Seized RD 400

[daves1977rd]

I seized up my rd. that I had completely rebuilt in 2023.Made a big hole in the top of the left piston,got a new ignition pickup installed and didn't retime it.What needs to be done to the bottom end when it is rebuilt?
  Has prox pistons now the place a local mechanic uses for boring uses wossler.What are the advantages or not of forged and cast pistons in my rd.? It is at 64.75 now. Any comments suggestions or help on what needs to be done. Thank You.                                       

[m in sc]

it depends on any damage has occurred to the bottom end. its a good idea to flush out the crank case and check for excessive movement/clearances. if that's ok, then do the top end only. more than likely if it didn't seize up HARD, its absolutely fine.

ive used wossners, in particular in the last build. they are good, really good, but the prox are good as well. I used them because im going to beat my motor pretty well, but to be honest, unless you are really raging on it it doesnt matter.

Have your guy measure the bore and see if he can only go to 65mm. thats likely so you should be in good shape. and yeah, def retime the pickup.

[Yamanatic]

Hard seize? If it was a sudden lockup at speed or under power, the rod big-end can oval enough to fail in the future without warning beyond the motor feeling 'rough.' The oval has to be fairly severe to be able to feel tight spots by hand, and still may run quite a while before failing.
A soft seize is usually OK.

WW

 

[John Ritter]

Did you pressure test the engine prior to starting it?