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Spark Plugs Check/Change

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spitonyourgrave22
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Location : Sheffield, UK

Spark Plugs Check/Change

Post by spitonyourgrave22 on Sat 30 Oct 2010, 4:47 am

It's wise to check the condition and gap of the spark plugs at every service. Honda recommend replacing them every 16,000 miles but personally I would do them at every major service (ie. 8000 miles)

Access to the plugs is tricky as they are very deeply recessed in the cylinder head. While it is just about possible to remove them without taking the bike apart, I recommend removing the petrol tank first especially if you haven't done them before.

To remove the tank, first switch off the fuel tap. Lift and preferably remove the seat, and remove the bolt securing the back of the tank. On faired models, remove the allen bolts securing the front of the tank to the fairing. Lift the tank slightly, detatch the two ridiculously short hoses that are connected to it, then lift it clear. Place it down gently to protect the tap and keep it upright.

Now you should be able to see the two HT leads (thick black wires) leading down into two round pits in the top of the engine, below which lurk the spark plugs. Label the HT leads with "left" and "right" and pull them off (pull the cap not the lead).

Before attacking the plugs, check there is no crud in there that could fall into the engine. Use a thin tube to blow out any dust or debris, then use your 16mm spark plug socket on your longest extension bar to remove one plug at a time.

Using the feeler gauge, check the spark plug gap -- it should be 0.8 - 0.9mm; adjust if necessary. Look at the general condition of the plug, it should be intact with a light brown, tan or grey coating.

If there is a lot of carbon build-up, your bike is running too rich. If it is oily then you have piston ring problems. If it is chipped, eroded or blistered then it has probably overheated due to being the wrong type, loose, or because your engine is running lean. If in doubt take the plug to your friendly garage and ask their opinion.

If reusing the plug, give it a clean with a little petrol and a toothbrush (don't use anything abrasive).

Take great care not to cross-thread the plugs when replacing them. Get them into position, then turn them slowly by hand anti-clockwise until you feel a slight click, then screw them in gently. In fact this is the best way to fit all nuts and bolts.

If you have a torque wrench, set it to just 12 Nm / 9 lbs-ft. Otherwise give the plug 1/2 turn more from hand tight (new plug) or 1/8-1/4 turn (reused plug).

Reconnect the HT leads, and replace the petrol tank, taking care to connect the two rubber pipes securely and not trap them under the tank.

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