Tecumseh LEV195EA - trouble getting stripped spark plug hole tapped for a helicoil-type insert

[PaulyT]

Hello,

I have an older Toro Recycler 22” (20073) with a Tecumseh LV195EA (6.5HP) engine. It was my mower many years ago (6+) when I was responsible for maintaining our first yard. Then it sat in a shed for 6 years and has only run a few times over that span.

Anyway, I’ve replaced many components trying to get to the bottom of this issue of it not starting. Replaced carburetor, spark plug (multiple), flushed & added new fuel, air filter, and then finally the magneto, which appears to have been the issue, as I’m now getting spark. However, through my many assemblies & disassemblies of engine parts, I managed to strip the spark plug threads pretty good.. tried a fix-a-thread type tool/thread chaser, but no luck. So, I’ve now turned to tapping a larger hole (16mm) for the spark plug (originally 14mm) and will install a Helicoil-type thread insert once I’m able to successfully tap out the 16mm x 1.25 that’s needed for the outer diameter of the thread insert to screw in to. The original spec spark plug will then twist right in to the new threaded insert once it’s installed, and I should be up & running then!

However, my issue is that I’m having a heck of a time getting the 16mm tap I bought to widen the hole in this cylinder head enough to where it will begin cutting new threads for the new insert to fit in to. I’ve been working at it for hours, hammering the tap down so it’s straight (at 90° all around) and then using a ratchet & socket to drive the tap down through the spark plug hole in the cylinder head. Been adding cutting oil, backing it out every few turns to loosen/clear the metal shavings.

I’ve only been able to get the very tip of the 16mm tap (which is more like 14.5mm at the tip before a gradual taper up to 16mm) all the way through the spark plug hole. I still have at least 2 inches of tap to run through the hole and cut 16mm x 1.25 threads along the way, but it feel like the tap is bottoming out, won’t go any further and it seems like it’s just not strong/sharp enough to actually start cutting the threads.

I’ve flipped the cylinder head around and tapped from the combustion chamber side as well, but to no avail. I’m starting to wonder if I should just fork up the money to buy a replacement cylinder head (Tecumseh 37714) for like $20-30 on eBay. But any recommendation would be greatly appreciated!

I’ll try to attach a photo or link to the tap & insert that I’m using (along with some red threadlocker, if that time ever comes! )

https://a.co/d/9PzcMB7

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[ILENGINE]

The issue may be with the tap. Just doesn't have a very good way to expand the hole prior to cutting threads. What I have read on similar thread repair kits is you may need to enlarge the hole with a 9/16 drill bit prior to tapping the hole. I have always used this style of repair kit with threads into what is left of the old spark plug hole threads that then reams the hole and then cuts the 16 mm threads


But also reading that the other style of tool like what you have requires a lot of force to make it ream the hole to size prior to new 16 mm threads being cut. Unless you pre-drill the hole to enlarge it.

 

[StarTech]

And here is another tip. You don't use cutting oil when tapping aluminum., you rubbing alcohol; something in the range of 70%. Oil just causes the tap to clog up.

I was having the similar problems tapping for standard Heli coils. So I decided the my machinist might know why. Sure enough he did. I took his advice and haven't any further tapping aluminum. And you still got go in so far and back out and clear the chips but the taps don't jam or clog nearly as much.

 

[PaulyT]

Thank you guys for the helpful tips! I FINALLY got the darn thing tapped & new spark plug thread insert installed. I followed the advice given and widened the hole to ⁹⁄₁₆” using a step bit from either side. That still wasn’t enough for the reamer I had, so I filed out some more metal using a round file. Used isopropyl alcohol with the reamer (after modifying the flutes a bit with a hacksaw) and an 18” breaker bar to get the whole threaded. Anyway, my ole mower is back to life and runs like a champ!