88 yamaha 570
New member
ok i just want to let steerjock know that i wasn't trying to be offensive, i was sincerely apologizing for not giving more info than i should have, and i do have the plunger and spring in the carb atm, i might see if my choke cables bad and install it back on the carbs, i also appreciate everyone who gave me long readings on what to do, should give me plenty of work for tonight, and hopefully should fix it, however i don't have any friends with a stock pipe for it but i will write down as much information for the needles and jets as i can. =) thanks guys. by the way, theo that's a perfect link, i couldn't find a guide for my carbs they were all different, but tonight ill clean them and get back to you guys =)
Last edited:
88 yamaha 570
New member
while reading the carb cleaning link, they said to remember how far out the pilot jet is unscrewed? is that what the 5/8th of a turn on the tech pages for fuel screw is? mines in snug, maybe that's my problem? i hope so and if it is im going to be psyched
88 Yamaha I think the screws that you are thinking of in the carburetor are actually the pilot jets, they're located inside the fuel bowl but attached theo the carb body right? It should be brass in color with a slot in it and an impression so to speak in the center of the screw. If so, yeah that is the "pilot" or low speed jet. Your main jets should look like miniture pencils so to speak... Be care ful readign the numbers on the ends.
The screw that is on an angle on the side of the carb towards the airbox is the fuel/air screw. This should be out any where from 1/2 to 1-1/2 turns out and only affects the circuit from idle to 1/4 throttle. There should be no fuel screw on the bottom of the carbs as this is the adjustment on the newer flat slides.88 yamaha 570 said:
88 yamaha 570
New member
what im trying to say is in the link theo send me hes pulling the pilot jet out and says to remember how far out it is so it can be placed back in the came, but its not the fuel/air screw its a screw inside the carb, im wondering if i should have it out some rather than in all the way...
The screw on the side of the carbs on your VM 38s controls the amount of air mixed with the fuel in the pilot circuit [zero to 1/8 or so throttle opening] The more you open that screw the LEANER the pilot circuit is.[more air mixing with the fuel + they should never be opened more then 1 3/4 turns].
This is exactly opposite to the FUEL screw on the bottom of the Flat Silide carbs on the SXs, SXRs. + SRXs.
If your screws were all the way in[seated] you would definately be running rich down low but it should have very little effect on operations over 1/2 throttle..
This is exactly opposite to the FUEL screw on the bottom of the Flat Silide carbs on the SXs, SXRs. + SRXs.
If your screws were all the way in[seated] you would definately be running rich down low but it should have very little effect on operations over 1/2 throttle..
Last edited:
88 yamaha 570
New member
if you look at the link theo sent, its not the air/fuel screw im asking about, i know what thats for, theres a screw inside the bowl of the carb that is labeled as a pilot screw, and he says
"Using a flathead screwdriver, screw the pilot air jet in until it is fully closed, while counting the number of turns. Now write this number down, and you can remove the pilot air jet by fully unscrewing it. You will need to make sure the air jet ends up the exact same amount of turns out as it was originally when you put it back together. Set this aside for cleaning also."
this is what im talking about when i say pilot jet. anyone know what it will effect if i had it screwed fully in to begin with? that would be my problem right?
Sorry, i miss read, i thought he said pilot jet, not pilot air jet, i was hoping that was my problem... looks like ill just have to clean them out and see what happens. anyone know a good recommended way to check for leaks in my fuel lines? i think i seen bubbles going up the fuel line opposite the primary clutch side
"Using a flathead screwdriver, screw the pilot air jet in until it is fully closed, while counting the number of turns. Now write this number down, and you can remove the pilot air jet by fully unscrewing it. You will need to make sure the air jet ends up the exact same amount of turns out as it was originally when you put it back together. Set this aside for cleaning also."
this is what im talking about when i say pilot jet. anyone know what it will effect if i had it screwed fully in to begin with? that would be my problem right?
Sorry, i miss read, i thought he said pilot jet, not pilot air jet, i was hoping that was my problem... looks like ill just have to clean them out and see what happens. anyone know a good recommended way to check for leaks in my fuel lines? i think i seen bubbles going up the fuel line opposite the primary clutch side
Last edited:
88 yamaha 570
New member
also, if my choke cables work fine what would cause it to do nothing when i pull on the cable for the clutch side choke cable, and bog out if i pull on the opposite side cable?
There should be a black coupler where the two cables connect to one cable it looks/sounds as if one o fthe cable came disconnected. OR reading farther above your choke circuit may be plugged...88 yamaha 570 said:
A couple items here:
-when you remove the float bowl, there are no jets or screws that have an adjustment without replacement
-The pilot + main jets are only exposed when you remove the float bowl and both of them are only adjusted by physically removing them and replacing them with a different size.
-The pilot jets are round and are replaced with a standard flat blade screw driver,
-The Main Jets are 5 sided and replaced with a socket.
-Both the pilot and main jets should be snuggly seated when installed
If you pull on one of the chokes and it makes no difference its one of two problems:
1] the ckoke circuit is plugged and no fuel is flowing to enrich your mixture regardless of the plunger position
or
2] the choke plunger is not seating and fuel is always flowing thru the enrichment circuit creating an overly rich condition to one cylinder, which would cause most of the problems you are experiencing
-when you remove the float bowl, there are no jets or screws that have an adjustment without replacement
-The pilot + main jets are only exposed when you remove the float bowl and both of them are only adjusted by physically removing them and replacing them with a different size.
-The pilot jets are round and are replaced with a standard flat blade screw driver,
-The Main Jets are 5 sided and replaced with a socket.
-Both the pilot and main jets should be snuggly seated when installed
If you pull on one of the chokes and it makes no difference its one of two problems:
1] the ckoke circuit is plugged and no fuel is flowing to enrich your mixture regardless of the plunger position
or
2] the choke plunger is not seating and fuel is always flowing thru the enrichment circuit creating an overly rich condition to one cylinder, which would cause most of the problems you are experiencing
Last edited:
I think your talking about the pilot /air jet thats located on the side of the carb thats the one that you should count the turns until fully seated before removing. The pilot jet is inside the float bowl and it is NOT ADJUSTABLE by turning out only way to adjust it is by installing a different size. Take your time and the members on this site will wok you thru it. If you have a digital camera and are having a hard time understanding or getting you point across sometime a picture will help.
88 yamaha 570
New member
mtnmax, i know whats what inside it, ive pulled it apart and cleaned it all out once, and from the diagram i know whats what and i read about it and did understand that they are always snug, i do not need to record my air fuel screw tho ive been tinkering with it for a few days thinking it affected my high end and thanks to you guys i now know not to, the tech section has stock specs for it tho and i do know the air fuel screw is 5/8th out and sideshow, that last post of yours is awesome, im going to follow all your guys instructions along with the link to clean them and ill report back, im on my way outside to remove my carbs even tho its 9:45 at night and i have it sitting in the side yard, ill get back to you with pics of the clean...
88 yamaha 570
New member
this is what the carbs look like right now just after pulling them off, do any of you have a windows live messenger account i can maybe add to get instant help with this if i need it?
88 yamaha 570
New member
i don't get how to check the float level on this, and i didn't find anything gunked up and in need of a cleaning...
88 yamaha 570
New member
this is my main jet correct? there is no numbers on it and it should have a 320, but the pilot jet is the stock jet
theo125
New member
Still need to press out the pin and take out that needle and seat. The thin metal "flapper that rides on the float pins. If it is sticking you will have problems. Clean, clean and clean again.
You have what are called "POWER JET" carbs.[They died in the 80s with Disco...thank goodness!!!]
That is NOT your "main jet"...that brass coupler screws on to the bottom of the long brass tube[needle jet] and its only purpose is to hold the "needle jet" in place and seal it to the float bowl.
Your "main jet" is the brass hex head jet that screws[with a small wrench or socket] into the actual float bowl and is pointing up into the fuel in the bowl.
A simple look at how it flows:
fuel flows through the mainjet into a passage in the float bowl, then up through the needle jet
To clean you have to remove the main jets, ensure they are clean and also ensure the passages in the float bowls are clean as well. This type of main jet configuration is very prone to plugging up[it was a real crappy idea]
Those carbs also have what is called "Power Jets".
They are the round cylinder type fittings that attach and project into the throat of the carbs. They have a fuel line that goes down to the bottom of the float bowls.
The "power jets" supply fuel above 1/2 throttlr right up to full throttle.
There should be a round headed brass jet that screws in, with a flat blade screw driver, in the bottom of the float bowl that controls the fuel to these jets.[LOL! another crappy idea]
All these have to cleaned as well:the jets, the air intake jet on the power valve can plug as well[if it has one it will be right where the vent line fits on the power valve]
Don't pull the whole power valve off of the carb as they are an interferance fit and they may not stay attached if you remove them then reinstall them.
So you have 3 fuel jets that all screw in:
1/ pilot jet - screws into the carb body itself very small flat blade screw driver
2/ main jet - points up in bottom of float bowl removed with small wrench
3/ power jet - points up in bottom of float bowl, round headed, removes with flat blade screw driver
Lots to clean!
That is NOT your "main jet"...that brass coupler screws on to the bottom of the long brass tube[needle jet] and its only purpose is to hold the "needle jet" in place and seal it to the float bowl.
Your "main jet" is the brass hex head jet that screws[with a small wrench or socket] into the actual float bowl and is pointing up into the fuel in the bowl.
A simple look at how it flows:
fuel flows through the mainjet into a passage in the float bowl, then up through the needle jet
To clean you have to remove the main jets, ensure they are clean and also ensure the passages in the float bowls are clean as well. This type of main jet configuration is very prone to plugging up[it was a real crappy idea]
Those carbs also have what is called "Power Jets".
They are the round cylinder type fittings that attach and project into the throat of the carbs. They have a fuel line that goes down to the bottom of the float bowls.
The "power jets" supply fuel above 1/2 throttlr right up to full throttle.
There should be a round headed brass jet that screws in, with a flat blade screw driver, in the bottom of the float bowl that controls the fuel to these jets.[LOL! another crappy idea]
All these have to cleaned as well:the jets, the air intake jet on the power valve can plug as well[if it has one it will be right where the vent line fits on the power valve]
Don't pull the whole power valve off of the carb as they are an interferance fit and they may not stay attached if you remove them then reinstall them.
So you have 3 fuel jets that all screw in:
1/ pilot jet - screws into the carb body itself very small flat blade screw driver
2/ main jet - points up in bottom of float bowl removed with small wrench
3/ power jet - points up in bottom of float bowl, round headed, removes with flat blade screw driver
Lots to clean!
Last edited:
88 yamaha 570
New member
ok thanks, i put the carbs back together, im going to pull them apart and clean the main jet, and how to i get the pin out for the float piece? it wont go out and i don't want to break it
88 yamaha 570
New member
ok took them both apart again, the pin for the float lever wont come out and if i keep trying i know it will break, so i just made sure it moved freely and the main jets are checked and match the 320 stock specs and i just put them back together... thanks again, gonna install them today, but does anyone know of a good way to find leaks in my fuel line?
theo125
New member
If went through the trouble of cleaning the carbs, I would spend a few bucks and replace the lines. Do you have a true Value by you? I bought clear fuel line by the foot there. Cheap insurance.