Mech

A blocked fuel filter or low fuel pressure could cause a lean mixture. Only at set speeds is probably significant.. I thought we'd sorted the model and got the right manual.. So what have you noticed about the bike that isn't as the manual says ?

Here's some examples.. not very relevant but.. http://www.autoshop101.com/autoshop15.html

That's all very interesting and fine Randy, but no carby is junk by default.. Just wrong for the bike or badly tuned/setup. Perhaps your mates, and all those people that could never get jetting right, didn't know how things worked, or what they were doing. Perhaps they were fitting carbies that were inappropriate for the bike. If you work at a dealer, they often send people away for training, training provided by the manufacturer. At those courses they provide things called "technical training manuals", which explain in great detail how every component/system works, then how the components/systems work on any machine in combination with the other components you may find on various models in their lineup, then often an explanation of them all working together on some specific model as an example. If you want to know how things work Randy, or anyone else, get hold of some "technical training manuals". They are out there... They have them for things like electrical systems, electronics, fuel injection, carbys, transmissions, a specific engine design or engine design in general, chassis, body repair.. anything about automotive machinery. It doesn't matter if the training manual you get is for some other make,(even a car one), the principles are all the same, they are just combined in different ways that the various manufacturers prefer to use. If we know how the components work, and interact, we can figure any makes running gear out. If we know what all the systems in a carby are, and how they interact, and then follow the recommended procedure/order of operations, we can tune any carb to a vehicle as long as it's an appropriate size for the engine and requirements. Carbies, even the most complicated ones, are really very simple bits of technology, using very simple principles. All the circuits in them overlap in operation and there is always more than one way to overcome any particular problem.. But we need to choose the correct change or we make things worse. hence following the correct process/procedure.

Some more thoughts, for those that are having problems... One thing that does get put together wrong is.. the slide needle has nearly always got a washer/spacer above and below the clip, and sometimes those spacers, especially plastic ones, can be different thickness, by up to about one mill. The manuals hardly ever explain which is which. One mill can be adjusted with the c clip on the needle, but it's always better to check/try which way the spacers are if the needle seem to be set wrong. Needles do get bent, and that can cause rough running at certain speeds. I've replaced needles for that reason. Slides wear, but I've got plenty of bikes running fine with really worn slides. Slide needles wear slightly after a long time, but I've got bikes running fine, with wear on the needle that could be seen with the naked eye. Jets, they say they wear, but we can buy jet measuring tools, which I've used, and the wear is minute even after a lot of use. To all intents and purposes, jets don't wear. Hope that's useful..

Often, a model of bike comes out with the same carby model, but with different specs, (and part number), which have different jets, slide, needle etc.. The details are found in the supplement section of the manual. Almost any of the variations will run pretty well on any of the year/version of bike they were made for, as long as everything in the carby is a matched set, as designed by the manufacturer and spelled out in the supplement section. Start thinking you can improve on their design work, and mixing and changing things, is not a good idea.

Ha.. In all my years I've never needed to modify a slide, or needle.. But, we are all at low altitude and a small market, so we don't have many variables. I have tuned bikes for competition though, and made up carbies and tuned them, worn parts and all. I'd recommend getting the manual for your bike, checking you have the correct carb, that all of it's jets and settings are right for that carb for that market, and then tune it as the manufacturer recommend.. which is the way I've been recommending. If it's not the correct carby for your bike, get a manual that has the specs for that carby, exactly that carby, for the market the carby was intended for, with the slide and needle it has, and then check/change jets from there till it's running right.

Randy.. I'm just not interested in you, or the problems you have.. I'm here for people that want advice and help.

I'm a mechanic Randy, trained and educated in these things, with fifty plus years of bike owning, riding, and repairing, working on bikes from every continent and models from the forties onwards. I've repaired, restored, modified and customized hundreds of bikes for a living.. Nightmares, days and weeks struggling to tune it... These are not problems I have..

Ok... I'm not familiar with the model. It's always the recommended thing to check or do a standard tune before trying to find defects. That would include the fuel filter and any vacuum hoses if the bike has emission control components, such as a vapour trap canister. A tight valve clearance could cause that, so could a defective or incorrectly adjusted sparkplug, or a lean mixture. Those, apart from the sparkplug though, will be temp related.. they probably won't be the problem from cold. They used to say on older models that as part of the standard tune and service that you should take a bung out at the back of the muffler and run the bike to drain any accumulated gunge.. I've tried it heaps of times and never got anything out, but they seem to think the mufflers block.. A blocked muffler could cause your symptoms, and it might be why the muffler's leaking.. A leak at the muffler won't cause the miss, but it perhaps it would be worth checking the exhaust isn't blocked. I'd check all those things first, then start looking for electrical/electronic problems.. Your observations have been good so far. It's useful, vital even, to note the symptoms in as much detail as possible, and also the circumstances such as throttle positions, temp, load, time running, rough ground, rain.. anything we notice that seems to consistently causes the problem because they are often the thing that helps diagnose the problem, and, then we can repeat the conditions after the work to be sure we have fixed it.

Haha.. Brain fart.. you are right Randy.. About the cutaway..

But but but... neither myself or any of the carby manufacturers think it is a good idea !! But what would we know... We all even think the slide has the cutaway on the other side.. Foolish us.. You're so smart Randy, you should run for President..

My previous design Bender was a bit simpler. It was like that tool I've shown above, but without the belt of outer pulley. It was used by holding and engaging the screwdriver with one hand, then reaching in with one finger and pressing on the gear hard enough to turn the screwdriver by the gear.. Yes I know Randy, you've already told me you come here because you enjoy arguing.. Which is why I've refrained for so long from responding. I'm familiar with the problems with old bikes, and carburetors. I'll leave it to the readers to make up their own minds how to do things.

The valve clearances have a bit of a habit of getting out of spec after their first adjustment after a stripdown. I'd recheck them. Sparkplug gap can effect idle too. Then the symptoms, if it's only the idle that's playing up, and it runs ok otherwise, sound like fuel problems. I'd be trying to adjust the idle mixture, which will either cure the bad idle, or reveal a blocked/faulty idle system. Probably requiring a clean and inspection. I'd very much doubt the cdi is the problem.

Is it a carby or fuel injected motor ? I know what a miss is, but what is a cough ? Do you mean it spits back out the intake ? I doubt the exhaust is your problem.

Nice quad in the profile pic there Bellarmine. I agree about the cdi, they rarely give problems.. the unit itself mostly go, or die. The fuel system gives more running problems. The charging is a common cause of bad running though too though.

Both ways have the right mixture at idle, but my way, as the throttle is opened the mixture gets richer, your way Randy, it gets leaner as the throttle gets opened.. And, just for the record.. It's not just my way, it's the way the carby was designed, and jetted, to operate.

Yeah well the reason you have that problem Randy is because the way you do it, you are using both the idle discharge holes as one. There are two discharge holes into the venturi right by the butterfly, one on the engine side and one on the aircleaner side of the butterfly, when it's closed properly. When the butterfly is closed off the idle mixture is supposed to come up from the adjustment needle and get sucked out the hole nearest the engine, but, the mixture is getting diluted by an extra measure of air getting drawn in through the second hole, the one away from the engine. Because of that extra air, we end up adjusting the idle mixture slightly richer to get it right. As the butterfly starts to open, the second hole starts to have vacuum applied to it and it starts discharging fuel as well, and, at the same time, the first hole doesn't get extra air anymore.That second hole discharging combined with the now undiluted mixture out the first hole is what stops the flat spot you have when you adjust it your way. The way you do it Randy, you have both holes discharging fuel at idle, and because of that, you have the idle mixture screw wound in more than it should be. It gives the right mixture at idle, but when the butterfly opens there is a shortage of fuel.. it's being restricted by the idle screw. If we want our bikes to run right, it's important to set the idle mixture with the least possible amount of throttle opening. Once the idle mixture is right, at a slow idle, we can wind the speed up a little if we want.. but don't start adjusting the mixture again or you will start going around in a vicious circle of mixture/speed/mixture/speed, which will lead to the symptom Randy describes.. a flat spot.

If the other end of the boot you have is right is right, then that 4KB might be the one. Looking at pictures I see some boots look like the big end is closer to the small end diameter than other boots.. The 2HR looks like it's big end is quite a bit bigger than it's small end diameter. The 4Kb the two ends look similar. Probably easiest to ask them what the diameter is before you buy though to be sure.

Looking around I see there are two numbers listed... 4KB-22189-00-00 2HR-22189-00-00 The 2HR seems to be the commonest..

Yes screwing it out makes the idle richer. They are mongrols to adjust alright. I made a tool to do it.. there's a picture in here somewhere. Probably a bit much trouble for occasional use, but the recommended settings is just a starting point really.they do run nicer with the mixture fine tuned. https://www.quadcrazy.com/atvforum/topic/16053-carby-adjusting/

If you tell us how many seconds, with what amount of throttle, we can probably guess where a fuel blockage would be. Best if you time it with about a quarter throttle, and then again at about three-quarter throttle.. Ha.. ok.. you were too quick for me. Well done on the repair.

Could be a blocked fuel filter, a bad pump if it has one, dirt or water in the carby.. Easiest is to check there is a good supply of fuel getting to the carby. If it has a drain screw on the bottom of the carb I'd undo that with the fuel tap off and catch the fuel as it drains to check it for water. Then I'd leave the drain open and turn the fuel on and make sure it flows out again at a reasonable trickle. If it doesn't have a drain screw, I'd pull the fuel hose off the carby and check for a good flow of fuel there. If there's plenty of fuel getting to the carby, I'd pull the carby and clean it..

I think you should check the cam timing..

Yup that's right, they prime them for a few seconds when you go to crank it over, and after it starts and you let the key off something like the crank or cam position sensor signals to keep the pump on. Your test is a good one.. But then you need to read up on how to get the trouble codes out of the dash, or what sensor it is that keeps the pump running.

Ok. That's a much more informative explanation.. It does sound like carby, not the idle but possibly the needle or main jet, or float height, but before I went pulling it off again(since you sound like you know your stuff), I'd check the spark was a good one at the plug. If the plug cap comes off the lead, you could take that off and jury rig the wire on the plug for a while, a small split pin can be poked into the wire and fitted to the plug end perhaps. The other thing is, are you sure you have the right heat range plug for your riding conditions ? Have you tried one one step hotter ? Are you using NGK plugs ?