Spark plug threads

O, Font of all Knowledge,

Is there any way of cleaning up the thread in a spark plug hole
without removing the head?

On refitting the plugs on the SOC, one wouldn't go in and seems to
have buggered up the first turn or two, so what it wants is a tap
putting in from the other end, where the thread is good.

Has Mister Snap-on invented an expanding tap that you can push in
and turn out, or is this a head off job?

 

I can't see why you can't clean up the thread at *this* end with a tap,
assuming you're very careful.

 

1. Grease.
2. It's a SOC, so who GAF?

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| ___ Salad Dodger
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(>|_|_|<) TPPFATUICG#7 DIAABTCOD#9 YTC#4 PM#5
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\|^|/ ANORAK#17
'^' RBR-Visited:38 Pts: 765 Miles:2743

 

AOL - BTDT and on a sump plug.

 

Getting a tap of appropriate size might be tricky.

Then there's the question of all the little bits of swarf that will
have fallen into the combusion chamber.[/QUOTE]

Vacuum cleaner and a bit of thin pipe shoved down the plughjole.

 

I'm assuming this isn't a wind up...

Yes, it has no disadvantages; especially should you wish to suck fuel air
mixture from the carb through the combustion chamber into the vacuum
cleaner and its sparky sparky motor.

 

Using the patented Mavis Beacon "Hunt&Peck" Technique, Champ

No problem at all: www.tracytools.com

This is a problem. Still, it's not like a bit of swarf in an engine's
going to cause any serious trouble, is it?

 

One could possibly ensure that the intake vlave is closed? or is it 'not
that kind of bike'?
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www.cuore-sportivo.co.uk

 

Because a tap from *this* end will probably cut a thread
out of phase with the original, so I'll need to take off
the head and get it helicoiled.

 

You can get a "thread-chaser" just for this job. Bit of thick grease and in
she goes (as they say in these rural parts). More importantly, 'out she
comes' with all the nasty swarf still attached.
Motor factors often stock these chasers. Sykes Pickavant (sp?) make them and
Clarke or Machine Mart also sell them.

JB

 

It was somewhere around Barstow, on the edge of the desert, when the

Hehehehehe.

And just at the right concentration too.

Nice one, TOG.

--

Dave

GS 850 x2 / SE 6a
SbS#6 DIAABTCOD#16 APOSTLE#6 FUB#3
FUB KotL OSOS#12? UKRMMA#19 COSOC#10

 

In the 3rd Millenium, on Tue, 20 Jul 2004 23:21:57 +0100, Eiron

I posted this last October which may or may not be relevant:

'On Monday morning I set off to work, whilst gently passing a couple
of
cars about a mile from home, there was a knock from the engine area
and the bike sounded like the header pipes had fallen off. I limped
back home.

Back at home it was obvious the noise was coming from the top of the
engine. Investigation revealed that the spark plug on no. 1 cyl had
blown out stripping the thread. Fucking Great[1].

Having used thread inserts in the past with great success I decided to
repair the sod myself. Also, I wanted to make absolutely sure no swarf
dropped into the engine.

The problem on the blade is accessibility, even with the camshaft
cover off the thread is around 4 to 5 inches down the hole and
there is a frame cross member above just to make things awkward.
Raking through my toolbox, I found a 1/4 inch socketed tool that I
could modify. The Recoil kit I bought had a tap with 2 cutters on. The
bottom is a standard 10mm plug size and the upper one is for the
thread insert, this makes aligning much easier.

I plastered the tap in grease and cut down about 3mm deep before
removing and cleaning the tap of swarf collected by the grease. I
repeated this until I was through to the bottom.

With the aid of a mirror and torch I could see that nothing had
dropped onto the piston top. Result.

The tool provided was not long enough to screw in the insert and so I
was going to make my own tool but longer. Then I had a brainwave. I
used the blown out plug with the thread turned off in a lathe. I
sawed a slot down the end of the plug to accept the tang on the
insert. The idea being that the plug electrode that was also slotted
could be nipped to hold the tang and prevent it falling into the
engine when it was broken off after insertion. The plug also has a
stepped, non threaded part which seats down the hole, so this method
would make sure the insert was put in far enough.

I screwed in the insert until the plug seated and then yanked it out
to break off the tang. Unfortunately the tang fell into the engine.
Bugger.
A small magnet [2] taped to piece of copper wire soon extracted the
foreign body [3].

Job finished, the new plug now tightens down nicely.

Well chuffed I am.

A bit boring I know but it might help someone one day.

[1] Obviously I hadn't tightened the thing enough, although it's
probably 6 months since I last had them out.
[2] Well actually, a larger 12mm dia magnet smashed to bits with a
hammer
[3] I'd checked before that the stainless insert was actually magnetic
just in case.'

 

What he said.

In any case, a vacuum cleaner and a small piece of pipe gaffa taped to
its nozzle (I'm talking maybe 5mm diameter) doesn't have that kind of
power.

Well, it didn't when my mate did his XLV750.....

 

Oi! Petrolcan! You're next experiment has been decided...

 

Get an old spark plug.
Cut a slot in the threads lengthwise down the plug with a hacksaw.
Smear it with grease and screw it in.
This`ll clean up the threads and the grease will collect the swarf.


--
Petel .
02 M2 Buell.
C90-ZZR.

http://homepage.ntlworld.com/peteh1/website/index.html

 

JB wrote:

Thanks for the advice.
Clarke Spark Plug Thread Chaser, a fiver from Machine Mart
did the trick.

Next time I get a head skimmed I'll check the plugholes
_before_ putting it back on!