Bear in mind, though, that this test is only a rough indicator, and charging problems should be checked out with the proper equipment as soon as possible. He says that he can't test it, so it might be the problem, but it might not. Some CDI units can be tested by a dealer with the proper diagnostic equipment. Sometimes it can quit completely, sometimes intermittently. The main thing to remember is that electrical parts are usually not returnable.
Blue smoke is a sign that the engine is burning oil, and that there is engine wear.
Another indicator of a blown head gasket is oily residue in the radiator. All of these conditions can lead to more serious problems, if left too long . Always insist on getting your old parts back, after repairs have been carried out. Get the mechanic to go over the worn or broken parts and ask him to explain what's wrong with the used parts. Understanding how things work is half the battle, and most things are simple, when explained in plain english.