Hi all, Rebuilding the top end on my 400ex, and found a few serious issues.

1) The gasket between the jug and bottom end rusted out badly, also rusting the small 8mm bolt on the outer edge of the timing area, causing it to snap when I was removing it.



I Imagine I'll have to rip apart the whole engine and take it to a machine shop to be drilled and tapped? May need resurfacing too. Any input?

2) Looking into the bottom end, the gears look good except for the second gear (I think). Some rounding to the edges and some line on the outer edge of the teeth.



another look


Does it look worn to the point where I should replace it? I'd prefer to not rip the bottom end up, but at the same time don't want to cut corners.
Also, the gasket between the bottom end halves is bulging out a bit making contact with the sleeve. Can anyone see this causing problems?

Lastly, There seems to be a rock in my engine...



Looks like a little rock lodged in the engine. This HAD to be there before I opened it up. I was extremely careful to not let debris inside the engine. I was hoping someone would say it just an oil passage or something, but it really looks like a rock to me. I don't think the engine was opened up by last owner. Had stock piston, cam and gaskets. You never know though.

Any advice is appreciated. I'm in for a lot more than I bargained for it seems.

Thanks in advance!

Edit- engine was fully functional before I opened it up. No leaks and good power.

 

If there is room i would try and get a pair of vise grips on that bolt and see if you can break it free. Some fine sand paper should take care of the rust. It looks like that gear might need replaced. Whenever you have a bad gear in a transmission it is also a good idea to replace any other gears the bad one has come in contact with.

 

Try soaking that broken bolt with Kroil before you try to get it out.