Mech

Apply to return it. They probably have a returns process which you'll have to follow, and you may have to pay freight, but I think I'd pay the freight and cut my losses.

Can the frame be straightened Mga ? I've straightened frames before. If they are bad we cut and then bend the tubes then weld them again. If it's just the entire frame a bit twisted they can be chained to a tree and tweaked using a long length of lumber and/or a come-along. The wheel alignment is nothing near as important as in a road going vehicle.

Partzilla have changed their layout.. here's what they say are directly interchangeable. 2001 YFM400 Big Bear 2x4 YFM400 Big Bear 4x4 2000 YFM400 Big Bear 2x4 YFM400 Big Bear 4x4

Look the frame up in partzilla and it should tell you what other models it fits.. which are also the other models that will fit your bike.

And the starter in the shed that looked similar is a mitsuba, but the two mounting lugs are different, one straight back like your's, and another lug at the back but poking out sideways.

Cleans it's plug I bet.. If it runs sometimes, and in these circumstances, it sounds to me like the plug is getting wet with fuel and missing, till the right combination of speed and throttle burn it clean. You should check the spark plug is the right temp and type, then, try lowering the slide needle in it's slide as a first test, then go out and note very carefully whether it takes less time to get it to burn clean. You could also try only opening the throttle till it starts to struggle/starts to sound gaspy or hollow, and then either hold the throttle steady or let it off by the tiniest amount till the engine sounds healthier again, starts to feel like it wants to pull again, then ease the throttle back on, and keep doing that, slowly coaxing the engine to higher revs. If we drive around in a vehicle that's not tuned just right in the fuel department they can get deposits on them which in the normal course of driving get burnt off again when we start driving a bit faster, but if we drive around for a while slowly, like in a town, then get to the open road and floor it, the soft deposits burn on hard and to a substance that can short the spark. We can drive carefully as I've been describing above to prevent the build up burning hard, and we can even clean fouled plugs by following the same driving techniques. Try driving like I suggest and if you can coax the plug clean, which is what it sounds to me like you are doing, then you need a different plug, or adjust the carb, or drive differently..

You said there was also a second version of side case, so it gets even trickier. I do notice though that the starter pinion has two different wear marks. There's the chewed bit, and then there's signs of wear that extends a little bit further along the splines towards the body of the starter.. Perhaps it was just the first replacement cog was too narrow.. Perhaps this new genuine cog will make good contact.. A bit of grease or bearing blue should reveal how much contact it has.

Is the gear going to mesh across more of the tooth now, and is it going to perhaps mesh further in on the start pinion ? That does look a bit munted alright. Pity to run that on the nice new honda part.. I'll look in my shed tomorrow.. I've got a shelf of those..

I've been tilting quads, and laying down scramblers, to work in the side covers for decades and have never spilt the oil.. Kicked the oil pan though !! haha. Come to think of it, I've driven over one once too.. That was messy.

haha.. It happens to the best of us. Good progress.

Good work Gw.. Better illustration than I could find.. So it goes against the flat on the shift drum ?

Try and find a service manual for it. If you can find one, it's probably repairable, parts are probably availiable, and it's probably ok quality. If you can't find a service manual I'd buy something else, something that does have manuals and parts availiable.

I've never been inside a yamaha quad Jonny. That lever is a part of the reverse interlock I suspect, and it might be that it sits in the right position once the outer cover is on and cables attached.. or something. You don't have to pay for manuals here if you are a participating member of the community.. You should be able to download. Contact an admin or moderator if you are having trouble. They're super helpful.. You didn't tell me if that is a spring loaded plunger..

That round bit with the sprung loaded plunger in it, is generally called a "shift barrel' or "shift drum", and it gets turned by the shift lever to move the "shift forks", which slide the gears in and out of mesh. When it's in neutral the plunger should be contacting the neutral contact and nothing else. There are service manuals for free download in here..

Yeah I added an answer to that at the end of my post there.. The lever should not be operating the switch. That lever must need rotating around a bit I'd think, or pulling outwards .. The manual will explain in the engine disassembly or as part of the reassembly process I'd think.

Is that a little plunger in the end of the shift barrel, or a spring with a cap on it ? Either way, I'd suspect the flat spot on the end is a contributing factor. A flat lets oil get between it and the switch contact and can make them not always contact. And, the flat, because it has more contact than a ball contact does, gets dragged sideways by the switch plate and contacts, so if there's any play the plunger, it can easily be left in the wrong position by a tiny amount. If it was mine I'd consider making a new plunger, a plunger as long as was possible while still leaving room for the spring, and a nice close fit in the hole, flat on the spring end and ball ended on the contact end. A fat piece of bronze welding rod does a good job. You can/could put a length in a drill to slim it down with a file wrapped in wet and dry sandpaper. Ha, and no that lever should not be operating the switch..

Yeah I just looked and it's not shown.. Presumably it comes with the shift barrel.. The plungers I've seen have been solid brass or bronze, about three mm diameter, and easy to improvise.. Just saying.. I think they mostly start off with a round/ball end that makes the contact. That would have good pressure and minimise the friction that would lead to the wear and getting bent to the side in the drilling.

Check in the online parts place to see if it is a plunger, and how much it is. Babbits have a good diagram based index page.. Partzilla though will tell you what other models and years a part fits, and which parts you may be able to use if your year parts are supposedly unavailable.

Hi Dave. Yeah I mostly just stick to giving advice where I think it will do some good, but I always respond when someone starts attributing things, words, ideas, or attributes, to me, that I don't accept. Attributing words, ideas or attributes to people that you don't know and that haven't said the words or expressed the ideas,.. that is trolling.

Yeah I believe you Gw.. Always. But threads get worn, wrenches get inaccurate and sticky, people don't always use them as they should be used.. And I'm a mechanic, I'm responsible for my work no matter what the books might say, If I strip it it's me buying a new shaft and doing the work for free. 70lb feet will keep that nut tight if it's all assembled right, and if there is something not right in there, 100 isn't going to save it. Anyway.. that switch.. You notice Jonny that that switch has no spung contact to make sure it contacts the shift barrel's contacts.. That means the barrel will have a sprung contact, and a common sort of contact is a plunger and spring in a drilling in the barrel, and those plungers get worn sometimes so they can wobble, and seeing the size of that contact i can see it wouldn't take much wear to cause the problem. Check the plunger real careful for wear..

Hey !! I object to that.. I'm a middle of the road troll thank you.. A Lassiez-faire capitalist I've been told.. haha. That I wear.

I've since found the wiring diagram and if there is only one blue wire, it should turn red after a splice/connector which connects it to the main loom, and then, as a red wire, go to a splice which branches red four ways to the fuse panel. The blue wire, or it's connection where it joins the loom is a fuseable link. The manual will tell if it's the wire or the connection. If there is a second blue wire from the battery it's the same fusable link setup(but a seperate one), and it then goes to the speed sensor..

He did .. So which part of the circuits is causing the heat, the windings or the contacts, or perhaps.. a diode in, or a diode missing/blown in the relay...

A relay shouldn't, and doesn't, usually get hot, not even under a heavy load and being switched on continuously.. The contacts should be able to carry a big load without getting hot, and the trigger winding should be able to carry it's tiny current indefinitely without producing any significant heat let alone being hot. I'd disconnect the load wire from the relay and see if it still ran hot, then I'd disconnect the trigger wire and see if it still got hot..

Some of the relays have a built in diode Gw.. Don't know if that would account for the ohms being to spec but not going.. Wrong relay for the job perhaps. And some relays are normally open contacts that get closed when activated, and others are normally closed and open the contacts when energised. Yamaha use all three versions.. We need to be very careful if ordering or swapping relays as a test..