The firing order on your bike is 1,3,4,2. These bikes use what is called a wasted spark system. They fire whenever the piston reaches top dead centre.
That is to say they fire on top dead centre compression as well as top dead centre rock-over( exhaust/inlet ). Each coil has two leads on them.
The left coil goes to number 1 & 4 cylinders.
The right coil goes to number 2 & 3 cylinders.
The GPX 750(like most road bikes) have a resistor type spark plug cap on them that was prone to cause problems.
To test the coils/caps, use a multi-meter to test their secondary resistance.
To do this set the meter to kilo-ohms(1000 ohms), place one meter probe in one plug cap & the other probe in the other plug cap( i.e. 1&4, 2&3 )
The meter should read 10kilo-ohms to 15 kilo-ohms.
If it reads higher than that try un-screwing each cap & test the coils with the caps removed by probing the leads. If the coils(without caps)read about 5 to
10 kilo-ohms, check the caps.
The caps should read 5 kilo-ohms each.
It is very common to find these open-circuited.
Replace any open circuit caps.
I hope this has been of some help.
Otherwise if you can be a little more spacific with your problem I will try to help further.
Regards Andrew Porrelli
Testimonial: "Thanking you in advance will try this tonight and let you know how i get on. Regards Paul"
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