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When I want a side cover off for a quick look I jack that side of the bike up. Yamaha cdi usually have some system to know when the electric start is being used. One way is to branch off a wire from between the start button and the start solenoid and send 12v into the cdi while the start button's being pressed. The other system takes the key switch's 12v right through the cdi and then to the start button, and then when the start button's pushed the voltage drops slightly and the cdi recognises that as a start signal. It's a good idea to be sure which system you have before trying to diagnose the starter not responding to the button. It's important if you want to fit some other cdi too. If you do take the side cover off you should take some photos of the stator.. there are several different versions.

Wiring mostly only breaks where the wire goes into the metal terminal on the end. It's pretty rare for a wire to break inside the loom. The exception is up around the steering hear where the wires flex, but that's not at all common these days. The other common fault looms get is they chafe through the insulation and short to the frame, but that is a simple visual check. You can probably tidy that wiring up and use it again..

Well Mch, in my experience it's fairly unlikely that any other model wiring loom is going to fit. All manufacturers change their components, and wiring, every year or two, and to make sure things won't be used on the wrong vehicle they change the plug shapes and colours and pin positions. Even if we swap plugs and reposition the pins, we don't know that the electronic part or stator is going to be compatable with the other parts. Yamaha use several different key switches, some have more wires and they have different internal contacts. They use at least three different types of stator, and each type comes with several different plugs. There are cdi with numerous differing numbers of pins, and pin positions. It's takes a lot of cross checking to make sure everything on a bike is all compatible. If you look a part up in partzilla and click on it as though you are going to buy it, it takes you to a new page with the part shown, and if you scroll down a bit it has a list of every other bike that part fits. If a bike isn't in that list, then it's part is not going to fit your bike. Here's what it says about your wiring loom... There are no other compatible yamaha wiring looms. https://www.partzilla.com/product/yamaha/2VA-82590-10-00?ref=58321c07f0aebcb46e55e4a5f60303e0d3f12fcd

I think that's probably a 1989. My data says so and Babbits agree.. Have a look here and see if it all looks like your bike.. https://www.babbittsonline.com/oemparts/l/yam/5003893df870021f60a0a008/1989-moto-4-yfm350erw-parts

This looks like a fair price.. https://www.heavy-equipmentmanual.com/products/1987-1990-yamaha-yfm350er-moto-4-atv-workshop-service-repair-manual

You may be right about the Moto 4 flaps being on the Big Bear, but what makes me think its a Moto 4 is the way the front fender wraps around the gas tank and the seat comes up and over that, the Big Bear didnt do that. Is it 2 wheel drive or 4 wheel Drive, all the Big Bears of that era were 4 wheel drive only.

It appears to be a Moto 4. I had the same trouble with their codes on my 400, YFM 400 can be Big Bear or Kodiak the letters after tells you more.