Spark Plug Wire Problem

Y700FZX · Mar 20, 2021

I have a spark plug firing problem with my stock 1997 VMAX.
Left rear cylinder is not firing regularly. (I can tell it isn't firing because it isn't getting warm like the other cylinders). I thought it might be the coil so I pulled the plugs and swapped the wires and the plugs fired.
I narrowed it down to the plug connection to the coil (right by the battery).
Now, I want to replace all the wires (because the bike is 24 years old) and when I try to order them, it asks if they are 7MM or 8MM. I can't tell which, the wires aren't marked.
Should I go with stock wires or is there a brand I should get (or stay away from)?
Should I go all out and replace the coils also?
Am I missing anything (like needing to order a connector or bracket)?
Thanks in advance!

gentsvmax · Mar 20, 2021

Y700FZX said:
I have a spark plug firing problem with my stock 1997 VMAX.
Left rear cylinder is not firing regularly. (I can tell it isn't firing because it isn't getting warm like the other cylinders). I thought it might be the coil so I pulled the plugs and swapped the wires and the plugs fired.
I narrowed it down to the plug connection to the coil (right by the battery).
Now, I want to replace all the wires (because the bike is 24 years old) and when I try to order them, it asks if they are 7MM or 8MM. I can't tell which, the wires aren't marked.
Should I go with stock wires or is there a brand I should get (or stay away from)?
Should I go all out and replace the coils also?
Am I missing anything (like needing to order a connector or bracket)?
Thanks in advance!

I've had the same ignition problem you describe. Turned out to be the coil connectors, each one, they were connected but just barely, some hanging on by just a strand or three. They all four have the red/white wire in common.

C.O.P.'s will be suggested for your stock coil replacements which is what I was installing when I discovered the bad connection's.

The discovery and repair of the bad connector's probably did the trick but the addition of the C.O.P.'s sure didn't hurt.
I now have a nice hot lightning colored spark in all 4 cylinders.

desert_max · Mar 21, 2021

The factory caps and coil towers are designed to accept 7 mm wire. You might be able to trim 8 mm down, but it won't make that much difference. If you don't plan on doing a COP conversion, make your life easier and source 7 mm wire for the job.

Speaking of COPs ignition, it is not a performance upgrade. It might seem that way, but only because you're probably replacing bad existing components. COPs coils typically generate less voltage than the factory coi!s.

MaxMidnight · Mar 21, 2021

All you need is basic copper core leads which you can normally buy by the length at your local motor store.
Before re-assembling check inside the coil tower that the spike that goes into the wire is still there and clean.
Also make sure that the rubber olive is in place as it is this which keeps the wire in the coil.
I also smear a little silicon grease on it so that it can be properly tightened.

cdgawatersports · Mar 21, 2021

NGK makes good wires and you just have to cut to length, silicone caps and wire coating lasts forever .
I haven't had bad coils ,but i guess if i did i'd go with the COPs eliminating problems down the road.