Hawk Talk

[Ariel Red Hunter]

Getting acquainted with carburetors. The thought crossed my mind that there is a large percentage of new riders that have never owned anything with a carburetor, unless it was a weed whacker or a lawn mower. And those carburetors work different. The motor cycles we are going to talk about use piston valved carbs. Instead of having a "butterfly" throttle plate, they use a round piston, which is raised or lowered to control the amount of air/fuel mixture to get more power or less power output. So, perhaps the carburetor can be described as the instrument that mixes the gasoline and air in the correct proportions to support combustion. While every body knows that gasoline is extremely flammable, not everyone knows that there is a mixture of volatile gas vapor with air that is virtually explosive. That mixture is between 12 to 1 to 13.5 to 1. That is 12 POUNDS of air to 1 pound of gasoline. Or 13.5 Pounds of air to one pound of gasoline. The carburetor can do this job very nicely, although it took a long time to work it out. About 25 years, believe it or not. All of the carburetors that come on China bikes are capable of performing the fuel mixture function very well. And why not? The basic design of today's carbs were applied and understood by 1927. Then they spent the next 92 years figuring out how to make it cheaper, but still funtional, and they have done a pretty good job of it. Yes, China bike carbs come too lean, but that is to pass emmission regulations. Basically they break down as two tubes, one if which is open to the atmosphere on one end and open to the engine on the other end. At 90 degrees to the first tube the second tube, threaded on one end, is attached about in the middle of the first tube through a hole cut in the horizontal tube, the joint soldered up and a cutter used to trim the vertical tube so that the interior of the first (horizontal) tube is very clean and clear. Next a cast brass venturi is sweated in the horizontal tube with pre-cut holes or ports designed to fulfill various funtions which we will explore later. A piston is made to fit in the vertical tube. It was made to accept the end of a cable that aallowed it to slide up and down a lite spring helps to close the piston, which goes far enough down the vertical tube to shut off all air trying to get to the engine. This worked but not very well, so a tapered needle was hung from the bottom of the piston in order to lean out the part throttle over richness of the mixture. Underneath the horizontal tube was hung (literally) a float bowl in which there was a brass float, all soldered together which controlled the height of fuel in the float bowl. As the fuel was consumed, the float dropped, allowing more fuel to flow into the bowl controlled by a tapered rod at the bottom of the float bowl. No needle and seat like now. Attached to the bottom of the horizontal tube was a small brass tube that was in perfect alignment with the tapered needle hanging from the piston valve. Although that brass tube is called a needle jet it's not really a jet at all. It could be called a jet holder, beause the main jet is screwed to the bottom of this tube. But it is called the needle jet because originally that is the way it controlled fuel flow, but by 1927 they figured out how to use the needle it self as the restrictor, AND so make it possible to have the midrange fuel mixture controlled by a fixed needle in the piston valve, instead of the earlier way of controlling mixture by setting the air for the power you wanted first, and the adjusting the fuel flow by manipulation of a second lever, controlling the needle. Next a pilot jet was added to give better control of the mixture below 1/4 throttle. The main jet feeds just after the main restriction in the venturi, the pilot circuit and idle air or fuel jet feeds a little farther into the venturi section. Air rushing through the venturi suffers a loss of pressure, so the fuel comes up through the various jets because THE PRESSURE IS HIGHER IN THE FLOAT BOWL THAN AT THE VENTURI. Hopefully, that's more than you needed or wanted to know about your carb...ARH For your kind attention.

[JerryHawk250]

Great explanation of the carb.

[Ariel Red Hunter]

Originally Posted by JerryHawk250

Great explanation of the carb.

I should have known. The only people who read this were those who knew all of this already. It is odd that new riders never seem to read things like this, but only show up with a cry from the wilderness for help. I still read every word I can find on every machine I've ever owned, because I don't like being bushwhacked by a problem I had never thought of. It would appear that logical and critical thinking is not taught in our schools anymore....ARH

[dpl096]

Originally Posted by Ariel Red Hunter

I should have known. The only people who read this were those who knew all of this already. It is odd that new riders never seem to read things like this, but only show up with a cry from the wilderness for help. I still read every word I can find on every machine I've ever owned, because I don't like being bushwhacked by a problem I had never thought of. It would appear that logical and critical thinking is not taught in our schools anymore....ARH

No it isn't.... They are however taught to accept utter bs as gospel and to depend on others, meaning the boobs holding elected office, to solve all their problems. Who Needs shop classes in a throw away society. Be a good little consumer and charge a new one... Not me or mine. Hell I still plug my own tires.

[Ariel Red Hunter]

I would like to say a few words about break-in. (LOL, like ARH even knows what a few words even means). Shut up!! Please think of this this way. Imagine that you are observing the factory assembly line. Parts are being bolted on by torque sensing air wrenches. Because air torque wrenches are adjustable, some of the bolts and nuts will be over tightened and some will be under tightened. So, therefore they ALL need to be checked. Including the wheel nipples. And you haven't even started it yet. Of course you will change the oil before you start it the first time. If you change out the fork oil before you even start to put the front end together, like Megadan suggests, so much the better. Yeah, I know it's hard to be patient the first time you assemble a bike, but patience really pays off. But I would not loctitite any thing untill you've got 500 miles (860 km) on the clock. This gives parts a chance to bed in together which are diss-similar, like the engine-frame mounts, and a lot of other parts that are hung (bolted) to the frame in a factory that produces a million motor cycles a year. After 500 miles, Loctite 'em! Like I've said before, keep your spokes as tight as it takes to "ping" middle "C" on them. No tighter. Check them every riding day for the first riding week (That is to say every day you ride until you've covered 7 riding days. And no, a ride around the block is not "a riding day". Then once a week. Then once a month. Unless you are really riding hard off-road. Then do the spokes every riding day. Re-greaseing the steering head bearings and swing arm bolt/bushes and the rear shock bolts bushes with marine grease will pay off from day one. Now the chain. The stock chain has a bad reputation, but I am not sure it is deserved. Clean the chain in Kerosene, the re-lube it in warm fluid chassis grease or warm liquid canning wax that you color black with colloidal graphite....ARH For your kind attention.

[Ariel Red Hunter]

I am amazed at how many new riders of Chinese bikes start chasing too lean issues by going immediatly to the main jet. thinking it will be THE ANSWER. Then they have trouble with starting, or mid-range issues. They are trying tuning these carburetors the same as a Carter AFB, or a Holley. They are not the same - they are so different one might as well have been designed on Mars while the other comes from Pluto. The sooner you put that Holley away in a little box in your miind, and think of these carbs as something new and different, the sooner you will find success. Here's the short, no frills way I've tuned these type carbs for more than 50 years. It's quick and easy. First thing is un-plug the idle mixture screw,screw it gently in until it just bottoms out. Then set the idle mixture screw at 1 1/2 turns out. Now,change pilot jets bigger and bigger until you have a very strong 1250-1450 idle. If you are too rich, you will see a little black smoke in the exhaust. Try to correct it by leaning out the idle mixture screw. If you have to go beyond 1 1/4 turns in order to stop the smokeing, change your pilot jet 1 step leaner. Once you have your pilot jet mixture right, the rest is easy. I don't go any leaner with the pilot jet then absolute necessity, as a rich pilot jet helps low end punch out of all recognition. Next, make sure the needle clip is in the middle slot on the needle. Now, find a 55 mph road, make sure the engine is warmed up , and run for a half mile or so at 50 mph, then pin it wide open. When it has settled in to pulling hard, back the throttle off 1/8th turn. One of three things will happen. If you get a momentary surge of power, main jet is too lean. If the engine acts soggy, or wooly, main jet is too rich.If neither of these things happen then your main jet is very close to spot on. THER IS ONE THING YOU WILL HAVE TO REMEMBER; THE PILOT JET AFFECTS FUEL MIXTURE FROM IDLE ALL THE WAY UP TO THE LAST GASP...ARH for your attention and patience.

[Megadan]

Originally Posted by Ariel Red Hunter

I am amazed at how many new riders of Chinese bikes start chasing too lean issues by going immediatly to the main jet. thinking it will be THE ANSWER.

The number one reason people brought their bikes in to the shop feeling frustrated because they couldn't get it to run right summed up in one sentence. Nobody takes the time to understand that there is more than 1 jet, and more than one circuit per jet.

The other big mistake is people will use the needle as a bandaid to other jetting issues.

Things the uninitiated should understand:
Pilot jet affects idle mixture AND low throttle. You might be able to get a good idle mixture setting, but the engine may still be too lean/rich under light throttle causing running issues. Just because the idle mixture works, doesn't mean

The main jet affects the needle jet and needle fueling just as much as it does the 3/4 to wide open range. Example: My PZ30b required the needle to be dropped down a notch when I went to the 125 main jet from the 120 because it was letting enough fuel through to become too rich.

It is important to find the main jet that works best and then tune the needle last. Not just in height, but diameter and taper as well. While this may be a little difficult to do with the cheap clone carbs, if you get something like my Nibbi that comes with a size stamp on the needle, this can be used to tune the mid range. Length of the straight section, diameter of the needle body, and taper can be used to tune the lower and upper halves of the fueling curve the needle provides. A larger diameter will lean out the bottom half in relation to the top half, where a more aggressive taper will richen the top half vs. the bottom half. A longer or straight section before the taper will alter how soon the needle starts to contribute fuel, which is great for dialing in jet transitions.

Getting jetting dialed in as precisely as most OEMs have to do is a very tedious process, because one change in one area may require changing another.

[Ariel Red Hunter]

Originally Posted by Megadan

The number one reason people brought their bikes in to the shop feeling frustrated because they couldn't get it to run right summed up in one sentence. Nobody takes the time to understand that there is more than 1 jet, and more than one circuit per jet.

The other big mistake is people will use the needle as a bandaid to other jetting issues.

Things the uninitiated should understand:
Pilot jet affects idle mixture AND low throttle. You might be able to get a good idle mixture setting, but the engine may still be too lean/rich under light throttle causing running issues. Just because the idle mixture works, doesn't mean

The main jet affects the needle jet and needle fueling just as much as it does the 3/4 to wide open range. Example: My PZ30b required the needle to be dropped down a notch when I went to the 125 main jet from the 120 because it was letting enough fuel through to become too rich.

It is important to find the main jet that works best and then tune the needle last. Not just in height, but diameter and taper as well. While this may be a little difficult to do with the cheap clone carbs, if you get something like my Nibbi that comes with a size stamp on the needle, this can be used to tune the mid range. Length of the straight section, diameter of the needle body, and taper can be used to tune the lower and upper halves of the fueling curve the needle provides. A larger diameter will lean out the bottom half in relation to the top half, where a more aggressive taper will richen the top half vs. the bottom half. A longer or straight section before the taper will alter how soon the needle starts to contribute fuel, which is great for dialing in jet transitions.

Getting jetting dialed in as precisely as most OEMs have to do is a very tedious process, because one change in one area may require changing another.

Yes, I agree completely. Especially about jacking the needle up and down, looking for Nirvana. I thought what I wrote was too long already or I would have recommended setting the needle in the middle slot (or removing the washers) either before or after the pilot jet is set to your satisfaction. Then do the main jet. You should use the needle slots to fine tune the mid-range only....ARH

[Ariel Red Hunter]

I've owned one and ridden or driven a few others. For American conditions, only three brands of motor-cycles, or more precisly one model each, are really satisfactory. Harley-Dacidson big twins, Indians, especially 80 inchers, and Ariel Square Fours. I owned a 1938 Indian with an Indian Princess side car. I've ridden a couple of H_D's with their sidecar, and one Square Four with a Sports chair, I think a Watsonian. One thing you will notice; these 3 beasties all had big engines. The Indian and Harley could cruise at 75 all day long because the had a big enough oil tank to keep temperatures under control. The Ariel didn't really have enough tank capacity, but if you added an oil cooler it was fine. I've ridden or passengered various 650 cc BritBikes, but they were 10 mph slower, and got hot too easily. So now you Know more than you ever wanted to know about sidecars. Except that they are fun...ARH

[buffalo bill]

When fitting the rear sprocket on a Hawk make sure you don't put it on backwards. The circlip will not seat properly and when the sprocket assembly comes off while going down the road it's scary. Ask me how I know.
And before anyone comments I've been wrenching on motorcycles for
over 65yrs and yes this was a foolish mistake but all is back together and well.

[GronkFries]

Originally Posted by Ariel Red Hunter

I should have known. The only people who read this were those who knew all of this already. It is odd that new riders never seem to read things like this, but only show up with a cry from the wilderness for help. I still read every word I can find on every machine I've ever owned, because I don't like being bushwhacked by a problem I had never thought of. It would appear that logical and critical thinking is not taught in our schools anymore....ARH

Sometimes readers who know the subject matter, possibly out of interest in the material, identify minutiae that was not noticed the first time around. Skills and knowledge initially learned is by far nothing compared to the perfected form after many years.

Kind of like cramming for a test - A procedure that lends more towards work ethics than learning. You're not going to remember half of it after the test but the pain and suffering to get there burns in true appreciation the next time the subject rolls around. Something a millenial would never understand (I say that tongue in cheek but some truth to it I think).

Share the words, share the experiences. Share the love. Now I need a hug bad lol...

[Megadan]

I am technically a millennial....

How does that crow taste?

[GronkFries]

Originally Posted by Megadan

I am technically a millennial....

How does that crow taste?

All apologies, I guess one made it lol!!

[Megadan]

Originally Posted by GronkFries

All apologies, I guess one made it lol!!

Way more than one. Granted myself and most of my friends are on the old end of the spectrum in our mid to late 30's, but even the youngest millennials are old enough to have Masters Degrees.

[Emerikol]

I was in a training class just yesterday with a bunch of 25 year olds with Masters Degrees. They were all pharmacy techs doing the equivalent of their residencies. At 40 years old, it was crazy. On the other hand, I have to hand it to them, they worked awfully hard to get there, and really broke my mental mold of what lazy, overweight, living-in-mom-and-dads-basement millennials are...