Hi All - i am putting my engine cases together on a DT400 and it only had one shim on the crank. Unless I lost one it looks like the parts call for one on each side. Does anybody have a manual / guide / video that's clearer than the factory manual.

Is the shim you have for the clutch or for the ignition side?
 

Really not to sure  - all the images I have seen on partzilla or CMSL show one on either side so i ordered new ones.

Mark, this is a theoretical question...

If the bearings are installed, then is this possible:

1. case half to L bearing face = A
2. case half to R bearing face = B

C=A+B, where C=total width between bearings.

D= Measurement outside of crank where bearing meets crank

S (Shim Space) = C - D

If A or B > 0.5mm, A or B is shimmed. (DT360A SM)

 CANCEL THIS THOUGHT : I think I was remembering axle clearances...

I'm surprised you can't tell which side?  There are different size holes in the shims if I remember correctly.   The most "critical" shim would be on the clutch side in my opinion*.  I have seen engines from that era with only one shim but I can't say conclusively they came that way from the factory.  

(*Without a shim on the clutch side the crank will often rub the case.  The nut holds that side tight against the bearing.  The ignition side ends up where it ends up and might not "need" a shim)

Thanks - I believe you are quite correct that the one I have is the clutch side. Wondering why the partzilla site shows the same part on either side - I will measure tonight.

I looked on cmsl yesterday & showed nothing either side. Main bearings are the same so shim center hole will fit both ends of the crank. I wonder it's all calculated into1975 for no shim & clearance so flywheels don't rub on the case. Conrod in the center is reasonably important-ish. In my warped opinion if you have 'any' shim on the left side it's free wheeling & doing nothing except wearing a groove in the crank. If there's ever a shim it's always right side as its bolted up hard to 'that' bearing so can't move. Happy to be corrected  or have an argument haha. Sorry, had smileys added in places but got rejected.

As a very experienced Yamaha technician, that shim would be on the "clutch" side. Crank width and bearing spacing should be measured to determine what thickness shim to use.

Rsteve, are you vintage only or do new stuff too?

I just took apart my 75 DT400s parts bike engine and it had a shim on the ignition side only. But the last person who had it apart ruined the cases with a screwdriver so their judgement is obviously not to be trusted.

The 1975 service manual says "note thrust shim position if any" in the disassembly section on page 47.

In the assembly section page 61, it says "place shim on left side of the crankshaft, set crank shaft into left side crankcase."

There are no mention so of a shim on the right side.

In my original 1975 parts book there are no shims.

I guess once I get the crank back from getting rebuilt and the bearings in I will have to measure and see. Its a different case and crank so original shim position is likely irrelevant.