|Changing the spark plugs is an medium difficulty operation and also, you don’t need to change them very often – it’s a real permissive engine. The best way to do the change is with the tank near empty (tank has to be removed) and with a cold engine.
Getting access to the spark plugs
Put the bike on the central stand (optional). Start by removing the seat and the small side-panels. Remove the fuel tank mounting bolt – don’t worry the tank won’t fall.
Switch the fuel to off and take the hoses out – fuel hose and vacuum hose (left side, just below the tank). Prepare a surface to place the tank once is removed – some fuel might leak (usually a few drops). Remove the tank slowly by lifting and dragging towards the end of the bike.
Spark plug removal
Once you have the tank out, take a piece of paper and pencil and draw the position of the spark plug caps (the cylinders are numbered 1, 2, 3, 4 starting from the left side, but that won’t help much if it’s an older bike and the numbers are not visible on the wires, unless you make a draw). Remove the caps& wires and look at the spark plugs from above – you will notice a lot of debris around them – you don’t want any debris in your engine. You can remove the debris with compressed air – if you don’t have, just use a small hose and blow air around the spark plugs until the debris is gone (use protective glass to protect your eyes). You can as well use a small paintbrush, or a vacuum-cleaner.
Using the socket, loosen and remove the spark plugs. After removing each one, it would be a good idea to inspect them.
Inspecting the spark plugs
Spark plugs can indicate any problems with the engine.
- light gray colored, normal gap – good engine
- damp oil film – most likely worn piston rings
- carbon deposits – fuel mixture too rich, clogged air filter
Installing new spark plugs
I’m using NGK DPR8EA-9 – the standard heat range spark plugs (work well, unless is really cold), or you could use Denso Hot U Resistor Plugs X24EPR-U9 . To install the new ones, screw them by hand to make sure they are not cross threaded. Once the gasket touches, tighten a little bit with the wrench. Put the caps back using the paper drawing, the fuel tank hoses, bolt, side panels and seat.