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Is my barrel a match to my engine?

Edward Buck

CB750 Enthusiast
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Great Malvern, Worcestershire
Hi all, I'm rebuilding a K4 engine (whole bike actually) and have split the cases and gone with new shells , pistons etc. I was lining up some 'O' rings I need to order when I noticed on the CMSNI web site that the barrel on the K4 USA version needed 8 'bolt packing pieces' and 8 'special pins' - dowels which correspond to the oil return holes in the barrel.
My barrel doesn't have the openings to take these dowels or the little rubber 'bolt packing pieces'. The barrel looks exactly like the one on my K1 bike.
So the question is were some K4 bikes made using older barrels or has mine been swapped out at some time?
I bought it as a project off an American dealer/seller and had it shipped here to UK as part of the deal. So no history at all.
I also wonder why the change was made? Were the earlier bikes leakier??
Anyone throw any light on this difference?
In the US they started those dowels and rubbers just after K4 i believe. Early k4 could have still had the old style cylinders without the dowels. Honda did have some oil weeping from the head gaskets.
Dirtdigger thanks for the reply. I thought it might be an improvement of some kind over the earlier set up. I guess I m going to need an earlier head gasket then as the one I have when I put it on the head seems to have the larger holes to accommodate the dowels and seals.
Thanks - you are a mine of good info
Many of the aftermarket head gaskets only come with the big holes so you can use them on either cylinder.