91 nighthawk stripped spark plug thread

[killian101]

as the subject states, the first few threads in the hole are pretty smashed and stripped...I guess the person who i got the bike from never did much work on it.  I have some questions

What size is that spark plug hole?  12mm?
what thread insert would you recommend?  Time sert, helicoil?
And, whats the a good way to go about doing this?  I sort of want to stay away from removing the head...

Any feed back would be great.  Thanks

[ariwhiteboy]

  to the forum! I have used helicoils on cars before but never tried one on a bike.

[muttstang]

if you can get the right sized time-sert for it, that would be better then the helicoil.  I put those in a mustang and they worked great

[Soupskin]

Timesert should do the trick.

The kit to set them properly is rather expensive though.  Call around and see if you ca find a shop that does them.  It will save you some money that way unless you have several you need to do.

[coffee_brake]

The head's not that bad. It's better to remove the head than risk getting drill  shavings all in the motor.

[ariwhiteboy]

Jen brings up a very good point (she always does)...better to remove the head than risk metal bits in the engine.

[killian101]

removing the head is always better...trying to avoid it.  But something to consider.  What about moving the cylinder to TDC?  So...is that Spark plug hole 12mm?

Thanks for all the input

[coffee_brake]

I don't remember the threads on the plug hole. All you have to do is take a plug to the fastener store or hardware store and get the thread size from there.

I have seen many successful helicoil inserts done while I worked at a bike shop. It is imperative to buy the right size, which seems too big but threads right in there. Many folks have screwed this part up.

I have a known good head to fit your bike, if it comes to that.....

[killian101]

much thanks...

[flynrider]

+1 on the Time Sert.   My '93 got one in the #3 spark plug hole this spring and it's still solid.  I went the Time Sert route for the spark plug because their insert is self locking.  I've had Helicoils back out over time.

  I ended up having a local shop do the install.  While the process didn't look real complicated, it turned out that the Time Sert kit required for installation would have cost more than having the shop do it.  Another plus was having experienced hands do the job.  You only get one shot at doing it right.

[coffee_brake]

+1, if you can find an indy shop that will do the job, it's worthwhile to let 'em do it on something so important.

[biometrics]

+1 on removing the head is the only safe way to do this.  Trust me, you don't want even a single metal shaving entering the cylinder and there is simply no way to prevent that from happening when modifying the hole.