Got the Right Tool...I think

So My first bike is a bit of a Fixer upper, I have one ignition coil that shot I think...after a little bit of reading here...I have another test to try....But this leads me to my problem....The guy I bought the bike from, told me i needed to change the spark plugs...No problem...What I didnt know is he wasn't smart enough to put them back in with out stripping the holes....my question is...I have a 14mm expandable chaser....I don't know...all i know is it works in reverse....but is a spark plug hole a spark plug hole...or are they different?....is this the proper tooL!....Help Forum! haha

 

I'm not sure about the tool. I have never had to use one yet. All I can do is tell you that they are different on different bikes. All of the maxims that I have worked on have had the same size hole. To answer your question though...yes there are different sizes. Someone else may be able to answer in more detail or even maybe tell you if that's a big no no with these bikes.

 

Your 650 has 14mm spark plug holes.

I'd be careful with an "expandible" chaser; better to use a conventional chaser especially if the threads aren't badly buggered. You could do more harm than good.

Goober a bunch of grease in the hole and all over the tool to catch any shavings.

 

so this tool is called a back tap, anyone familiar?

 

your back tap is designed to use the threads on "inside" end of the hole as a guide.
but if, and only if they are in good shape.

look inside the hole and note where the damage is.

if the person cross threaded all the way through.
i would leave it the way it is.
it would be nearly impossible to line up any tap properly.
conventional or otherwise.

if the damage is near the outside then you have the right tool.
the tool collapses, you insert it, expand it, and chase backwards "inside-out".

it is critical that the back tap engages good threads in order to guide properly. make sure its perpendicular to the hole. be gentle and use the smallest amount of force necessary.

however, if the previous owner threaded the spark plug all the way in.
he made a new thread via unintentional thread rolling.
which is just fine. the seal is made by the compression washer on the spark plug.