yankeeslover
New member
2000 sxr 700.... last season sled ran great other then small idle hang.... every now and then i would have to adjust the idle screw to bring it to 16-1700 but sled ran great...this year i had my mechanic do the carbs again for me and he advised that instead of stock 1.5 turns out for fuel screws he put them at 2 turns out...said this will help with idle hang.....what exactly do the fuel screws do? does this only control the amount of fuel into the carbs during idle? so has no effect when im actually riding? and if the screws are out too far(2) what kind of damage can happen? im no mechanic which is why i have others to do my work...does the carbs have to come off to adj the fuel screws back? is 2 turns out for a sxr 700 ok? specs say 1.5, and if its ideling low this year, with the fuel screws at 2 can i still adjust the idle w/the idle screw? every now and then as the weather got warmer or colder i had to adjust a tad last year, will the idle screw have any effect on the sled w/the fuel screws set at 2? thanks and sorry about the dumb questions...
yankeeslover
New member
also, will having the screws out 1/2 turn more then stock really mess up my good gas milage? how much of difference will this make?
JETTING: Always remember to change one carburetor component at a time and keep a record of your changes and effects.
IDLE to 1/4 THROTTLE: The AIR JET, PILOT JET and FUEL SCREW are most effective in this range When you want a leaner mixture use a LARGER AIR JET, SMALLER PILOT JET or turn the FUEL SCREW in. The opposite holds true for a richer mixture.
1/4 to 3/4 THROTTLE: The JET NEEDLE is the most effective component in this range. Raising the needle by lowering the "E" clip position at the top of the needle will richen the mixture. Lowering the needle will lean the mixture.
WIDE-OPEN THROTTLE: Changing the MAIN JET affects this range. Select the size, which offers the best wide-open throttle performance, then there is the option to install one size larger MAIN JET for ideal engine longevity.
FUEL SCREW:
(TM 33) This screw is located at the bottom of the float bowl, the screw meters fuel and opening the screw (counter-clockwise) out results in a richer mixture.
AIR JET, PILOT JET, FUEL SCREW, AND SLIDE CUTAWAY:
Keep in mind that the fuel screw gives a good indication of a properly sized Air Jet and Pilot Jet. The Air Jet and Pilot Jet calibrate the mixture from both the idle bypass and the idle orifice. If the idle screw is properly adjusted, but the engine does not have good response when the throttle is snapped wide-open, it is usually a sign of a lean mixture and the Air Jet/Pilot Jet will need to be replaced with one size (richer) and the fuel screw re-adjusted. Consequently, if the throttle is only partially opened, such as in a trail riding situation, and the sled loads up (slow to build rpm) when the throttle is returned to wide-open, it is usually a sign of a rich Air Jet/Pilot jet. If the Air Jet or Pilot Jet does not clean up this part of the circuit, the slide can be substituted for one with a different cutaway (not recommended). The higher the number, the larger the cutaway will be, allowing more air to the nozzle leaning the mixture and, conversely, a smaller cutaway will richen the mixture with a greater effect up to 1/4 throttle.
JET NEEDLE:
Straight diameter section - By going to a thinner needle, there is a larger area between the jet needle and the needle jet supplying a richer mixture. Length of the straight section - This determines at which point the needle taper will start relative to the clip position. If you have to run a needle in the highest clip position (needle raised out of nozzle), a needle with a longer straight section should be used. Needle "E" clip position - This works in conjunction with the length of the straight section. If the engine is too rich above 1/4 throttle, raising the needle "E" clip (effectively lowering it into the nozzle) will lean the mixture. Needle Taper - A larger taper will result in a leaner mixture in the first half of the taper and a richer mixture in the last half of the needle. Needle Jet: The needle jet (nozzle) controls the fuel/air mixture up to 3/4 throttle. How it overlaps with the jet needle depends on the jet orifice inner diameter, air bleed holes and type of nozzle. Most modern Japanese carburetors use a fixed needle jet (nozzle) assembly, which cannot be removed, but with the TM 33 replacement is possible.
Caution: this is where MOST burn-downs occur. To see where you are on the "MID" (needles) run the engine half throttle on a long straightaway hit the kill button or turn key off while holding throttle in "MID" position (USE EXTREEM CAUTION NOT TO CRASH INTO ANYTHING OR ANYONE ELSE). Then pull the spark plugs. The parts of the plug you should be looking at are the positive electrode and first 1/4 of the ground electrode. Best power will usually result in a cardboard colored insulator tip and light colored ring around the tip of the positive electrode. For the ground portion should be a light cardboard color running no more than halfway towards threads. The first three threads should be oily if you’re running the correct heat range.
MAIN JET:
Fully load the engine (wide-open throttle) on a long straightaway or long hill, hit the kill button or turn key off while holding throttle wide-open (USE EXTREEM CAUTION NOT TO CRASH INTO ANYTHING OR ANYONE ELSE). Then pull the spark plugs. The parts of the plug you should be looking at are the positive electrode and first 1/4 of the ground electrode. Best power will usually result in a cardboard colored insulator tip and light colored ring around the tip of the positive electrode. For the ground portion should be a light cardboard color running no more than halfway towards threads. The first three threads should be oily if you’re running the correct heat range. Keep in mind that the different types (race gas or aviation) and different brands of gasoline can give different readings.
IDLE to 1/4 THROTTLE: The AIR JET, PILOT JET and FUEL SCREW are most effective in this range When you want a leaner mixture use a LARGER AIR JET, SMALLER PILOT JET or turn the FUEL SCREW in. The opposite holds true for a richer mixture.
1/4 to 3/4 THROTTLE: The JET NEEDLE is the most effective component in this range. Raising the needle by lowering the "E" clip position at the top of the needle will richen the mixture. Lowering the needle will lean the mixture.
WIDE-OPEN THROTTLE: Changing the MAIN JET affects this range. Select the size, which offers the best wide-open throttle performance, then there is the option to install one size larger MAIN JET for ideal engine longevity.
FUEL SCREW:
(TM 33) This screw is located at the bottom of the float bowl, the screw meters fuel and opening the screw (counter-clockwise) out results in a richer mixture.
AIR JET, PILOT JET, FUEL SCREW, AND SLIDE CUTAWAY:
Keep in mind that the fuel screw gives a good indication of a properly sized Air Jet and Pilot Jet. The Air Jet and Pilot Jet calibrate the mixture from both the idle bypass and the idle orifice. If the idle screw is properly adjusted, but the engine does not have good response when the throttle is snapped wide-open, it is usually a sign of a lean mixture and the Air Jet/Pilot Jet will need to be replaced with one size (richer) and the fuel screw re-adjusted. Consequently, if the throttle is only partially opened, such as in a trail riding situation, and the sled loads up (slow to build rpm) when the throttle is returned to wide-open, it is usually a sign of a rich Air Jet/Pilot jet. If the Air Jet or Pilot Jet does not clean up this part of the circuit, the slide can be substituted for one with a different cutaway (not recommended). The higher the number, the larger the cutaway will be, allowing more air to the nozzle leaning the mixture and, conversely, a smaller cutaway will richen the mixture with a greater effect up to 1/4 throttle.
JET NEEDLE:
Straight diameter section - By going to a thinner needle, there is a larger area between the jet needle and the needle jet supplying a richer mixture. Length of the straight section - This determines at which point the needle taper will start relative to the clip position. If you have to run a needle in the highest clip position (needle raised out of nozzle), a needle with a longer straight section should be used. Needle "E" clip position - This works in conjunction with the length of the straight section. If the engine is too rich above 1/4 throttle, raising the needle "E" clip (effectively lowering it into the nozzle) will lean the mixture. Needle Taper - A larger taper will result in a leaner mixture in the first half of the taper and a richer mixture in the last half of the needle. Needle Jet: The needle jet (nozzle) controls the fuel/air mixture up to 3/4 throttle. How it overlaps with the jet needle depends on the jet orifice inner diameter, air bleed holes and type of nozzle. Most modern Japanese carburetors use a fixed needle jet (nozzle) assembly, which cannot be removed, but with the TM 33 replacement is possible.
Caution: this is where MOST burn-downs occur. To see where you are on the "MID" (needles) run the engine half throttle on a long straightaway hit the kill button or turn key off while holding throttle in "MID" position (USE EXTREEM CAUTION NOT TO CRASH INTO ANYTHING OR ANYONE ELSE). Then pull the spark plugs. The parts of the plug you should be looking at are the positive electrode and first 1/4 of the ground electrode. Best power will usually result in a cardboard colored insulator tip and light colored ring around the tip of the positive electrode. For the ground portion should be a light cardboard color running no more than halfway towards threads. The first three threads should be oily if you’re running the correct heat range.
MAIN JET:
Fully load the engine (wide-open throttle) on a long straightaway or long hill, hit the kill button or turn key off while holding throttle wide-open (USE EXTREEM CAUTION NOT TO CRASH INTO ANYTHING OR ANYONE ELSE). Then pull the spark plugs. The parts of the plug you should be looking at are the positive electrode and first 1/4 of the ground electrode. Best power will usually result in a cardboard colored insulator tip and light colored ring around the tip of the positive electrode. For the ground portion should be a light cardboard color running no more than halfway towards threads. The first three threads should be oily if you’re running the correct heat range. Keep in mind that the different types (race gas or aviation) and different brands of gasoline can give different readings.
It will richen it slightly but won't affect your fuel milage much at all because it's basically idle to 1/4 throttle.
sockeyerun
Test Dummy
pro116 has given you a very good explanation on how the carbs work. Idle hang is very common on these motors. I personally haven't seen one that will run right at 1.5 turns. If your motor is completely stock 1 3/4 should be enough to cure this but you can go to 2 with no problems.Basically your motor is running lean(not enough air) till it catches up at idle. Yes, they basically have to be pulled to adjust as the screws are on the bottom of each carb on the air box side. I'm suprised your mechanic didn't just turn them out when he had them out cleaning them. you guys must have discussed the issue after he had finished. It's not difficult job and he should be able to do it in 30 min. or so, if your not up to trying yourself. Soc
yankeeslover
New member
mechanic did turn them to 2 turns while he was cleaning them... i was just wondering if i should put them back to 1.5 and if so, how...... im not gonna even atempt to remove carbs, im that non mechanical........ im just afraid that 2 turns is gonna be too rich at idle and kill my gas milage..
Trail riding your pretty much in the needle range the whole while except when you open it up then your in the main jet.The fuel screw isn't going to affect your milage.
SWEDE
New member
I agree about not running right at 1.5 turns, with 1 layer head gasket, reed spacers and leaner jetting mine wanted 1 7/8 turns out. That was the sweet spot for mine 1 3/4 wasn't enough and 2 turns was too much.It idles great with no hang ever and is crisp on the throttle also.sockeyerun said:
I also agree on the 1 3/4 -2 turns out settings. If your fuel screws are adjusted just a little to far open you may have an issue where you may have to hold the throttle slightly to get the sled to fire and stay alive when warm. Depending on how strong you are this may be a chore as you'll have to only use 1 hand on the pull rope. If you have electric start no big deal really, turn the key and tap the throttle.
bluemonster1
LIFE MEMBER ONLY ONCE!!!
I have my fuel screws open 2 1/4 turns out on both sleds....helps with idle hang.
yankeeslover
New member
blue monster
any issues with keeping sled idleing with it turned out so far?
any issues with keeping sled idleing with it turned out so far?
bluemonster1
LIFE MEMBER ONLY ONCE!!!
no.got the SRX idle at 1800...so it is fine.I don't play with the idle once set because of the TPS.On my SXR .it is set approx the same.My 600 always has an idle hang.I should actually increase my pilot jet size 1 up.
super1c
Super Moderator
I run all my vipers at 2 turns out. No effect on MPG and helps with the idle hang. I also keep the idle around 1200RMP. Takes care of the rest of the idle hang. Common problem on vipers but not sure on the SXR. But turning it out will hurt nothing.
