafts and was wondering if I got the left side 2003 case half would it mate directly to the right 2003, and is it possible to leave out the starter? microfiche can only tell you so much.

At this point I am a little frustrated and wouldn't mind taking the gamble on the 2001-2002 crankshafts. The part numbers are updated for the assembly but I cannot find a lick of information on what was changed. I am thinking not much considering that none of the big dogs seem to be making a crank anymore for 01-02 besides OEM. If you know where I could get a crank, let me know!

EDIT: http://www.thumpertalk.com/forum/archive/index.php/t-889686.html found the link I was talking about. I'm gonna try to contact them so we can clear it up for me unless you guys know how he got it to work or can decipher how he managed to get a 2003 crank working in the 2001 with so little work...

Well, If you have free access to a machine shop, you can make anything fit (and some people with a lot of spare time on their hands do that).

Here's the scoop with your bike;

In '01 and '02 the YZ250F's and WR250F's used the exact same crankshaft. In '03, the WR's went to electric start and use cases, mag cover, stator and flywheel and crank different from earlier bikes and '03+ YZ's.

In '03 Yamaha also increased the crank-pin diameter 2mm on both the YZ and WR. Owners of '01-'02 WR's can use the '03 and later YZ crank as a direct replacement.

I can't say for sure at the moment (but I will know for sure in the next day or two), but I believe all '01-'02 flywheels (WR and YZ) will swap onto a '03+ YZ cranks.

So, you have two options;

Use the '03+ WR cases, mag cover, stator, and flywheel with the crank you have,

or;

Use a '03 or later YZ crank (available from Hot Cranks, Wiseco, Yamaha, and maybe e few others).

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EDIT: http://www.thumpertalk.com/forum/archive/index.php/t-889686.html found the link I was talking about. I'm gonna try to contact them so we can clear it up for me unless you guys know how he got it to work or can decipher how he managed to get a 2003 crank working in the 2001 with so little work...

It sounds like the OP got a '03 and later WR crank by mistake. His post confirms that your '01-'02 WR stator should work with the '03+ YZ crank but I'm still not certain if you'll need to use the '03+ flywheel.

The only thing that I know for sure is different on the YZ cranks from '01-'02 and '03+ is the crank pin diameter (diameter of big-end of connecting rod). Like I posted earlier, I'll know shortly if the Flywheels interchange.

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Okay, just pulled apart a 2002 WR250F magneto and a 2005 YZ250F magneto;

The stators and covers WILL interchange But the diameter/taper is 1mm bigger on the YZ. The WR stator is HUGE and there's no way it will work with any YZ flywheel.

So.....what I would is this; use a '03+ crank, an aftermarket '03+ YZ stator (with lighting coil), and a Steahly heavy flywheel for '03-'09 YZ.

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So far from your wonderful help I've gathered:

2001-2002 WR250f cases

03+ YZ250f crankshaft assembly and bearings

03+ YZ250f stator and flywheel.

So the CDI and ignition from the 01-02 wr250f will work with the yz250f 2003+ flywheel?

I can't imagine why the ignition magnets would be different but I'm just trying to be sure. I want people reading this to know for sure so that they don't have to go through the same stuff I did. (hastily, I admit)

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So the CDI and ignition from the 01-02 wr250f will work with the yz250f 2003+ flywheel?

Yes, it should since the '01-'02 WR's use the same AC ignition as all of the YZ's.

Before you go buy any parts though give me a few days to see if there is another flywheel that will work with thw YZ crank and WR stator.

The WR flywheel is sooooo close to working on the YZ crank I'd be willing to bet money that I can find a flywheel (from another machine) that will work (saving you the cost of having to buy a stator).

The WR426 flywheel is the same as yours, but different from the WR400's. I started a thread on the WR400/426/450 forum asking for help with dimensions on a WR400 flywheel.

Let's see what comes back.

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Ok. I think I have the whole '01-'02 vs. '03+ issue figured out.

In addition the the crank-pins being 2mm bigger, there are some subtle differences to the left side (magneto side) of the crank as well when comparing the '01-'02 cranks with '03+ YZ crank.

It all starts with the flywheel. If you notice in the pic, the trigger bar for the pickup coil on the '05 YZ flywheel (left) 'appears' to be about 3mm higher than the pickup bar onthe '02 WR flywheel, but when you compare the location of the pickup of the coil on the '02 WR stator to the pickup coil on the '05 YZ stator, they are exactly the same height (I also compareed both to a '01 YZ stator and they are all the same).

CIMG1134.jpg

Now, if you look at the two cranks, you'll see that the '03+ YZ crank looks shorter (well, it is and it isn't). What's really different is the threads are 2mm bigger on the '05 crank (12mm vs. 10mm), and the machined relief on the '05 crank (the shoulder just outboard of the cam sprocket) is about 3mm farther out on the '02 crank.

This is the '02 crank;

CIMG1133.jpg

This is the '05 crank;

CIMG1132.jpg

After doing some measuring, it looks like the taper, diameter, and position of the taper relative to the stator are the same ('01-'02 YZ stators are the same part number as '03), the difference is that the '03+ later flywheels sit about 3mm closer to the main bearing. That's why the pickup bar is moved 3mm farther 'out' to make up for the difference.

So what does all this mean?

Can't say for sure at the moment, but I think I can just open the nut-end of the '02 flywheel to 12mm and it will work on the '03+ YZ crank. I'll chuck it up on the lathe tonight and see if I can make it fit without too much work.

If this is the case, that means that flywheels and stators from '01-'02 WR250F's AND WR426F's (426's flywheels and stators are the same parts as 250's) can be used on '03+ YZ250F's and possibly YZ 250 2-strokes from '98+ with only minor modifications to the flywheel.

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If this is the case, that means that flywheels and stators from '01-'02 WR250F's AND WR426F's (426's flywheels and stators are the same parts as 250's) can be used on '03+ YZ250F's and possibly YZ 250 2-strokes from '98+ with only minor modifications to the flywheel.

Wow, hoping it holds true. :bonk:

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