Fixing a Cross Threaded Spark Plug

J

jthiessen

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My left spark plug is becoming cross threaded and I want to fix it before a spark plug shoots across the highway. Is it possible to rethread the hole without disassembling the engine? If not, can I take the cylinder head off the bike without taking the engine out of the frame?
 
A tap will probably fix it, but you'll definitely get crud in the chamber. That being said, I have done that on my jetski motors, and then let the starter pump for about 10 seconds, flushing it all out the exhaust. Nothing bad ever happened. But I can't condone the practice. Last thing you need is those shavings tearing up the cylinder wall or getting stuck between the valve and seat.
 
Okay...What is all involved with removing the head? This would be my frontier experience inside the motor and I would be doing the job basically in a covered parking lot. I would want to do as minimal dismantling as possible.

And I would probably need a torque wrench...any recommendations on brand and weight range for that?
 
Definatly be easier with the engine out of the frame. But then you will definatly need some else to hold the motor while you torque up the acorn nuts on assembly. And when you undo them on disassembly, you don't wanna strip them. Its no big deal to get in there and do it. But its going to be much easier with a second person. And make sure you have a manual!
 
One of our members did use this tool to repair the spark plug threads: http://www.amazon.com/Powerbuilt-64...=UTF8&qid=1426819842&sr=8-1&keywords=back-tap
It taps from the inside out, starting from the threads most likely to be in good condition. Supposedly it doesn't drop bits into the cylinder.

Trying to hold the motor while torquing the acorn nuts properly was tricky but possible. Probably wouldn't take much to bolt it to something with the bottom mounts.
 
I did it to my xs400 sohc with head on. Easy job. Bought a cheapie knock off time sert kit. Used high temp loc tite to hold it in. Used my shop vac with a small hose taped into the end of the big hose to stick inside the plug hole into the cyl. To clean it out of shavings.
 

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