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paul_roca

Will a Yzf Engine work in a Wr450

10 posts in this topic

Hi guys,

I have a 2004 Wr450 and have seized the big end bearing and it ended up snapping the conrod. The lower half of the conrod rotated round and has shot through the bottom of the engine while the top half has dented the cylinder.

As the engine is more or less shot i need a new engine.

I live in UK and these engines are as rare as rocking horse sh!t

I was thinking of buying a yzf450 and dropping the engine in the wr, along with front forks and rear shock.

My question is...

What will i need to run a yzf450 engine in a wr450, Will i need to change the loom, Ecu, Flywheel etc?

Thanks

Paul

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The answer to that is a little complicated.

To answer your question as directly as possible, yes, the YZ450F engine built between '03-'05 will fit right into your bike. If you go that route, you will have to give up the electric starter, and the lights, and use the YZ450 CDI and harness.

There is some interchangeability of parts between the engines but it's limited. The trans can be swapped over as a complete unit; the whole WR 5 speed can be installed in place of the YZ 4 speed, or vice-versa. The YZ cams, or the whole YZ head, or for that matter, the entire YZ top can be dropped straight onto a WR crankcase.

The crank and anything connected to the left end of it is another matter. The WR flywheel and stator (as well as the starter clutch, etc.) requires the use of the WR crank (at least the left axle) AND the WR crankcase. That's because the WR stator cover is needed for the WR stator and the starter, and it won't fit the YZ cases.

Probably the best three ways to go would be to...

  • Drop in the YZ450 engine as is
  • Put the WR 5 speed in the YZ engine and use that
  • Rebuild your WR

Of course, you could just buy the YZ and ride that. :moon:

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Do you mean the YZ450F bike engine, or the YZF450 quad engine? The quad engine has substantial differences.

If you mean the YZ450F bike, why go to the trouble of swapping engines and suspension, when you could just ride the YZF?

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The quad is designated YFZ450, not YZF450, but you're right, the crankcases will not fit a bike frame, just for starters, and either way, there's no such animal as a YZF450.

I assumed since he stated he wanted to use the fork and shock that he was indeed speaking of the YZ450F motorcycle.

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Yer i mean a yzf450 bike, Also my my wr450 is Road Registered and Tax, Mot'd and insured. I wouldnt be able to ride the Yz on the road.

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Yer i mean a yzf450 bike, Also my my wr450 is Road Registered and Tax, Mot'd and insured. I wouldnt be able to ride the Yz on the road.
Once again, it's YZ450F, NOT YZF450. :moon:

The trouble with using the electricals from a YZ is that the stator is impractically small to be used as an AC/DC power source for lights and ignition both. The WR CDI is also incompatible with the AC output of the YZ, so unless you can find an old E-Line external stator for sale somewhere, using the YZ crankcases and crank would mean surrendering the lights. There are aftermarket stator/light wiring kits for the YZ450F, but none of them really work well enough to be considered practical.

I'd say you're going to have to at least rebuild your WR bottom end. Then you can utilize the YZ top if you need to.

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The quad is designated YFZ450, not YZF450, but you're right, the crankcases will not fit a bike frame, just for starters, and either way, there's no such animal as a YZF450.

I assumed since he stated he wanted to use the fork and shock that he was indeed speaking of the YZ450F motorcycle.

Oops. You're right, I didn't read his post very well, did I? :moon:

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Thanks for the detailed answers, Im just used to calling them yzf450 must be a country thing.

I cant get hold of a wrf450 engine or parts at a reasonable price anywhere.

I have found 400's and 426's though.

If i was to use one of these engines id obviously lose my electric start but what else would i have to change? Would i have to change CDI or Cdi and loom. Are the Carbs interchangeable etc?

Thanks Alot

Paul

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How do I change out the wr 450 cdi and wiring harness to the yz 450 cdi and harness? All the electrical fittings don't match up

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This thread is pretty ancient...

 

He said that, if you use the YZ case/stator, you'd need to use the YZ CDI as well. I imagine it's one way or the other: complete YZ electrical system or complete WR electrical system. Mix and match will be difficult.

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