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Thread: How to set the fuel mixture and jetting Reply to Thread
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  Topic Review (Newest First)
07-22-2015 06:33 PM
TRX2fiveO to the top
05-09-2015 11:19 AM
TRX2fiveO Here is another write-up .. not mine but it's also got some great info.
Terms and Definitions

Jetting: The term comes from the two main circuits that control fuel flow in a carburetor. The pilot jet and the main jet.*

Main Jet: This is the main fuel circuit in a carburetor. It's a common misconception that this circuit only effects engine performance at wide open throttle. The main jet actually has a trickle down effect on other adjustments and should be adjusted first.

Needle: The needle is attached to the carb slide and is raised and lowered when you push and release the throttle. When you let off your throttle, the needle lowers into the main jet circuit, cutting off fuel flow as it goes down.

Needle Clip: This is the small circular clip that is used to adjust the needle position.

Pilot Jet: This is second jet in your carb. Much smaller than the Main Jet and typically has no effect beyond approximately 1/4 throttle. It's used to adjust your mixture at idle and low throttle.

Air/Pilot Screw: The air screw works in combination with the pilot jet. You can consider it a fine tuner for the pilot circuit. It's most obvious effect is noticed by throttle response.

Float: The float controls fuel level in the float bowl at the bottom of the carburetor. It has no effect on jetting but can cause some symptoms that can be easily confused with a jetting problem. If the fuel level is too low for example, it can cause a bog similar to a lean condition.

Float Seat/Valve: Basically the valve that stops fuel from flowing into the float bowl when the float reaches a specified level.

Rich: A "rich" condition is what occurs when you have too much fuel in your fuel/air mixture. Symptoms of a rich condition can be a rough running engine (sputtering), a black spark plug, a wet plug or excessive plug fouling.*

Lean: A "lean" condition is what occurs when you have insufficient fuel in your mixture creating an over abundance of oxygen. Symptoms can be a rough running engine (bogging), a white or light gray spark plug and sometimes can result in overheating or even severe engine damage.

Sputtering: This isn't exactly a technical term but is commonly used to describe how an engine runs when jetted too rich. For example, using too large of a main jet will cause more fuel to enter the combustion chamber than it can efficiently burn. This will result in a "sputter" at full throttle. It could best be described as a rapid misfire. Note: a rich condition is not the only possible source of this type of problem.*

Bogging: Again, not a technical term but commonly used. Bogging can be a result of a lean setting where not enough fuel is entering the combustion chamber for the motor to run properly. In some instances this can cause the machine to "bog" as if it were actually running out of gas. Note: a lean condition is not the only possible source of this type of problem.*

WOT: This an acronym that stands for Wide Open Throttle.

Plug Chop: Plug chops are the most accurate and easiest way to check your jetting. A proper plug chop should be done with a clean spark plug. Example; to check your main jet, put in a clean spark plug and run the trike at Wide Open Throttle (WOT) for several seconds, then in one motion, pull in the clutch (if applicable), kill the engine and let off the throttle. Remove the spark plug and check the color (refer to chart in this thread).

Float: The float controls fuel level in the float bowl at the bottom of the carburetor. It has no effect on jetting but can cause some symptoms that can be easily confused with a jetting problem. If the fuel level is too low for example, it can cause a bog similar to a lean condition.

Float Seat/Valve: Basically the valve that stops fuel from flowing into the float bowl when the float reaches a specified level. If worn it can cause the float bowl to overflow.
10-26-2014 12:12 AM
crankestein At last, a pic in detail, thank you!
07-13-2014 01:40 PM
Dj300EX I like this one better then the one stickied at the top of the performance section.

Maybe this should replace/update it? Just add a pic of the bottom of a carb for those who don't know where stuff is exactly.

Click the image to open in full size.

I also put the link to this thread in my signature for future reference/ ease to find.
07-06-2014 01:22 PM
TRX2fiveO
Quote:
Originally Posted by jcooperpcola View Post
How do I do this with a Rincon? Throw it in nuetral while running it then kill?
Not real sure? As I based this on sport quads hence the "pull in the clutch" statement... Most people o. Here asking about jetting are riding Sport quads...
07-06-2014 01:20 PM
jcooperpcola How do I do this with a Rincon? Throw it in nuetral while running it then kill?
07-06-2014 07:34 AM
TRX2fiveO
Quote:
Originally Posted by fallguy View Post
You should sticky this!!!!!!! Like now.lol
done.... I stuck it.
07-05-2014 09:05 PM
TRX2fiveO
Quote:
Originally Posted by stu5969 View Post
^^^I agree Moose, we get asked this allot! Now how to do it with an auto clutch,,lol! I always though well kill switch, and maybe push down on the shifter some on a manual shift to get it into a engaged clutch mode to stop the engine from turning over after you killed it, but never tried it. Always had to go the route of checking speed from one set mark to another with a roll on in 4th gear and go with the best time...food for thought on auto clutched machines,,not to mention the dreaded cvt,,lol! A quick shift on the fly into neutral perhaps? It can be done if done very carefully.
As far as the foot shifts you can simply hold up on the shifter until you stop.. CVTs are a bit trickier I agree.... you're probably right on target with the neutral shift.
07-05-2014 04:18 PM
stu5969 ^^^I agree Moose, we get asked this allot! Now how to do it with an auto clutch,,lol! I always though well kill switch, and maybe push down on the shifter some on a manual shift to get it into a engaged clutch mode to stop the engine from turning over after you killed it, but never tried it. Always had to go the route of checking speed from one set mark to another with a roll on in 4th gear and go with the best time...food for thought on auto clutched machines,,not to mention the dreaded cvt,,lol! A quick shift on the fly into neutral perhaps? It can be done if done very carefully.
07-05-2014 03:27 PM
fallguy You should sticky this!!!!!!! Like now.lol
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