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Problems Tapping/reaming new spark plug hole

#1

J

jquack

I had a spark plug blow out of the engine, damaging the threads. I've got a combination tap/reamer that's supposed to remove the old threads, and cut new ones, so I can screw/loctite an insert into the new threads to hold the spark plug. I watched a few videos that make it seem pretty straightforward and simple; the tap engages the existing threads, and the torque applied to the ratchet removes them and cuts new ones.

The problem I'm having is that the tap doesn't seem to be engaging the threads. It's cut most of them out, but that seems due to inward pressure I applied to the ratchet in an attempt to engage the threads as opposed to the threads themselves engaging, and the reamer doesn't seem to be getting any purchase to cut new threads. Now all I'm really doing is just spinning the tap without any real result.

I don't know if I've got the wrong tap/reamer, used it incorrectly, didn't realize how much pressure the guys in the videos were applying, or what.

Any help or advice would be very much appreciated.


#2

M

mechanic mark

Please post engine manufacturer, model xxxxxx, type xxxx, trim xx, & code xxxxxxx
If you're having trouble making repair take to Dealer or machine shop.


#3

J

jquack

It is a Tecumseh LV195XA, spec 362089E, D.O.M. 07074GG1785, FAM: 7TPSK.196BC, off a Toro 22" Recycler.

That's all that was on the engine identification decal. I don't know the type, trim or code, or where to find them.


#4

Hammermechanicman

Hammermechanicman

More importantly, what type of plug hole repair kit are you using? Pic? Pic of plug hole?


#5

J

jquack

1621804720564.png


#6

J

jquack

this is pretty much what it looks like. it's an OEM TOOLS 14mm Spark Plug Rethreader Kit.


#7

J

jquack

this is the spark plug hole. It looks like most of the threads have been removed by the tool without new threads having been cut. I have no idea if that's how it's supposed to work, but I suspect not.

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#8

Hammermechanicman

Hammermechanicman

Cover the tap with grease and press hard as you turn it in. It should start cutting in the new thread. You want to apply a lot of pressure to get it to "bite in" and start cutting the thread. When you back it out most of the chips ahould be caught in the grease. Any small chips usually blow out the exhaust valve. You always run the risk of leaving chips in that score the cylinder but the grease trick usually works.


#9

B

bertsmobile1

And do not use a ratchet .
Use a drill with a socket adapter so you can push down HARD.
Or if you can't get your hands on that kit a T handle so you can apply direct down force with you can not do with canter levered device like a ratchet or plain wrench.
Follow Hammers instructions
I like to fill the cylinder with kerro after the threads are cut then pull the rope hard to expell the kero a couple of times , prefferably with the engine positioned with the plug hole uppermost.
Get some copper anti seize and from now on a little dab on the plug threads to ensure the plug comes out & the sleeve stays in.


#10

J

jquack

I will try this as soon as I can and get back to you.

Thank you both very much for your suggestions!


#11

B

Born2Mow

1) I have done this job dozens of times.

• If the plug blew out, then most of the threads are gone and THERE ARE NOT ENOUGH THREADS remaining to engage.
• In your case, the cyl head has to come off so that you can tap from the INSIDE going in the reverse direction.
• Due to the need for the spark plug sealing ring to lie FLAT against the plug surface you MUST follow the old threads. Thus you need to go extremely slow in order to go straight.
• The only way you can go slow AND straight is to use a T-handle, so that you don't push the tap off course due to uneven loading of the tap handle. Bert is correct, DO NOT use a ratchet. And DO NOT use a drill motor.
• I highly suggest you buy a 14mm spark plug repair kit from Heli-Coil. Spend the money and buy the real thing because they work the best. They come with a 2-diameter tap (starter and finisher) to give you the best chance at success. The solid inserts always back out. Solid inserts are trash.
• Tapping is done with LOTS of lubrication. The best results are obtained by cutting in 1 turn, then reversing by at least 1/2 turn. This breaks the chip... which is necessary due to the design of the tap itself. Coming all the way back out, blowing out all the chips with compressed air, and then applying all new lubricant is the best method. This back and forth is why a drill motor is NOT recommended.
• Install the Heli-Coil from the outside. The coil end should end up below flush. Again lots of lubrication.

2) A stripped plug hole is merely a SYMPTOM of another problem: Incorrect technique.
A stripped plug hole is COMPLETELY avoidable by adding one simple step. Cyl heads are typically aluminum. Spark plugs are typically steel. Steel and aluminum REALLY do not like each other, especially in high-heat situations. That is the very nature of the 2 materials. So the installer must find a way to separate the 2 materials. The correct technique is to add a compound to the spark plug threads BEFORE installation that keeps them separated. Products like Never-Seeze which add nickel or copper work the very best. But, simply dabbing 2 drops of motor oil from the dip stick onto the threads is better than nothing. The oil bakes on and forms a patina, which is strong enough to give the needed lubrication and more importantly, the separation.

If you ever see a mechanic install a spark plug without so much as 2 drops of motor oil, you'll know that person is an idiot. Lubricating spark plug threads is Mechanic 101. It's basic information. Stuff you learn the first week on the job.


Bottom Line: You're probably doing this entire job for the lack of 2 drops of motor oil.


#12

R

Rivets

Then if you look up “an idiot “ in the dictionary you’ll see my picture. In my 50+ years of experience I’ve never used oil, nor will I ever use oil on spark plug threads. They are designed to be installed dry.


#13

Hammermechanicman

Hammermechanicman

Here we go!?

Back in the old days of cast iron cylinder heads and blued steel spark plugs you had issues with plugs literally rusting and seizing. Especially the taper seat plugs used in some ford engines. Fast forward to aluminum heads and spark plugs with plated threads. Rusting not an issue and plating stops the galvanic reaction. What i do see is folks who think you need to install the plugs like it is a lug nut and over torque them to the point they damage the aluminum threads and the plug blows out. I have watched people install plugs with a 1/2" ratchet and pull them down like a head bolt on a big block chevy. Everyone has their way to do it. I change over 100 plugs a year no and i put no oil on them. Of course, i am just another random hack on the internet.


#14

cpurvis

cpurvis

I've never used oil but have used anti-seize. Don't know if it helps but so far has not hurt anything, either.

15-18 ft-lb is about what I put on them, if that, using my un-calibrated hand and a 3/8" ratchet to compress the gasket. Have never had one come loose or stripped a thread, either.


#15

B

bertsmobile1

Depends upon the application.
The plug holes on the RR are helicoiled from the factory, in fact every threadded hole in their block has a stainless steel insert.
So plugs must be lubed or you end up ripping out the insert.
As for mowers or motorcycles , plugs go in dry


#16

S

slomo

You are not supposed to apply anything to the plug threads. You are looking for a good ground to fire the plug. Oil is an insulator. Besides the plugs are plated to resist dissimilar metals and the corrosion that the two fighters cause.

slomo


#17

StarTech

StarTech

This should done with the head removed in this case.

Now the tool pictured looked to be the Performance Tool Spark hole repair tool. It is probably just a poor copy of the OEMTOOLS version. And only one of the PT tools set and it was poor quality: otherwords, they did not hold up very well at all.

Also taps in aluminum will stick and cut poorly even when using oil. The trick is to use rubbing alcohol instead. It only breaking off a couple taps to realize this sticking can be a major problem. Plus you only use high quality taps and dies in the first place. They are well worth the extra expense.

The question here is since the OP say the just spins in hole is it at the starting point or is it already most of the way in. If just starting then tool is already too dull to start threading for the new inserts. Otherwise if halfway or most of the way in then the hole is already too damaged.


#18

B

bertsmobile1

The actual lubricant for machining aluminium is kerroscene .
Grease is to trap the chips
And yes I would be doing it head of on a mower engine


#19

Hammermechanicman

Hammermechanicman

I have done head on and off and both ways seem to work. Or just wrap a piece of 14ga solid copper wire around the threads of the plug and just crank it into the head.


#20

cpurvis

cpurvis

slomo said:
You are not supposed to apply anything to the plug threads. You are looking for a good ground to fire the plug. Oil is an insulator. Besides the plugs are plated to resist dissimilar metals and the corrosion that the two fighters cause.

slomo
Click to expand...
I'm guessing the number of plugs I've installed is in the high hundreds, if not thousands.

You'd think if installing plugs with anti-seize on them would cause problems, it would have shown up by now.

But it hasn't.


#21

J

jquack

For all of you who replied, I would like to say thanks. I really appreciate the time and effort you all took.

Combining what you all suggested I do, with what I COULD do, I abandoned the ratchet in favor of a drill on the very slow setting. I put the mower in a position where I could put some shoulder into it, lubed the crap out of the tap, went in straight very slowly, backing out frequently to lube and clean the tap and hole, and reamed new threads in less time than I thought it would take. All in all, following your advice, it turned out much easier than I expected. I cleaned everything thoroughly, and the insert went in without a burp. Now I'm just waiting for the loctite to dry, and I expect I'll be good to go.

Or have ruined my lawnmower for good. The jury's still out. I'll let you know tomorrow.

J


#22

P

pickateer

I've used those kits many times to repair VW engines with 100% success Most people buy Champion plugs but the problem with these plugs finds the thread in not rolled into an Apex shape, but simply has a very sharp peak at the end. This along with not clearing out the carbon in the plug tread on the engine results in blowing plugs out at a later time. Now here's the challenge, put a vacuum hose on the exhaust pipe and as someone suggested use a T drive and put pressure on the tool to bite into the plug opening. Once the new tread is cut then blow out the cylinder with compressed air. Then carefully and SLOWLY turn the engine over to ensure all the cutting chips have been removed. If the engine stops while slowing turning, then back it up, spray in carb cleaner and repeat the process until the engine turns freely. The install an NGK plug and TORQUE it in at 15 to 20 foot pounds, and use a torque wrench every time


#23

P

pickateer

One more thing do not put anti-seize or anything else on the plug thread since this will result in the plug being over torqued and stress the threads in the plug bore


#24

9

905sharpie

jquack said:
I had a spark plug blow out of the engine, damaging the threads. I've got a combination tap/reamer that's supposed to remove the old threads, and cut new ones, so I can screw/loctite an insert into the new threads to hold the spark plug. I watched a few videos that make it seem pretty straightforward and simple; the tap engages the existing threads, and the torque applied to the ratchet removes them and cuts new ones.

The problem I'm having is that the tap doesn't seem to be engaging the threads. It's cut most of them out, but that seems due to inward pressure I applied to the ratchet in an attempt to engage the threads as opposed to the threads themselves engaging, and the reamer doesn't seem to be getting any purchase to cut new threads. Now all I'm really doing is just spinning the tap without any real result.

I don't know if I've got the wrong tap/reamer, used it incorrectly, didn't realize how much pressure the guys in the videos were applying, or what.

Any help or advice would be very much appreciated.
Click to expand...
Worst case is you go to a local dealer that has scrap lawnmowers and get a used head and a new head gasket I'd possible. Tecumseh has been out of business for many years now and parts are getting hard to find. I might even have a old head leftover my from my repair days.


#25

C

Caregiver5354

jquack said:
this is pretty much what it looks like. it's an OEM TOOLS 14mm Spark Plug Rethreader Kit.
Click to expand...


#26

M

mystic240

Is the head removed? Unless the spark plug is over the piston
I don’t think there is room for the tap.


#27

C

Caregiver5354

pickateer said:
One more thing do not put anti-seize or anything else on the plug thread since this will result in the plug being over torqued and stress the threads in the plug bore
Click to expand...
Looking at your picture of the tool you have there your missing the drill bit that should of come with that tap and the replacement threads. It is a kit usually. You need the drill bit that is the correct size for that tap. You should first drill the spark plug hole with the bit which will leave the hole a perfect size for the tap.


#28

P

pickateer

What I saw in the photo was a standard KD kit 2126 14 MM Spark Plug repair kit

1622044410825.png


#29

C

Caregiver5354

pickateer said:
What I saw in the photo was a standard KD kit 2126 14 MM Spark Plug repair kit

View attachment 56723
Click to expand...
On every kit that I have used came with a drill bit. The drill bit sizes the hole for the tap.


#30

P

pickateer

That kit has a combination reamer and tap and does not need a drill bit - 50 years in the business and never bought one with a drill bit, does not mean to say the KD kits never included a drillbit


#31

L

ltcsloan@hotmail.com

Also, make sure the piston is down so that the tap does not touch the top of the piston and stop the downward movement of the tap.


#32

gamma_ray

gamma_ray

jquack said:
I had a spark plug blow out of the engine, damaging the threads. I've got a combination tap/reamer that's supposed to remove the old threads, and cut new ones, so I can screw/loctite an insert into the new threads to hold the spark plug. I watched a few videos that make it seem pretty straightforward and simple; the tap engages the existing threads, and the torque applied to the ratchet removes them and cuts new ones.

The problem I'm having is that the tap doesn't seem to be engaging the threads. It's cut most of them out, but that seems due to inward pressure I applied to the ratchet in an attempt to engage the threads as opposed to the threads themselves engaging, and the reamer doesn't seem to be getting any purchase to cut new threads. Now all I'm really doing is just spinning the tap without any real result.

I don't know if I've got the wrong tap/reamer, used it incorrectly, didn't realize how much pressure the guys in the videos were applying, or what.

Any help or advice would be very much appreciated.
Click to expand...
Does the piston happen to be TDC? It's entirely possible it's keeping the end of the tap from going far enough to start threads.

In college I had a VW Beetle and had to install a couple of these. Before starting to cut, I would turn the crankshaft to the exhaust stroke of that cylinder (exhaust valves open) and piston down, so any aluminum slivers could be blown out with compressed air.


#33

P

purse

jquack said:
I had a spark plug blow out of the engine, damaging the threads. I've got a combination tap/reamer that's supposed to remove the old threads, and cut new ones, so I can screw/loctite an insert into the new threads to hold the spark plug. I watched a few videos that make it seem pretty straightforward and simple; the tap engages the existing threads, and the torque applied to the ratchet removes them and cuts new ones.

The problem I'm having is that the tap doesn't seem to be engaging the threads. It's cut most of them out, but that seems due to inward pressure I applied to the ratchet in an attempt to engage the threads as opposed to the threads themselves engaging, and the reamer doesn't seem to be getting any purchase to cut new threads. Now all I'm really doing is just spinning the tap without any real result.

I don't know if I've got the wrong tap/reamer, used it incorrectly, didn't realize how much pressure the guys in the videos were applying, or what.

Any help or advice would be very much appreciated.
Click to expand...
You Need a spark plug Helicoil repair kit . You also need the plug size when you purchase the helicoil kit. comes with the tap , insert and the tool to install . Never had any luck with a thread insert they usually pull out when you take out the plug.


#34

J

Joed756

I would never do this with the head on the engine. Buy a new head gasket and do this job with the head clamped to a bench. You really don't want to have even one little chip of metal roaming around in there.


#35

M

MGT01

At the risk of asking the obvious is the piston at the bottom of the stroke and out of the way of the tap? in my experience soft aluminum does not resist sharp hard steel without a good reason. I also second the recommendation of using grease on the tap to catch the cuttings. Hope that helps.


#36

J

jquack

After I let the loctite cure for the full 24 hours, I cranked that sucker right up, and it ran like a champ! I'm going to change the oil, and get to work!

thanks for all your suggestions and help. I can't tell you how much I appreciate it!


#37

S

sparkplug55

jquack said:
I had a spark plug blow out of the engine, damaging the threads. I've got a combination tap/reamer that's supposed to remove the old threads, and cut new ones, so I can screw/loctite an insert into the new threads to hold the spark plug. I watched a few videos that make it seem pretty straightforward and simple; the tap engages the existing threads, and the torque applied to the ratchet removes them and cuts new ones.

The problem I'm having is that the tap doesn't seem to be engaging the threads. It's cut most of them out, but that seems due to inward pressure I applied to the ratchet in an attempt to engage the threads as opposed to the threads themselves engaging, and the reamer doesn't seem to be getting any purchase to cut new threads. Now all I'm really doing is just spinning the tap without any real result.

I don't know if I've got the wrong tap/reamer, used it incorrectly, didn't realize how much pressure the guys in the videos were applying, or what.

Any help or advice would be very much appreciated.
Click to expand...
Make sure piston is down so tool does not hit the top of piston and grease tool with wheel bearing grease to catch shavings. If available blow out hole with compressed air.


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