Mech

That is a strange looking diff Gw.. There's no room for a crown wheel.. I must be looking at it wrong. That's looking up from below, and those are the two axle shafts poking up and down.. right ?

The parts book says the centrifugal clutch nut is 20mm and the plate clutch nut is 18mm. You can sometimes lock the shafts to undo the nuts by putting a bit of soft metal in the teeth of their gears, positioned so it will be drawn in and jamb.. Copper, aluminum or lead are all ok..

lol..

Doh.. The parts books say it's a limited slip diff.. Still no manual shift though.. no shift at all for the 2000 year.. Yeah it's an oddball. I looked for any model around that year or engine size looking for a manual shift diff and couldn't find anything.. Later ones had an electric select..

I've been looking through 2000 year big-bear 400 manuals and it seems they don't have front differentials.. There are no differential/spider gears. So there would be no diff lock. All the manuals I have around 2000 show the 4wd engagement as being by electric motor at the front diff. I can't find any with a cable to the front diff 4wd engagement. You'll have to jack it up and see if the 4wd engages, and/or whether there is a differential action in there.

It will be a diff lock I'd think.. Does it have a four wheel lever ?

Yup. If the start shaped washer turns and changes the gears then your problem is just in some of the linkages you are seeing right in front of you there where the start washer is. The fix will be easy. That star washer has a roller sprung loaded against it to hold it in each gear, and a ratchet that turns it. You should be able to turn the star washer without using the ratchet mechanism. If you lever the roller out from contacting the star you should be able to turn the star using your fingers as long as the gearbox shafts are turning at the time.

Sounds like there is a problem with the internal shifter mechanism then, that being the shafts and linkages and ratchet etc.. The manual shift and the electric shift both use the same shift mechanism down in the front case. If neither manual or electric shifts work then you have a shift mechanism or gear problem. There is a star shaped washer in there that the shift linkages act on, that's meant to turn to move the gears inside the box. If you operate the linkages there should be a ratchet mechanism that turns that washer and drum one bump on the star washer every time the lever goes up or down(with the rear wheels turning). If it doesn't seem to turn then I'd take the linkages off and try turning that star shaped washer by hand(with a pail of big pliers), while turning the gear shaft or back wheels. If the shift drum/barrel that's attached to that star shaped washer won't rotate, then there is a problem right inside the cases and the motor needs to come out and be stripped right down.

Well wires do break. You need to use either a test light or a volt gauge and trace the wire from battery to fuse to switch, checking power is getting through. Sometimes we can find a broken wire by wriggling them one at a time near their ends where they connect to the metal terminal and they feel too flexible if the wire is broken inside, and if we have the key on at the time, the power might flash on. When you say you traced the power to the reg, and had power in but none out, do you mean it was running and not charging ?

No Ps, those are for welding tips and they are like tiny files. Don't use those. If jets are dirty it's nearly always a lump of dirt or bit of fluff and you can see it if you hold the jet to the light. Most things can be blown out easily. Sometimes the jets get a build up of verdigris which doesn't blow out, and people use chemicals, but I just use any small bit of hardwood whittled down to a fine point to ream then out, and then give them a blow through and reinspect against the light. It's important to take out the emulsion tube, which is the brass tube the slide needle drops into. A few taps from the top with the handle of a small screwdriver and it comes out the bottom. It has several tiny holes halfway up the tube that need a good blow out because they are too small even for a whittled down bit of wood. Don't try cleaning them with a pin, a single wire from a wire brush some times fits nicely but they mustn't be enlarged or distorted.. or blocked with a tiny point of whittled down wood !! The holes in the tube are arranged on opposite sides of the tube, so you can look right through if you are very careful, and you will see light if they are all clear. The drilling in the carb body that the emulsion tube fits into, is a precise diameter and volume and needs to be cleaned out of it has a build up of chalky or gummy crud.. Apart from the fuel jets there are air jets near the air-cleaner end and some of those can not be removed, and even the ones that can be removed don't really need to be taken out. They are so big you can see and blow straight through them. Blow every passage you can in the carb body, in the opposite direction to normal fuel or air flow, as much as possible. Blow a little one way to see where it comes out before blasting it through from the other way. The idle discharge holes are the smallest passages in the carb body.. Try not to force any fluff or dirt up towards them by blowing from below. It's awkward, but best to open the butterfly or take the slide out, and blow down through the idle discharge holes as best you can, before blowing back the other way from below. If you have compressed air it's a good thing to make a long tipped air nozzle out of four mill steel brake pipe. It's handy for getting down the hole where the slide drops in, and blowing the drillings there or under the butterfly.

Castrol's usually reliable. It's thick though....

You need to find two parts in the manual. One part has a flow chart of questions about what you need to check at each step, and that is normally in a trouble-shooting section near the end of the book, or near the end of the section, such as near the end of the gearbox shift section. Then you find the gearbox section of the manual where it should also have a diagnostic section where it will tell you where every component is and how to test it to get the answers you need in that first trouble shooting section. There is a manual for your bike in the manuals section of this site. If you download that and confirm which one it is you have grabbed, I will help you find the right bits to read, and work through the process from the same book..

Unless the regulator is draining all the battery power, in which case you will be getting flat batterys, then I doubt it's the regulator. You would I imagine have turned the key off when you stopped it, and if it was running up to that moment, then I'd be suspecting the key switch as the most likely thing to have changed between it running and your now trying to start it. Nothing else should have changed once it's turned off.. I'd check the key switch, and the kill switch first.

If the starter solenoid is clicking then I don't think you have a bypass problem, you have a starter or solenoid problem... To answer your question though, yes you can bypass the neutral switch..

Exactly what I was about to say.. put your hand over the carb's intake for a second while you crank it and feel for suction, and then see if it's getting petrol through.

Partsman, if you look a part up on partzilla, and choose the part as if you are going to buy it, or just click it if it\s unavailable, it will take you to a new page with the shipping and a picture and all that, and if you scroll down a bit there will be a list of other models that part fits. It shows the other models part number for each part and sometimes that other number is the superseded part number which can be handy. Here's what it says about that part... https://www.partzilla.com/product/yamaha/2HR-2510F-01-00 Lots of parts places have a similar function, so you can double check a site if in doubt.

It could be a switch, they have an opportunity to play up every time they are used/switched. If it was running and got switched off.. check the switch.

And you'll be able to turn the gearbox shaft and shift gears to your hearts content.. we hope. Then suss why the electric shift doesn't.. And.. if you're interested.. when it's all assembled and going, there are two clutches, one centrifugal one that controls the take off from idle, and one flat plate type, and that gets operated by your shift mechanism so the gears don't graunch. There is also another sort of ratchet mechanism in the centrifugal clutch that keeps the clutch driving and providing engine braking when you are rolling down a hill at low revs. It's that ratcheting mechanism(which they call a sprag clutch), that's causing it to be easy to push back, but not forwards, while it's stuck in gear. It's trying to provide engine braking..

Actually.. if and since you have the side cover off it might be easier and surer diagnosis to take the pressure plate off the clutch pack and remove the plates so the gearbox turns and can shift independently. Is it still apart ?

Do the headlights work ? The horn ? Brake lights ? The later models will start in gear if you apply the brakes hard enough to make the brake lights go. Put the brakes on hard and see if it will crank. Then, as Gw says, you should look at the wiring all around near where you were working.. and the fuses etc. Oops. Just looked at a manual and it looks like those ones don't have a brake light so that test is out.

Is this a four stroke or a two stroke ? Have you taken the carb off and stripped it and cleaned it ? That's first I think.

It should shift with the lever. If the wheels rotate backwards but not forwards then it is in gear. Given the circumstances I'd say it is almost certainly just needing to have the wheels rotated back and forwards enough while operating the shift lever enough times that it slowly makes one shift at a time down to neutral. Sometimes when you are moving the shift lever you may feel it only goes a half distance when you try shifting down. When that happens it can get the ratchet on the lever jammed and you have to change back up again(while rotating the wheels) then have another go at changing down. You just keep rocking and turning the wheels back and forwards quite forcefully while trying to down shift with the lever. If it goes down try for another down shift, if it feels like it moved half a travel, change back up one gear and then start moving down again. Just keep rotating the wheels quite forcefully so the engine turns and it should eventually get to neutral. Once it's in neutral and you can start it, try riding it using the shift lever. That will test the shift linkages inside the unit and the gears themselves. If the bike rides and has all the gears then start checking the electrical shift mechanism.

Yeah.. be safe.. and don't do those silly things.. I normally tell my sons, "have fun. but don't get caught". I'll have to change it to "have fun. but don't get hurt"..

Regarding the noises.. You can deduce a lot by taking note of the circumstances when it makes noises, like under load only, or not under load but only when floating, or both, and whether it's better or worse when cold, or hot, or always there, and how long the noise lasts from cold if that is the case. It's good to try all the load tests while it's cold and then when it's hot. It's harder to do on quads with centrifugal clutches but on manual clutches you can tell if it's gearbox by pulling the clutch, and you can load them up o the spot using the clutch, which is way better than trying to lean over the side as you drive along on a quad.. haha. The video didn't sound too noisy to me for the distance the phone was away.. There were a couple of what seemed like intermittent clack sounds, but nothing too serious. I'd do another oil change and then ride it getting used to it and testing things out... As I'm sure you are going to do.

Eek ! That's nasty Gw.. Better out than in. They must hold a bit hidden in the oil cooler and places huh.. Glad to hear it's running great, and it looks good too mate.. well done.