Mech

I think it's eight mill/five sixteenths. Fuel hose works. Also, some aftermarket carbs don't have the large sized vacuum port on the carb, the brass fitting. The originals had a hole in it about five mills but I've seen aftermarket with a smaller hole, about,,er.. a bit over two mills I think it was from memory.. That didn't work and I swapped brass fittings.

Ha. Yeah well don't let it get to be a compulsion with you... I know a fellah (not mentioning names) that pulls going machines to pieces to get the part he needs to get a broken one going.. just because he can't resists..

If it runs ok when the bowl is full then you need to figure why the bowl isn't staying full.. When the tank is full the fuel will/should flow out the carbs fuel hose if you pull it off.. You should check that happens first. If there is fuel getting to the carb then use the drain bung to check it's flowing through the float needle and into the carb fast enough. If there was no fuel to the carb then check for restrictions or vacuum in the tank. That new pump might restrict the fuel when it's not getting vacuum. To test the fuel pump you lay the fuel hose from the carb into a bottle. Lay it on it's side with the hose laying flat. If the hose is dangling down you won't see the fuel pumping out properly. Then suck hard two or three times on the vacuum hose going to the pump, and then let the vacuum off suddenly. You should see a single slug of fuel come out of the fuel hose. The slug should be full diameter of the hose and about ten mills long. If that works then your pump is ok and will work if it's getting good pulsating vacuum. To test the vacuum you reattach the vacuum hose and start the motor and let it idle. It should pump fuel out of the fuel hose into the bottle at full diameter of the hose and slugs about eight mils long. If that works then the pump is working and it should start and idle at east. Then you need to check the vacuum is still strong enough when the motor is under load. To check that you leave it all as is but sit on the bike, put the brakes on hard, engage first gear and open the throttle until the motor starts straining against the centrifugal clutch. As the motor starts to labour the pump will likely slow down it's delivery of fuel, but it should keep pumping some. If it stops pumping then you have weak vacuum or a malfunctioning pump. The vacuum has to be strong, and pulsating when it gets to the pump. If the vacuum hose has been swapped with some soft thin walled stuff the pulsations can get lost as they suck the vacuum hose flat and then let it out again. Low vacuum can be caused by low compression, tight valves, or air leaks.

Oh ok.. You you need a wreck to strip.. A good condition bike that's blown it's motor big time.. Something like that.. (We should be so lucky !).

I meant that hose and it's fitting are cheap... One is $2 and the other $6 I think it was.

The fuel pump vacuum has to be pulsating. If it's got a steady vacuum then you have a restriction in the hose somewhere or the hose is too thinner walled. If the carb is full of fuel, then it should run. Check the fuel is getting to, and into the carb by undoing the drain screw on the bottom and checking fuel keeps coming out after the bowl has emptied. It should flow by gravity if the tank is full. Then, if you take the fuel hose off the carb and lay it in a bottle it should be pulsing out fuel when it's idling.

There are three things I can think of that would burn out a coil. One is that the coils isn't made for a cdi system, they need to be very low impedance coils. Second is that the earth is bad. Third would be that there is some DC flowing from the cdi unit all the time. That would still take time to burn out the coil though, and I'd expect that to be causing other symptoms such as a drain on the battery and/or the cdi getting hot.

Looks like the genuine is cheap.. https://tinyurl.com/3nu2af64

Good work Gw. That's an unusual setup for a bowl vent.. More water-proof ?

Those plungers I've got out before by soaking and then tapping along the outside of the carby where there's a thin walled bit of aluminium housing the plunger, that works the oil in, and if done enough spreads the bore slightly. Then the best way I've found is to make a small screwdriver that goes in the slot and right to the bottom, but isn't the usual tapered to the end screwdriver shape, but hollow ground to the end so it only contacts deep down in the plunger, only the tip touches, and it touches before the further back parts of the screwdriver tip touches up near the top of the slot.. where it won't bend the very soft material they are made of, or splay the two sides of the slot.. Then working it around (rotating and pulling) you can sometimes get the slot in the plunger to cut away a small amount of burring or corrosion.. If you do decide to drill it out you should get a new plunger first and measure the depth you need to drill to. They have a thinned down inner end which the spring rests upon and if you drill too far the drill hits the spring and cocks things over and makes it difficult.. cant quite remember the details but know it's best to measure and drill to the needed depth and no more.

Yeah, and watch out for the angry men... the ones with a chip on their shoulder.. they're the worst.. Phew...

Fancy arguing with a man that knows nothing... That is stupid..

Basmin.. we've had additives in oil since the mid seventies at least.. They only set the jaso standards in the late eighties. Just because an oil hasn't been given a jaso standard doesn't rule it out from being suitable for a wet clutch. If you found an apple tree out in the wild, would you refuse to eat an apple off it because there wasn't a organic certificate attached to the tree ? The standard/certification is just a nice assurance for people that can't read/comprehend or think for themselves.

Being able to weld is a great thing.. especially in the country.

Tiha, a lot of yamahas feed a voltage into the cdi while the starter is being operated, it's to make them start easier. That wire branches off the starter wire. Some of the models though, instead of branching off from the starter wire have a feed wire from the cdi going to the start button. On those models the cdi notices the voltage drop when the star button is pushed and causes the same easier starting. If your bike needs that second type of cdi with the starter voltage going through it, and you fit one of the other model, or a cdi that doesn't have that power going through it, then you will get a no starter situation. You need to refer to a service manual and check the bikes wiring before buying a cdi for a yamaha.

Valkman... if it runs fine in the wet clutches in your bikes then it will be fine in the wet clutches in your quad... The oil won't be your problem.. Good observation too about the up change prompting the fault.. Do that test I suggest, change donw from a high gear, and then accelerate hard.. If it is definitely bad after an up shift only then it's likely the shift cable.. or linkage wear.

Most manuals for most bikes and machinery say to test everything else, including the wiring, and if nothing else is faulty, change the cdi..

Are you sure they are coils suitable for a cdi system ? Did you check the new coil was good before you fitted it on ? Perhaps you got a dud coil..

You could have a little preview peek using the pull start..

Also... the standard test as set out in the manual, testing first engagement revs, and then full lock-up under load revs, should give a good indication of centrifugal clutch wear.. and allow us to deduce if the plates are the culprit.. sometimes.. maybe.. haha If the first engagement revs are right, then the centrifugal clutch shoes are not very worn, and so if we get slippage at and beyond full lockup revs, then we are likely seeing plate slippage. If it's late to start moving at the start of engagement revs though, then we can assume the centrifugal shoes are worn, and if we then get slippage at full lockup and beyond revs it might well be the centrifugal clutch.. but it might be both clutches worn.. The only way to be sure we are replacing the correct clutch is by stripping them and measuring and inspecting..

Actually, there's a better way to test your clutch.. The first bit of movement of the shift lever operates the clutch, and then the gears move. If you change down a gear and keep your toe on the lever you will be holding the clutch in, and if you then let the bike roll down to a lower speed and then rev the engine before letting your toe up, that plate clutch is going to get dropped with the engine revving and it should try to rocket you forwards. If the slippage is caused by a worn out clutch then dumping the clutch like that is going to make it slip badly. If the clutch is good still, and it's only the non-self centering that's the problem , then dumping the clutch like that after a down shift will hopefully make the clutch grab and rocket you forwards as it should. You could try the same technique on a down and an up shift and compare the results to try and decide whether it's a worn clutch, bad linkages, or a bit of both.

Ok, if it's made worse by shifting up but not down then it sort of points to the plate clutch. The shift lever has some linkages that operate the plate clutch. The clutch gets operated before the gears begin to shift, so the first bit of lever movement up or down is only operating the clutch.. If an up shift causes the clutch to slip, but after a downshift the clutch feels fine again, even if you are accelerating in that lower gear after a shift, then I'd say your lever, or the linkages, aren't coming right back to center after an up shift, so the clutch is being held slightly on(slipping). I'd disconnect the shift cable at the box and check it's free and then I'd feel by hand whether the shift lever on the side of the box seems to self center fully after an up shift... Then, if you are sure the upshift is making it bad, and the downshift fixes it(test it by doing a downshift from fifth to forth and then accelerating hard), I'd inspect the internal linkages operating the clutch.. as I was inspecting the plate clutch.

The book I looked in shows the cam cover breather going to the airbox front upper left.

Doh... forgot we were talking yamaha.. haha.. I have no idea where yamaha breathers run.. But the book will tell you.

You'd be best to download the service manual and have a look. The manuals tell us exactly where to route the hoses and cables and wiring.. The engine breather is often connected to the airbox breather, and they both have a branch that runs up and around the range selector panel and then ends in two open hoses up there. And that splined thing on the carby there.. are you sure it's not some sort of sintered metal and actually a breather..