You can easily reserve the idler serving, just have to take the string off the bow. I use #2D endserving, but there's other materials that work as well.
When you say "come apart" do you mean that the serving has gaps in it but seems solidly in place, or that it is really unwound? Because a lot of the single cam bows develop minor gaps in the serving, and I don't consider that much of a problem. A spiral provides a good degree of protection as long as it doesn't seem to be getting worse, and eventualy loose.
I use 2D also. If your familiar with serving the center serving then you'll be able to serve the idler wheel area. You can make a jig out of B-Line (used to hold up track lighting). If you want directions on how to make one let me know and I'll e-mail you a copy. Mine cost me about $35.00 I think. Only hard part was the posts and my brother tolled them for me.
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