davefrombc

If the motor will rev up ok , I'd suggest blocking the quad up with back wheels off the ground.. Make sure it can't fall off the blocking and can't move. With the cover off the CVT so you can see what's happening , rev the motor up and watch the clutches.. The motor clutch should close until the belt is at the top of the groove and the driven should open until the belt is almost down to the bottom. . Without a load on the tires , it may not open all the way since opening and closing of the clutches is determined by the load on the system as well l as the RPM. The motor should rev well over 3500... should go to around 6000 - 8000. Have you also checked to be sure you don't have a brake dragging ? The tires should turn fairly easily when off the ground. There will be some resistance from the drive train , but it should not be difficult to turn the tires

My guesses ....Bad ground, neutral switch or relay, wonky ignition switch.

The symptoms you describe all point to fuel problems , and a stcking float needle valve is the most likely culprit .

That sounds like the float or needle valve in the float bowl is sticking and not letting the fuel into the float bowl. . You might als try disconecting the fuel line and asee if fuel flows freely from it .. There could be an obstruction in the line or fuel petcock.

A lot more information is needed before anyone can begin to try to help you . There is a download of the service manual for the 400ex in the forum's archives .. Go to Browse at the top then click downloads and click through to the Honda section service manuals. If the motor turns over , check the spark plug for spark and the carb is getting fuel. If it doesn't turn over, then check battery, fuses and neutral switch for starters.. Then use the service manual as a guide to check other components .

I wouldn't think they'd interfere with the spark.. They are part of the charging circuit.. The pickup coil uses voltage produced in the stator to send a pulse to the CDI at the proper point in the cycle to fire the spark plug. The stator is producing a constant 3 phase ac voltage the regulator / rectifier changes to the 12v DC for the charging system .

Here is the link to download the yfm 250xl 1998 service manual .. Your 2000 250cc motor most likely has the same stator and pickup coil.

Did you check the pickup coil that works with the stator to produce the pulses necessary for the spark?. .The stator not only produces the voltage pulse the pickup coil uses for the spark circuit , but also the voltage for charging the battery. The stator and /or the pickup could be bad and still produce some voltage.

Sounds to me like either there is still some blockage in the fuel passages of the carb making it run lean without the choke on, or possibly the throttle slide needle is set wrong .. This video on rebuilding the carb might help:

Check that the quad is in neutral for certain. From that point it is a case of trouble shooting the wiring . You can download the service manual for that quad here: Page 327 has the wiring diagram for the starting system

I also came up with Bayou 185 searching on that info. Lots of hits on sites offering parts for it.

I looked at the title of the request and realized it was actually an mz 100 you needed info on ...Searching on that didn't bring much of help up. Seems it was a Chinese quad imported into Europe by a German company .. Searching on it brought up a forum where someone stated it was a licensed copy of a Jehm Blazer. Searching on that, I found there are some US dealers in them and parts.. You may be able to get more info from one of them. I hope this helps and you're able to get the little mz running .

Searching on mx 100 ATV and muz mx100 ATV brings up references to Yamaha mx100.. That is quite possibly the quad you have.. Try searching on that and see if it is the same quad you're working on .

Then all is working as it should.. The fan won't cut off unless the engine cools below the temperature sensor switch turn on point and the switch opens.. You could just wire in a switch to disconnect the fan switch. I wouldn't recommend it though. Kawasaki had a reason to set it up that way , and if you wire in a switch to disconnect the fan switch it is too easy to forget to turn it back on when you want to run the quad and end up overheating it. You could wire in a master disconnect between the battery and the wire to the ignition to disconnect all power so nothing will be powered with it off; but as long as your battery is good it won't hurt anything to let the fan run until the engine cools to the point the fan switch opens and the fan turns off on its own... It easily could take a half hour or more on a hot day. but the fan motor shouldn't draw a lot of current and deplete the battery. I would be inclined to just wire in a battery disconnect. Not only does it ensure there are no powered circuits when it is opened, but it also slows down a thief who just tries to hotwire the ignition . It won't stop determined thieves who knows to look for a disconnect , but it does slow them down and could be just the delay needed to make them look elsewhere.

Something you could try with a cold engine. Try jumping across the temperature sensor to turn on the fan and see if it still stays latched on when you disconnect the jumper.. Don't disconnect the temperature switch, just jumper across it.

What I was saying in the last paragraph is that if there is a hot wire to the fan when ignition is on or off, and the temperature switch switches the ground side of the fan wires then a spurious ground would keep it running....From what you say , once the fan is turned on by the temperature switch then it stays on until the coolant cools to the point the switch opens whether the key is on or not. It sounds odd to me, but that may be the way it is designed and there is nothing wrong. I have no idea if that is the way with your machine , but I know in the automotive world that is the way some electric fans work and also some oil pumps for turbo charger coolers. My reference to "Fun" was really meant to refer to the frustration that is far too common trying to trace down electrical faults... It certainly isn't enjoyable .

The thermostat shouldn't cause the fan motor to keep running ..unless there is an electrical connection to it. The temperature sensor should only trigger a relay to start the fan. Whether it also shuts it down when the temperature drops is the question. The fan breaker is likely just there to act as a resetable fuse, it could be integrated with the fan switch, but I don't know.. I would say the fan motor relay is the same as the fan switch; just different wording for the same item in different publications. Does the fan shut off when you turn the ignition off, and not start from cold until the coolant reaches operating temperature? One thing I noticed in the wiring diagram I saw for the 750 is the fan motor shares a common connection to another sensor , I forget which it was , an air temperature one I believe. I wonder if those switches are wired so that the positive wire to the relays is hot and they are switched by the ground side , and a faulty ground in the circuit is causing them to trigger.. Where I get all the questions from is your statement the fan shuts down if you disconnect the temperature sensor. The problem you have with the fan has to be something in the circuit it is part of. Either something staying latch on, or maybe as I a faulty ground in that circuit i=or one connected with it . Isn't tracing electrical problems just a whole lot of " fun" ? More than one person has had a balding problem because of them.

Check the shop manuals posted for the Brute Force 750.. The wiring is most likely very much the same for the 650. Here is the link to download the 2008 manual for the 750 in the forum's downloads section ( Mouse over Browse and click Downloads to find the lists of all the manuals and information there) :

I would contact Yamaha and ask them for assistance ... Since your d number is so low , my guess would be it could be 124.33 , and the crankcase number 12 (.12) Please don't take those guesses as accurate .. It is merely speculation on my part. Hopefully you can get a response from Yamaha to help you . Here is their contact page for Yamaha Canada . https://www.yamaha-motor.ca/our_company/contact_us.php

According to what I could find the AC motor is actually built by Kymco. The 366 has an 81 mm (3.188") bore. This L.A. outfit sells a sleeve kit for them. . I couldn't find any mention of oversize pistons, so it may be sleeving the bore and new stock piston is the only way to go. https://www.lasleeve.com/downloads/2013-Catalog-ATV-Section.pdf

Did you also change the oil and filter?.. Water vapor could be coming from water in the oil boiling off and entering the intake through the breather tube for the crankcase. Try adjusting the idle air screw and or the needle valve settings. Bogging on acceleration sounds like it isn't getting enough fuel (running lean) when you open the throttle.

The problem could be in the stator or the pick up coil. The regulator shouldn't have had anything to do with the lack of spark.

That sounds more logical to me .

Water pump can't run if the motor isn't running unless it is electric, and fan shouldn't run unless the water temperature is over it's turn on point.. If you haven't changed the relay, that's what I'd suspect the most. If it has an unswitched hot wire then it could be feeding the power to the sense side of it and keeping it on. Something in the fan circuit is getting power with the ignition off. The water pump runs with the motor. The fan should only run when the motor reaches it's turn on temperature. You changed the temperature sensor, so most likely culprit is the relay itself. I can't see an electric water pump or any other circuit feeding the fan. Have you disconnected both the hot and ground jumper wires you installed ? Your extra ground wire could be the problem if for some reason the relay in that circuit switches the ground rather than the hot wire .. I'm only giving you stabs in the dark since I don't have an electrical schematic of your circuit to make guesses from.

Let us know when you find the problem.. I never thought to mention it before, but it might be the relay itself at fault.