Topic: Tested by a sparkplug

[Don R]

  I had a CB750 #2 spark plug that didn't want to start its thread in the head today. I stopped, took a breath and tried a couple times, got a different plug-same deal, got a different socket and bingo screwed right in.
 On the bike, I normally start them with a piece of hose that has a barbed plastic tee in the end, today I had good access on the engine stand and didn't get the hose out.
 I have taken a die grinder to the socket space on a #2 before, it seems like it's always #2. Even getting an 18mm chrome plug socket back out can turn into a chore. 
 The original K0 tool set spark plug socket may very well be the best one. 

[PeWe]

#2 is the tightest entry for the spark plug.
The Honda tool box spark plug socket is designed for it.
Its waist to avoid where valve cover sit against the head, cover included. This is the most important Honda tool in the stock tool box.

I noticed that my K1 head has even tighter holes for plugs than later heads.
Even the holes for the 4 M6 bolts. I could not use a thin 10mm socket (1/4 wrench/socket kit) thru the tight hole as I used on the later heads.
To avoid JIS screw bit I used allen headed M6 bolts with washers. I could manage the washers.
I think I placed a magneto on the tool.

The tight hole thru the fins.

[newday777]

I've always found the tool kit plug tool to work the best. I've tried multiple sockets and found the same results of sockets not fitting in the head of #2 and #3 holes. And yes the old shop wisdom was to start the threading with a rubber hose slipped on the plug to feel the threads turning properly.

[M 750K6]

No.2 is a problem on mine also. I use the Honda tool. If i crack the initial seal with the T-bar, the other 3 come out (and go in) by hand. No.2 thread is too stiff and needs the T-bar for most of the thread. Very difficult to tell when the plug is finally seated, even with anti-seaize on the plug threads. Very cautious with it, in case I damage the thread.

[BenelliSEI]

Don……… Using a rubber hose to start a plug makes me nervous. Never quite sure what angle the plug is at. Not that long ago, I watched a guy use an old NGK (straight) plug cap instead. With rubber caps at both ends it holds the plug straight and is easy to align. Try it.

I agree….. I did turn a deep socket down to almost nothing and it works well on most of the Hondas. For the Sandcast and the K1, only the original “tube tool” works.

[MauiK3]

Ditto on the Honda plug tool. Works the best.

[beemerbum]

The Motion Pro socket seemingly designed for the CB 750 works darn well, Even on #2. Sometimes you just need a friend with fingers less chubby than yours

[bryanj]

For some reason the 500 four has a different shap, 89216323000, and i find it fits better and holds the plug better.
The 750 is same for 350, 400 and lots of other Hondas

[Don R]

  This head is a late K0 and like Per said, I couldn't even get my brand X ground down 1/4" drive socket into the end holes under the nickel washers. I remember tightening one set with a flat end wrench between the fins.
  I own 4 K0's and honestly this is the second k0 engine I have assembled. One was a sandcast engine that I sold, two haven't been opened, and one has a K4 motor.  This is the motorcycle that ate my brain.
   The moral of the story is that sometimes it's easy to get frustrated and make a mistake like turning that plug when it's sticky. You have to stop and remember your other options.

[newday777]

The Motion Pro socket seemingly designed for the CB 750 works darn well, Even on #2. Sometimes you just need a friend with fingers less chubby than yours

I bought one a couple years ago and it doesn't fit in the 2/3

[BenelliSEI]

The Motion Pro socket seemingly designed for the CB 750 works darn well, Even on #2. Sometimes you just need a friend with fingers less chubby than yours

I bought one a couple years ago and it doesn't fit in the 2/3

The cheap tin tube that vintagecb750.com seems to work in all mine.

[Johnie]

John thanks for the tip on the NGK cap. I will give it a try just for kicks. I have either been using the HM tool or the rubber tube. The NGK deal sounds like a neat idea. Great thread...

[HondaMan]

Yeah, the #2 (and on pre-K4, the #3, too) plug holes are really tight! I like to use the CB500/550 sparkplug wrench like BryanJ: the tapered top portion gives a bit more wiggle room.

For that 6mm bolt on the sides of the head: I have a (cherished) old flat Indestro 10mm that fits between the fins, and a ground-thinner Craftsman 10mm for when i can't find the Indestro wrench. It's easier on the K4 and later engines, though, as they have more space between the fins right there, and also less casting flash.

[Kelly E]

We use a 550 spark plug tool on all of our Japanese bikes.

[rotortiller]

I've always found the tool kit plug tool to work the best.

     +1

[Don R]

 This thread was started as a reminder to be patient when a thread is balky, stop, take a breath and try something else because boogering a thread can become a nightmare.
 What it turned into is a great discussion of ideas that we can all try. Thanks for sharing.