fine tuning carbs

brianbailey440

brianbailey440

Member
Joined
Jan 22, 2012
Messages
379
Age
55
Location
berlin n.h.
ive been tuning my sxr, and i have a question about the fuel screw.what i need to know is how much of a turn on the fuel screw will compensate for 1 pilot jet size?ive been thinking about getting some remote fuel screw adjusters,i would like the be able to adjust for different temps.lots of people swear by them, and say it makes a huge difference with pipes, especially in warmer temps.right now my setup is bender tripple pipes,#3 position on the clip with one washer underneath, and one on top,150 mains,52.5 pilots,fuel screws 1.25 turned out.took it out and rode it in the field,seems like a small blip on the bottom end.have not taken it on the trails yet, lack of snow up here.:o|
 
I have used them before on my old viper. They are more of a thing to get your idle perfect without removing the carbs to adjust while using carb sinc tools. You may want an attack or tempaflo for changing jetting for the day.
 
ive heard good and bad about the tempaflow,probably not something ill try.does anyone know the # of turns on the screw that will equal one pilot size?
 
there is no such turns equal a pilot jet size, its just basicly if you need to be more then 2 turns out and still have a stumble or lean spot youd go up to the next size pilot jet, and reset the screws to about 1.25 turns out and start there.... it does not work backwards! The reason is after 2 turns out from seated theres very little thread holding the pilot screws in and little tension on the springs and they can vibrate out.

you cant tune the sled with the fuel screws as far as pilot size needed, its just fro idle and low speed acceleration, not low speed fuel mixture in the carbs, you gotta get the right pilot jet size.
 
thanks mr viper, thats the kind of info ive been trying to find out.i was running 55 pilots last year, and it was too rich,i put the 52.5 pilots in, and turned the fuel screw from 1.5 to 1.25.took it out for a test ride, and it seemed to stumble a little, so i turned them back out to 1 5/8.im gonna try that and see what that does.so two turns is the limit,then up the pilot.next ill be working on the needles.whats a good place to start with the bender pipes and 52.5 pilots?right now i have the needles all at #3 position with one washer under, and one on top.
 
is this a good place to start with the needles and a 52.5 pilot?also how many miles should i ride before i start checking a new set of plugs for optimum jetting?they seem very hard to read when the plug is new,5 miles?10 miles?just enough to get some color on them first?i really want to get this right before i take it out and let her eat!!!
 
ok, so i talked to justin fuller @ full power performance, and he told me that when him and tim bender were testing they put the center needle in the #4 position because when in deep snow conditions the center cylinder would get hot.they did it just to be safe.im gonna trail ride, and keep an eye on the plugs with the needles in the stock position.he also said it takes about 15 miles on a new set of plugs before you can get a good reading.just in case anyone wants to know.great guy to talk to,his dad is pretty cool too.
 
soo is 1.25 turns out the ideal setting for the screw with the correct pilot jet?whats the least amount of turns you would recomend?im trying to fully understand the carb curcuit, and the more i know the better.i have more questions,but ill save them for later
mrviper700 said:
there is no such turns equal a pilot jet size, its just basicly if you need to be more then 2 turns out and still have a stumble or lean spot youd go up to the next size pilot jet, and reset the screws to about 1.25 turns out and start there.... it does not work backwards! The reason is after 2 turns out from seated theres very little thread holding the pilot screws in and little tension on the springs and they can vibrate out.

you cant tune the sled with the fuel screws as far as pilot size needed, its just fro idle and low speed acceleration, not low speed fuel mixture in the carbs, you gotta get the right pilot jet size.
Click to expand...
 
brian, make your life easier & buy the remote fuel screw adjusters. go 1 size bigger on the pilot then you think you will need ( 55's ). when it gets warm out turn them in. when it gets colder turn them out. very simple & no PIA pulling the air box & carbs to adjust pilots. also, since the pilot circuit never closes you can run the main jet a little leaner ( as long as pilots are a size larger than what the motor needs ) & when it gets colder out just turn the pilots out more than normal to add extra fuel throughout the circuit. the adjusters come w/ new pilot needles already attached to a cable & work smooth as butter. bob
 
bufalobob said:
brian, make your life easier & buy the remote fuel screw adjusters. go 1 size bigger on the pilot then you think you will need ( 55's ). when it gets warm out turn them in. when it gets colder turn them out. very simple & no PIA pulling the air box & carbs to adjust pilots. also, since the pilot circuit never closes you can run the main jet a little leaner ( as long as pilots are a size larger than what the motor needs ) & when it gets colder out just turn the pilots out more than normal to add extra fuel throughout the circuit. the adjusters come w/ new pilot needles already attached to a cable & work smooth as butter. bob
Click to expand...
i will call you next friday bob, and place my order with you for the adjusters.also i would like to know where needles and shims should be when running the 147.5 mains.ill put the 55 pilots back in, and give it a shot.
im glad you chimed in on my thread,mr viper says no more than two turns out because of the threads and spring on the pilot, but how far can you turn them in?3/4 turns?1/2 turn?i need this info also.thanks again bob. brian
 
needle @ #3 w/ both washers under clip ( stock position ). 55 pilots, install remote adjusters which have a new pilot screw needle attached, put the old needle screws in your spare parts bin but use the existing rubber washer, metal washer & spring. turn indexed adjusting knob in till lightly seated. turn out as far as you want & will not fall out ( there is a internal stop built in ) but +3 turns is about max for additional fuel flow. you will be surprised how much a 1/4 of a turn affects low end performance. the pilot jet flows through all throttle positions. since these are fuel screws & not air screws you can actually richen the main jet on a cold nite by simply opening the fuel screws. i've done this many times running the lakes @ nite in canada. i've got 5 sxr's & srx's & they all have them. bob
 
bufalobob said:
needle @ #3 w/ both washers under clip ( stock position ). 55 pilots, install remote adjusters which have a new pilot screw needle attached, put the old needle screws in your spare parts bin but use the existing rubber washer, metal washer & spring. turn indexed adjusting knob in till lightly seated. turn out as far as you want & will not fall out ( there is a internal stop built in ) but +3 turns is about max for additional fuel flow. you will be surprised how much a 1/4 of a turn affects low end performance. the pilot jet flows through all throttle positions. since these are fuel screws & not air screws you can actually richen the main jet on a cold nite by simply opening the fuel screws. i've done this many times running the lakes @ nite in canada. i've got 5 sxr's & srx's & they all have them. bob
Click to expand...
im definitely gonna give this a try, still need to know how far is the limit on turning them in,dont want to lean it out too much!!!i guess that would depend on a few different factors, but im sure you know what the limit is for 0-30 degrees f.thats about the temps i usually ride in, so thats where i need to start.thanks again for the help.very much appreciated. brian
 
Mikuni TM-carbs...

bufalobob said:
Make your life easier & buy the remote fuel screw adjusters.
Go 1 size bigger on the pilot then you think you will need.
When it gets warm out turn them in.
When it gets colder turn them out.
Very simple & no PIA pulling the air box & carbs to adjust pilots.
Also, since the pilot circuit never closes you can run the main jet a little leaner ( as long as pilots are a size larger than what the motor needs )
& when it gets colder out just turn the pilots out more than normal to add extra fuel throughout the circuit.
The remote fuel screw adjusters come w/ new pilot needles already attached to a cable & work smooth as butter.
/ Bob
Click to expand...
brianbailey440 said:
Bob, i will call you and place my order with you for the adjusters.
Also I would like to know where needles and shims should be when running the xxx,x mains. ill put the xx pilots back in, and give it a shot.
im glad you chimed in on my thread
/ Brian
Click to expand...
bufalobob said:
Install remote adjusters which have a new pilot screw needle attached,
put the old needle screws in your spare parts bin but use the existing rubber washer, metal washer & spring.
Turn indexed adjusting knob in till lightly seated.
Turn out as far as you want & will not fall out ( there is a internal stop built in ) but +3 turns is about max for additional fuel flow.
You will be surprised how much a 1/4 of a turn affects low end performance.
The pilot jet flows through all throttle positions.
Since these are fuel screws & not air screws you can actually richen the main jet on a cold nite by simply opening the fuel screws.
I've done this many times running the lakes @ nite in Canada.
i've got 5 sxr's & srx's & they all have them.
/ Bob
Click to expand...
brianbailey440 said:
Bob, im definitely gonna give this a try, still need to know how far is the limit on turning them in, dont want to lean it out too much!!!
I guess that would depend on a few different factors, but im sure you know what the limit is for 0-30° F.
Thats about the temps i usually ride in, so thats where i need to start.
thanks again for the help.very much appreciated.
/ Brian
Click to expand...
abranz said:
Where can I find remote fuel screw adjusters?
Click to expand...

Pictures on the remote fuel screw adjusters for Mikuni TM-carbs ?
Price ?
 
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