Carburetor 4 Stroke Carburetion Troubleshooting

[snipermxmalayaklan]

4 Stroke Carburetion Troubleshooting
Notes on Carburetor

Bike Runs-On or Won't Idle Down When Throttle is Chopped

• Idle set too high
• Air leak in intake or engine
• Pilot too rich (when bike is hot)

Bike Wont Start When Cold Temp Outside

• Pilot jet too lean
• Air filter over-oiled
• Motor oil too thick for temperature

Bike Sputters / Wont Clean Out at High RPM

• Main jet too rich
• Air filter over-oiled
• Spark plug has debris on electrode

Bike Coughs & Stalls in Slow Turns

• Pilot jet too lean
• Idle set too low
• Valves set too tight
• Decompressor is set too tight, so turning the bars engages release slightly

Bike Hesitates or Bogs Over Deep Whoops or G-Outs

• Float level too low
• Carb vent tubes blocked
• Main jet splash shield not installed
• Float level too high, gas is trapped in vent tunes (install T-vents)

Bike Starts But Wont Take Throttle Without Sputtering

• Pilot jet too rich
• Water in fuel
• Debris in main jet

Bike Suddenly Starts Sputtering / Gas Flows from Vent Tubes

• Stuck float check valve
• Debris in gas or carb

Bike Runs Hot / Feels Slow & Flat on Straights

• Main jet too lean
• Fuel octane too low, causing detonation

Bike Coughs & Stalls When Throttle is Whacked Open

• Needle too lean
• Slide cutaway too lean
• Pumper circuit blocked or too lean

 

[snipermxmalayaklan]

Carb Keep NOtes
I'm new to rejetting, how do I know if the engine is lean or rich?
If the bike seems to be lean then partially cover the intake to the air filter housing with duct tape, if the carburetor improves it is running lean.
If the bike seems to be rich remove the airbox cover, if the carburetor improves it is running rich.


Here are some things that affect jet size:
-Changing air cleaner, air box will affect how much air gets to the carburetor.
-Cleaning or oiling the air filter will affect how much air can get through it.

How do I tell if I am running Rich or Lean?
When rich, (too much fuel) the engine sputters, acts like it is cold, won't warm up, does not clean out, chugs, spark plug gets black, plug fouls, won't rev up.\ When Lean, (Not enough fuel) Dies out, Wheezes, runs out of gas, Seizes, gets hot, spark plug is white, spark plug has little melted gobs on it, warms up fast, you can start engine cold and rev it right up.

What can I do to experiment?
To make it lean open up the air box a bit make sure the intake boots are not shrinking down clean out the air filter remove the air box. To make it rich: Close off the intake holes in the air cleaner box. Hope this helps.




Idle and low rpm is the job of the pilot jet. Larger pilot jet will make things richer at low rpm, smaller--->Lean

From about 1/4 throttle to 3/4 throttle is the needle jet. The basic adjustment here is the height position. Higher--->Rich, Lower--->Lean.

Full throttle is the main jet, large--->Rich, Small--->Lean. This is where most people need a change when a free flowing pipe is added. More air means you need more fuel to keep the ratio right.

 

[CesarMontano]

I bought my Sniper Mx 2012 model 1 month ago and it is a second hand from CASA. When i finally drove my mx it feels like there was something wrong with the Decceleration. My Decceleration Drops "gradually" so i went to my trusted mechanic to fix it. Finally this gradual decceleration gone. There's more that i have noticed, my mx can't start quickly even if i use my kick start. Maybe because of the oil and tune up because this motorcycle was stock for 5 months. So i went again to my mechanic to change oil and tune up. My mx respond better after this but still i'm not satisfied. I have tried to open the air box and i noticed that the vaccum can't breathe properly"too much hesitation like the engine doesn't want accelerate" i also tried several things to adjust air/fuel adjusments still, it occurs the same thing. But when the air filter and air box cover attached, my motorcycle functioning well. it's just weird when the airbox was fully opened then hesitation starts. I am planning to get my carburator to get fixed but i need some advise from the experts because i have doubts maybe something more.

Thank you in advance for any response