WR450F, YZ450F and YFZ450 - Crankcases interchangeable?!?

[schattat]

Hey gang,

I was able to get hold of a used 2003 WR450F yesterday for REALLY cheap $$$ (also only has 1000km on the clock) The reason for why it was so cheap, is this:

If you can't already tell what this is, let me describe it to you in more detail. What you're looking at is the rear side of where the kickstarter shaft sits. The problem is the support for the shaft has broken off, whilst the previous owner attempted to kickstart her. Without this support, kicking the bike is impossible, as the kickstarter just gets stuck while pushing it down

Now my question for you guys: I need to know whether it would be possible for me to replace the right hand crankcase with one from a YFZ450 (quad) or even YZ450F.

I was able to track down the part numbers from thumpertalk and this is what I got (for the entire cranckcase assembly).

WR450F 2003: 5TJ-15150-10-YX

YFZ: ???

YZ450F 2003: 5TA-15150-11-YX

As you can see, the numbers are quite similar to one another, yet they differ in 2 spots. The "J" and "A" (I assume this is for WR and YZ); the "10" and "11". What does this exactly mean?

Does anybody know for certain whether the YFZ/YZ right crankcase will fit 100% onto the left crankcase of the WR, whilst everything else will fit on to it? From what I can tell from the technical drawing of the YFZ and WR crankcase is, that they look EXACTLY the same.

I have been able to track down a really cheap right hand side crankcase from a YFZ450, which I intend to buy if it does for my new ride so I need to know ASAP!

Cheers,

Tony Schattat

[grayracer513]

It is never advisable to mix crankcase halves. They are bored bolted together as a set, and are only sold as a set for that reason.

Also, the '03-'06 WR450 crankcase is not interchangeable with any other model. The '03-'05 YZ450 crankcases could be used, but only if the YZ crank, magneto, and electrical system is used in conjunction with it. The quad case just simply won't fit in the frame.

[grumbs]

Hey man,

Did you get a reply on this. I have a WR450 2003 and the same thing has happended to my crank case.

You mentioned the support for the shaft had broken off... Can I email some pics of mine to you and get some advise.

Im in Australia and looking for another Crankcase. I wasnt sure that a YZF450 would fit becuase they dont have electric start.

Any info I would appreciate.

Cheers

[grayracer513]

Hey man,

Did you get a reply on this?

Did you read my post?

[grumbs]

My question is why these Crankcases break and is there a support function that is meant to be there that prevents it from happening?

Is there many crankcases available second hand in the states?

Sorry for all the questions, just trying to learn as much as I can about the problem I have.

Cheers

[schattat]

Hey man,

Did you get a reply on this. I have a WR450 2003 and the same thing has happended to my crank case.

You mentioned the support for the shaft had broken off... Can I email some pics of mine to you and get some advise.

Im in Australia and looking for another Crankcase. I wasnt sure that a YZF450 would fit becuase they dont have electric start.

Any info I would appreciate.

Cheers

Hi there,

Sorry to hear you've got the same problem as me...

In the end, I wasn't able to get hold of a crankcase set, so I decided to fix the hole myself.

What I did was this:

- Remove the engine from the bike

- Remove the right hand side cover

- Make a support out of wood to hold the engine to be able to mill the broken area flat, like so:

- Lathe an aluminum ring, inside diameter that of the kickstarter shaft, outside diameter that of the engine. Weld it into position.

- Cover the remaining space with some thick sheetmetal and weld that on, too.

End result (unclean):

- Easy as that ?

The reason for this problem happening in the first place was because of the "kickstarter stopper". This part (made of steel) prevents the kickstart from moving too far towards the front of the bike. Apparently, the bike backfired, causing the kickstarter to fly back so hard cracking the stopper in half, so I had to replace it (look for a used part). You may also want to check whether your kickstarter shaft is still straight and true, as mine wasn't!

ENTIRE RECOVERY WORKS LIKE A CHARM!!!

Hope I was able to help out!

[grayracer513]

The failures of the crankcase in the area of the kick start shaft usually result form one of two things: A violent kick back against either your foot or the stop plate, or a broken gear in the train that runs between the starter and the clutch (or a coincidence of these two). There is no reinforcement that falls off or gets omitted.

There are a couple of things I'd like to say about the repair process illustrated. To avoid being offensive, I won't say some of it.

While the underlying concept of welding and re-machining the case is right, as far as it goes, the correct way to do this is to disassemble the engine. That way, the center case surface can be bolted to the mill table as a positve means of squaring up the shaft axis. A wooden fixture such as the one shown is simply not precise or rigid enough for the job. The crankcase cover can be used to locate the center line of the bore in the crankcase, and, obviously, the rest of the engine will not be contaminated with the metal debris from the machine work. All of that was probably as obvious to most readers as it was to me, but for those to whom it wasn't...

[grumbs]

Hey guys,

Thanks alot for your advise nd help with this.

Below is a pic of my crankcase.. do you think in your opinion that it needs replacing or could it be welded?

You are totally correct grayracer this happended after a kickstart violently kicked back...

When riding the bike back to camp it was making a griding sound like a cog was griding against something. Not sure if there more interanl damage or that was just to noise coming through the crack...

Is there a spring that can give way or break that will grind agaisnt the cog??

The kickstart seems to be a little lose aswell.

Im finding it hard to find a second hand crankcase but still looking.

Thanks again, all this info is helping me alot.

Cheers

[grayracer513]

Below is a pic of my crankcase.. do you think in your opinion that it needs replacing or could it be welded?

That should be repairable, but look for a machinist/welder to do the job, not just a welder, and tear the engine down before you take the stuff in to him.

[schattat]

That doesn't look to serious I.M.O! My part just flew off and was never found ?

Just remove the right hand side of the engine, and make sure the kickstarter stopper isn't broken (is fixed with 2 screws next to the shaft).

Start by sticking a rod (e.g. brass) of the same diameter into where the crankshaft sits. Then, use a clamp, or similar, to press the 2 cracked sides together, and weld away!

[grumbs]

Ok, thanks for your advice guys. I will let you know how I go.

Cheers

[timmytimmytimmy]

i have same problem what causes this?

[fixitandy]

Way to go boys, necessity is the mother of invention, a difficult problem is just an opportunity to show are smart we are. ROOSTA out

[Sean Doyle]

Hey guys! I've got this dreaded problem as well.

I jb welded it and it held for exactly 1 week.

I don't really have access to a TIG welder/ machines.

My question is, could I braze this? If I grand a vally on each side along the crack? Or is MIG welding the way to go of Tig isn't an option? 

I have hobart aluminum brazing rods and think it may suffice but I need to be reassured.

This bike has 351 miles on it. I did sand smoothe after cure.