I have the formula at home, I will get it and post it. If you go more than 2 1/2 turns to get rid of backfiring, change the pilot richer (bigger). Richen up by turning pilot (fuel) screw out.
Another way is by backfiring on a YZF on decel, too lean.
If not running (idling around 1k RPM) optimally between 1/2 and 2 1/2 turns out, change the pilot. You need to determine this by pilot screw position. You can also use it for pilots, but pilots sometimes go the other way (larger at high altitude). Probably about the same on the YZ426F, I am one clip leaner here in Denver, which is about CF=0.9, depending on temperature. Needles are a little trickier, I think each needle clip was worth a change in CF of 0.1 on my KX. This gives you a good place to start your fine tuning. Multiply 200 by the CF=.9 to get 180 as the new main jet. You take your main jet that is for a CF=1, say a 200. If it is 80 F at 5000 ft, you calculate a new CF, say 0.9 (this is just an example). (this is a good article we found on the net) Take 0.948(Denver atmospheric pressure at 70 degrees) x jet size(60) = new jet size(56.88) round up 57 would be the proper jet size to start at for a stock scooter using a 12mm carburetor. How to determine the proper jet size on a Chinese scooter:Ĭarburetor diameter(12mm) x 5 = 60(or number it calculates) x 0.9 = sea level jet size In most cases screw adjustments won't correct the lean back firing, installing a one size larger pilot jet will do the trick for higher elevations (Colorado). 2-2.5 turns out on a fuel screw is proper for Colorado. Fuel screws are towards the front of the carburetor and air screws are toward the rear of the carburetor. Any more than 3 turns out go one size larger on the pilot jet. Try richening up the fuel mixture by turning the fuel screw out or the air screw in to allow more fuel. If the motor is back firing at decel this is a good indication the pilot jet is to lean. Be sure you are full throttle under load for at leased 200 yards or so. At this point you can do a plug chop to verify jetting. This will give you a good place to start. Here is a table made from the formula: the temperature and altitude with give you the correct atmospheric pressure, the numbers below have been pre calculated. Main jet tuning: perfect air fuel ratio is 12.5-1ĭenver formula for 70 degrees at 5300 feet is : 0.948
0 kommentar(er)
