GS400X cylinder studs v/ 450

[John Park]

I'm wondering if the cylinder studs on a GS450 block are the same length as those on a GSX400 four valve. The 'Twin Squirrel' studs measure 160mm, installed, from the block deck to the top of the threads.

Anyone have a bare 450 block with studs to measure?

I hear of fitting a 450 top end to a 400X block, but has anyone actually done it and can share any foibles - if there are any?

[John Park]

Given that things have been slow on the twins forum, I thought I'd answer my own question. As rumoured, the 450 top end drops right on, with no glitches or things to know. The carb spacing is identical. The oil jets feeding the head are the same size. Couldn't be easier.

It isn't running yet, as it's White Christmas out there, and I've left the head loose so I can put it on after I wrestle the block in the frame. A whole top end used came to about $250 [had the gaskets] even buying the nicest and shiniest low mile bits on Ebay. Unlike 400X parts, which are getting beyond scarce, you can have your choice of many of anything 450.

I'm hoping the 9:1 CR of the 450 is less gasoline fussy than the 10:1 on the 400X 4 valve. It certainly was on the old roller crank 400.