Carburetor Cleaning & Tuning 101
#232
05-09-2012, 02:17 PM
Hopefully someone can answer this for me. Been restoring my F2 and after cleaning and putting back together my carburetor, it idles fine but dies after turning off choke when the bike has warmed up. Starting it back up without choke is fine too and idles / revs nicely, but as soon as I go to bring the bike upright off of the kick stand, the rpm slightly climbs (noticeably) then stalls! After this, pressing the ignition alone won't start it up.
I'd have to apply throttle a couple of times while pressing the ignition button to get it going. I've tried even just rocking the bike and sometimes it won't stall and other times it will. It will 90% of the time stall when brought upright though from a leaning position. Checked cables for kinked lines and don't see any at all so I doubt it's that. If I keep the bike upright and start it, it won't stall when leaning back on the kick stand or rocking back and forth, but occasionally it will start to decrease in rpm like it's about to stall so I'd have to apply a quick rev and it'll go back to normal.
Is this a float bowl issue? The only thing I could think of that would cause a bike to stall when put upright is a loss of fuel somewhere, and with my tank a little over half full, it has to be fuel moving around in the float bowls. Like I've said, I've cleaned the carbs before but maybe I didn't do a good job at it and caused this to happen? Before the carb cleaning, this problem didn't occur. Any help would be greatly appreciated because I've taken apart that damn thing more times than I can count. By the end of the day my brother and I are so burnt out from trying to figure this out that I feel like just throwing the carburetor off of a cliff!
I'd have to apply throttle a couple of times while pressing the ignition button to get it going. I've tried even just rocking the bike and sometimes it won't stall and other times it will. It will 90% of the time stall when brought upright though from a leaning position. Checked cables for kinked lines and don't see any at all so I doubt it's that. If I keep the bike upright and start it, it won't stall when leaning back on the kick stand or rocking back and forth, but occasionally it will start to decrease in rpm like it's about to stall so I'd have to apply a quick rev and it'll go back to normal.
Is this a float bowl issue? The only thing I could think of that would cause a bike to stall when put upright is a loss of fuel somewhere, and with my tank a little over half full, it has to be fuel moving around in the float bowls. Like I've said, I've cleaned the carbs before but maybe I didn't do a good job at it and caused this to happen? Before the carb cleaning, this problem didn't occur. Any help would be greatly appreciated because I've taken apart that damn thing more times than I can count. By the end of the day my brother and I are so burnt out from trying to figure this out that I feel like just throwing the carburetor off of a cliff!
#233
05-10-2012, 08:27 AM
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Hopefully someone can answer this for me. Been restoring my F2 and after cleaning and putting back together my carburetor, it idles fine but dies after turning off choke when the bike has warmed up. Starting it back up without choke is fine too and idles / revs nicely, but as soon as I go to bring the bike upright off of the kick stand, the rpm slightly climbs (noticeably) then stalls! After this, pressing the ignition alone won't start it up.
I'd have to apply throttle a couple of times while pressing the ignition button to get it going. I've tried even just rocking the bike and sometimes it won't stall and other times it will. It will 90% of the time stall when brought upright though from a leaning position. Checked cables for kinked lines and don't see any at all so I doubt it's that. If I keep the bike upright and start it, it won't stall when leaning back on the kick stand or rocking back and forth, but occasionally it will start to decrease in rpm like it's about to stall so I'd have to apply a quick rev and it'll go back to normal.
Is this a float bowl issue? The only thing I could think of that would cause a bike to stall when put upright is a loss of fuel somewhere, and with my tank a little over half full, it has to be fuel moving around in the float bowls. Like I've said, I've cleaned the carbs before but maybe I didn't do a good job at it and caused this to happen? Before the carb cleaning, this problem didn't occur. Any help would be greatly appreciated because I've taken apart that damn thing more times than I can count. By the end of the day my brother and I are so burnt out from trying to figure this out that I feel like just throwing the carburetor off of a cliff!
I'd have to apply throttle a couple of times while pressing the ignition button to get it going. I've tried even just rocking the bike and sometimes it won't stall and other times it will. It will 90% of the time stall when brought upright though from a leaning position. Checked cables for kinked lines and don't see any at all so I doubt it's that. If I keep the bike upright and start it, it won't stall when leaning back on the kick stand or rocking back and forth, but occasionally it will start to decrease in rpm like it's about to stall so I'd have to apply a quick rev and it'll go back to normal.
Is this a float bowl issue? The only thing I could think of that would cause a bike to stall when put upright is a loss of fuel somewhere, and with my tank a little over half full, it has to be fuel moving around in the float bowls. Like I've said, I've cleaned the carbs before but maybe I didn't do a good job at it and caused this to happen? Before the carb cleaning, this problem didn't occur. Any help would be greatly appreciated because I've taken apart that damn thing more times than I can count. By the end of the day my brother and I are so burnt out from trying to figure this out that I feel like just throwing the carburetor off of a cliff!
Make sure your idle screw is set properly, as well as your pilot jet screws.
Take your time on reassembly. Be sure all vacuum and breather hoses are connected correctly and that you have good seals and no air leaks.
Could also check the battery terminals. Loose wire will cause a stall.
That is all I can think of :/
#234
05-26-2012, 02:45 PM
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This diagram illustrates where your carb fuel circuits are active and will help enhance your understanding the operation of the system and with performance tuning. See the CV Carb Tuning link in Dissevered's sticky for details.
There are so many questions that are answered by cleaning or tuning your carbs so I decided to write up a "How to."
On a scale of 1-10, 10 being the hardest thing to do on a motorcycle, I rate Carb cleaning at a 4 and tuning at a 7. Some mechanical know how helps, but as long as you have the right tools, patience, and the willingness to learn, you will be fine.
On the pictures I have numbers. The numbers are not an order of which to do things, but just things I point out for you to keep note of.
This is just a guide to show you around the carburetor. A good tuning guide can be found at Factory Pro's website. Here is the link:
CV Carb Tuning Procedures
Tools needed:
Screwdrivers - Flat head and Phillips, stubby and long
Pliers - not required but helps with pulling off some hose clamps
Wrenches - 7mm up to 12mm does most jobs on this bike.
Pilot screw adjuster - D shaped driver, but not needed with a little mod...
Remove Tail fairings, seat and gas tank (set the tank to OFF position first). If you can't get this far, then carbs are out of your league for the time being.
---
1. Breather hose - Be sure to reattach this when you put everything back together
Remove the air box cover, filter and everything else down to the carbs. Those only requires a phillips head, but an electric driver really speeds things up. As you can see there are a bunch of screws.
---
1. Another breather hose, pull it off and don't forget it later
2. Throttle cables
3. Choke cable
4. Gaskets, don't lose these
Pull off the rest of the air box
---
1. Vacuum hose that goes to the gas tank, another thing to not forget during reassembly
2. Carb Boot screw
Loosen up each screw on all four of these boots which are on the bottom of the carbs. They are a pain to get to. I use a stubby but I have small hands, you may need a long screw driver. Once loose, rock the carbs front to back to loosen them and pull up. This can be a chore if you have not taken them off for a while.
---
Now for the worst part of the job. Remove the throttle cables. Loosen up the throttle cables, slide them out of the holder and push the cable in closer toward the other end of the carburetor. This puts slack on the cable so that it is easier to remove.
---
1. This is where the throttle cables are locked in.
2. Idle adjuster screw - Just so you know where it is... If you look, you can see what it does as well. It just slightly opens the throttle plate.
There is no easy way to exlpain how to remove the cables. It sucks and it's a pain in the ****. You need to put enough slack in the cables in order to slide them out of the little holder. have fun.
---
1. Float bowl drain screw
Unscrew all of these and let the fuel drain out of the bowls. Do it somewhere you don't mind getting messy.
---
1. Float bowl screws
Take these out
---
1. Float
2. Float needle/valve
3. Float pin
Here is a common trouble area. The float and needle here are what regulate the fuel coming into the carbs. A bike that sits a few months without stabilizer in the carbs can get gunk in many places and this is a common one. Lift up on your floats gently and make sure the needle moves without sticking. If you are due for a cleaning, knock out the float pin in order remove the float and needle. Use carb cleaner and a scotchbrite pad to clean both the needle and the seat. Also the tip of the needle is rubber, be sure it still V shaped so that it seats properly.
---
1. Pilot/Slow jet adjustment screw
2. D shaped adjuster tool.
Pilot jets control how well your bike Idles, comes off of idle, and operates at cruising speed around 4k RPMs
*TIP* If you don't have one of these dumb tools, you can get a mini hack saw, or a hand grinder dremmel tool type thing and cut in a small slit down the center of the Pilot screw. This makes it adjustable with a standard flat head screw driver.
---
1. Main jet
2. Needle jet - Main jet screws into the top of this.
3. Pilot/Slow jet
More things to clean. Pretty much anything with a hole can get carb cleaner squirted into it and an air compressor is a very nice thing to have. It is not required but it makes everything 100x's easier. If you don't have an air compressor, I recommend unscrewing the 2 Jets with a flat head, then unscrewing the needle jet with a 7mm wrench and soaking all of them in carb cleaner over night.
WARNING! Do not get carb cleaner on anything non metal. It eats paint, it eats plastic and destroys rubber!
---
If you have a jet kit, this is 1 of the things you may have to tinker with. Main jets control the air/fuel mixture at high RPMS. There are numbers on the jets, a bigger number = a bigger hole which = more fuel.
When you are done here, screw it all back together. Be sure to put the float bowl gaskets back on or you will have a big mess later.
---
1. Unscrew these
2. Diaphragm/Vacuum Piston
Unless your carbs have been sitting for years, you probably won't have to touch this side. No fuel enters here (maybe just a little mist) so not much gets gunked, however its rubber and can rot if neglected for years. This side is more for jetting
---
Hand screw one of the cover screws into the center of the diaphragm to remove it.
---
1. Jet needle
2. Vacuum piston/Slider
While holding on to the slider, be careful not to bend or break the needle, pull on the screw which you have threaded into the center of the diaphram. Give it a good tug, nothing will break unless you smack the needle off something.
---
1. Multi slotted jet needle - this is aftermarket and what comes in a jet kit. the clip position on this controls the 5-7.5k RPM range.
2. Plate set - This is the thing you just yanked out of the slider.
This is where you find out if your carbs are OEM or you have a jet kit. ANY alteration to your bikes intake, engine, or exhaust will require a jet kit if you want your bike to function properly.
To change clip positions, lay the needle down on a table like in the picture. Feel free to use another finger on the other side of the clip, and push down. It is a C clip. Do the same thing in order to snap the clip in. Again, be gentle, do not bend your needles.
Jet kits also come with shims (little washers). These shims are used to alter the needle by half of a clip position. All you do is put a shim on the pointy side of the needle down to the clip and drop it back into the slider.
To assemble, just put the needle back in and snap the plate set down into place.
---
1. Jet needle sliding into needle jet.
Drop the slider gently back into place and be sure that the needle goes into the jet.
---
Screw the cover back on, and once you are done push down on the sliders, they should resist a little and slide back into position smoothly.
Warning! Do not over tighten ANYTHING on your carbs. Make everything snug but don't put all your might into it. The jets are a very soft metal and easy to ruin, and all of the cover screws can be stripped if you aren't careful.
At this point, you just start putting everything back together. Attach your choke and throttle cables (have fun with that again...), push the carbs down onto the engine and be sure the are seated properly and tighten up the boot screws. Attach your air filter box, breather hoses, air filter, gas tank (don't don't forget the vacuum and fuel lines), seat and fairings.
Edit: Adding a pic and link on reading spark plugs.
Below is a picture of my current spark plugs. This is the best tuning I have yet to achieve. It is tuned for horse power, and thus close to being lean. However, there are no signs of detonation, or over heating therefor it is still safe.
How to read spark plugs: Reading Spark Plugs Correctly
Enjoy
On a scale of 1-10, 10 being the hardest thing to do on a motorcycle, I rate Carb cleaning at a 4 and tuning at a 7. Some mechanical know how helps, but as long as you have the right tools, patience, and the willingness to learn, you will be fine.
On the pictures I have numbers. The numbers are not an order of which to do things, but just things I point out for you to keep note of.
This is just a guide to show you around the carburetor. A good tuning guide can be found at Factory Pro's website. Here is the link:
CV Carb Tuning Procedures
Tools needed:
Screwdrivers - Flat head and Phillips, stubby and long
Pliers - not required but helps with pulling off some hose clamps
Wrenches - 7mm up to 12mm does most jobs on this bike.
Pilot screw adjuster - D shaped driver, but not needed with a little mod...
Remove Tail fairings, seat and gas tank (set the tank to OFF position first). If you can't get this far, then carbs are out of your league for the time being.
---
1. Breather hose - Be sure to reattach this when you put everything back together
Remove the air box cover, filter and everything else down to the carbs. Those only requires a phillips head, but an electric driver really speeds things up. As you can see there are a bunch of screws.
---
1. Another breather hose, pull it off and don't forget it later
2. Throttle cables
3. Choke cable
4. Gaskets, don't lose these
Pull off the rest of the air box
---
1. Vacuum hose that goes to the gas tank, another thing to not forget during reassembly
2. Carb Boot screw
Loosen up each screw on all four of these boots which are on the bottom of the carbs. They are a pain to get to. I use a stubby but I have small hands, you may need a long screw driver. Once loose, rock the carbs front to back to loosen them and pull up. This can be a chore if you have not taken them off for a while.
---
Now for the worst part of the job. Remove the throttle cables. Loosen up the throttle cables, slide them out of the holder and push the cable in closer toward the other end of the carburetor. This puts slack on the cable so that it is easier to remove.
---
1. This is where the throttle cables are locked in.
2. Idle adjuster screw - Just so you know where it is... If you look, you can see what it does as well. It just slightly opens the throttle plate.
There is no easy way to exlpain how to remove the cables. It sucks and it's a pain in the ****. You need to put enough slack in the cables in order to slide them out of the little holder. have fun.
---
1. Float bowl drain screw
Unscrew all of these and let the fuel drain out of the bowls. Do it somewhere you don't mind getting messy.
---
1. Float bowl screws
Take these out
---
1. Float
2. Float needle/valve
3. Float pin
Here is a common trouble area. The float and needle here are what regulate the fuel coming into the carbs. A bike that sits a few months without stabilizer in the carbs can get gunk in many places and this is a common one. Lift up on your floats gently and make sure the needle moves without sticking. If you are due for a cleaning, knock out the float pin in order remove the float and needle. Use carb cleaner and a scotchbrite pad to clean both the needle and the seat. Also the tip of the needle is rubber, be sure it still V shaped so that it seats properly.
---
1. Pilot/Slow jet adjustment screw
2. D shaped adjuster tool.
Pilot jets control how well your bike Idles, comes off of idle, and operates at cruising speed around 4k RPMs
*TIP* If you don't have one of these dumb tools, you can get a mini hack saw, or a hand grinder dremmel tool type thing and cut in a small slit down the center of the Pilot screw. This makes it adjustable with a standard flat head screw driver.
---
1. Main jet
2. Needle jet - Main jet screws into the top of this.
3. Pilot/Slow jet
More things to clean. Pretty much anything with a hole can get carb cleaner squirted into it and an air compressor is a very nice thing to have. It is not required but it makes everything 100x's easier. If you don't have an air compressor, I recommend unscrewing the 2 Jets with a flat head, then unscrewing the needle jet with a 7mm wrench and soaking all of them in carb cleaner over night.
WARNING! Do not get carb cleaner on anything non metal. It eats paint, it eats plastic and destroys rubber!
---
If you have a jet kit, this is 1 of the things you may have to tinker with. Main jets control the air/fuel mixture at high RPMS. There are numbers on the jets, a bigger number = a bigger hole which = more fuel.
When you are done here, screw it all back together. Be sure to put the float bowl gaskets back on or you will have a big mess later.
---
1. Unscrew these
2. Diaphragm/Vacuum Piston
Unless your carbs have been sitting for years, you probably won't have to touch this side. No fuel enters here (maybe just a little mist) so not much gets gunked, however its rubber and can rot if neglected for years. This side is more for jetting
---
Hand screw one of the cover screws into the center of the diaphragm to remove it.
---
1. Jet needle
2. Vacuum piston/Slider
While holding on to the slider, be careful not to bend or break the needle, pull on the screw which you have threaded into the center of the diaphram. Give it a good tug, nothing will break unless you smack the needle off something.
---
1. Multi slotted jet needle - this is aftermarket and what comes in a jet kit. the clip position on this controls the 5-7.5k RPM range.
2. Plate set - This is the thing you just yanked out of the slider.
This is where you find out if your carbs are OEM or you have a jet kit. ANY alteration to your bikes intake, engine, or exhaust will require a jet kit if you want your bike to function properly.
To change clip positions, lay the needle down on a table like in the picture. Feel free to use another finger on the other side of the clip, and push down. It is a C clip. Do the same thing in order to snap the clip in. Again, be gentle, do not bend your needles.
Jet kits also come with shims (little washers). These shims are used to alter the needle by half of a clip position. All you do is put a shim on the pointy side of the needle down to the clip and drop it back into the slider.
To assemble, just put the needle back in and snap the plate set down into place.
---
1. Jet needle sliding into needle jet.
Drop the slider gently back into place and be sure that the needle goes into the jet.
---
Screw the cover back on, and once you are done push down on the sliders, they should resist a little and slide back into position smoothly.
Warning! Do not over tighten ANYTHING on your carbs. Make everything snug but don't put all your might into it. The jets are a very soft metal and easy to ruin, and all of the cover screws can be stripped if you aren't careful.
At this point, you just start putting everything back together. Attach your choke and throttle cables (have fun with that again...), push the carbs down onto the engine and be sure the are seated properly and tighten up the boot screws. Attach your air filter box, breather hoses, air filter, gas tank (don't don't forget the vacuum and fuel lines), seat and fairings.
Edit: Adding a pic and link on reading spark plugs.
Below is a picture of my current spark plugs. This is the best tuning I have yet to achieve. It is tuned for horse power, and thus close to being lean. However, there are no signs of detonation, or over heating therefor it is still safe.
How to read spark plugs: Reading Spark Plugs Correctly
Enjoy
#235
05-27-2012, 09:00 AM
Join Date: Jul 2009
Location: Pittsburgh, PA
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1 thing confusing about that chart is that it says throttle, when in fact it is just air flow that activates the jets and therefor both throttle position and RPM have an effect. When I do test runs on a carbed bike I do full throttle runs and pay attention to what a feel from 2k up to redline. That is probably the most accurate test you can do.
If you go based off only throttle position, it doesn't work well because the RPM's will most likely climb, increasing airflow and activating different jets.
Just something to keep in mind.
If you go based off only throttle position, it doesn't work well because the RPM's will most likely climb, increasing airflow and activating different jets.
Just something to keep in mind.
Last edited by Dissevered; 05-27-2012 at 09:02 AM.
#236
07-23-2012, 07:07 PM
Member
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#237
08-02-2012, 02:40 AM
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Yeah, thread is g8, thats true.. but can someone respond to this related thread as well? Dunno if i placed it in correct "topic".
https://cbrforum.com/forum/cbr-600f2...roblem-140763/
Many thanks...
https://cbrforum.com/forum/cbr-600f2...roblem-140763/
Many thanks...
#238
08-11-2012, 10:53 PM
Easy fix of off-idle stumble/hesitation..
We just brought home an f2 with a slight stumble when going onto the throttle. Made it very difficult to ride properly through corners at speed.
So I am somewhat familiar with the carbs on bikes and this one came to us with a K&N filter and aftermarket exhaust, but no other information besides the bike had sat unridden a while and had just been cleaned (fuel system)
I began with the fuel tap....which had some cracks in the vacuum line that I cut off and re-attached when done with the rest. Then I went to what I thought would actually be the cause....improperly adjusted or perhaps too small pilot jets. Pulled the carbs and took my dremel tool to the idle air screws, those dumb D-shaped things. I figured they maybe had never been changed since the aftermarket air/exhaust swaps, so I just gave each one a quarter turn richer and put the bike back together...
Runs perfect now...no hesitation no stumble...smoooooth! And it actually was pretty easy to get the carbs off, unlike the one I last dealt with on my KTM 520...or the nasty nasty flatslide carb conversion I had on a Honda Hawk NT 650...That one was an epic struggle to get the carbs off, and I had to do it about half a dozen times after letting the bike sit with gas in it for over 5yrs....
Anyway, the carb tuning guides were correct for the F2....
Don Hanson
So I am somewhat familiar with the carbs on bikes and this one came to us with a K&N filter and aftermarket exhaust, but no other information besides the bike had sat unridden a while and had just been cleaned (fuel system)
I began with the fuel tap....which had some cracks in the vacuum line that I cut off and re-attached when done with the rest. Then I went to what I thought would actually be the cause....improperly adjusted or perhaps too small pilot jets. Pulled the carbs and took my dremel tool to the idle air screws, those dumb D-shaped things. I figured they maybe had never been changed since the aftermarket air/exhaust swaps, so I just gave each one a quarter turn richer and put the bike back together...
Runs perfect now...no hesitation no stumble...smoooooth! And it actually was pretty easy to get the carbs off, unlike the one I last dealt with on my KTM 520...or the nasty nasty flatslide carb conversion I had on a Honda Hawk NT 650...That one was an epic struggle to get the carbs off, and I had to do it about half a dozen times after letting the bike sit with gas in it for over 5yrs....
Anyway, the carb tuning guides were correct for the F2....
Don Hanson
#239
09-28-2012, 09:14 PM
#240
10-24-2012, 09:16 PM
Help, bike running erratic, seems like its out of fuel
92 F2, 2,300 miles, sat for 8 years with gas, yuck. Tank was presurred cleaned by a radiator outfit and sealed. Carbs removed via great article here. I replaced the pilot jets and cleaned everything else. Bike started, ran perfect for 6 miles. Idled and was responsive, literally ran like a brand new bike. Then after steady cruise around 55 for 4 miles or so it acted like it was running out of fuel. Took it home and took everything apart. Needles, jets, floats, everything looked fine. There was no sediment or anything in carbs. I removed the pilot jets and they looked clean. Put everything back together with an in-line fuel filter. I've ridden around 100 miles. The bike starts easily with choke but runs rough. After a minute or two without choke it idles reasonable well. Accelerating with partial throttle the bike seems hesitant. Somewhere between 3,000 and 4,000 rpm the bike seems to start running better and pulls reasonable well and generally sounds okay. If I run around 5,000 for more than 3 or 4 miles the bike eventually acts like its running out of fuel and dies. Today, after sitting by the side of the road for about 5 minutes, the bike started with the choke. I immediately shut the choke and it idled fine. I rode home (10 miles) not going over 4,000 rpm. The bike ran rough but I made it home. The weird thing to me is the first time out after new jets the bike idled and ran like brand new. The floats are not adjustable.