Changing a spark plug

N

Newblet

Well-known member
I bought a new spark plug for my 125r and was wondering how to replace it and if there is anything I have to do before replacing it? [like disconnect the battery, and how tight the plug should be, gaskets, washers, etc?]

I am a noob so, sorry if this seems like a dumb question.

Thanks
 
It's fairly straightforward..especially since you only have one.. :-) Expose the plug somehow (tank off or whatever is required), sparkplug socket to remove it, examine the plugs to assess how the engine is running (colour, wet), gap the new plug (most are pretty close from the factory), start the new plug by hand to make sure it's not cross-threaded, put your socket back on to tighten it and MAKE SURE YOU DON"T OVER-TIGHTEN IT!! :-) There's a torque spec in your manual, I suggest you try to use a torque wrench to get the correct force. If you pull the threads out on head you'll have a bad day. Plug the boot back on, put it all back together and away you go. You don't have to disconnect the battery..just make sure the key is off..
 
Awesome thanks! I have a torque wrench but I dont have a sparkplug socket so I guess I will go to crappy tire after work and get one.
 
Newblet said:
Awesome thanks! I have a torque wrench but I dont have a sparkplug socket so I guess I will go to crappy tire after work and get one.
Click to expand...

I should say, depending on the engine design, you may have to use the socket to start threading the plug, just do it by hand..or you may need an extension on the socket as well to reach the bottom of the plug well. Just do it with your fingers first so you can feel whether it's cross-threaded or not. It should turn quite a few times by hand before it gets tight..then use the ratchet/torque-wrench on it.
 
On the cbr125 it is dead simple. No need to remove any bodywork, you can reach the spark plug without taking anything off, and you can thread it in with your fingers and use the socket only for torquing it. Easy peasy 2 minute job. As already mentioned, don't overtighten it.
 
I can second what invictus said....be damn sure the plug is NOT cross threaded or over tightened.
 
Ack - no proper advice.
Very important to blow out sparkplug cavity with compressed air before removing sparkplugs!
The objective is to have nothing fall into the cylinder when plug is removed, ie. grit, pebbles, mung, petrified bugs etc.
Newblet is asking "is there anything I should know before I remove this sparkplug" and he's receiving advice to not cross-thread his new plug...?
Please, no offense, but no technical advice if it is not thorough and competent.
 
Gryphon said:
Ack - no proper advice.
Very important to blow out sparkplug cavity with compressed air before removing sparkplugs!
The objective is to have nothing fall into the cylinder when plug is removed, ie. grit, pebbles, mung, petrified bugs etc.
Newblet is asking "is there anything I should know before I remove this sparkplug" and he's receiving advice to not cross-thread his new plug...?
Please, no offense, but no technical advice if it is not thorough and competent.
Click to expand...

Wow..nice attitude. I think we can assume that since he intends to change his plug and has never done it before that advice on not cross-threading and overtorquing is significantly relevant. Wouldn't you agree? No offence..

Good advice on the dirt though, I did neglect to mention that.

Have a great day sport..
 
I'd like to add it's good practice to coat the plug threads with graphite anti-sieze.
 
Gryphon said:
Ack - no proper advice.
Very important to blow out sparkplug cavity with compressed air before removing sparkplugs!
The objective is to have nothing fall into the cylinder when plug is removed, ie. grit, pebbles, mung, petrified bugs etc.
Newblet is asking "is there anything I should know before I remove this sparkplug" and he's receiving advice to not cross-thread his new plug...?
Please, no offense, but no technical advice if it is not thorough and competent.
Click to expand...

So you're technically thorough and competent advice is to only make sure he blows out the cavity before removing the plugs?!? Sounds like you're missing a few steps yourself.
 
Hey Newblet!

In addition to the advice above, the plug will already have a crush washer on it, so you won't need anything else other than the new plug, a suitable spark plug socket and a torque wrench that measures in inch-pounds. Spark plugs generally have a very LOW torque to properly seat them (it will be measured in inch pounds, so you might need a smaller torque wrench.) Those tiny torque settings make it very difficult to feel the torque wrench click as you reach the required torque. As a general rule, if you hand tighten the spark plug until you can't tighten it any more by hand (it should thread in several turns), then give it a quarter of a turn with the socket wrench (or torque wrench) that should be sufficient. If you torque it in too tightly, you may never get it out, and in addition, you may strip the aluminum threads in the head of your engine. Use a tiny amount of anti-seize compound on the threads of the spark plug to prevent the steel spark plug from chemically reacting with the aluminum head (which can cause the plug to seize in the head.)

You will find a FAQ, tech tips etc. here: http://www.ngksparkplugs.com/products/motorcycles/

Good luck!
 
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