Mech

Yeah the cables are real tough, there's no way you could snap one.. it must have been a crook cable, with broken strands snagging, till you broke the last few,

Older model but it may be the same.. https://www.manualslib.com/manual/998189/Yamaha-Yfm400fw.html?page=2#manual

This looks air cooled... https://www.manualslib.com/manual/659758/Yamaha-Big-Bear-4x4.html?page=10#manual The pages load quickly if you want to preview it before downloading..

I generally look up a parts place online and start comparing parts. Some parts places when you look up a part, will tell you what else that part fits. So.. if you look up your brakes, and fuel system, and transmission, and then check what other models have those same combination of features, that narrows it down often, then you could look up seats and bodywork, speedo, lights.. racks, electrical parts, carbies are a good one to check, they vary a lot with markets and years..

Thanks.

I was trying to imagine last night what could cause it to get two gears at once, because they have interlocks to prevent that, and the only thing I could think of was that perhaps the shaft can get end float causing it. It might pay to check the shafts can't move end-wards if one of the nuts holding the clutch on, comes loose.. or the selector barrel looks like it's located in a bearing that prevents end float, by the detent plate and a small bolt.. If the denent plate was loose, the changes wouldn't work right, and the shifter forks could move the gears along and possibly engage two gears at once. The detent is in the outer case.

Those things don't have a vacuum operated tap do they, or a vacuum operated fuel pump ? If it doesn't have either of those, then I'd ignore it for the time being. If it has either of those, check the vacuum hoses for fuel in them. I'd ignore it and see if it plays up again. If you've checked the tap, and it is closing off correctly, then I'd guess you might have turned the tap on intending to start it up and move it, then pushed it out instead, and forgotten to turn the tap off ? The float needle that sets the fuel level can leak if the tap's left on, and cause a carby overflow, but still operate fine in use without any problems..

I was just thinking it might have be easier to pull the sensor wire off and out to where you can get at it, then back probe it and refit it up in the confined place, but if not then not. Keep riding and see if it doesn't just come right. The suzukis over here seem to be fitted with an after market handlebar push-button switch to turn the fan on. They originally came out with only the oil temp switch for the fan, but within about two years started appearing, from new, with a handlebar switch as well. I'm in a forest here and on steep land, and it's often sweltering and no wind, so I use my manual switch quite a lot on summer. Easy to rig up.

Good stuff. For what it's worth, I'd recommend NGK spark plugs.. I don't know why but as long as I've been riding jap bikes(fifty plus years), nothing seems to last as long or be as reliable as NGK..

It does sound like inside the main cases but it's a good idea to take the control cables off first and check if it can be changed and put out of lock up somehow. They have to come off to get the motor out anyway. Then if you end up taking the engine out it would be an idea to take the side cases off and inspect the gear change mechanisms for some simplish problem, before taking the head and barrel off. I'll have a look at a manual...

Yup, if the output shaft is locked solid it's either something seized, such as a bearing, in which case you'd probably be able to get a bit of movement out of it by forcing/rotating the output shaft back and forwards, or as Dave says, the gears are stuck in two gears. The later sounds more likely since the shift doesn't seem right. If it's a four wheel drive.. perhaps the front diff is playing up.. It's a solid drive between the front and rear drives, and four wheel gets engaged in the front diff.. Well that's what our local models are like, but we don't get eigers. If you can't suss it let us know, and what you have found, and I'll download a manual and have a read..

Ecu coolant temp sensor... https://www.mickhone.com.au/partFinder/fiche/suzuki/2011/lt-a500xp/cylinder-head#next Part 31. The air temp sensor would have to be a mile out to cause your problem probably.. Ignore that one. The ecu water sensor, I haven't had a read up but it's possible you may be able to test it roughly with it in place. You could pull the plug off and try a resistance test on the sensors terminals, estimating what the water temp is by either having a temp probe in the top of the radiator, or using a temp reading gun thingy, or, you could test it by carefully getting the water-proofing plugs out of the back of the plug where the wires go in, and poke pins in there carefully and test it running with the ohm or volt gauge.. Don't damage the water proofing. they are sensitive and getting water in the plug could cause problems. The radiator fan sensor/switch is on the top of the radiator, and that's the one that is probably causing the red light. If it seems nearly right now, it may come better with continued use..

Once you have the manual, you could trace every wire using an ohm gauge to check for continuity from one end of each wire to the other end.

Inspect the loom for any signs of chafing, then check at the ends of the wires where they go into plugs looking for dirty/corroded connections, and wriggle the wires just there looking for any that flex too easily, indicating the wire's broken inside it's insulation. All of the electrical component tests are spelled out in the manual.. Most of the testing you can do without the bike running, using an ohm gauge. After you've made ten posts you can download a manual from this site, up the top, in "More", then "atv service manuals", which takes you to a new page, in the new page on the right and down a bit you choose your make.

Sudden loss of power, yes check the spark. If it slowed and faltered first.. check there's petrol getting though..

Reverse the wires.. See my post above. It's too complicated to explain all the possible variations but it's very likely that turning the key off allows the cdi to drain of power, which then means the first negative pulse of the trigger fires the cdi, after that, the cdi's charged(incorrectly) to a positive charge which won't allow the negative pulse to take the trigger voltage low enough to trigger the cdi.. Cdi can need a positive or a negative pulse to trigger them, and they can trigger on a rising or a dropping point in the ac wave. Swap the wires, one pair at a time. First reverse the cdi charge wires and try, then try reversing the trigger wires and try. Then, leave the trigger wires reversed and swap the charge wires back to how they were originally. You need to try every combination..

You mean the cam timing ? If it always seem to be a half tooth out, you need to move the crank one tooth which equals a half tooth of cam movement. Put the crank on it's mark, and take hold of the timing chain at the top next to the cam sprockets mark. If it doesn't have a mark at the top, use a marker and put one there. Holding the chain by one link, by themark, slip the sprocket down and out of he chain, then holding the chain up tight, rotate the crank till one link slips through your fingers. Now lift the cam sprocket back up into position and line that link you are holding up with the mark on the cam sprocket. Now when you rotate the crank back the other way by one links worth of movement to line up it's timing marks, you will rotate the cam by a half a tooth, and things will all line up.

Apart from cam timing, gearboxes seem to be the second most common problem people have putting bikes together.. They shouldn't, it's so easy to test they are shifting right before you even put the second case on, but... People just seem to prefer to hope it will come right even thought they know somethings not right..haha If you are having to do the work yourself, remember, it's better to backtrack and get it right before you go any further. The further along you are, the least inclined you are going to be to backtrack when you have finally accepted there's a problem. As mechanic I know, we can write off some hours, it's only an hourly wage and I can make that back up, but my reputation, and the customer confidence and trust, that can't be easily won back..

Did the guys that did the work have the whole bike when they did it ? They should/would have test run it surely, and tried the gears ?

It's not a model we get here so I haven't had one exactly like it apart, but I had a look in the manual last night and it certainly seem to be that it must be inside the center cases, a gear on a shaft wrong, or a selector fork in the wrong place. You should probably take it back to who did the work. They should fix it for free if they are reasonable. They won't want to take responsibility though if you have pulled it right apart so they can't be sure it is their work that caused it. So far, with only the clutch side off they shouldn't be able to quibble. As for the clutch, I don't understand what the problem is there. Once the springs are done up on the clutch the clutch is meant to be locked up, it should only slip if the cover's on and the clutch lever pulled in. It doesn't really sound to me like there is any problem there. I suspect you are mistaking the gearbox getting two gears at once(which will lock the gearbox solid), for a locked up motor. If I was you, I'd take the clutch off, take the drive chain off, and disconnect most of the gear change mechanism. I'd leave the detent that holds it in gears, that's a lever with a roller on it that presses against the selector barrel. Then while spinning the gear shaft the clutch goes onto I'd try getting all the gears by rotating that selector barrel. If you have the problem then, I'd leave it like that and take the bike back to the shop and show them what's happening. They shouldn't object too much to your having confirmed there is a problem before bringing it back to them. Other than that I'm pretty damn sure you are going to have to strip the motor and center cases to cure that. It's a worry though that they aren't competent. Perhaps they would agree to you taking it to a local honda dealer and them paying for the repair.. You would need to be confident and diplomatic to wrangle that though.. An independent mechanic to argue your case might help.

Yeah and second is really reverse you said.. I think ? That's not right.. My guess would be(because it's probably the easiest if you aren't reading the book or being careful), that they have muddled two shift forks up.. I don't think the gear change mechanism in the outer case could cause the reverse problem.. That mechanism is really just a ratchet so the lever goes to center.. The gear shifting/selection is all about how the gears are on the shaft, and how the shift forks engage in the shift barrel. If you have the side case off you can remove the ratchet mechanism and rotate the shift barrel, and the gears should all engage in order R-N-1-2-3-4-5- and without two gears being engaged at a time. The clutch dragging/locking is a different matter and should be relatively easy to suss. Check the clutch doesn't have an extra steel or friction in it.

That one spark and then quit could be because the ac that's charging the cdi is not in the right phasing with the trigger coil.. The way the cdi charges up is often important. Some of the electronics(in the cdi) count the number of pulses of charge before they will allow a trigger event. They sometimes need two positive pulses say, with a negative pulse between, but if the ac windings are back to front they can get two negative pulses and one positive.. something like that, or backwards from that.

Is the cdi original ? Or aftermarket ? It could be that you need to reverse the charging wires to the cdi, or reverse the trigger wires to the cdi, if it's not an original cdi unit. Some(lots) cdi need to have the ac going into them the right way. They may need to have a positive first wave, or a negative first wave of charging, to set them up to be triggered.. The trigger probably only works with the right trigger voltage, positive or negative, and rising or falling.. You could just try swapping things and trying.

But now diagram huh... Well check for continuity/resistance from the cdi, down to the various windings in the stator. Each wire at the cdi will either have a there and a return wire from the stator, or just one that goes to earth. Just check there is continuity with your ohm meter to start, don't worry about the exact readings.. Then try the same process to trace the wires to the key switch and kill switch.. Try and make a wiring diagram.. Just draw where each wire goes as you check it's continuity. Some wires might go to the switches and to the cdi or stator.. Draw switches as boxes till we figure whether they are meant to be open or closed for run. Draw the stator real basic and don't worry about what set of wires is inside, just where the wires run on the bike. We can probably make a wiring diagram.. Or a whole new loom if need be. To test those broken wires on the motor, put it in gear and use the ohm gauge on the bits of wire you can see to check if they are earthed or connected or open circuit. Then put it in neutral and repeat the process.

I don't suppose you have a wiring diagram.. It's just possible those wires might go to a neutral switch, that effects the ignition.. Some small two-strokes start up with rev limiters for safety reasons, till they are in gear. If it has a centrifugal clutch, that would be a possibility..