Mech

Also Mga, it's always worth looikng up the parts online, then seeing what other models they fit, because often the other model uses a different part number, and sometimes that other part number is available. They change the numbers if it's a superseded part, or got a different colored paint or any number of trivial things..

I don't know whether it applies to yamahas but some makes and models have different suspension arms in different years, some are longer to make the bike wider. It's something to watch out for if buying second hand parts.

Undo the carb drain bung and make sure the fuel is getting right through the carb. Just because it's getting to the carb doesn't necessarily mean it's getting into the carb. Have you tried a new spark plug. It could be as simple as that. And what about this question ... "So bogs and then just stays the same, struggling to go faster ? Or does it start dying out.. Actually get slower." "

Inside the guts of it there's a centrifugal clutch which is used at takeoff, and another clutch, a multi plate clutch, that's operated off the gear shift mechanism. The multi plate's there so when you change gears at a rev above the centrifugal clutches lock up speed, the gears don't graunch or be hard to slip in and out. The shift mechanism slips the clutch before the gear's start to move in or out of gear. That clutch operating is probably that "mushy" feel you detected (just an incidental bit of info). You should check the adjustment of that multi plate clutch. It's on the right behind the rear wheel, behind a bung. If it's not slipping enough they are hard to shift. The real secret to good changes though is in A: getting the torque load off the gears at the instant you move the lever, and B: synchronizing the speeds of the gears. The process when changing up is , give it a little extra throttle(more than you had been) just before the lever gets moved, so the bike is accelerating, then throttle off just as you move the lever. That way the bike and the engine are both under a sort of float condition, both are neither accelerating or decelerating. The process when changing down is throttle off till the revs are low enough to change down, then blip the throttle just at the instant you are moving the lever down a gear. The throttling on takes the load off the gears you are in, and then brings the revs on the lower gear shaft up to the speed of the other shaft and gears. Depending how fast you are going at the time and the gears being shifted you sometimes need to give it quite a rev, but at low speeds just a little rev.

Onya.. Cheers.

Put it in two wheel drive, high ratio, and try rotating the rear wheels.. While you have it up.

So bogs and then just stays the same, struggling to go faster ? Or does it start dying out.. Actually get slower. Have you checked the fuel is coming right to and through the carb fast enough. You could open the drain bung on the carb and make sure it keeps flowing after the bowl has drained. Have you checked the exhaust isn't blocked..

Parham.. the idle jet(inside the carb) may need cleaning, or the mixture might need adjusting. You should try adjusting the idle mixture screw and see if that cures it. If the adjustment screw doesn't seem to make any difference, or if you have to wind it more than about one turn in either direction to get it adjusted right, it's a sign the jet is dirty.

Well the gearboxes are pretty robust and it's not very likely to have a fault/damage with the gears if you haven't notices any sign of metal in the oil. That's why I suggested you look in the oil filter. It's very likely that it just needs the two gearbox shafts to be rotated so the gear it's in(second), isn't under any load on the teeth when you try to move up, because that is required so it will come out of that second gear. Then as the shift lever moves further after moving out of second it needs to have the third gears lined up so they can slip together. To achieve both those two things you need to keep rocking or rotating the rear wheels I'm thinking. When we are riding the alignment part mostly works itself out, but it's always a good idea with any bike, two or four wheeled, to accelerate slightly and then throttle off smartly just as you change up. That takes the load off the gear you are in and lets it slip out of gear easily. If we don't use that technique, and especially when the clutch isn't adjusted or operating correctly, then we can get the problem you are describing. This I suspect is where your problem lays. But... Inside the gearbox there is a ratcheting mechanism that notches around to select each consecutive gear. If that works in first and second then that should work in the higher gears too. There is one exception though, and that's why I asked you how the lever feels, how far it's traveling when it won't engage third. You haven't told me that yet.

The book I have says you have to pull the motor out and take off a side cover.. but it's not the exact model as you are looking at..

There's a service manual in the manuals section of this site.. it will tell you.

No the cable should be ok where it is. I'm trying to figure whether it's a problem with the shift mechanism, or inside the gearbox, or no problem at all. Did you jack the back wheels up and try as I suggested ? Have you tried driving it at a proper speed for those higher gears while you are changing it ? And were you using the throttle to "unload" the torque on the gears as you shifted the lever ? They are a long travel shifter and always a bit heavy and clunky. Gearboxes also don't shift if the gears have a load on them as you try to shift, or if the gears aren't rotating enough to allow them to slide together. Have you ridden bikes before ? Was it two wheelers or four ? And are you familiar with the technique for doing clutchless changes on a two wheeler ? It'd be a shame to pull the side case off if there's nothing wrong, let alone pulling the whole engine out and stripping it only to find it's technique that was the problem. You could try pulling the oil filter out and seeing if there are signs of gear damage.. metal in the oil.. flakes or chunks of metal..

Ok, I'll presume then that the lever only moves a short distance when the problem is happening. It gets a full travel for first and second, and then after that it only moves half the distance ? If it's traveling full distance but not changing then it will be a different issue. It probably just needs to have the output shaft turned more to align the higher gears. Try jacking the back end up and turning the rear wheels as you try changing. You might have to rotate the wheel several turns before it will change up into each consecutive gear. Try turning, and turning backwards. It's pretty much standard for a stationary bike to need rocking to shift gears, and they need rocking further for the higher gears.

Were you riding it when you were trying to change gears. If not, was the motor running at the time, and were you rocking the bike back and forwards as you tried to move the lever ? How did the lever feel, did it move but not change the gears, or did it just move a small distance and then come up solid ?

And I just looked in the wiring diagram and see that in the early 2004 model that 8 brown wire actually goes to the diagnostic plugs earth, where it branches, and the other wire goes to the high beam light where it branches again, and then from there it goes to an earth described as C. If the high beam light works brightly then you can forget the earth C.. it will be in the speedo end, or where it crimps into the diagnostic plug terminal or the high beam light terminal. And, if it's a late 2004 the 8 brown goes from the speedo straight to the high beam light and then to earth C. It doesn't go to the diagnostic plug first..

Well wires mostly give trouble where they end in their metal terminals. Sometimes they get corrosion, and sometimes they break the wire inside the insulation. You could try flexing that 8 brown wire and see if it will make a better contact, and you should look in the back of the plug at the wire, and look for any sign of green verdigris where it goes into the terminal. Other than that, locate the places the wiring goes to an earth and do the same checks at each of them.

Some of the fan's have a water drain hose, I've filed them up with wd40 through that hose before to shut them up. Most service manuals tell you exactly what model carb the bike should have.. It will be in a table of specs about the jet sizes and settings. You should use the drain bung I'd think.. though I don't know yammies. I think to get the new carb spring in you will have to take the butterfly shaft out.. it's got screws holding it that are splayed out at their ends so they can't come loose. If you try and wind them out it will bugger the threads in the shaft. Try to grind/file the ends back or pinch them into shape before removing, and it's best to have new screws to go back in.. and do re-munt the ends after they are in..

Score !! That'll keep you amused for a while..

Hey. My wife died and left me with two very young sons and a house to finish and land to tend and a workshop to run.. If I ever thought she kept me to it (which I didn't), I soon learn just what an asset a good wife is.. Be thankful.

Yeah, power and earth are the first things.. Process is key and stop switch on, does the gauge work, if not check there is 12v between pins 1 and eight, and between 2 and 8. If there is 12 volt there, replace gauge, if there isn't power to those plug terminals then check the wiring. 1. Red-- 12V Ignition Switch 2. Red/White-- 12V ETC and AWD Switch 3. Grey/Orange-- Mode/Override button 4. Black-- Ignition Kill 5. Green-- Diagnostic (Factory Use Only) 6. Blue-- Diagnostic (Factory Use Only) 7. Yellow/Red-- RPM Input 8. Brown-- Ground 9. Blue White-- Engine Overheat Switch 10. N/C 11. N/C 12. Purple/White-- Fuel Sender (if equipped) 13. Brown/Red-- Trans Switch Ground 14. White-- Gear Shift Signal 15. N/C 16. Brown/White-- AWD Coil Yes on the plug on the back of the gauge. It doesn't matter if it's plugged in or not.

cheers.. Have fun.

Most yamaha seem to have a lot of wires going into their cdi.. Perhaps just drape the wiring over the bike and connect it up and see what you find.... If it's a wiring problem it should be easy to find, it's either going to be a short, which needs chafed or melted wires and so can be seen, or a broken wire, which mostly happen at the ends of the wires where they connect.. or occasionaly up near the steering head. The steering head breaks are the hard ones to find..

I'm on hilly country too Geezer and I've never found quads to be top heavy. I avoid going around the sides of hills though, but I go up and down some really steep hills. If you've driven a tractor places, the quad will feel way safer. I've driven quite a few yamaha, suzuki, and honda quads and my favorites are the suzukis. They have firm suspension, though not the best design, and a really heavy and low motor/gearbox. Suzukis also have the best ratios for steep land. They have standard, low and super low ratios, with a five speed box, which is excellent on steep land. The low ratio gives you close ratios and extra torque in the same way as four wheel trucks in low ratio. The lowest gear and ratio is such a crawler that you could literally get off and crawl faster.. haha.

I couldn't find a manual for your exact model which I think is a ymf450fas or fahs. I had a look at the parts though and there is no relay shown, just a thermal/bimetal circuit breaker before the sensor/switch.. That must be going ok if bypassing the sensor makes the fan go. So far it's looking like either the sensor is defective even though it passes the test, or, the engine is not getting too hot, or not too hot where the sensor is anyway.

First thing is.. did you change the thermostat in the end, and/or, are you sure the thermostat is opening ? The other thing is, if the fan's not coming on, why do you think it's getting too hot ? Perhaps it's not.. Have you tried reading the temp right close to the sensor to ascertain if it is actually getting hot enough to turn the fan on. Where the fan switch is may not be the same place as a temp gauge sensor, or where you may be measuring the temp. The bike's temp gauge(if it has one), may be reading wrong. Not sure if there is a relay but I'll have a look. If bridging the temp sensor makes the fan come on though then it doesn't seem likely the relay(if it has one) would be playing up. The temp sensor may have dirty contacts so that even though it shows as having closed with an ohm gauge, there might not be a good enough contact in there to run the fan. You could disconnect the wire at the fan and check it doesn't have power cold, then use a test light on there until the sensor switches on and check there's enough power coming through to run the light. A headlight bulb would be a better test than a tiny test light bulb. The other simple cure to the problem is to rig up a handlebar switch to turn on the fan.