import silvia

WR426F Stator on YZ400F

5 posts in this topic

Using a few threads on here and other sites as reference I installed a WR426F stator and WR400F flywheel on my '99 YZ400F. I have only been able to run it up and down the street a few times, but the mod seems to have worked. Here's what I did:

I go a stator and flywheel of ebay, $99 each, it took a few weeks of watching to get them at that price.

I modified the stator to work with the YZ CDI and to floated a ground so I can run 12v DC in the future.

 

The first thing to do is find the light pink wire. On the plug it is on the clip side in the left most position

IMG_20150417_223224.jpg
 

 

On the stator it connects to the large taped coil, when looking from the top it is on the right side of that coil.

IMG_20150417_223134.jpg

 

In order for the YZ CDI to work this pink wire needs to go from the plug to a chassis ground, not the stator coil.

I accomplished that by slicing open the sheath about 6" from the plug and cutting the pink wire.

IMG_20150417_231328.jpg

 

To the plug end of the pink wire I spliced on a black lead with a ring terminal that had been fed down the sheathing.
IMG_20150417_234045.jpg

 

These are all the steps needed to use the WR stator with the YZ. Attach the Yellow lead to a regulator and you can run lights off AC and ground them to the chassis.

I wanted a floating ground that I could use with a 12v DC system. To get a floating ground I did the next few steps.

Clip the pink wire right where it meets the stator coil.

IMG_20150417_223134.jpg

 

Unsolder the copper coil from the ground lug in the middle of the stator, it is the silver blob next to the upper left black screw.

IMG_20150417_223201.jpg

 

I then routed the free end of the pink wire behind the blue and brown wires on the opposite side of the coil form which it had been cut. I also slipped a bit of heat shrink over it.

IMG_20150417_230243.jpg

 

I soldered the pink wire to the end of the coil that I had removed from the ground lug

IMG_20150417_230304.jpg

 

I covered that joint with the heat shrink that I had placed on the wire.

IMG_20150417_230631.jpg

 

On the other side of the pink wire that was left loose in the wire harness I spliced on a lead that would be the floating ground. I don't have a pic of that splice, but it was spliced to the left wire shown here.

IMG_20150417_231328.jpg

 

I feed that wire out the end of the harness and covered the loose end in heat shrink to protect it. It is the orange wire next to the yellow lighting lead.

IMG_20150417_234045.jpg

 

I then wrapped the harness in heat shrink tape and re-tapped the plug end.

To get the bike running I just plugged it into the YZ harness and grounded that black lead. It runs great, I can't really tell any difference from the YZ stator/flywheel.

When I add the 12v and Lights I'll write that up as well.

 


 

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looks good i did the same thing but i didnt float the ground. you couldnt even feel a difference from the heavier wr flywheel? i sure did.

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Yeah, I took it out for some trail riding and I could tell the difference with the heavier flywheel. It is much easier to keep going in really tight stuff.

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The thing that everyone fears is that the heavy flywheel will retard the engine's acceleration noticeably.  That is not really noticeable at all, even in side-by-side acceleration against a stock bike.  You should notice 3 things, though, each of them fairly subtle, but definitely there:

 

  • The rear holds traction better in the loose stuff under acceleration.
  • It really does stall less often
  • Power at low speeds is smoother, with less chain slap, and it may in fact actually produce more power at low speeds than it did with the lighter 'wheel.
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The thing that everyone fears is that the heavy flywheel will retard the engine's acceleration noticeably.  That is not really noticeable at all, even in side-by-side acceleration against a stock bike.  You should notice 3 things, though, each of them fairly subtle, but definitely there:

 

  • The rear holds traction better in the loose stuff under acceleration.
  • It really does stall less often
  • Power at low speeds is smoother, with less chain slap, and it may in fact actually produce more power at low speeds than it did with the lighter 'wheel.

 

I am going to perform this modification soon.  I have ordered the flywheel and stator from the 99 wr400f.  I am using it in conjunction with a baja universal kit complete with rectifier, and small battery.  Thanks for all that have contributed to this.  Electrical work is one of my weaker points and having these detailed examples to follow are a great help.

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