Hawk Talk

[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.

[NzBrakelathes]

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.

This is something almost no one (in my limited experience and my self included) knows anything about.
This comes up over and over and over again when I sell my kits and also others who public;y show stuff.

I understand it in a basic form but I couldn't tell you or even be sure what I have is 100% correct.
Most Hawk folk and other prob make the bike 'run ok" and that is it - hence I have several jets in my kit as that seems to cover most peoples expectations.

Reality the day and temperature/weather conditions of the day will technically want a slight rejet and that is what road racers on old bikes do - they have a whole chart with known settings jets and worked out pretty much the scale when the air temp or conditions of a day change to jet it the best they can for THAT condition on THAT race at THAT specific temp/conditions.

Jets typically increase by 0.01mm on jets or there abouts

New Hawk/TBR7 or any Chinese bike I suggest something like stock pilot to 40/42 and main jet 105 and needle 1 lower then center as a starting point (screw out 1.5 to 2 turns) and THAT is a starting area only not the true final end.
Can take several hours to get it right and that's assuming you know what your'e doingish. if you don't then its a long learning curve.

My bike I have slightly wrong as main is 105, pilot drilled 45 clip, 1 lower ) then center, screw 1.75 turns (best idle), but I never ride that bike so I can't be bothered as I have other things I wanna do (it stumbles at 7500 RPM and suspect a little rich)

[Ariel Red Hunter]

Originally Posted by NzBrakelathes

This is something almost no one (in my limited experience and my self included) knows anything about.
This comes up over and over and over again when I sell my kits and also others who public;y show stuff.

I understand it in a basic form but I couldn't tell you or even be sure what I have is 100% correct.
Most Hawk folk and other prob make the bike 'run ok" and that is it - hence I have several jets in my kit as that seems to cover most peoples expectations.

Reality the day and temperature/weather conditions of the day will technically want a slight rejet and that is what road racers on old bikes do - they have a whole chart with known settings jets and worked out pretty much the scale when the air temp or conditions of a day change to jet it the best they can for THAT condition on THAT race at THAT specific temp/conditions.

Jets typically increase by 0.01mm on jets or there abouts

New Hawk/TBR7 or any Chinese bike I suggest something like stock pilot to 40/42 and main jet 105 and needle 1 lower then center as a starting point (screw out 1.5 to 2 turns) and THAT is a starting area only not the true final end.
Can take several hours to get it right and that's assuming you know what your'e doingish. if you don't then its a long learning curve.

My bike I have slightly wrong as main is 105, pilot drilled 45 clip, 1 lower ) then center, screw 1.75 turns (best idle), but I never ride that bike so I can't be bothered as I have other things I wanna do (it stumbles at 7500 RPM and suspect a little rich)

You will not be far wrong if you accept that the factory needle jet and needle is correct. This may change in the future if or when emission regs get tougher, but for now they took the easy way out, i.e. leaned out the idle and the main jet in order to pass....ARH