head studs / nuts

[richmond]

I've tried searching this for my son, but he is rebuilding an XS400 and the head studs/bolts have acorn nuts instead of regular nuts. We torqued the head to spec and per the pattern, but I'm thinking the acorn nuts bottomed out on themselves giving a false torque reading. My reason for thinking this is we are seeing a slight leaking at the head gasket.

Does anyone see a problem with using regular nuts for torquing down the head? Also, with cars I've sprayed head gaskets with the aerosol copper spray to ensure a leak-free head/block/gasket seal. Any experience on their XS650 with this?

 

[angus67]

I don't see why u could'nt use a nut instead of a acorn. a acorn is just a nut with a cover.
If you still get some leaks, try a drop of oil on the threads. it will prevent 'stiction'. There is also a thread here about using yamabond a thin line of it around the camchain tunnel, and around the head bolts that carry oil to the rockers. Im not sure of the specifics of the 400, but I think they are basically the same. as in oil delivery.

 

[angus67]

found it!
A knowlegable member here, 5twins, has found a way that works on our 650 head gaskets using yamabond. His post is in this link with info. hope this helps.
http://www.xs650.com/forum/showthread.php?t=24564&highlight=leakless+head+gasket&page=3

 

[xjwmx]

If the acorn bottoms out good, you can feel the bolt end through it. In fact it can poke right through the top of the acorn; before it ever feels bottomed out, in my experience.

Measure the depth of the acorn hole and how much bolt is there. If you still aren't comfortable use an extra washer to keep it from bottoming. You need a minimum of six threads above the washers.