Changing spark plugs

[the Ferret]

I didn't remove or even move my fuel tank when changing plugs. Here's how I did it (from my original pictoral on How To Change Spark Plugs).

Tools needed:
Air hose with spray nozzle
Stock Honda spark plug wrench or Motion Pro equivalent (what we are using here)
14 mm box end wrench
Spark plug gapping tool
4 Honda Spark plugs LMAR8A-9S Honda Part Number 31908-MGC-003

Start by putting the bike on the center stand. We started on the left side of the bike but that really is unimportant.

First thing you need to do is check the gap on the new plugs. Spec calls for .031-.035. Mine all came out of the box from the factory at .033. We re-gapped them to .031 to allow for wear down the road.


Take an air nozzle and spray the outside plug cavity to remove any debris. We don’t want any of that falling into the spark plug hole once the plug is removed.

Take off the outside spark plug cap and slide spark plug tool over the plug. Remove using 14 mm box end wrench. We also used a swivel head long handled ¼” drive ratchet since we had one available, but ended up using both tools as was necessary.

Inspect removed plug. As you can see mine was still in good shape, had a nice tan color on the ceramic, but gap had opened up to .037 (as electrode and ceramic wore over time). These could have been wire brushed clean, gap reset to factory spec and reinstalled. However as per my practice after 25,000 miles I went with new plugs.

With outside plug removed we had good access to the inside plug. Be sure and stuff some wadded up paper towel into the outside spark plug hole so nothing gets down in that cylinder, and again use spray nozzle to blow out any debris from spark plug cavities. Remove spark plug cap from inside plug.

A note here, if you have large hands there is not a lot of room to work on the inside plug.

Use your spark plug wrench and 14mm box wrench to loosen and remove inside plug. The Motion Pro tool has a rubber gripper inside which makes plug removal and installation easier than the factory spark plug tool.

Install the rear spark plug. Torque spec is 12 ft lbs on a spark plug. We couldn’t figure any way to get a measurement on this given the small confines of the space to work in. So we ran the plugs in until they touched then gave them a bit more, snugging them up. You certainly don’t want to over tighten them and risk stripping the threads of the spark plug hole.

Reinstall rear spark plug cap.

Remove the paper towel from the outside spark plug hole, and install a plug there. Install the spark plug cap.

Move to the other side of the bike and repeat the process for that side’s two plugs

[max]

In addition to Ferret's comprehensive description i would like to add some pictures to illustrate, i have just removed the inside plug and found;

small rocks inside the sparkplug well just to the right of the spark plug;


The ratchet does work in the confined space, one click at a time but do the rest by hand;


And easier with a "wobble extension";


and the extension;


So there is a risk of debris ending up inside the cylinder, unless you can prevent this it may be time to postpone until the area around the plugs can be cleared out completely, i used an empty weed sprayer which had enough of a blast of air to clear all debris out and the reach to get in behind the spark plugs.

[Houtman_imp]

Changing the spark plugs on a CB 1100 is not as difficult as changing a light bulb , only one person is needed for the spark plugs.

[misterprofessionality]

Thanks for all the tips about debris Ferret. I knew how dangerous that was but I didn't know how badly it can get stuck in there. Thankfully, my CB is not nearly as dirty as yours :-p

[misterprofessionality]

ok! for science, and for reference, for anybody that's asking "how often do i really need to change these?"

here's what they look like after 34000 miles of neglect





this was enough wear and tear to cause a very slight but noticable hesitation in the bike when maintaining a very small throttle opening at speed. about 55mph in 6th gear was the sweet spot to generate that hesitation. it didn't do it all the time, and the first time i think i ever noticed it was at around 33000 miles. it's also worth mentioning that upon measuring i found the gap to be way off. almost .4

Having swapped them out though the bike is back to 100%, and I can feel the power gain (or more accurately, i can feel the power i lost back in my hands). I figure i probably shoulda changed these at around 16k to keep everything in tip top shape.