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Motorcycle Repair/02 TTR - stripped spark plug hole


I read on another post that using a heli-coil kit to repair a stripped spark plug hole is not recommended for the TTR125.

Any idea why a heli-coil wouldn't be acceptable?

Also, is it necessary to remove the head in order to use a helicoil or can it be done on the bike?

My other option is to simply replace the head but that gets expensive.

Amy other alternatives?

Thanks in advance!

Hi Daryl,

The Heli-coils are okay for awhile but can sometimes fail
due to the heat on the cylinder head.

Another alternative if you can find it is the "Time-Sert"
which is a more permanent repair.

You can find videos of that on you tube.

It can be a little tricky doing it on the bike.
It is possible but a bit risky.

Put the piston a little down from top to protect it
and on the compression stroke so valves are closed.

You take the thread tap from the heli-coil or time-sert
kit and coat it with a sticky or thick grease.

You start threading the hole and then very often
pull the tap out and clean the metal shavings and grease
off and then grease again and clean again until you get the
hole tapped.

If you need to drill the hole the same
technique applies. Keep the drill greased and remove often to
clean off the metal chips.  The key being to prevent any metal
pieces from falling into the motor.

If you are careful and keep it clean you should be okay.
Turning the engine over a couple of time by hand after
or blowing the spark plug hole out with compressed air might help.

Take it slow to keep the metal out of the engine.

The "Time-Sert" kit might be more expensive so do what
you can, the heli-coil will work better if you can get
one for high temperatures.

On my old Kawasaki I one time just drilled it and threaded it
and put in the next bigger size spark plug thread.

This works in heads that have enough room for a bigger plug.
The heat range has to be similar too.

The last alternative is to find a used or new head with good threads.


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Wayne S.


Licensed Motorcycle Mechanic, Knowledge of motorcycles from 1960 up, Japanese, British and most other brand motorcycle repairs.


Worked for Yamaha, Honda, Suzuki, Kawasaki British: Triumph, Norton, BSA Other: Most Scooters and Mo-Peds

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