Damaged threads to spark....

Do the bad one first and if it goes well you can decide if you want to do the others.
I go by the saying " don't fix what ain't broke"
With a trip coming up why take a chance

bluej58 wrote: Do the bad one first and if it goes well you can decide if you want to do the others.
I go by the saying " don't fix what ain't broke"
With a trip coming up why take a chance

God point take last 3 later

I would also suggest ensuring that whatever insert you use has a surface at the end of the thread to seal against the spark plug crush washer - I believe timeserts do, as do many other brands. Don't go for a helicoil or similar where it is just a thread, as this relies on the existing metal to make a seal between the spark plug crush washer and the head.

I've never repaired a spark plug thread before, but I've done and seen many sump plug repairs. All the helicoil repairs I have ever seen leaked, because the reapir wasn't 100% straight, so the plug wouldn't seat straight against the sump. This isn't a problem with timeserts or any other threaded insert with the mounting surface as part of the insert.

Thank you, I think you are 100% correct there, it is the same I have seen other saying on other sites.

The Wurth kit was really expensive, but I have lucky and found a used one, where one insert only was used approx 70% discount. Will try sell it when I’m finish

I haven’t found useful information if a Timesert is better then good used original threads....
Is a good idea to take all 4 or not... before I sell the kit.

In my head the Timesert should me stronger?
One thing was if these was a new bike, but it is really old....

After I have installed Timesert I will torque up spark plug according to speck from NGR to the specific plug, 20-30nm correct?

So happy I don`t need to take of the top... will you grease when I make the threads and vacuum line the whole after, I also have a inspection camera I will check with before firing up.

I would NOT install inserts into all 4 positions. No need unless the threads are damaged now. It's just asking for trouble.

Nessism wrote: I would NOT install inserts into all 4 positions. No need unless the threads are damaged now. It's just asking for trouble.

Can I ask why?
The high quality time insert is stronger then original threads?

gordone wrote:

Nessism wrote: I would NOT install inserts into all 4 positions. No need unless the threads are damaged now. It's just asking for trouble.

Can I ask why?
The high quality time insert is stronger then original threads?

The original metal has plenty of strength to seal the spark plug. There's a fair amount of time, effort, and risk involved in using a timesert, and since it doesn't actually improve anything , it's just not worth it to replace.

The only reason threads are damaged is from over tightening. Provided you don't overtighten the spark plugs, the threads will never wear out. I would inspect the remaining three threads, make sure they're not visibly damaged, and then insert a spark plug and torque it to spec. If it tightens to spec, all is well, no need to create more work.

Irish Yobbo wrote:

gordone wrote:

Nessism wrote: I would NOT install inserts into all 4 positions. No need unless the threads are damaged now. It's just asking for trouble.

Can I ask why?
The high quality time insert is stronger then original threads?

The original metal has plenty of strength to seal the spark plug. There's a fair amount of time, effort, and risk involved in using a timesert, and since it doesn't actually improve anything , it's just not worth it to replace.

The only reason threads are damaged is from over tightening. Provided you don't overtighten the spark plugs, the threads will never wear out. I would inspect the remaining three threads, make sure they're not visibly damaged, and then insert a spark plug and torque it to spec. If it tightens to spec, all is well, no need to create more work.

So it cannot be that the threads is close to get broken? If it has been over torqued many times before and suddenly brake next year example?
I will take some photos on Sunday and post from the other cylinders, so we can check them. I`m afraid all is on the edge...

If it's close to broken I would expect to see visible damage to the threads. There is a chance that someone has over-torqued at some stage, and felt the 'give' when the metal of the cylinder head begins to yield, and left it at that. But even if that's the case, if it holds with the correct torque once, it should hold every time.

You could potentially try over-torquing each thread by 10-20% to see if it takes the extra torque, but then you risk damaging a perfectly good thread just by testing it. The bottom line is that threads don't just wear out. If it works once, it should work each time. Sure, there's a chance that your torque wrench changes calibration, or you use a different torque wrench that reads slightly different, but it's such a low risk that I personally wouldn't worry about it.

Patton wrote: The initial threads may be cross-threaded (often resulting from some earlier ham-fisted plug installation) making it impossible to get a plug properly started into the hole.

Often, there's a lot of good undamaged thread remaining deeper inside the hole past the shallower cross-threaded area.

The challenge then becomes how to perfectly re-thread the shallow cross-threads to sync perfectly with the deeper good section.

It may be possible to re-cut the cross-threads by starting at the deep end with a reverse tap, also known as a back tap.

The reverse tap inserts all the way through the spark plug hole, and then the tool's deep end expands to begin tracking along the good threads from the deep end, and re-cuts the cross-threaded section as the tool proceeds upward and out of the hole.

It's akin to having the head off, and re-threading the hole in the normal manner starting with the good threads on the piston side of the plug hole.
A reverse tap accomplishes the same result, but without needing to remove the head.

Here's a pic of the reverse threading tool.

Successful reverse tapping depends on having sufficient remaining thread area inside the sperk plug hole.

Good Fortune!

.I've always tightened carefully by hand and after checking with a wrench I was a good 30% under what the manual calls for (Forget the value right now)..... I always have used a small amount of anti seize on em too. Some don't and some do so decide for yourself on that. Had mine out hundreds of times and feel the anti seize has kept em in good shape.

Thanks for the 411 on the reverse tap Patton. Surprisingly I have never heard of them or even seen one until now.

Rick H.