I had some intermittent sputtering and my local dealer said I had some corrosion on the rear spark plug wire. He said he cleaned it and afterward it ran great. The sputtering is back so I pulled the spark plug wire from the coil end and the connection looked weak. Soldered the connection and it ran better but seems to be an all or none kind of deal. Runs great for a sprint then falls into a kind of a limp mode. It's definitely temperature driven. Once it settles into the operating temp it won't run normally. Since its been cool outside it takes longer for the temp to be a factor. My plan is to replace the coil and rear spark plug wire with the hopes that it correct the problem. I looked on Alpha Sports but couldn't find the coil or SP wire. I look forward to your insight!

[2015 Z Force 800 53/Trail EPS]

There can be a number of things wrong like some bad connection between the coil and power source or any reason there is low power to the coil(s). The CPS also can be at fault as well as the ECM but..on any coil that has had a problem charging and discharging through the plug there is the distinct possibility of an internal fault which can be very temperature sensitive depending on where it is. I think I would start by testing the coil voltage while running on both. It should be the same as the battery but CFM's electrical components are so cheap, there usually is at least a volt drop between the source and loads. Still, should be above 13.5 volts. If below 12 and the battery is above 13.5, then there is an issue with supply somewhere. If all is low..there is something wrong with the battery or charging system. If all is OK, then I would swap coils and see if the problem now moves to the other cylinder. If so, I would consider replacing that bad coil. I would think the plug lead would come with it but who knows with these guys. 

My plan is to replace the coil and rear spark plug wire with the hopes that it correct the problem.

Diagnosis is always key before spending any money.

My first thought was that you are taking the mechanic's observation of corrosion as an indication that the problem is with those components. I would not do that.

Clark gave good advice to check all voltages first. Then check the resistance of both coils when hot and cold (compare). Check the condition of the plugs (bad electrode, cracked ceramics) and ohm check the plug leads (wiggle them around when doing this). A little dielectric grease on the lead boots is a good idea as well.

If the sputtering is consistent enough (running on one cylinder), you can try pulling the lead off of each plug while running to see if that makes it worse.  If it stalls, then you've eliminated that cylinder. If little or no change, you've identified the failing cylinder.

You might run the engine in the dark and look for any arching (a spray bottle of water can help in this regard).

If all that checks out, then you need to start looking elsewhere.

I assume there are no codes thrown by the ECU.

**Update**

I replaced the spark plug wire and coil. Seems to be running great now. The only way to truly tell is to haul it three hours away and unload it for a weekend ride. That's what normally causes a malfunction of some type.

[2015 Z Force 800 53/Trail EPS]

**Update**

I replaced the spark plug wire and coil. Seems to be running great now. The only way to truly tell is to haul it three hours away and unload it for a weekend ride. That's what normally causes a malfunction of some type.

Hope it takes care of it. Think I'll fire mine up today..been over a month sitting in the shop.