Mech

There should be a short brass tube on the bottom of the carb for a rubber hose I'd think. The leak.. There's a drain screw on the bottom of the carb I think, and that might be leaking. Other than that it shouldn't leak unless the fuel level inside the carb is too high. I think you can check the fuel level before removing the carb. To adjust the fuel level, or fix the leaking float level valve, you will be best to remove the carb and clean it and check the rubber parts aren't worn or perished. You might be able to remove the bottom of the carb in place but it's best to take the carb right off, strip it entirely, clean and inspect it all and then reassemble it and it should be right for years.

I'm not familiar enough with yamahas to be much help here, but I would definitely say repair the old wiring rather than trying to jury rig some other model wiring in there. To figure what the cut wires are for I'd look at what's near by on the frame or engine, and then go check a or several wiring diagrams looking for those coloured wires being shown connected to one of those things I'd identified near the wires. I'd also keep referring back to partzilla to see what other model wiring diagrams I should be looking at. When I looked a few parts up it seemed that your bike shares parts with wolverine, moto4, BB and kodiak, and over a range of years.. To identify exactly what components you have on your bike is going to take a lot of familiarising yourself with the bike and looking through partzilla, and even then It might be tricky to know the exact details about electronic parts. The shape, colour and pin locations of plugs, and wire colours, are clues when looking at wiring diagrams and identifying parts.

You mean the length seems wrong now ? Have you tried lifting or lowering the bike so the shock mounts line up ?

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'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.

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

#3 Yup well better check why oil is going straight through the oil pump... Unless.. new thought.. Someone has got the hose from the oil tank going straight to the carb or engine, so it['s just draining all the time. That would explain the high flow rate. A pump should take weeks or months of slow leakage to fill a sump. Check the plumbing !

Simple test is to look for a pulse of voltage coming out of the stator plug. Most of the wires will have a regular AC voltage and be insulated from the earth, and one wire or a pair of wires will have a pulse.

I'm pretty sure the oil pump will have a spring loaded valve(check valve) to prevent oil from the oil tank draining straight through the pump and into the engine. The weight of oil under the influence of gravity isn't enough to open the valve, but the vacuum/pressure applied to the oil by the pump does open the valve. To test that valve you might be able to disconnect the hose going from the pump to the carb or inlet and watching to see there is no slow leak of oil from it. I say might because I'm not sure that will have a oil pipe, some models might pump oil through a hole in the cases to the main bearings. If the oil isn't leaking out of the hose it may be leaking from the pump into the engine due to wear, but, even with wear it should only leak when it's not running, if the check valve I described isn't working. And.. All that said.. Are you sure it is oil overflowing out of the engine ? Those oil tanks don't hold much oil. Are you sure it's not fuel with a bit of oil in it ? Have you checked the fuel tap is operating properly ? And to answer your questions.. The insides of older two-strokes were lubricated by oil mixed into the fuel in the fuel tank. In those models they got too much oil at light duty, or too little oil under sever conditions, depending how much oil you pre-mixed into the fuel. In later models they used a small oil pump to inject oil into the carb or inlet. The pump is adjusted by a cable from the throttle so that the pump puts out more oil at larger throttle settings. That tends to ensure the engine gets the right amount of oil for the load it's under. That system though still didn't distribute the oil to the critical places as well as we might hope so in even later designs they started pumping the oil straight to the main bearings and it got mixed and distributed with the fuel to lubricate the rod and pistons in the crankcase. Some models they used oil straight to the bearings, and to the carb or inlet, at the same time, using hoses or drilled passages. .

It only takes a single flake of steel, bridging between the trigger coil's steel core and the flywheel, to short out the magnetic field between the flywheel and the trigger coil's pole, and the cdi won't fire. A build up of iron dust on the trigger pole can do the same thing. You need to get an analogue volt gauge and check there is a pulse of voltage getting to the cdi. A digital gauge won't always detect the brief pulse but the needle on the analogue gauge will flicker so you see it. Some kawasaki use a 12v system of ignition so if the trigger pulse is getting through and it still isn't sparking then we need to get a manual and check the resistances and output voltages of the stator. If there is no pulse from the trigger coil then you check there is continuity from the cdi unit to the trigger coil and if that's ok you need to take the side cover off and get every flake of steel off the flywheel and stator pole. Steel flakes or dust can also short out the charging cores of the stator. The best way I've found for getting dust or flakes off is to use a rag and grab it and wipe it off. It takes a while fighting the magnetism but eventually it's possible to get every little flake out and enough dust off to prevent it bridging the gap between pole and flywheel.

You should download the service manual, it tells you everything you need to know and has suggestions about the limitations and use of belt drive. There'll be a manual on this site I'd think.

Ouch ! How did that happen ? Yeah it looks like part #1 800398.

That does sound mighty like what it could be Gw.. Good call. I'd still clean and lube the moving parts of the sheaves though when changing a belt. It's important they are all moving nicely or the gear ratios and so load on the engine get out of whack, and that could cause the belt to slap more than it should.. But I'll bet Gw's right.. Even if the ratios are hanging a bit high, it can probably be overcome by either throttling off slightly, or changing gear.

Variations of zinc have been used as friction reducers for a long long time. That does work. Quad bikes have a lot of roller and ball bearings though, and those don't wear from friction, they just work and flex the surface until it starts lifting off. A friction reducer in the oil of a quad would help piston scuff and gear wear, and a few bronze bushes, but you wouldn't want to get it on a wet clutch.. It wouldn't be good if you had a catalytic converter on your bike either.. Or perhaps, an O2 sensor.. not sure about that though but they are generally pretty sensitive.

Does he bed the new belts in as they require ? Have the sheaves been dismantled and cleaned, lubed etc ?

Anti friction is good, but I'm dubious about their claims it repairs wear. I mean, if it builds up a hard layer on metal, how does it know the difference between crank shaft and bearing journal, and if it builds up the surface, by how much, and does it cater for the different clearances required between roller and shell bearings. If it only puts on a layer one nano-particals thck, then that's not going to effect several thou of wear, and if it keeps building up thicker and thicker, then how does it know to stop building up for the required clearances things need to allow for expansion and oil flow. Truth is it's probably no better than any of the other friction reducing compounds we use.. nano or not.

NGK plug.

Are you sure you are adjusting the chain the right way ? I think that bike has a pinch bolt and a rotatable axle housing. You undo the pinch bolt and then rotate the rear housing which is eccentric with the axle... I think. Unless the axle housing is worn out it shouldn't prevent chain adjustment.

I'd generally only change oil if it had got enough moisture or water in to cloud the oil, or(and this never seems to happen) the oil looked really thick and black. Mostly an oil seal goes before the oil looks bad and the oil gets changed then.

The code list I looked at said that code relates to a brake switch. It didn't stipulate which brake switch. Check the brake lights work. Check the handbrake light goes out if it has one. Check the brake fluid level.

Not idling ? Or dieing in use, or flooding the spark-plug ? The original post had a series of symptoms. If it's not idling I'd try adjusting the idle mixture as a first step. That may cure the problem and be all that's needed, or it may be that the idle adjustment is unresponsive or needs a lot of adjusting one direction to get it to idle, either of which would indicate problems in the carb. Depending how it adjusted and how much it needs we might get some idea where the problem is.

I think it's built into us to want to make something good.. It's what the religions are all about.. Explaining "creation", when we think of it as a verb. We're all the product/result of creation(v), and it's what keeps us alive and prosperous. It's an integral part of us this"creation" business.. Of course there's always someone (not you Gw) that takes things a bit too far and want's a bit too much, and then the trouble starts.. haha