Mech

If you can give us the colours of the wires on the stator Jim it might help identify the system.  I have several wiring diagrams from those makes I suggested you look at, three of which are for Kazuma, and all of those generic engines use the same or similar wiring diagrams and stators, but they use different coloured wires.

Not getting at you in particular Beast, but for everyone reading through the thread...

Service manuals, well the Jap ones anyway, are very well written, and tell us everything we need to know. Sometimes though we need to read right through them to garner the information we are after. Sometimes the information is mentioned in conjuncture with some other aspect of the bike. This is especially so with the diagnosis of fuel injection, electronic and  and transmission diagnosis.

The manuals are written for trained mechanics, and trained specifically on the make the manual relates to. The information we need as mechanics is always there somewhere though.

It's always a good idea to read right through the manual from cover to cover familiarising yourself with how it's layed out and what is in there.. before starting to read any particular part that relates to what we are working on.

Reading through the manual I see they use a "breather chamber", which is presumably in behind or made up of that outer case. In most engines there is some sort of chamber to separate out the air from the oil as it breathes, and in most bikes that separation chamber is cast inside and a part of the crankcases and does have a spigot on the case for the hose to fit onto. In this case I think the hose is just meant to be a good fit into the case. The hole it goes into must be sealed and in communication with, or is, the "breather chamber".

In the manual it's described in the emission control section...

"1. Crankcase Emission Control System
A sealed-type crankcase emission control system is used to eliminate blow-by gases. The blow
-by gases are led to the breather chamber through the crankcase. Then, it is led to the air cleaner.
Oil is separated from the gases while passing through the inside of the breather chamber from
the crankcase, and then returned back to the bottom of crankcase.".

if there's no tube to the airbox to let air in if you drove into water, then the two dangling down tubes would suck water up when you drove into deep water with a hot engine. I'd run one of the hoses to the airbox.

It is quite common to have a rubber lipped end in breather hoses to let air out but stop water getting in.

What colour are the wires down at the engine ?

And it appears that there are only Europe and Ociania versions, so that narrows things down a lot.

The carbs change between 2005 and 2006. And the headlight bulb changes between 2004 1nd 2006, so take nothing for granted..

I found a BAV owners manual which I've just put into the owner manuals section.. It'll appear after it's been approved.

There's not much helpful in it but it might be handy.

Well you really need to identify the engine first. That looks like it could be a copy of a minarelli engine that's commonly used by a lot of Chinese and Taiwanese bike makers. You could start looking at bikes made by Kayo, Kazuma, Kymco, Lifan, Linhai, and Taotao.

Once you identify the engine the wiring may not be the same colours but with a bit of figuring it should be possible to match it up.

I gotta say though that you need a better front wheel. The spokes in that aren't going to be strong enough, and the wheel bearings aren't good enough for that use either.

Do you have the service manual and have you been tracing the power through the wires as it shows them ? Are you using a test light or a gauge, because a gauge will show power even when it's going through a dirty connection that's not letting enough power through to run anything. You need to test with a light, or do what's known as a "voltage drop test" with a gauge, and it has to be done with the circuit you are testing under a load.

I'd start at the key/main switch and check there's power to there and going through it, and it may be that it has two seperate switching movements in there, and on some models one earths to kill the ignition and one turns the power on, and in others they both turn on separate powers. Then I'd check that relay Gw's mentioning, and then I'd check the starter solenoid.

The mechanical parts and procedures are all pretty much the same through model runs as far as working on them goes, but you do need the model designation or to know exactly what you have for ordering parts. The carbs and electricals in particular are very model/market/year specific.

So you are sure it's a 2006 ? You figured that from the vin number ?

And are you in America ? They have Europe, Canadian or American and Oceania versions. And if it's American it's possible it will be Californian or general. All things to consider when ordering parts or looking at the carbs or electrics.

I just checked in a bayou manual that covers that year and it does have the routing diagrams in the appendix section.

It doesn't show any hose going to the crankcase though, only from the head to the airbox, and in some years a branched hose going from the head to airbox with the branched hose capped off. That capped hose is for draining water out almost certainly and it will dangle down behind the engine.

If your bike has a breather off the head, and another breather on the crankcase they are probably both meant to be joined and connected to the airbox. That's almost always how quads are. There shouldn't be any open hoses that could suck water in. If there's a hose going nowhere, it's a drain hose and will either have a rubber lipped end that lets pressure out but stops water going in, or it will have a removable cap for routine draining.

Good point Gw.

We really need the model designation too though, or an engine or frame number. The frame number will be on the lower left frame tube near the foot peg, and the model designation should hopefully be on a sticker on the top frame tube near the back of the tank I think they are.

A quick look in the parts shows that the headlight bulb changes between 2004 and 2006. The later appears to be a halogen bulb.

If you look in the partzilla or babbits atv parts online it will show you all the models availiable with suffixes. If you browse through looking at various parts for various years you might be able to narrow it down to which exact model you have. Good parts to look at are body colours, carbs, cdi if you can get a number off it.. but just about anything can change.. handlebars even are sometimes higher or lower. 

Have a look at the suffixes. B indicates 2WD and F is for 4WD. S is for 2004, T is for 2005 and V is for 2006.

FAS is a 4WD 2004, and BAS is 2WD 2004. A 2006 would be FAV or BAV

The S on the end indicates it's a 2004 model. Are you sure that's the right suffix, and/or year ? It could also be BAS.. The B indicates 2WD,

Do you have a frame or engine number ?

You may be right about that designation, being as you are in Europe, the models do vary from place to place, but that  makes it all the more important to get the correct service manual.

Gw knows yamaha better than I do.. Perhaps he will have some insights.

Most service manuals have a section where they show exactly where the wires, control cables and hoses get routed and attached. In some yamaha manuals it's in the appendices section.

It sounds like there might be several problems. If you wind the idle speed screw right out, and make sure there is play in the throttle cable so the butterfly is closed, then it shouldn't rev. Get it to run slow first, then find out why it's backfiring. If it won't slow down even with the butterfly closed off check the choke is right in and that there aren't air leaks around that new rubber inlet manifold. Some manifolds have a gasket or an O ring between the manifold and the head. It's been known to happen that the O ring gets dropped out during installation.

There are two types of backfire, one out the carb, and one in the exhaust.

This is the manual the supplement is to.. If you are sure about the year, then that's what you need. If you give us the frame number or model designation I can check it for you.

If you tell us what year it is I might be able to find the main manual.

Did you read what the supplement is to ? It's possibly a supplement to cover some particular model, or some later year.

The bike's model will start off as YFM350 then there will be a suffix of two or three letters. If you have the suffix let us know that as well.

Yup. Gw's a treasure..

Oh yeah, so you did. I must have been reading the post name but missed it in the post.

Well you know, it's a bit weird for all those different systems to all fail at once because of the ecu. Ecu use different circuits internally for the different actuators and sensors.

Does that thing have trouble codes you can read out ? Have you checked for any codes ?

If there are no codes it's likely that one of the several power feeds or earths for the ecu have failed. That's far more likely than the ecu has failed several circuits internally.. unless of course the battery had been connected backwards, or something unplugged while it was on or running. If it just failed in service, or refused to start one day when nothing had been done to the bike likely to cause all those problems, then I'd be checking every earth and every power supply.

Do you have the service manual ?

Do you have a part number ? That's the first thing I'd try to get, then enter that into google.

You should mention the year as well if you want us to try and look one up for you.

And.. are you sure your ecu is buggered ? They are normally hard to diagnose. The usual advice is to eliminate every other possible cause for the problem you are having, and when every other suspected possibility is tested and eliminated, to assume it's the ecu. Have you tested every other possible cause of your problem ? Ecu are normally very reliable, and expensive.

Welcome along, this is a good site. I'm sure you will find it helpful.

Something to be aware of is that it's primarily an American site, and the models vary from country to country, so you need to make sure you are looking at the exact right model when reading the service manuals or ordering parts. This is particularly so with the electrical systems, carbs and body parts. Most of the mechanical parts are pretty standard.

The site has a good selection of service manuals but if it doesn't seem to have your model let us know and we can try to find one for the collection.

Whoo. Score. Patience is a virtue.. As my gran used to say.