Occasionally the sensor mounting plate used in our Shockwave ignition system may not exactl fit in the igniton chamber of the 360 engine. It only happens every now and then, but it does pop up. Here is what is going on and how to fix it.
The 360's ignition chamber is made from 2 haves (upper valve cover and lower cylinder head). The diameter measured top to bottom is slightly variable due to Honda's use of gasket sealer between the two parts rather than a gasket of a fixed thickness. Thus depending on how thick the gasket sealer was applied it will vary the vertical diameter ever so slightly (thus making an ellipse rather than a true circle).There were no less than 3 different points mounting plates used on the CB360 / CL360 / CJ360 during production all slightly different design. The majority of the plates have a half round notch cut out at the bottom of the plate that looks like a frown. This notch was there to deal with the various heights that may occur in the ignition chamber. Due to the senor position on the Shockwave we decided against machining the notch in the plate.
The way to make the plate fit in your particular engine is to sand a small flat spot on the bottom of the sensor plate at the 6 O'clock position. Think about a tire that has locked up the brakes and is skidding down the road. The tire will now have a flat spot on it where it was touching the pavement. Same idea here, you are not going to have to remove very much material. Try taking a few passes on the bottom of the plate with some sandpaper on a flat surface or a sanding block or a machinist file and test fit. Stop when the plate pops in the chamber and allows you to rotate it 20 degrees back and forth or so easily. We have seen in some extreme cases where the entire circumference of the plate need to be lightly sanded to fit in the chamber. If you find yourself in that situation we suggest using a fine sandpaper like 220 and test fitting until the plate fits just right. If you have a caliper handy you might take some measurements to give you an idea of how much material to take off typically only a few thousandths.