Mech

If it idles steadily and runs right at throttle then it should be ok.. If the carby is about right, when you adjust the idle mixture it shouldn't take more than one full turn, or a half turn either way, to change from rich to lean. If you have to or can wind the screw turns, then there's something wrong.

Did you ride it when you went to look at it ? If it was going fine, and you went for a ride at the point of sale, then surely it's something simple, and the carb doesn't need stripping.. If you bought it untested then that new carby is probably the problem, but it's not likely to be as simple as needing a clean.. it probably needs retuning for the bike. I'd contact the old owner and ask if they still had the original carb and could you get it please. It's easier to clean an original carb and get it running right again that retune a new after market carb that might need new jets. About the only simple adjustments are the idle mixture and speed, and the slide needle height. Your symptoms sound like it could be the slide needle, and the easy test is to take the top cover off and move the slide needle's circlip down one notch and see if that improves things. Before pulling anything off the bike though you should check the fuel tap and filter's aren't blocked by undoing the drain screw on the bottom of the carby and making sure fuel runs out freely. That checks the tap, filters and that fuel is getting into the carb fast enough. If that's good, try adjusting the slide needle. Oh.. and that side cover will be availiabe from the dealer. They have a rubber seal and will be much better than a home made one of plastic.

Spark plug cable got knocked half off.. If you're saying it's got this problem on the trip home on the truck then it must be something simple surely. Are you sure you got the tap in the right position ? Plenty of gas? No rags stuffed up the exhaust ? (hey I don't know.. but humans do stuff like that ). Hasn't got a tap on the fuel tank breather ? Check anywhere wires might have got pinched by tie-downs.

Down load a service manual and have a look at the wiring diagram. Follow the wires to the fuses and relays and then to the key switch perhaps, checking for continuity. You need a multimeter or a test light.

Well on the air-cleaner end of the venturi there are one or more brass air jets, one of them will be to restrict air to the idle circuit. It might be way to big or missing. And the idle mixture screw I hope you are familiar with. That might be missing..

Well there you go then..

A wrong one wouldn't do it, but a badly made or assembled one might be able to.. But I don't see how. If the butterfly is shut then there's only the idle circuit operating.. If there was no air jet for the idle circuit perhaps ? Or the idle mixture screw not there at all. Also.. do you have an emission diagram on the side of that carb..Could check that.

Hmm.. Well as you no doubt know, the slide gets lifted by vacuum.. So how is that vacuum getting to the top of the diagram I wonder.. That aside for the moment though, even if the slide lifts, nothing should happen if the butterfly's closed.. so.. somewhere there's air, and fuel getting in.. Is this a knock off copy carby ? Have you looked at all it's drilling to make sure there re no unusual ones ? The yamaha doesn't have a fuel pump Huh ? Does it have a auto fuel tap tapping on the carb, or a pump tapping ? All I can think of without inspecting it is that the choke's causing this.. it bypasses the butterfly.. If the plunger was open, and if the aircleaner was badly blocked, the choke passage could let vacuum to the inlet side of the venturi, and so to the slide diaphragm.. perhaps ? Or, a combination of the choke supplying fuel(way more fuel than they are meant to, plus extra air getting in somewhere.. Some choke plungers have a tapered needle to alter the amount of fuel going through as you use less than full choke, and some plungers dont.. Maybe something there..

I'm in New Zealand and no I haven't dealt with partzilla. I'm just trying to help you with your question.. I was just suggesting them as a possible source of the information you want to know. If you want to know what else it fits.. that's how you do it. I use this guy, he shows what else the part fits. I look up the part and then over by the price there is an arrow.. that shows what else the part fits. https://www.mickhone.com.au/

Yeah I had a look at the parts book. Well the obvious question is, and don't take offense here, are you sure the butterfly is going right closed, have you wound the idle speed screw right back ? If the butterfly's right closed then it doesn't matter what the slide's doing, no fuel's going to get in. If the butterfly's closed then the slide shouldn't rise. If the butterfly's closed then even if air was getting in through a fuel tap vacuum hose or a manifold vacuum leak, it would take a combination of problems, like the vacuum leak, and excess fuel from somewhere like a hole in the diaphragm of an auto fuel tap or the choke. Is the choke in and working ? That bypasses the butterfly. I can't think how or why but perhaps a breather pipes swapped with an auto fuel tap hose.. if it has an auto fuel tap..

Right. Well what you do is you go online to a parts place and you look up the ecu for a 2005 king quad 700, one just the same model as they say this thing fits, and then if you are lucky the site will tell you what other models that part fits.. Partzilla should show you. Then if you still aren't sure, look up the ecu for your model bike and see if that part fits this bike they are saying it's for..

Where'd you disconnect the throttle cable ? Did you check the slide's going right down ? Is this an old fashioned carb with the cable straight onto the slide, or a more modern sort with a diaphragm on the slide ?

Start looking for the things they all have in common. so I'd check all the fuses, relays, and power supply wires, and all the earths are not broken or having bad contacts. Inspect the wiring for chafing and perhaps try wriggling the wiring while the bikes sitting idling. Wriggle the wires where they go into plugs. I'd get a manual and check how to get the trouble codes out of the engine and PS computers. You should also read the manual about the four wheel drive system to make sure it isn't the way it's meant to operate. They are a four wheel drive when needed system.. You pushing the switch doesn't mean it's going to go into four wheel drive necessarily. That;s probably the first things to do.

It does sound like a fuel problem, but it might be a blocked exhaust, or an electrical problem, possibly as simple as a crook sparkplug. As has been said in here many times before, the cheap aftermarket carbs are not tuned right.. They all need work it seems. I'm highly recommend you just put the original carb on. I very much doubt it's going to need any parts. You should strip and clean the carb before fitting it, but you need to strip it completely. We really want to be absolutely sure the carb is right, then if it doesn't run right we can start looking at blocked exhausts and electrical problems. You need to take out all the fuel jets, and the brass emulsion tube that runs up from the main jet to the slide needle. You need to take out the mixture screw and blow through all the air jets and the passages in the carb body. You need to blow and look through the fuel jets. They should look round and clean. If they aren't round, sharpen a small bit of hard wood and gently ream them out with it. You need to clean the tiny holes in the side of the emulsion tube, and you need to clean out the drilling the emulsion tube goes in. You need to take out the float needle's seat and check it's O ring. You shouldn't need to touch the slide needle unless you have had that apart before and there is a chance it's had the circlip moved. Just spin it in your fingers to make sure it looks straight, not bent. When you are putting it back together, before you put the bowl on, to test the float needle you tilt the carb on it's side so the float tilts away from the needle and start blowing into the fuel inlet, then slowly tilt it back until the float touches the needle and stops you blowing through it. The float should be about parallel with the bottom of the carby.. The metal part of the float should be about parallel. It should close off fully with very little weight of the float on the needle. Clean the air cleaner and oil it if it's meant to be oiled. Wring it out after oiling it, and wringing it while it's wrapped in a rag is best. It gets the excess oil out. Too much oil can make them flood. Have a look at the plug. If it's got a metallic sheen to the porclain, a slight grey look, it might be buggered. Stale fuel can wreck them in just a few firings. If in doubt get a new one. With the original carb on you should undo the drain screw at the bottom and make sure fuel runs out fast when the tap's on. Try the tap in both positions. That tests the fuel tap and filters and that fuel is getting into the carb, and in at a good rate. Then you should start it and warm it up and adjust the mixture and speed. The idle mixture needs to be set with the slide down as far as possible. You speed up the idle till it will idle, then adjust the mixture to give the highest speed, then back the speed screw out to a slow idle and then re-adjust the mixture to highest speed again. You keep doing that till the mixture screw is in the center position between starting to slow because it's getting lean, and staring to slow because it's starting to get rich, and all with the idle as slow as possible for a steady idle. Then check the choke works, and that it closes right off and doesn't effect the idle. Then you go for a drive and see how it goes. If it plays up, try and detect how much throttle it gets to before it starts misbehaving. There are certain points where the mixture is controlled by different jets. The points are, idle, idle up to about a quarter throttle, a quarter to about three quarters or seven eights throttle, and near full to full throttle. If it starts to falter then just hold the throttle steady and note what happens for a few seconds, then ease the throttle off very slightly and see what happens.. Take careful note of these things because they are important and will tell us what the trouble is. Hopefully with a clean air filter, clean fuel and carb, and a new plug it will be cured. If not, get back to us and we will figure out what to do next.

Any competent mech or tech would know all this and realise straight away what was wrong as soon as you gave that second description of it not wanting to turn one direction. Find a competent tech and they will find the problem no trouble.

Actually Audie, I was thinking... (don't laugh).. The easiest thing to give that problem would be, if the steering shaft from the bars to the short plate the rods attach to had splines, and someone had the plate or the bar mount off and put it on the wrong spline, then the plate would be swung one way when the bars were straight ahead, and the rods would have to be adjusted to get the straight ahead alignment right, but it would have the same effect as I had been describing earlier.. One direction it would be traveling through the right angle with the rods, and the other direction it would be swinging further away from the optimum right angle as you turned. What's the bet that's what it is.. No bending needed quadnut, I'll do if for you cheap.. cheaper than bending.

I can fix that.. Bring it around and I'll bend it for you..

I found a wiring diagram and it does show the starter circuit's connected into the ecu. The starter solenoid has power to it, then the start button earths it for crank. The wire going to the start button though branches and goes into the ecu as well, which means the ecu has 12 volts showing at that wire until you press the start button, and then the voltage gets dropped as the start button earths that line out. It's pretty foolproof. If the wire broke the ecu would think the starter was being operated all the time and so lock the timing and mixture. Then the engine would run like crap, all the time. It won't be your problem..

You are right, the thing will probably start misbehaving when it gets warm. If there is a starter feed it will just come off the starter solenoid wire somewhere.. It's on just about every car, and, of all the bikes/quads, yamaha alone seem to do it with their cdi ignitions too.. even on carby models. They must retard the timing I think on the carby models. I'll get a manual and see what I can see. I've always enjoyed mechanicing.. it is a challenge and there are rewards, not least being able to help people. I worked in rural communities and everyone knew me, and that I was honest and sincere and could be trusted, and I used to be honored to have their confidence too when they were broke, or had domestics, or health issues. I've been helping people with all their troubles nearly all my life(now I'm old Haha).

I wouldn't think there should be any connection to ground if it has two wires. And if one of the two wires was an earth, and it had an internal earth as well by design, then there shouldn't be that 10-12k reading. You're a thorough bugger.. Good onya. Have you checked about that starter feed.. that will do this hard start and backfire thing.. What years the bike Sha.. I'll get a manual and have a read.

I don't know those things and I doubt there is a manual for it.. I'd have thought though that the ignition would have run straight off the stator and wouldn't need the battery to keep going, but, if it runs with a jump start, and keeps running till you take the jumpers off, then it is presumably running the ignition off the battery. Confirm it keeps running as long as the jumper is attached.. then.. That being the case, it should keep running even with an old battery if the charging was working. So.. it sounds l to me like either the charging isn't working, or it might be working but the battery is defective and drawing all the power. It might be a combination of both, a dud battery and no charging..

Nope. Do you do a lot of full speed reversing ? Sounds dangerous... haha. You might find you can achieve the same result by wiring a switch that tricks the ecu into thinking it's not in reverse..

I think the first thing to do is check the compression.

Gw's right.. check the air filter.. If foam elements have too much oil they restrict the air flow, and paper ones can swell and block in humid weather if they aren't being used. Otherwise.. It's almost certainly the carby.

Yup well that spike in the tps wasn't right so good work on finding that. The trouble is it didn't fix it so now you have to explain it to the customer.. And that of course is why it's so important to be professional and do things systematically, which it sounds like you are. We always have to be able to explain, and justify, our practices and methods. it's what being professional is all about. You sound professional and shouldn't have any trouble but if you do, send them in here and I'll vouch for your methods and thoroughness. That throttle reading of 15-20, if that's at idle it sounds a bit much to me.. I'd have thought 20 percent throttle was quite a lot. Most efi throttles with a bypass isc are almost completely shut at idle because they have the isc to let air in. Every throttle body I've seen the set up was for the butterfly to be closed as much as it can go without actually touching the bore too hard which can cause wear and jambing. I'd suspect the throttle sensor needs a move, unless the book says that's the right reading ? Up further I mentioned a starter feed into the ecu.. Have you looked into that ? The sensors aren't accurate at cranking speeds, or cranking voltages. They set the timing and fuel at fixed values at starting while the start feed gets fed in. If the timing is trying to work off a trigger coil that's not putting out enough power it can throw the timing right out. Same with the airflow or map sensor. Some wiring issues we can find by letting the bike idle and then go around wriggling the wires hoping it will falter. That's not going to work so well with the start feed into the ecu but it might be worth a try. If you confirm it has the start feed, you could perhaps improvise a feed and try it. And I suppose you already know, most wires break at the ends, where the wire goes into the metal terminal at the plug. That's the place to wriggle. It's a bit of a long shot and unlikely but, if it's a two cylinder, check nobody's swapped the injector wires over. They still run like that but give hard starting, with backfiring, mostly out the inlet, and poor performance, but only slightly poor performance. Once you get them started it's hard to tell they are swapped.. And about the only other advice is to always check the sensor readings right at the ecu whenever possible. It helps eliminate wiring problems straight off. I'll be interested to hear what this is eventually. To me, this is interesting.. Haha.