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rossonza

YZF426 top end onto WR400 bottom end

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Is this possibleicon1.png?

 

Ive got the crank cases of a wr400, but i need a complete top end. Can i just put the yzf426 barrel/head onto the wr400 cases? or do i need a different bottom end etc?

 

 

Thanks

Ross.

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I am not 100% sure of my memory but back in the early days of the Yamaha  426 you could convert a 400 to a 426. It was fairly common to do this conversion. As I remember you had to use the 426 rod, piston, and wrist pin as the 400 rod has a smaller wrist pin. I do not remember if the bottom end was the same size or if you had to change the crank also. There has to be someone on here will remember the process & speak up. Try searching for it on the internet. Here is one link  http://www.thumpertalk.com/topic/680150-wr400-convert-to-yz426/  Good luck.

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Thanks for  the reply!. I did search but my browser returned a script error :-(

 

Trying to source a complete engine to make my life easier, but its tough so far.

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You would have to double check this, but as I recall, the 450 piston has the same size wrist pin as the 400, while it has the same bore size as a 426.  The snag may be the compression height of the piston (from the wrist pin to the edge of the crown).  The 450 has a longer stroke, so the comp height could be off, or the difference may have been compensated for in the cylinder height.

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Haven't delved that far into it yet, but thank you for the reply. Waiting for funds before i decide on what to do. Can pick up a cylinder head for £200 - $350? and a barrel for £150 $225 (Not sure on the the exchange rate).

 

currently looking at buying the parts separately as all the full engines are for sale in the US and i bet import tax on those isnt going to be too fun.

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426 rod piston and barrel is all you need or a complete 426 crank to save changing rod but then u need the balance shaft gear as the 426 and 400 had different key way set up on the crank and crank drive gears aren't interchangeable I have all the bits in my shed but the rod is not on the crank and the jug needs replate

Edited by ehoward381

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Thats interesting to know ehoward381, as I am about to convert my 99 400 to 426. 

I have researched extensively and thought I had all the information required.

I have ordered the parts and everything.  My rebuild started with an "about to grenade" 4th pinion gear, and will include crank (because the machined teeth on the left side crank half for timing chain were chewed! i wish I knew how), bearings, rod, piston, cylinder, new 4th gears, oil pump gears and all seals/gaskets/lock washers.

I guess I'll find out when I go to put it all together ehoward381, but will I just need the 426 crank gear and keyway or new balance shaft gear as well.

 

rossonza, i was going to replace the left hand crank half only and get my local shop to balance it up with the original rh half, with new big end bearing/rod/piston/cylinder, but then I discoveded that the crank is sold and an assembly with big end pin/bearing/rod for around the same money, so i went with all new!

 

Sounds like ive got further issues to sort out! Bugger!

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Thats interesting to know ehoward381, as I am about to convert my 99 400 to 426. 

I have researched extensively and thought I had all the information required.

I have ordered the parts and everything.  My rebuild started with an "about to grenade" 4th pinion gear, and will include crank (because the machined teeth on the left side crank half for timing chain were chewed! i wish I knew how), bearings, rod, piston, cylinder, new 4th gears, oil pump gears and all seals/gaskets/lock washers.

I guess I'll find out when I go to put it all together ehoward381, but will I just need the 426 crank gear and keyway or new balance shaft gear as well.

 

rossonza, i was going to replace the left hand crank half only and get my local shop to balance it up with the original rh half, with new big end bearing/rod/piston/cylinder, but then I discoveded that the crank is sold and an assembly with big end pin/bearing/rod for around the same money, so i went with all new!

 

Sounds like ive got further issues to sort out! Bugger!

You can buy just a crank 1/2 as I did. I had to replace the left hand on my 99 YZ400. As I remember it wasn't too much money.

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Ok, ive been offered a YZ 400 barrel and cylinder head. Will this go onto a WR400 crankcase/bottom end without mods?

 

Thanks

Ross.

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Ok, ive been offered a YZ 400 barrel and cylinder head. Will this go onto a WR400 crankcase/bottom end without mods?

 

Thanks

Ross.

 

Directly, yes.

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Thanks, So just all i need then is a wr400/yz400 piston and im golden?

 

Cheers
Ross.

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I forget exactly but...I bought a 02yz426 crank to put in my 99yz400- I ended up getting a 02 426 balancer , balancer drive gear,and crank gear to match the new crank as the 400 stuff was different but I thought only the 02 / 426 was different than all the other 400/426 stuff ?

I know the pin size is different from 400 to 426.

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thanks for the info guys but it looks like the bottom end isnt as i thought.....so im looking at just replacing the engine now!!!!

 

anyone know of any engines other than the following that will go in (dont mine a few mount mods etc)

 

wr400

wr426

yzf400

yzf426

 

Will a 450 engine go in?

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