swapping cyl heads

[thewiz]

Who can say with any degree of certainty if a cylinder head from an '80 motor will swap directly to a '79SF motor? For starters: I'm told the '80 valves themselves will not swap to the '79 head. Can anyone verify that offhand, or if not, does anyone know where to find valve specs for each year?

[red bandit]

The heads will swap. But the valves 78-79 will not swap to 80-81. Or visa-versa.

[thewiz]

Thx .... I love this forum :-)

[MAXIMAN]

Wiz

Whatever you do KEEP THE 79 CAMS!

On thing you can do for performance is use the late (80-81) head with the larger valves but swap the late cams for the "hotter" early cams. And yes they should fit fine in the late head.

[John]

Valve clearence

Which clearences should one use? The 78-79 or 80-81 dimensions?

[xschop]

hey maxx

yes, I was going to PM you the same question, and does it matter if the shims have to go back into the donating head since the lift/duration of the early cam is different. You see this is what I get for staying up late and reading my xs1100 manual!!!....chop

[mro]

Valve clearence

Match w/cams used


mro

[trbig]

Match w/cams used

That's probably good advice, but I did use a bigger valved head on my '78 motor, and shimmed it to the specs for the head.. (Didn't know any better) and haven't had any problems in that department. No valves bumping pistons or anything...

Tod

[xschop]

inquiring minds want to know

why did yamaha have diff. valve clearances?

[GNEPIG]

.. the taller/pointier cams in the newer bikes makes more noise with the old valve lash spec.

[xschop]

now that makes sense

thanks gene. So should I go with the lowest valve clearance with the 80 head, 79 cams?

[trbig]

Just to make sure you are understanding.. I don't know for sure if the 80 model head had the same valve clearances that my 82 did, but the book said to shim to .11-.15mm intake and .21-.25mm on the exhaust. I think I saw somewhere that it was .21-.24mm for the exhaust on an 80 model.. but don't quote me. The earlier model cams (78-79) had an adjustment of .16-.20mm for the intake side. This is the number you should shoot for. The exhaust was basically the same.
The closer you can get to the higher number, the better (IMO) As your valves wear (Or valve seats) over time, the gaps will actually get tighter between your shim and your cam. They will set deeper into the head. If you begin with it tight already.. just less time until you'll need to do this again.


Tod