Help, I'm going thru plugs every couple hours

[Baja 252]

Typical SJ, 701 with some porting, a B pipe, ADA girdled head, 180psi and stock 38's. Runs great, plugs look spot on, it starts instantly and idles great. But, put a couple hours on the plugs and it looses power. At first is like you have 90%, then 80%, and finally down to about 70%. It still will idle fine, just starts running bad across the whole powerband. Let the ski sit overnight and it's still down on power. When you crank it over to check the spark, it will jump a 1/4" gap easy. Fuel is 91 octane with 40:1 Klotz Ski Craft oil. It's fresh and runs in other skis with no issues. The plugs look good, piston wash is good, so if it's not fouling them or excessive oil or anything like that what's happening to the plugs. I've tried both 8's and 9's and it does the exact same thing.
With no cool down, if I swap the plugs out with new ones it instantly is back to 100% power for a couple more hours.

In another thread someone said it could be the CDI going out (I have the MSD one), but I hate to buy a new one if that's not it. (I don't have the stock one to try it.)
Can a bad CDI cause a plug to breakdown or damage the plugs so they stop firing right? Seems strange to me.

Any ideas of what's wrong or how to know if it's the CDI for sure?

 

[OCD Solutions]

Sounds like a weak ignition system that is only outputting enough spark to jump a clean system. The MSD makes more spark by getting additional power from the battery so if there's anything wrong with your battery, wiring or charging circuit, you would see a loss in spark energy.

What are you gapping the plugs to? I would try 0.024" and see if that improves anything.

Top suspects would be weakening charge coil on the stator or possibly either a bad/loose connection or water/corrosion in the ebox.

I'd pop the ebox off and open it up before I bought any parts.

 

[Baja 252]

Inside ebox and the stator look like new, no corrosion or water. But I know still could be the issue even though. They look great.
I’ll try the 24 gap, I run 30, could that be the issue?

 

[OCD Solutions]

.030” wouldn’t be an issue if all your parts were working correctly.

Gapping down to .024” isn’t a fix, it’s just a troubleshooting trick to feel out the situation.

I don’t have my test bench setup in the new location yet to run scenarios. I know the MSD will run dodgey with low voltage but if you have enough to crank the ski, it should run just fine.

If you are short of spare parts, I can put together a “troubleshooting” package with a coil, CDI and possibly even a stator. Swap what you need to get running and then just send back what you didn’t need.

 

[OCD Solutions]

How much compression are you running?

 

[Baja 252]

180 psi