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Yamaha RZ-350 engine question

Discussion in 'WERA Vintage' started by CalgaryMotoBros, Feb 23, 2022.

  1. CalgaryMotoBros

    CalgaryMotoBros New Member

    Hello to all . . . we are working on a Yamaha RZ-350 engine that came to us in multiple boxes. The rebuild is going well and ready to button up the crankcases BUT we have a bit of a puzzle that we hope someone here can help with. The are two factory machined through-holes in the merged cases and we've not been able to find any parts that would obviously fit the holes, nor have we been able to find any WebInfo about the holes. One hole is located directly behind and between the cylinder bases, the other hole is on the left side, just forward of the clutch actuator bearing. Any info on these two holes will be greatly appreciated, thanks !!

    Attached Files:

  2. BlueR32

    BlueR32 Well-Known Member

    If it's anything like the aircooled RD motors that center hole between the cylinders just goes right through and I suspect its only purpose is to be a drain hole for any accumulated fluids on top of the crankcase. If you post your question in the link below you will be connected with the master jedis of all things RD & RZ:
    Hope this helps!
  3. ChemGuy

    ChemGuy Harden The F%@# Up!

    I think that middle one is like Blue said. It should be sealed and not let air in. Does the other hole lead into the transmission? Maybe a breather for the transmission?

    Its been too long since I took one apart. But both of those holes are in other pics I see on the net.
  4. yamageezer

    yamageezer Well-Known Member

    Yes, it's a just a drain hole.
  5. dave3593

    dave3593 What I know about opera I learned from Bugs Bunny

    I have an rz350 engine apart in the shop now so I checked. The upper/lower cases are apart so I can get a good look.
    Yes it is as you said with both through holes. The holes are in the top and bottom cases and they mate when the cases are put together so that they keep the transmission case sealed but still allow two through holes from top to bottom.
    I took this engine apart myself and there was nothing that went in the holes.
  6. expat

    expat Active Member

    I believe the hole on the left could be for the generator wiring, there should be a rubber seal that locates in it… pics would help to be more sure…

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