Home of  my Yamaha RD400  Drag racer.

Ora et Labora


RD400 Crank Rebuild Guide.


Rebuilding the Crank.

Hydraulic Press
Crank Stand...a piece of pipe with a slot cut in it.
Various bits of 10mm plate.
Spacer Blocks...Bits of rectangle scrap steel.
Feeler gauges
Dial indicator and stand.
Vee Block
Crank aliment jig...an old die set

So people like to press together the center section with new bearings and labyrinth seal. Then press on each outer web. I prefer to press together the outer webs then bring the two assemblies together.

Assembling Outer Webs.

Here you can see an old die set that I have converted into a die alignment fixture. The holes drilled thru the top and bottom plates have aluminum sleeves in then to accommodate the different shaft sizes on each web. You can see the crank webs on the right hand side of the picture. One of them has one of the aluminum sleeves on it.

Here you can see the inner and outer webs that are sitting in the jig. Ignore aluminum plugs that are either side of the crankpin hole. They are the balance holes on an RD400E model crank that I have plugged.

Here you can see that both webs are held parallel to each other and once the crankpin is in place the will be aligned almost perfectly.

Now we have put our new thrust washer/bearing/crankpin and conrod in position we are ready to start pressing the webs together. So that we press the webs together to the correct dimension I place some spacer blocks between the die set halves and press down until spacer blocks are reached.

The total side clearance at the conrod is 0.75mm MAX and 0.25mm MIN. Distance measured across the webs is 52mm.

Here is another style of aliment jig made by Bill Givens

Home | Rebuilding the crank