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07 rebuild and performance upgrades (with pics)

By tribalbc,
in WR400F/426F/450F

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Grand Master

tribalbc

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Well yesterday I got started on my rebuild/upgrade on my 07. I now have 9,000 hard km's with 2 seasons of racing HS's. So I figured it was time to replace the piston and cam chain. I figured while I was in there I might as well try some YZ cams and bump up the compression on the piston to 13.5-1.

My clutch inner and outer basket was also pretty badly notched so I figured if I had to spring for a clutch anyways I may as well go for a quality clutch so I got GYTR (Hinson) inner & outer hub as well as pressure plate. I also got a set of OEM plates and springs.

Last on the list is a water pump shaft/seal replacement. I did the seals earlier this summer but didn't order a new shaft :bonk:

It was heavily grooved. It's still holding out but might as well fix now.

So yesterday the motor came out. Took about 2hrs. Biggest pain was getting the shifter off. The end of the shaft had a nick from an impact so I had to really spread the shifter clamps to get it off.

bikerebuild017.jpg

Removed parts

bikerebuild015.jpg

bikerebuild019.jpg

Today I tore the motor apart and replaced the cam chain.

Valves still haven't moved from new

bikerebuild023.jpg

Cam caps removed

bikerebuild026.jpg

Can still see original cross hatching

bikerebuild032.jpg

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sabrecat700
sabrecat700

I have had no problem with the YZ cam and starting. It still has the decompression built right on the ex cam just like the WR cam. What I have found and you should try is to give the throttle two quic

Grand Master

tribalbc

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Head, piston cylinder

bikerebuild036.jpg

Cams

bikerebuild037.jpg

Cylinder after polishing the cross hatch back out with scotchbrite

reb001.jpg

I found a little trick for holding the flywheel while pulling the nut. The manual shows a band type holder for the flywheel but I noticed 2 notchs on the shaft made to fit a 24mm open end wrench

reb011.jpg

Pulling the flywheel

reb005.jpg

Cam chain removal is done by removing the rear chain guide and then the chain.

reb006.jpg

reb009.jpg

My old cam chain on left. It was smooth with no kinks but definately longer than the new one.

reb010.jpg

Tomorrow the head gets cleaned up and the piston and cams go on.

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Grand Master

tribalbc

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I love it (not that it surprised me either) :bonk:

So are you gonna do a quick hone? Are you doing valve springs and valve seals? For the price you might want to...

Other then that, keep the pictures coming:thumbsup:

Too hard for me to get a hone here other than Snap on- $$'s- so scotchbrite and my arm were my hone. Came out pretty good.

I figure since the valves haven't moved I will just leave the head alone this year. When my valves start moving I'll do the seals and springs,etc.

But I haven't really fully gone over the head yet. We'll see tomorrow.

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Grand Master

tribalbc

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The coolest thing I think about doing that with the motor out is that you can get a straight approach with your torque wrench on the cam cap bolts...

Don't over torque those..... word:busted:

That was my thought's, as well as many other things being easier. Besides, by the time you have the carb off you're really just down to the motor mounts anyways.

The only pain so far of this method was torqing the flywheel nut back to 65NM, twice. It was a bit of a wrestling match :bonk:

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sabrecat700

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I just got done a week ago rebuilding my 03 Wr450. It is plated so I would guess at 20,000 miles on her and maybee more. Over the summer it slowly got harder and harder to get it to start when it was cold. It also started to use oil and never have had done that before. I went and bought all the parts for a complete rebuild $1200 dollars worth. Then I took it apart and the only thing that was wrong with it was all the intake valves were all cupped out and sank into the head. This let the compression leak up the valve stem and burnt the valve seals out and thats were the oil was going. I had the valve seats recut and the head ported and put it all back together. It run great now and starts right up. After inspecting the piston, cylinder, crank, cams and any other parts I could not believe how good every thing is. The crosshatchs are still on the cylinder plating and the rod is as tight as the brand new one. The rings are still in spec. Incredable!!! For a motor that hold only a quart of oil and I beat the piss out of it, I am very impressed with this yamaha. BTW I checked the valve every year and only made two small adjustments over 6 years. I even checked them this year and all was good. When they go bad it happens quick as all three were junk at the same time.

Yamah,s 450 is kick ass and i would find it hard to believe that the other brands would last this long.

Almost for got to tell one of the main bearings on the left side was getting bad. I could hear it hammering at mid range constant speed if you spread your left leg out to the side. I thought thats what it might be and it was.

Good luck with you rebuild and I would not touch the valve unless they need a adjustment.

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Grand Master

tribalbc

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Well today I got the piston and cams in and buttoned back together. Took a couple try'son the cam timing and some help from some fellow TT'ers. I was a little confused as I counted links on the cam chain between the marks on the WR timing. When I put the YZ cams this way the timing was out a tooth. Turns out there is one less link timing YZ cams.

Finished the day with taking right crankcase cover off and replacing the water pump seals and impeller.

On to the clutch tomorrow :bonk:

Old piston and new JE 13.5-1

cams010.jpg

cams011.jpg

The stock piston looked surprisingly good with all the hard hours on it

cams012.jpg

New JE piston

cams013.jpg

Piston in cylinder

cams014.jpg

cams019.jpg

Cylinder head cleaned up. Managed to get almost all carbon off

cams016.jpg

New cams timed and ready to go

11005.jpg

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Grand Master

tribalbc

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your engine looks in remarkably good condition given the hours. How did you run in your engine?

cheers

If you mean how I broke it in I actually didn't. I got the bike with 600km on it of my buddy who used to own the local Yami dealership. My guess would be he broke it in on the throttle though :bonk:

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sabrecat700

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I don't think you got the exaust cam timmed right. Thats how it would look with the cam mod with the stock cam. If you got the yz cam it need to be done like the WR cam was done from the factory. I also have the YZ cam and did not do it like that. I think you need to move it back clockwise one tooth.

Anybody else no anything about timming a YZ cam?

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