ATV Help & Brand Specific Topics

Will try and confirm the VIN on the frame but the title says JY43HPW05KC000565. The wire colors on the ATV side of the CDI match the 1990. The wire colors on the stator side of the CDI match the 1988 except that the 4 pin connector is missing the grey wire.

Frame JY43HPW0*KC000101 Engine 3HP-0000101 Model 1989 YFM350ER W Moto-4 JY43HPW0*LC024101 3HP-0024101 1990 YFM350ER A Moto-4 JY43HPW0*NA049101 3HP-0049101 1992 YFM350ER D Moto-4 JY43HPW0*PA059101 3HP-0059101 1993 YFM350ER E Moto-4 JY43HPW0*RA070101 3HP-0070101 1994 YFM350ER F Moto-4 JY43HPA0*SA080101 3HP-0080101 1995 YFM350ER G Moto-4

Yeah the switch is like the 90 model. So the atv's plug shape and colour should match the stator's, and they should match the wiring diagram in that pdf "output", where the 90 is the ERA. The wire colours should probably match too, but, I have followed along in here when people have used parts with the right plugs but a wire or two different coloured.

When I check my main switch in the off position the ground pair is shorted together and the power pair is open. When in the on position the ground pair is open and the power pair is shorted. Not like in the schematic for the 88 but like the one for the 90. The main switch is original. In fact the only thing that I have changed out is the coil and that is because the secondary was open on the original. This Quad has been in the family since the late 90's and had very little use when purchased. My father used it to get around our property and plow some snow in the winter so has not had rough use and has need very little other than routine maintenance sinch we have had it. Almost done with the carburetor just waiting on Amazon and then will try to get back to the electrical. We will be traveling in a couple of days so it might have to wait until I get back.

So only the last supplement in the manual has switches as you describe, shorting to earth to kill. The earlier models had the main switch killing for run and the kill switch operating earth to kill.. I also noticed that the two relays are different.. one NC and the other NO.. If the main switch wasn't original it would cause problems..

The 89-90 model that doesn't have a wiring diagram.. that usually means use the first model in the book, sometimes though it says whether to use the first model the manual is based on, or to use the model supplement before the missing wiring diagram. I was just looking in the main model where all the detailed instructions are for diagnosing the ignition, and it had this diagram.. but look at the switches.. Might be a misprint.. output2.pdf

That cdi unit then has a integrated circuit that takes care of the spark and timing, and the IC also controls the start isolate relay. It monitors the brake lever and the neutral and doesn't let the relay work if it's not satisfied. I'd suspect that one of those two earth wires might be to handle the power for the relay.. Just something they would do on cars;. These yamahas are absolute mongols for changing a lot and in many different ways. The start isolation can work in two different ways in yamaha cdi. In some the voltage from the start button being pushed gets fed into the cdi, and in others the power goes through the cdi and then to the start button and they detect the voltage drop. The reason they want to know when the starter's being used is probably so it can retard the timing for an easier start. The way they detect start in them puts them into two wide categories where there are several options.. It5 always pays to check which way they detect the start signal. Also, the colours of the wires, and the colours and shapes of the plugs have to be completely right before you can be sure the match is correct.. That applies to the wiring diagrams and original parts.. You really need the good manual. In manuals they describe some of those stator cdi charge windings as anti-kickback or some such, and in some stators all the cdi charge and battery charge windings look identical, some have a slight difference in windings and some have one huge winding and the rest small.. Keep posting till you can get the manual In the pdf manual index they say they have a model 87-90 YFM350ER, and it has a wiring diagram,the next model covered is 88-90 and it has a wiring diagram, the next model is the 89-90 model and it doesn't have a wiring diagram, then there's the 90 model and it does have a wiring diagram. They have slight variations in bikes in different markets, and they release/use different spec bikes at different times too.. If you find a service manual that seems perfect in some regards, it's often wrong in some other matter. All the makes are like it, but yamaha ignition systems seem/are particularly prone to differences.

Interesting. I have the original CDI unit along with the original stator. This is something that I will keep in mind if I have to start swapping in parts. I did buy a CDI from amazon for the 87-88 and that did not work and if I put that back in will try swapping wires around. Also, there are 2 different pickup coils on it although they have changed the wiring on the stator so that the second one is not hooked up. On the 87-88 schematics there are 4 wires going to the stator connector and on the 89 there is only 3. On the 90 stator they deleted the second pickup coil and placed the source wiring in the 4 pin connector instead of on bullet connectors. OK I am beginning to understand all the imputs and outputs of the CDI on my ATV. On the ATV side of the ATV you have 2 3 pin connectors and one bullet connector. On my 1989 ATV and on the schematic for 1990 and later ones Bullet connector is the input to the coil. 5 This is ground 6 Kill switch. This is ground provide by either the "main switch in off postion" or the "handle bar rear brake switch in the on position". 7 No wire on the 1989 and later ones. 8 This is a output to provide a ground to the Starting circuit cut-off relay. Not sure of its function but assume that when the ATV is running that it turns off the relay disabling the starter. 9 Front stop switch for the rear brakes. 10 Neutral switch. Same lead that powers the neutral light. On the Stator side of the CDI. On my 1989 2 bullet connectors which are the source coil. 1 Pickup coil #1 2 Pickup coil #2 ? 3 Pickup coil #1 4 No wire On the schematic for the 1987 and 1988 there are 2 pairs of contacts. One pair going to ground and the other going to power. It shows both being enabled in the on position. On the schematic for the 1990 and later same 2 pairs of contacts. One pair going to ground and the other going to power. It shows the ground pair being enabled in the off position and the power being enabled in the on position. On my 1989 it works the same as the 1990 ones. In the online parts places and on Amazon it shows that there is only one part # for all the years so I am assuming that the 1988 and older schematics are wrong.

Thanks for the schematics. They are the same as the ones in the manual that I have. It is weird that my 1989 more closely relates to the 1990 model. They do not have upgraded schematic in the supplement that I have for the W or 89 model and as you mentioned I expected it would be represented in the prior year instead of the later year. I think that the next step for me is to open the stator housing and look in there. I had thought about some rust as you mentioned but as it was in oil I was kind of ruling that out. I was getting ready to clean the carb so will finish that before going further.

You could try swapping the trigger wires about. Some cdi fire at a certain rising voltage of the trigger's output, and later models fire as the trigger winding's voltage peaks.. at the top of it's voltage wave. Those later ones need to be the right way about too. If that doesn't work you could try swapping the capacitor charging wires about too. Some cdi seem to need a certain number of AC pulses before they will start, or it might be they need to finish charging on a positive wave, I'm not sure why, but it's so. And, you need to try all four possible combinations to be sure you have both windings right for that cdi unit.. And.. to make it more interesting for you, you have extra wires to try I suspect.. Also.. not sure if it applies here but my sons used to be forever swapping cdi and stators etc trying to keep their fleet of two wheelers going, and they found that the manufacturers swapped the position of the keyway in the flywheel sometimes, and, even if the key was right, they sometimes swap the magnetic polarity of the magnets. All that aside, they did mostly get a combination that would work eventually.

Better still.. output.pdf

Try these... output.pdf

Ok. It sounds like you know your way around electricals.. The manual does 87-88, 89-90. It has the diagrams. If it's not in the supplement for your year, then the details/specs/diagram for your model/year are the same as the first model covered.

The bike has been in a garage for the last 7 years or so and for most of its life was stored inside. This bike was my fathers until he passed several years ago and he used it to get around the property as well as plowing snow in the winter. I did check the outputs from the stator and had 92VAC on the source coil. The trigger coil had just mV and I was using a Fluke digital meter. It has a bar graph on the bottom of the display but I will have to remember where I put my analog meter but haven't used it for awhile.

On my unit as well as the schematics for both the 1988 and 1990 the brake switch input just goes to the CDI and not the brake light. I wish that I had the schematics for the 1989 but have been unable to find them. I do not have access to the downloads yet so am unable to see if what you uploaded is for a 1989. I assumed that it was a interlock to prevent it from starting without the brake on but a rev limit also makes sense.

OK I made some progress. I purchased a pit bike CDI and put it in the circuit. This is something that I would not want to run with but for the price it was OK for checking some things. When I put that in I now have spark and it will attempt to start. I do know that I need to go through the carburetor still but this is a start. This is what I know now. With this CDI I am getting spark and it is attempting to fire. That tells me that the stator inputs are good. So this brings me back to either bad input signals to the CDI or a bad CDI. Unfortunately, the CDI for this unit is not available.

Also.. I thought that connecting the rear brake lights made the light come on. It also doesn't make sense that connecting the wires would effect the spark, not if it is the brake light. Some models though do have a feature to stop you trying to drive with the handbrake on, and the left handlebar brake lever switch if it's playing up(or if you have the handbrake on), will rev limit the bike at barely above clutch lockup speed. I donated that manual in downloads but I've never read it. haha.. I better go read it..

You should check the resistance value of the stator windings and the trigger/pulse windings; the windings may be ok. A flake of metal, or a finger of rust powder, that bridges the air gap between the flywheel magnets and the winding core, can stop them working. You should check the kill switch too for dirty contacts or rusted spring, and the main switch if it sits out-side getting wet can likely get water into it causing the same problems. The handlebar switches though on most bikes are fairly prone to dirt and water. There's a service manual in here in the manuals section. That will have the4 diagnosis process and all the readings for checking the cdi. They will tell you to check the resistance readings, but they probably wont tell you to check there is actually power coming out of the windings. There are several things that can prevent the windings working properly even though they have continuity and the right resistance. The wires to the cdi can have bad connections too so I'd suggest you check the windings resistance and output at the cdi plug, or, at the plug and down at the engine plug so you can compare the two readings. To check the main charge and cdi charge windings you can use a digital meter but to check for output from the trigger/pulse winding you should buy an old fashioned analog/needle gauge. The needle on the analog gauge will flicker and you will see it has some output and know the flywheel is turning, the winding is bolted on in the right place, there is no build up of metal dust shorting the magnetic field etc.. Most digital gauges don't detect the brief single pulse on the volt range. Doh.. Just reread and noticed you do have the manual and have done the process.. still check for out put though, and do the tests up at the cdi plug.. Wires get dirty connections in plugs or where the terminals crimp onto the wire.

1989 Moto 4 YFM350ERW intermittent spark. Quad has set for about 7 years and was running when parked. When I replaced the battery and attempted to start it had no spark. What I have done. Followed troubleshooting in the manual. 1. Coil failed the resistance check so I replaced it. Still no spark. 2. I performed resistance checks on the stator and they all pass. 3. Found a bad rear brake stop switch and unplugged it and connected the wires in order to disable. Now I have intermittent spark. I believe that the issue is with either the stator or CDI and not sure which. 1989 seems to be a transition year for electrical. I can get new aftermarket CDI units for 87-88 and 90-94. I cannot get ones for a 89. I can get new stators for 87-89 and 90-95. Looking at the schematics the wiring on my moto is closer to the 90 ones on the ATV side of the CDI and closer to the 87-88 on the stator side of the CDI. Looking at part supply sources the stator housing is the same part # for all the years and looking at some of the stators on Amazon that have the dimensions on them both of the stators are the same size. What I am thinking of doing is to replace the stator and CDI with a 90-95 one as these parts are all readily available. Does anyone know if this has been tried before and if there are any issues with doing this. As a side note I also have a 1993 Moto 4 YFM350ER that has been sitting longer but it is located about 400 miles from me at this time. By doing this change in addition to being able to get parts I will also have 2 ATV’s that are the same electrically.

All excellent advice Magnolia..

if you have room put a bigger battery in it. never run your winch for more than 15-20 seconds at a time under heavy load, look up duty cycle. run it out and back in once a month or so. it's better electric motors to run than to sit unused.

It sounds like the drive (primary) clutch is getting hung up somehow and can't move properly. I've seen bits from a broken belt get into the sliding sheave bushing making this happen. You'd likely need the proper clutch puller to get it off to clean & inspect.

As long as you leave the engine running and stop winching if the winch starts to get slow it should work, but if you do it often, or let the winch struggle going slow, you may overwork the charging windings and make them too hot so the varnish melts and they burn out. Drawing a lot of power out of the charging windings, for prolong periods of time, isn't good for them. Short winches and keeping the battery well charged should be ok though.

The genuine carbs are generally better tuned. If we have to use a aftermarket they can be tuned to a degree, but if we need to change jets then it gets tricky because we have to make changes in steps and sometimes swap two components at the same time etc, and sometimes the threads on the jets are not the same threads as the original carb used. You could try moving the slide needle in it's clip. They are generally easy to get at without removing the carb. Move the clip one notch and if it makes it better, move it another in the same direction, keep going if it has more grooves till it's been moved too far, then go back one groove. If the first step makes it run worse, then you move the clip two grooves in the other direction, and then keep trying one more step till it's gone too far, then back one step. If you compere the slide needles(original and replacement) you may find they are a lot different. Sometimes, if the two discharge/emulsifier tubes are both the same, we can change the needles, then adjust them, and cure the problem.

I had a quick look at some parts diagrams and it doesn't appear to have a clutch. The three models I looked at were all belt drive. I also have the 2008 750 manual so looked in there and it looked like the same engine/trans setup, and it has no clutch. It seems the belt and pulleys are the only "clutch".. I would suspect that the variable ratio system of the belt drive is playing up. That's the variable width belt pulleys I'm talking about. One of them is possibly moving apart at too lower revs, or one of them isn't moving apart when it should. He should get a manual. They can be downloaded for free, from right here in quadcrazy quite likely..