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Well it appears you have been busy. You definately have a project, thats a good thing if you like working on them. As far as the wiring harness goes yours looks fairly descent, you can professionally repair your existing harness easier than replacing it. What you have to do is study the wiring diagrams, very carefully to determine where the butchered wires go and what it connects to. The dangling down cable you were referring to goes into the carb, that is your choke cable. You may have somethings missing like the starter cutout relay i didnt see that which might have been cutout and wired together. You should have a plug next to the soloenoid that controls the power going to the starter, maybe. It looks like your air box is missing and the hoses that connect it to the carb. You can see diagrams of what all is missing by looking up your model on Babbits, or Partzilla. The white with red and white with green may go to your pickup coil im fairly familiar with Yamaha wiring, but havent worked on one that old in a while. The only problems you may encounter with your harness if you want to put it back to original is if plugs have been cut out or missing. Your in a good place a lot of us know these older bikes, look forward to helping you piece it back together. Where would you like to start. My advise would be , do not get overwhelmed, take it one piece at a time, one day at a time. It will eventually come together. I know iv been right where you are many times, a great learning expierience.

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.

I found a standard $10 starter solenoid. With the connector meant for the YFM350 (amazon). I looked around for an exhaust and the best i can seem to do is $160. Since it seems to have a standard sized pipe past the heat-shield, is there another more generic exhaust for a 350cc engine? Carbs... carbs all over for $40 new. Any suggestions? Apparently, Walmart sells the Valvoline ATV motor oil for wet clutches. Or Rotella T 15-40w is supposed to work. Suggestions? Any opinions on those NOCO batteries? The black lithiums. Or what do you suggest? I can stick a small solar panel on the back, with a built-in regulator, to keep a lead-acid charged. This is going to be really loud with that rust hole jn the exhaust.. can't wait.

@MechThank you. It's 'ranch' like the dressing, my bad. I asked admin to change it and add the 'A' so it's easier to read. Of the two mystery wire issues, one in the front under the tank and one in the rear under the seat, the rear has a black & blue w/white stripe wire coming from the loom underneath the seat near the battery and near where the starting solenoid should be, and there's a connector with a red w/white & blue w/white wire connected to it, in the video. The wire then just terminates in stripped wire, like the connector was cut-off something (original solenoid). Then, the solenoid that is there, has got what looks like a white w/green and a white w/red wire, coming out as control wires (to fire the solenoid), but not connected to anything at all, again just dangling in air. So here's what I propose as a theory: the starter solenoid failed on the previous owner, then a very bad attempt was made at rewiring it. Looking at the 1990 - and 1987; there is no '88 or '89 - wiring diagram from the above PDF, the control wires for the solenoid would be from the harness, black & blue w/white, going into a connector with red w/white & blue w/white wires. So some other year/make/model of bike/ATV had a solenoid that had a white w/green stripe & white w/red stripe control wire, and they swapped the other solenoid in as a replacement. Feel free to post a link to a suggested replacement solenoid. That one on it now, might work, but it looks sketch, and I'd prefer to start over fresh with whatever is the best, without going overboard. Then I'll strip out their weird wiring repair stuff and try to figure out what those connectors are upfront in the video that seem to be wire-nutted into that romex, where those two connectors aren't connected to anything. Accuse me of being lazy, but to pull off that stator cover and try to fix-up those wires that go into the stator/generator, where the outer jacket is missing, to protect the individual conductors, do I need to drain the oil? I'm going to do that anyway, drain the oil and check some other things before trying to fire it up. I assume that cover is a dry cover... It's been ages since I worked on motorbikes. Oil brand suggestions etc would be welcome. I normally use Mobile 1 0-40 syn on everything, but I understand with the integrated clutch that motorcycle engines are different. I don't remember all the details.

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'd misunderstood and thought it kept filling the crankcase repeatedly. If it's taken a couple of years to drain the tank then I think I'd just invert the bike and let the oil drain, then get it going.. It's likely be fine.

@Gwbarm2 wheel drive. Fine by me, less to fail/fix. Further inspection of electrical: It seems the harness is in decent shape, with the exception of whatever happened with the solenoid. So I can keep it, but there are some parts that need to be sorted-out. If either of you have a similar model, I would like to see what your layout looks like in a video. Just shot this with the Telegram app, saved to gallery, and uploaded to youtube as an unlisted video.

Here are some available wiring harnesses on ebay. They want a lot of money for them. Here is pages 348-350 of the 1987-1997-yamaha-big-bear-350-service-manual.pdf, both as a PDF and PNG image files. Here is an Amazon offer of a wiring harness from the same year of a YFM350X Warrior https://www.amazon.com/Caltric-compatible-Complete-Harness-1992-1995/dp/B09JC8YZ5J/ Despite the link saying 1992-1995, the text says "Caltric Complete Wire Harness Compatible with Yamaha Warrior 350 YFM350X 1990 1991 1992-1995 Wiring Harness" @Mech Whether it's a 1989 or 90, that harness should work, no? I'm thinking you and several other people like @Gwbarm can have an eyeball at these, and figure out if that Warrior harness at ~$35 would work sufficiently. I included the ebay images for completeness; and you know, someone else may need this post in the future. Not because I can afford to buy them (I can't). There are several other Amazon offers for wiring harnesses https://www.amazon.com/dp/B0BVVY5W4S and I'm wondering if they are all that different, or can be modified to work. Part number from that babbit website: 2VA-82590-10-00 Video of the electrical system: Pages 348-350 from 1987-1997-yamaha-big-bear-350-service-manual.pdf

I think that would be the best solution. Good luck!

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.

Good thoughts. I just picked the quad up and drained crankcase. I'll replace oil pump and try again. Thanks for everyone's help!

My thought was it's so full, it's sucking it back up in the cylinder. I don't have fuel or oil line connected, yet oil is still filling the cylinder to the point it won't turn over because of high compression. Oil also continues to leak out of exhaust port. After sitting a couple years, all the 2 cycle oil was gone from tank. It filled the entire carburator including bowl. I'm assuming the rest drained into crankcase. I just don't see any fill, drain or level ports to confirm.

thanks, im hoping that it will last me a while even though it was only 500$

Nice little rides, i think i like the Polaris the best.

The flaps all say MOTO 4 embossed. Maybe hard to see in the photos. I am/was not sure if that was separate from a Big Bear, etc, or in addition to the model #. Has someone done a document explaining the differences? E.g. will a wiring harness for any 1990 YFM350 work on a MOTO 4? I'll ring a stealership next and try to get the harness part # out of the guy.

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.

I havent tried premium instead of Non Ethynol maybe it s better, just as cheap, the non ethynol here only comes in one grade i think its 89.

Those are great machines good luck good luck with it.

I have had this happen before on a 2 stroke scooter, it had been sitting for 10 plus years, it did the same as you describe lock up engine, took me forever to get all that 2 stroke oil out of the crankcase, and it still fowled 2 or 3 plugs before i got it right. I took the hoses all off and drained the oil tank, ran it on premix. Couldnt really disable the oil pump without tearing the engine down it ran off the crankshaft, and was not really on my high priority list, After deleting the oil supply i realized that this pump wasnt going to pump very long without oil and it was always turning when ever the engine was running. So hooked the oil back up to the pump, but instead of rounting into the carb i routed it back into the oil tank. Didnt work well because oil was not getting into the crankcase VIA the carb it was from a bad seal at the oil pump. So my recommendation after all this howee is to replace the oil pump seal or pump itself, or dont store it with a full tank of oil.

VinDecoderz says it's a YFM350 (Moto4 350) trim YFM350ER Is that a Big Bear? Or a Moto 4? Or are they the same thing? I've google'd around for information, and was able to find a (czech board in english) that had a Yamaha service manual for the YFM350X series, LIT-11616-YM-37. The 'Warrior' type. I'm trying to get something more accurate. I'm not sure which manual I need. Pictures included in this post. I'm also looking to get a wiring harness for it.

Thanks for the tip