Valve guides

[strom]

I'm having some trouble taking out the valve guides.
I don't want to damage them, so... do I just whack the weasel or is there a finer approach.
The yamaha service manual says I have to heat it in the oven to a 100 degrees centigrade, but for that operation I'd rather wait till my mom goes somewhere for a few days.
Manual says to use the valve guide removal tool... looks like a piece of pipe to me.

LP

[Do Lee]

When removing valve guides you have to be careful because if not done properly you can cause hair line cracks around the valve guide hole in the head.
During the years when I worked for Yamaha USA corp., we would heat the heads of the bikes in an over and have the replacement valve guide in dry ice. "HEAT" to expand the alloy head for a easier extraction of the valve guide. "COLD" Dry Ice to cause the replacement valve guide to shrink allowing the valve guide to slide easily into the Heated Head. I think that there is a tech tip on valve guide replacement.

[Geezer]

Originally posted by Do Lee
When removing valve guides you have to be careful because if not done properly you can cause hair line cracks around the valve guide hole in the head.
During the years when I worked for Yamaha USA corp., we would heat the heads of the bikes in an over and have the replacement valve guide in dry ice. "HEAT" to expand the alloy head for a easier extraction of the valve guide. "COLD" Dry Ice to cause the replacement valve guide to shrink allowing the valve guide to slide easily into the Heated Head. I think that there is a tech tip on valve guide replacement.

That mirrors my experience changing guides exactly. I've found that over night in a deep freeze will shrink the guides enough to get them in but the freezer compartment on a refrigerator usually isn’t cold enough.

Don’t even try without heating the head first. I’ve found that about 350 degrees Fahrenheit is about right on most kitchen ovens. The imprint from the first time I did this is still on the breadboard at a friend’s house. We flipped the head over after installing the guides to let it cool and it burnt an imprint of the mating surface that can still be seen 30 years later. ;o)

Geezer