1999 Yamaha Big Bear 350 4x4 no spark

[Kaz]

Troubleshooting a no spark issue, was running OK, maybe a little rich, turned it off, now no spark. I've checked/ohmed out the main key switch, the start/stop switch, neutral switch, brake switch - all good. It will crank the starter, but no spark with the starter or when I try the pull start. I've checked all fuses and diodes. Swapped battery. New plug. New coil. Swapped in a used CDI - no help. Traced, removed, cleaned, reattached all grounds. Removed things like my winch from the circuits to be sure a bad relay or something was dragging it down. When testing voltages, the orange wire going from the CDI to the ignition coil shows no/very low voltage-shouldn't it have 12V on it? Sometimes I get a very weak, intermittent glow on my spark tester, but not enough to fire the plug. I've checked continuity on just about all wires in the harness. Checked/cleaned/lubed w dielectric grease- all connections, redid a few that looked old/dirty. I've checked the stator resistances, all good, but have a stator and rectifier ordered anyway, will arrive Sunday. I verified that the rectifier has a voltage output back to charge the battery while cranking - 10.5-11V, low, but expected while starter is engaged. What else can I check as part of troubleshooting? I have a Haines service manual, but the 1999 350 4x4 seems to be an odd model, there isn't an exact electrical diagram for it, but found one for another year that has all the same number of wires and same color wires, so I've referenced that. Any hints, tips or advice would be appreciated! Thanks!

[Mech]

Check the resistance of the two ignition windings in the stator that are to charge and trigger the cdi. If the resistances are ok then replug that connection and go to the cdi and check the resistances of the two same windings and wires on the pins in the plug there, that confirms the wires are ok. The resistance readings should be very close to the readings down at the engine/stator. Then you should check that the windings are putting out some power, because sometimes the magnets drop off or get shorted by metal dust and even though the resistances are ok, they don't put out power. The winding that's to charge the cdi will put out an AC current, and the trigger coil will put out one pulse/wave of current per revolution. To detect the trigger it's best to use an analogue gauge because you'll see the needle flicker but digital gauges miss a short pulse often.

The orange wire from the cdi doesn't have power in it till the cdi fires, then it has hundreds of volts and huge current, so you shouldn't put your gauge on it.

[Gwbarm]

It sounds like you have replaced everything ignition related, maybe check connectors and wires to make sure they are not corroded and have continuity.

[Mech]

We don't know that the second hand cdi is "a known good unit", to use the manual's phrase.

[Kaz]

Thanks for the tips-I went the ‘budget route’ for the cdi, for now. $60 vs close to $500. I have a couple pretty high end Fluke meters-I do see some voltage on the orange wire while using min/max mode, but not a lot. I’ll recheck all wires n connections tomorrow-I have a new stator n voltage rectifier being delivered that I’ll install. If I still have no spark, and everything checks out, I guess I’ll either buy a new cdi or rig up a cheap generic one for testing. I just have a feeling that when I do find the issue, it’ll turn out to be something I should’ve noticed already. I think I know the answer, but would the type of engine oil have anything at all to do w the stator n coils? I recently put STP 10W-30 high mileage oil in it, but if understand how the stator system is set up, I dont think it should matter. I’ll post again after I finish the stator install. Thanks again!

[Mech]

#2

"Then you should check that the windings are putting out some power, because sometimes the magnets drop off or get shorted by metal dust and even though the resistances are ok, they don't put out power."...

[Mech]

And non genuine cdi are a bit of a gamble about it being the right one for the bike.. They make a lot of models of cdi to match a lot of model bikes, and they rewire the cdi charge, and trigger windings, so they don't always work with a different version with same numbers of wires, or plugs, or colours of plugs.

Sometimes swapping the two charge wires about, and/or the two trigger wires about, which requires a total of four different ways of connecting those two sets of wires to have tried all options, sometimes that gets a wrong model cdi going. Sometimes though the resistance readings of the stator and trigger are different and put out more or less power and sometimes it doesn't work, or perhaps works briefly before something fries..  haha.

[Mech]

The readings and behaviour you are getting from the orange wire to the coil, that would be consistent with a trigger coil letting the cdi discharge all the time, so the capacitor never built up to a high voltage. That could be caused by a backwards(for the cdi) trigger winding. The other thing you get is that the cdi expects to get a certain number of AC waves, both/either to build up a high enough voltage or as part of the timing, and/or if the windings start on a positive wave after a trigger and discharge, when they should be starting out with a negative wave, then they miss some waves getting rectified into the capacitor and it gives a weak discharge on the orange wire.

There are several problems if we put the wrong cdi onto a stator not designed for it, or a bike with the wrong stator for the wiring and cdi, but some of them we can fix by experimenting swapping the two cdi charge and the two cdi trigger wires. Oh, and they send a start signal to the cdi, and some models send a voltage into the cdi when the start button's pressed, and other models run power through the cdi to the start button and then detect the voltage drop when the buttons pressed..  You really need the right wiring diagram and resistance figures.

I'd try that before fitting a new stator, which might not suit the bike or the cdi and so complicate things even more.

If you give us all the details you can about the bike, including the numbers of course, and tell us what coloured wires are going into what shaped and coloured plugs at both the cdi and the stator, I or someone might be able to find you the wiring diagram.

[Kaz]

Thanks for the comments, tips. Didn’t have a chance to work on it today, but will soon. Attached is the electrical schematic I have for it, pick up and source coil resistances in upper right. I’ve checked the brake switch, the gear position switch, the start/stop switch. They all check out. By the way-if one of them isn’t right, the starter won’t have power when I press the start button, so I’m pretty sure they’re all ok. I’ve tried 2 ignition coils, have another but hesitant to install it. I’ll ohm it out n post results when I can. Thanks again!

 

Edited November 10, 2024 by Kaz

[Mech]

You've already checked the stator's cdi windings resistance.. what you need to do now is check they are putting out some power..

Edited November 10, 2024 by Mech

[Mech]

Does your cdi have three pigtails with round plugs, or two rectangular plugs right on the cdi body ?

[Kaz]

2 rectangular. An 8 pin w 7 used and a 4 pin w 3 used. 

[Mech]

ok. Then I think this will be the electrical section for your bike, from the yamaha manual.. Doesn't look to be much different, but.. 

I still think you should check there is  power coming out of the stator's cdi windings, and that it's getting to the cdi.

If there is power from the stator to the cdi, then I'd disconnect the kill wire at the cdi and try it.

 

output.pdf

[Kaz]

I finally had some time to tear this thing apart. This is what I found. I’d say the magneto is trashed. But what about the rotor? Can I just de-burr it the best I can and go w it? I do not have a puller to fit it unless I break out a big as* slide hammer.  I realize I might destroy it w that but if I have to replace it so what?  Thanks in advance for any advice!

[Mech]

Did you find what got between the flywheel and stator to cause that damage ?

That's a magnet we are looking at right ? I think I'd use an engineers scraper and clean that up if I could. It might be too hard to scrape though. The important thing about those magnets is that there is/has to be an air gap between each magnet and the next, so no ferrous metal chips or dust, and the same between the magnets and windings.

Since the resistance readings were right, I'm assuming that you found there was no output from the stator on one or more circuits ? Well if the resistance readings are right it's normally either a magnet or trigger tag dropped off or the magnetic field is being shorted out by ferrous metal dust or chips. That being the case I'd suspect that in this case it's likely that if you can clean everything up good, removing any metal that could short the magnetic field by bridging the air gap, then it might come right. I'd want to know what got in between the pole and the magnet though, and remove it. It must have been something quite big I think, and quite hard to munt the magnet. When you are cleaning the metal dust or flakes off everything, for which a wipe with a rag does as well as anything, it's important to make sure there are no small flakes, or build up of dust, that could get drawn up by the magnet as it goes past, so it shorts the air gap. Sometimes cleaning it, then assembling it temporarily and giving it a few yurns will reveal more dust/flakes.

I'd try cleaning it before putting parts on.. All of course based on the assumption that you had found no output but good resistances.

Would pay to check the crank for bearing play too.. 

[Kaz]

I did not take the time to test for output again. I had previously read the output of the rectifier, but with this much damage, I’ll replace it all. If you look carefully, in the housing directly below the magneto coil, there are a few chunks of metal, from the coil itself, I’d guess. I really can’t tell where it came from originally, or how it broke, but right now important thing is it looks like I found the issue. Better pic of magneto below. I was able to pick up a new magneto and coils cheap enough that I’m not going to reuse these. The mag coil is pretty ugly. I was able to smooth the rotor pretty well w some 800 then 1200 sand paper, not going to replace it.  I’ll clean everything well, then rebuild.  I’ll post the outcome when I finally get it done. Thanks again!!

[Gwbarm]

It might clean up and work, but i think i would first try to figure out what the stator was hitting the rotor, loose bolt flywheel key sheared off etc. I think the rotor has been replaced already the green kind of says aftermarket. I would keep my eyes open for a used one on Ebay sometimes you can find them as a set cheap . 

[Mech]

Yeah I'd really want to know it wasn't going to happen again. I doubt the flywheel was loose because it would rub on a wide area. I reckon there's something in there that's big enough to fill the gap between flywheel and stator. I'd want to find that thing.

[Kaz]

Finally had time to work on this again. I found a missing tooth on the starter idle gear set-pic attached. This is obviously where the chunk came from that damaged the magneto. I assembled it w this gear set, and a new magneto/coil set, just to see if it ran, and it started right up, ran well. I have the gear set on order n will do final assembly after it gets here. Thanks again for all the advice. 

Edited November 27, 2024 by Kaz

[Mech]

Ha.. Glad you found it..  Well done.

[Gwbarm]

Good job finding that those little gremlins are always around

[Kaz]

Dug a little farther and found this woodruff key. OK got a new one. Finally got it back together and it’s stuck in neutral. Dash lights up for reverse and neutral, lights go out when I shift into 1st, but that’s it. Why did I miss/screw up this time?

[Gwbarm]

Yeah that must have happened when the gear broke. I dont think you went deep enough to screw anything up, but check to make sure your shifter mechanism is working properly.

[Mech]

That key must be from the flywheel surely ? It looks a bit too rounded to be a key though.. Wrong proportions too..  haha.

Are you sure the gear problem isn't just the lever on the case, or the adjustment if it's got a cable or rod ?

[Kaz]

That key is from the magneto rotor/crank shaft. That’s what I found when I pulled it. And as far as the problem now-the shifter feels normal, the indicator lights function normally. But I can’t get the damn thing to shift out of neutral.  It acts like it does, sounds and feels like it does, but doesn’t. To be honest, this thing was free to me 10+ years ago and I’m tired of dumping $$ into it. Shifter is back on the shaft exactly as I marked it before taking it apart. Obviously something else is broken too-I have no idea what and not much desire to find out. If I need to check the linkage in the case I had apart, that’s another $20 in oil wasted-again. Unless this is an easy fix, this thing will be headed for the junk yard. Thanks for all the help along the way!!! 

[Mech]

Well we can take side cases off without loosing the oil by jacking (and blocking) the bike on one side.

It's hard to see what you could have done wrong inside the case since you say the shift feels normal. It couldn't be that the plate clutch adjustment has got out again could it ? The clutch is slipping so bad it feels like neutral.. 

[hfrost112]

thats crazy a piece of the gear broke off!! what a find

[littleguy]

WOW not what I'd want to find!