WR 400 to 426

Sorry to bring this up again. (I know there's been lot of posts as I've spent the last two nights researching them) .

I'm changing a friends wr400 to 426 due to big end rattle/scored bore/worn piston.

I am using the same crank with 400 crank pin, 426brg +rod, + 426 piston + cylinder.

The problem arises with the piston part number, some say use 5NG-11631-10-00. Others use 5JG-11631-10-00.

Does anyone know the difference, or what the 5NG and 5JG Denotes?

And can anyone confirm the cam chain part number.

I need to get the parts right as am ordering from thumper store and shipping to England. (Returns are going to cost time and agro).

Thanks in advance. :thumbsup:


yes i am having some difficulty ascertaining the exact difference between model and part numbers.

i am still unable to get someone to definetively say what the difference is.

so far i believe the following

the 400 piston 5gr is smaller diameter than the 426 piston 5ng but the 450 piston is the same diameter as the 426 one, only the stroke is different.

so we can assume that 5be is 400, 5ng denotes 426 and 5jg is 450

i also believe that where a part is carried over, like the same sized piston, the part number defaults to the latest part number, so if a 426 piston is same it will be given a 450 part number for the sake of ordering and stocking.


ring part numbers are

PISTON RING SET (01/426) 5JG-11603-00-00

RING SET,PISTON (99/400) 5BE-11603-00-00

PISTON RING SET (03/450) 5JG-11603-00-00

hope that helps.

at least if i'm wrong, someone is sure to point it out and we'll learn the real story.

good luck

the part # for the piston that I used when I converted to a 426 was 5NG-11631-10-00

that was only a couple months ago...

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