|When you have a engine related problem, there is order, or there is maddness...
With a running engine the first thing that should be done is a compression test.
With a well warmed engine, you pull the spark plugs, and the air filter if you have constant velocity carbs. prop the sliders up with a finger once the comp tester is installed, and hold the grip wide open as you push the start button.
Record this reading and do each cylinder this same way for as many clys as there are.
Then do a wet comp test by adding 6 to 10 drops of what ever engine oil you use to each plug hole. Spin the engine over one time before you install the comp tester to distribute the oil you just added.
Repeat the same test procedure.
On paper you will then have Dry.... cly 1 cly 2 cly 3 cly 4, and that test reading..
Under that will be wet and cly 1 cly 2 and so on for as many clys as you have...
Then you have a know set of figures...
Next test each wire and plug for visual spark. A plug pliers is nice... You might not get zapped if you use them. In any case don't support your body with the bike.
With the key ON hold the plug tight against the engine and push the button and watch the plug spark... it should be bright fat and blue.
Set engine timing if it is possible... These days on many bikes this is not possible with out doing tricks. Older bikes can still be adjusted mechanicly...
If a plug fails test the plug wire first, as the ends tend to fail first. One way is to remove the wire when possible. Some bikes have built in sets with the coil these days..
With a ohm meter hooked to the ends of a wire wiggle it... A good wire will have a reading as book spec. A dead wire will not read.
Check the wires to the coils, and to the ecu (electronic controll unit)
Obviously if there is a compression problem the engine is sick and in need of repair.
If you get no spark or weak yellow spark there is a problem.
Weak spark can be a weak battery problem!!!
If you were able to crank the bike well 13 times as stated above probably the battery needs no testing. If the cranking became weak, and or you get yellow spark the battery needs a charge and some testing.
So in order comp , spark and finally fuel should be tested in ORDER.
Once Comp, and spark pass, then and then only can fuel be considered.
For fuel related problems please see vac leaks.... Mac
When all else fails read the instructions...