Mech

Engines, if they are too rich, tend to chug and run irregular and rough for some time, either a second or three or more than a minute, before they get slower and slower and finally die. Engines that are too lean tend to idle quite regularly except every few seconds they give one single miss, then go straight back to a steady idle till the next one miss. They can sit idling with that intermittent single misfire sometimes without dieing, but if they are going to die it will generally be idling fine then suddenly cut right out. Doesn't always show up like that, but mostly a single cylinder engine with an idle mixture that's not right will behave like that..

I think the mixture at idle is too rich. That would explain it idling cold but then cutting out once it warmed up. And winding the idle mixture screw in doesn't make it too lean by the sound of it... Both things point to a rich mixture. Check the air filter is clean and oiled, and not over-oiled. Check the breather hoses on the tank and carb are fitted correctly and not blocked. The dieing when warm could also be a tight valve clearance so it would be a good idea to check those. The idle mixture needs to be adjusted at the slowest idle speed it will idle steadily at. So you slow it with the idle speed screw then wind the mixture screw in and out till it is in the place that gives the highest idle speed, then you wind the speed screw out to slow it right down and you adjust the mixture to it's best idle again, then slow it, then adjust it, and you keep going around in a circle slowing it and adjusting the mixture. Once it's idling slow and steady then you can speed it up if you want to but leave the mixture where it's best at the place where it will run nicely with the least amount of butterfly opening. If it doesn't come right, if the idle can't be adjusted in both directions with similar rev changes, and/or it keeps dieing once warm then I'd check the float level, which can probably be checked with the carb in place using a bit of clear hose, and I'd check the jetting.

You should put the hoses back to how they are meant to be. The sump might have too much oil in it, or the oil may have fuel in it, or the engine may need an overhaul. Those are the usual reasons oil gets into the airbox. Your bike may have a PCV valve somewhere, and that maybe clogged and need cleaning.

One year later and a DC cdi. Coil Primary 0.1-0.5, secondary 12-20K ohm with cap. Pickup coil 90-140 Ohm. They recommend a peak voltage test of at least 2.5v.

Coil primary 0.5Ohm, secondary 10-16K Ohm. Pickup/trigger coil 90-140 Ohm, cdi charge coil 106-160 Ohm.

And for the price of one manual you get access to hundreds...

Hi Dave. Yamaha did make one model in the early days that did have a power takeoff shaft at the rear, but it ran at unusual revs and had to have special yamaha implements.. as I understand it. There's one thread about one here and specs on the net

Is the cdi unit providing an earth for the start circuit when either the brake switch, or the neutral relay, is closed ? Not all cdi do. The one in that diagram does.

Gw's right about in being leaner, but try turning the mixture screw in and out making sure there is a sweet spot in the middle, and that winding it too far either direction makes it run bad.. That checks the float level's not too high or low, that there are no bad air leaks, and that all the jetting is about right. Checking it's responsive in both direction often reveals a problem. And yeah, stale fuel is something to watch for.. We generally do suggest stale fuel if it sounds like the bikes been parked up for a while.. Good work changing that...

Ha.. good point Gw.. Quads are for fun, not work.. They were using the quad engine though in this case which isn't designed for that type of work, and doesn't have a governor.. It would be horrible to operate !

#66 Easier for who Rancher ?

You Guys are spoiled by your parts availability ! Over here the selection is limited and expensive.. Good find with the fender.

If you have a timing light put it on and watch to see the spark isn't dying when it gets hot. Check the idle mixture, make sure that turning it either way has the effect it's meant to. Check the fuel flow to and through the carb is sufficient. Undo the drain bung on the carb and make sure it keeps flowing even after the bowl is drained.

Sorry about the slow reply. Been away on a family emergency. In that PDF service manual you posted the relays are numbered in the wiring diagram. That's where I get the numbers, but the index says what their role is. Check the idle mixture screw turns before you go to far on that carb. In my opinion a seized idle screw is a more difficult problem to cure.. The rest will probably be fairly easy to clean up. Not sure about that main jet removal. Is that a plastic housing the main is mounted in ? Never seen that before, perhaps the whole plastic tube slides out then there's a flat to hold the brass or something.. I'm short of time but I'll check the manual if I get a chance.

Probably better to just buy a mid-size tiller and keep the quad to ride around I think. Machinery is designed for a purpose, and designed to the finest detail to ensure they have every thing they need and nothing in excess. A quad bike engine isn't designed for that sort of work and won't have the power needed, nor the cooling capacity.. An industrial engine is designed to run slowly and economically producing power at low revs, and they can keep producing that power for hours at a time without overheating.

Relays 14 and 17 are shown as normally closed. And it's really the cdi unit that's acting like a relay to operate the start solenoid. If either the brake light or the start relay contacts are closed when you push the start button, the cdi provides an earth for the start solenoid. If neither the start relay contacts nor the brake light switch contacts are closed, then the starter solenoid doesn't get it's pull in coil earthed through the cdi unit.

Ah no I figured out the switches, but note the two relays are different.

#48 The few manuals I've bought offline as pdf files have all been as described and good value. I don't have any particular pay site, I just browse their site checking that they don't just advertise the same manual for all models or anything like that, check the details shown in the manual looks right, then trust Visa to have checked the company is reliable. Mostly though I manage to find free manuals.. Not for that bike though. The electrical system is likely similar to several other models, but, because partzilla say the wiring loom only fits your year and model, it must have some odd combination of switches, relays, stator, cdi, regulator. You could mix and match manuals of different models to get the right stator specs and cdi wiring etc, but it would be quicker and safer to get the correct manual. Show us the site where you saw the manual for download and I'll check it out. Also, in one of those earlier simple diagrams it shows two different types of relays. One relay is a normal open type, and the other relay is shown as normal closed type. It may be that the two sets of contacts are in one unit, the manual will have more details. The neutral and forward/reverse switches operation is not logical as shown. I suspect they must have connected poles if they are all in one unit. The manual will explain. If you don't get the right manual, to narrow down which other yamaha models might have similar wiring, you can use partzilla, or check what the cdi has going into and out of it. It's a good idea to start by counting the number of wires and plug shape of the cdi, then looking through several manuals gathering those diagrams up to be cross checked against the start button wiring.. Once you have a few likely looking possible wiring arrangements as diagrams, then it's a good idea to check resistance readings of the stator and pickup coil and look through the manuals seeing what models had those specs.

If that wiring diagram you posted is correct then the cdi is a part of the start circuit..

I'm not sure if it's this Dyneema or not, but some of the ropes that flatten on the drum seem to hold a lot more than would fit with steel.. I think I'd go with steel though...

Good work Rancher.

I just had a look at some yamaha manuals and their routing diagrams aren't the best, but the side notes do describe how to fit the cables, to left or right, under or over things...

I think pay sites for manuals are generally ok. If it says ER I'd believe it. Partzilla tell you what other models a part will fit, babbits doesn't do that. You have the electrical component positions(hopefully correct) but you don't have a routeing diagram for the loom.. that might help. The routing diagram and the electrical component positions should solve most of it, then you start looking at wiring diagrams for pairs or triple wires of the colours you have left over to see what they might be. If the positions or the routing don't seem right/possible then you might need a different manual, but there should be a manual that has that right. That sort of thing gets carried over from year to year for a long time.

The manufacturers service manual, well the japenese ones anyway, always have all the information you need. It's best to read right through the manual familiarising yourself with the sections and what's where. In this case the manual will probably have a diagram showing the main electrical components position on the bike. It will have a routing diagram showing exactly where to route each branch off the main loom. The routing diagrams are often in the form of plans and side views and it takes a while studying them to get the three dimensional view. And there should be a wiring diagram showing wires and plugs. The three different diagrams are likely in different sections of the manual. The real trouble here is that we don't have the exact manual. It should be possible to find a wiring diagram that will have the same components and wire routing, but probably different colours and plugs. I'd refer to partzilla to see what other models the voltage regulator, stator and cdi all interchange with. If there's a model that shares all those parts, then it likely shares the kill and key switch as well, and the wiring diagram will probably work with your bike.

Rancher, you could use the continuity setting on a meter and test from one cut end, to the end of any other wires the same colour, anywhere on the loom. That would give a good idea about what the cut wire's meant to be for.