Bonneville America Forums Forums Technical Forums General Tech Spark Plug Screw Up

As some of you may know, I am a nut about torquing everything. When I see a number, I am usually able to etch it in my feeble brain. I remember seeing 20Nm on the spark plugs. 6 years ago, I converted converted 20Nm to 27.18 ft/lbs by dividing 20 by 0.73756. I locked it in my "brain?" and I have been using 28 ft/lbs since (about 10 times). Sunday afternoon after installing a DynoJet kit, I figured it'd be a good time to change plugs. I inserted the left plug with a piece of Tygon tubing as always to prevent cross threading the spark plug. I put the wrench on it after it bottomed out and tried to tighten the plug. It never even snugged up. The threads were stripped. Long ago, when I initially converted the 20Nm to 28 ft/lbs, I divided when I should have multiplied. The proper torque should be 14.75 ft/lbs. I'm gonna end up on the cover of "DUH!" magazine.

THE FIX:

1. Obtain a HeliCoil kit #5523-12, retailing for about $78.00 US. You'll have lots of parts left over to lend to other members who are stupid like me. Send me a PM if you need to do the same thing.
2. Attach a leaf blower to applicable exhaust using a large shop-vac hose. Turn motorcicle engine to place that piston near top with the exhaust valve open. You'll be amazed at the volume of air flowing through that little hole.
3. Grease up the tap to catch shavings and tap away, following the HeliCoil directions. At this point, I had stuffed some material from old panty hose (which will even catch fingerprints) into the upper cylinder to catch stray shaving chips but the airflow blows the nylon up into hole.
4. Insert helicoil as directed using a very light coat of thread lock on the outside of coil.
5. Coat spark plug with never-seize and torque to 15 ft/lbs.
6. RIDE!

p.s. you can find a cheaper spark plug repair kit on ebay but I wanted it as quickly as possible and got mine at a chain auto parts store (because of overnight shipping).

That explains the price,as I read your post I thought $78 was a bit steep. I never torque my plugs I just snug them up and I mean just snug.I doubt I even hit the 14ft/lbs but probably close. Been doing it this way for over 30 years and have yet to strip one or have a leak.

Be lucky you never had to do that job on a worn out exhaust spigot on an old Triumph,that kit is about $300 US. Most guys would just weld an aluminum collar on instead for a fraction of that cost.

What really makes me feel stupid is:
I didn't notice our heads are aluminum, even after a couple valve adjustments. I thought 31 ft/lbs was OK.

well good luck with the job,always scared me doing that on the bike. I have had a few bikes that I aquired with that problem,good news is it seems if done correctly it is as good or better than it was. In the case of the exhaust spigots I think better.

"MASTER CONVERTER" is the ants pants of conversion programs. Easy to use and its shareware. Download at http://www.savardsoftware.com/ I use it frequently for other stuff as well so I actually registered and paid the small fee for it.

Once you download it, go to the "Energy" section. place N-M on left and conversion to in-lb, ft-lb and quite a few others are displayed on the right.

Heli-coil is the way to go for thread repair. So don't feel too bad about the cost, ya got the good stuff.

I always torque,especially on aluminum and my own stuff.
Back when I was working flat-rate, an impact wrench tightened everything. And all was coated with Hi-tack.

The danger is more in not getting fasteners tight enough or consistent where that's an issue, like a head.

I use a free program that, I think, Soren linked to some time ago called "convert".

There are two types of wrenches: Those who have stripped out a spark plug hole and those who will strip out a spark plug hole.

I did it on a VW bug over 20 years ago (also HeliCoiled, but I had to pull the head). Been super paranoid about it ever since.

A loot of folks insert helicoils even if the original threads are good just because they are stronger. Good idea if you are doing something that requires frequent plug removal.

Erwin,
The panty hose will catch any shaving that touches it. But they weren't used since the leaf blower on the exhaust pipe blew the nylon right out of the spark plug hole as soon as it was started. I used my electric leaf blower through a 2.5" shop-vac hose and tied it snug against the end of the left muffler, then turned the engine until exhaust valve opened with piston near top. The spark plug hole gives off a loud, reassuring whistle and sends the shavings all over the carport. Visual inspection of piston and cylinder reveal no particulates of anything (I'm gonna get me one of the fiber optic viewers like the one I borrowed from work).

Skillet,
That's one of those life lessons that makes you grow as a wrencher.

Good Job with the write-up

Thanks for the info. Ill have to remember this reverse airflow trick in the future. Ive been down the same road as you before but have always removed the head.

I always use my "german" torque wrench.. gudentight. Usually covers spark plug install.