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Wombat221

Fuel Screw question

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Hey guys i recently rejetted my Kehin slant with the JD Jet kit and opened up my airbox, i have a 168 main jet and the needle for low altitude on the 4th position with the fuel screw currently 2 turns out, the bike runs pretty great now except when i give it full throttle quickly it bogs out for a second, i tried running it with a 2.5 turns on the fuel screw but it would just stall out should i go 2.25 turns out? Thanks

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2 hours ago, Wombat221 said:

Hey guys i recently rejetted my Kehin slant with the JD Jet kit and opened up my airbox, i have a 168 main jet and the needle for low altitude on the 4th position with the fuel screw currently 2 turns out, the bike runs pretty great now except when i give it full throttle quickly it bogs out for a second, i tried running it with a 2.5 turns on the fuel screw but it would just stall out should i go 2.25 turns out? Thanks

Hi mate,

Just going through the motions myself here learning about tuning this carb on my 09 E.
Which year model is it?

Did it have the standard 165 main before?
What needle were you running before? OBDXP 4th clip?
Did you use the 45 pilot jet from the kit? Or confirmed/left the 45 already in there in place.

Assuming you have a 45 pilot and you had the 165 main before I would look at the AP ( accelerator pump ).

Is the bogging happening at high or low speed?
From closed throttle or at any throttle opening?

The AP squirts fuel before the airspeed picks up and enable the fuel to flow through the jets.
Without the AP, the bike will run lean for a bit before the jets pick up the slack.
It can bog because it's too lean or too rich.

Given that you are running a 168 and the blue needle it is very unlikely that you are running lean and more likely very rich.
If you add to that a worn linkage ( if your bike is not new ) on the AP which will cause the AP timing to be out AND run too long in duration it could explain your problem.
This will make the bike even richer on initial throttle opening while the AP is squirting fuel.

Ideally the AP should just miss the slide when opening the throttle and only spray for 1-1.5second.
If you take the carb off and twist the throttle you will see it in action.

One thing you could test without changing anything is to run the bike without the air box cover which will lean it out a bit.
If it runs better with more air, you need a smaller main jet.

On the fuel screw ( if your float is correctly set at 9mm )
There are reading you can do on how to adjust it correctly.
Basically when the bike is fully warm, adjust the idle screw until the bike can just about stay idling ( 1100rpm or so )
Then turn the fuel screw in until it dies. If it doesn't die, your pilot jet is too rich or your idle is set too high.
Then turn it out until find the highest RPM.
This should be between 1-2.5 turns. More than 2.5 turns is too much and apparently the screw could fall out.
 

 

Edited by Chicane

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4 minutes ago, Chicane said:

Hi mate,

Just going through the motions myself here learning about tuning this carb on my 09 E.
Which year model is it?

Did it have the standard 165 main before?
What needle were you running before? OBDXP 4th clip?
Did you use the 45 pilot jet from the kit? Or confirmed/left the 45 already in there in place.

Assuming you have a 45 pilot and you had the 165 main before I would look at the AP ( accelerator pump ).

Is the bogging happening at high or low speed?
From closed throttle or at any throttle opening?

The AP squirts fuel before the airspeed picks up and enable the fuel to flow through the jets.
Without the AP, the bike will run lean for a bit before the jets pick up the slack.
It can bog because it's too lean or too rich.

Given that you are running a 168 and the blue needle it is very unlikely that you are running lean and more likely very rich.
If you add to that a worn linkage on the AP which will cause the AP timing to be out AND run too long in duration it could explain your problem.

Ideally the AP should just miss the slide when opening the throttle and only spray for 1-1.5second.
If you take the carb off and twist the throttle you will see it in action.

On the fuel screw ( if your float is correctly set at 9mm )
There are reading you can do on how to adjust it correctly.
Basically when the bike is fully warm, adjust the idle screw until the bike can just about stay idling ( 1100rpm or so )
Then turn the fuel screw in until it dies. If it doesn't die, your pilot jet is too rich or your idle is set too high.
Then turn it out until find the highest RPM.
This should be between 1-2.5 turns. More than 2.5 turns is too much and apparently the screw could fall out.
 

 

Hi mate, Mine is a 2004 DRZ400E, it did have the standard 165 main jet before and and i cant remember if it was a 65 or 45 pilot jet but i replaced everything with what was given to me in the kit, the bogging is only happening when i slam the throttle to full quickly, i think my ac is okay because it never used to do it before i installed the jet kit and it only sprays for about a second like what you said. whats the best way to adjust the fuel screw while the carb is connected to the bike? the starter motor is in the way for me.

i have the screw turned to about 2 turns out now, what should i do now?

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45 minutes ago, Wombat221 said:

Hi mate, Mine is a 2004 DRZ400E, it did have the standard 165 main jet before and and i cant remember if it was a 65 or 45 pilot jet but i replaced everything with what was given to me in the kit, the bogging is only happening when i slam the throttle to full quickly, i think my ac is okay because it never used to do it before i installed the jet kit and it only sprays for about a second like what you said. whats the best way to adjust the fuel screw while the carb is connected to the bike? the starter motor is in the way for me.

i have the screw turned to about 2 turns out now, what should i do now?

The fuel screw is a bitch.

Standard or the one that came with the JD kit and is too long and touches the starter......

I modified mine last night because the extended fuel screw that came with the JDS001 kit it too long and the starter is in the way.
I took it off and sawed of the existing head plus a bit of the shaft, drilled a hole through a suitable nut, carefully pressed the fuel screw shaft into the tight hole in the nut and added some Q-bond glue for good measure.
Now it sits nice and close to the carb with room to spare and I can adjust it easy.

Otherwise the R&D flex screw looks good.

...

Well maybe your bike was running lean or lean enough before that the AP didn't cause a problem.
If it is already running rich now and you add to that the AP.... well.....

If bike starts and idle fine I'd forget about the fuel screw and leave it at 2 turns out and first make sure my main jet is the right size.

Seems like your bike ran fine before and now you added a richer needle AND a bigger main jet, so I'm going to guess you are running too rich if you now have an issue.

As a suggestion, run the bike without the airbox cover and see if it runs better.
This will make it run leaner ( more air ), if it runs better - you need a leaner main jet / needle combination.
Assuming your AP is not the issue.

Here is some good reference material if you don't believe you should start with the main jet.
http://www.factorypro.com/tech/tech_tuning_procedures/tuning_FCR_Burns,Pat.html

Edited by Chicane

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16 hours ago, Chicane said:

The fuel screw is a bitch.

Standard or the one that came with the JD kit and is too long and touches the starter......

I modified mine last night because the extended fuel screw that came with the JDS001 kit it too long and the starter is in the way.
I took it off and sawed of the existing head plus a bit of the shaft, drilled a hole through a suitable nut, carefully pressed the fuel screw shaft into the tight hole in the nut and added some Q-bond glue for good measure.
Now it sits nice and close to the carb with room to spare and I can adjust it easy.

Otherwise the R&D flex screw looks good.

...

Well maybe your bike was running lean or lean enough before that the AP didn't cause a problem.
If it is already running rich now and you add to that the AP.... well.....

If bike starts and idle fine I'd forget about the fuel screw and leave it at 2 turns out and first make sure my main jet is the right size.

Seems like your bike ran fine before and now you added a richer needle AND a bigger main jet, so I'm going to guess you are running too rich if you now have an issue.

As I suggested, run the bike without the airbox cover and see if it runs better.

Here is some good reference material if you don't believe you should start with the main jet.
http://www.factorypro.com/tech/tech_tuning_procedures/tuning_FCR_Burns,Pat.html

 

FYI.

I'm in Canberra, so running at about 600m / 2000ft.

Snorkel removed and Staintune exhaust ( massive header ).
Airbox had a hole bigger than 3x3 as standard.
To my surprise the throttle stop was still restricting the bike to about 80% throttle, cut that down and adjusted cables to make sure it allows going WOT and having slide just clear the carb.

You would think this make the bike run leaner, so...
I thought after reading the JD kit instruction, sure, I have a modified exhaust let's try the 168.
And I though yeah, sure, I'm not over 3000ft, let's use the Blue needle at 4th clip.

The standard instructions actually requires you to have no snorkel. And with that you have to run a 162 and blue needle at 4th clip at sea level in temperatures below 27 degrees.

The bike ran with the 168/Blue needle 4th clip.

Was still faster than my mates DR650, but just didn't feel right and used lots of fuel.
18km/l on a 600km adventure trip ( Before on 165 main, OBDXP needle clip 4 this would have been 23km/l )

Changed back to 165 last night, went for a ride and did lot of testing, felt a little better.
Took off the airbox cover - way better in the mid/top at WOT - closer to what I think it should be, bike squats and pulls hard.
So now I'm going to fit the 162 and give that a go.
If the 162 still runs better with the airbox off, then I'm going 160.
I think every bike/conditions are different and you have to test your main jet https://thumpertalk.com/forums/topic/695061-how-to-confirm-your-main-jet/

After main jet is confirmed, depending on test results, I may go a little richer than best performance for engine durability and to not run too lean if heading down to the coast and having to play with the needle all the time.

Then I'll move on to....

Needle: ( blue / red JD in my case, maybe try the original OBDXP as well but look very much like red JD)
   a. root diameter
   b. taper
   c. clip position (which includes the L1 measurement)

Slow fuel and air jets.

Fuel screw

AP

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1 hour ago, Chicane said:

 

FYI.

I'm in Canberra, so running at about 600m / 2000ft.

Snorkel removed and Staintune exhaust ( massive header ).
Airbox had a hole bigger than 3x3 as standard.
To my surprise the throttle stop was still restricting the bike to about 80% throttle, cut that down and adjusted cables to make sure it allows going WOT and having slide just clear the carb.

You would think this make the bike run leaner, so...
I thought after reading the JD kit instruction, sure, I have a modified exhaust let's try the 168.
And I though yeah, sure, I'm not over 3000ft, let's use the Blue needle at 4th clip.

The standard instructions actually requires you to have no snorkel. And with that you have to run a 162 and blue needle at 4th clip at sea level in temperatures below 27 degrees.

The bike ran with the 168/Blue needle 4th clip.

Was still faster than my mates DR650, but just didn't feel right and used lots of fuel.
18km/l on a 600km adventure trip ( Before on 165 main, OBDXP needle clip 4 this would have been 23km/l )

Changed back to 165 last night, went for a ride and did lot of testing, felt a little better.
Took off the airbox cover - way better in the mid/top at WOT - closer to what I think it should be, bike squats and pulls hard.
So now I'm going to fit the 162 and give that a go.
If the 162 still runs better with the airbox off, then I'm going 160.
I think every bike/conditions are different and you have to test your main jet https://thumpertalk.com/forums/topic/695061-how-to-confirm-your-main-jet/

After main jet is confirmed, depending on test results, I may go a little richer than best performance for engine durability and to not run too lean if heading down to the coast and having to play with the needle all the time.

Then I'll move on to....

Needle: ( blue / red JD in my case, maybe try the original OBDXP as well but look very much like red JD)
   a. root diameter
   b. taper
   c. clip position (which includes the L1 measurement)

Slow fuel and air jets.

Fuel screw

AP

hi mate. i have tried the 162 main jet today and it still bogs the same that the 168 did. if i take a look at the accelerator pump what should i be looking for that could mean its broken? thanks

also i have noticed now it only squirts fuel for about half a second, could this be my issue?

Edited by Wombat221

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2 hours ago, Wombat221 said:

hi mate. i have tried the 162 main jet today and it still bogs the same that the 168 did. if i take a look at the accelerator pump what should i be looking for that could mean its broken? thanks

also i have noticed now it only squirts fuel for about half a second, could this be my issue?

I would love to help, but you have to give the people on here the information they will need.
There is many questions I asked that you haven't responded to so it's a bit hard to give useful feedback.

Quote

 

"Is the bogging happening at high or low speed?
From closed throttle or at any throttle opening?"

 

 

 

Quote

"What needle were you running before? OBDXP 4th clip?"

Quote

"Ideally the AP should just miss the slide when opening the throttle and only spray for 1-1.5second.
If you take the carb off and twist the throttle you will see it in action."

 

That doesn't sound normal.
You have to have

- the spray must only just miss the slide if you wack it open.
- a proper volume of fuel that needs to spray
- apparently 1 - 1.5 seconds of spray is ideal

If the slide opens a fair bit before it starts spraying and then only spray a little fuel for 0.5s then really you don't have a working AP.

This will be much more of a problem at low engine speeds and from closed throttle.
If you also have a bog issue at higher engine speeds going WOT from lets say 1/2 throttle then the AP will play less of a role and there are other things too.

But before we go down a rabbit hole.....confirm please.
You said the bike was working fine and did not bog doing the exact same thing, right before you installed the JD kit?

 

Edited by Chicane

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16 minutes ago, Chicane said:

I would love to help, but you have to give the people on here the information they will need.
There is many questions I asked that you haven't responded to so it's a bit hard to give useful feedback.

 

That doesn't sound normal.
You have to have

- the spray must only just miss the slide if you wack it open.
- a proper volume of fuel that needs to spray
- apparently 1 - 1.5 seconds of spray is ideal

If the slide opens a fair bit before it starts spraying and then only spray a little fuel for 0.5s then really you don't have a working AP.

This will be much more of a problem at low engine speeds and from closed throttle.
If you also have a bog issue at higher engine speeds going WOT from lets say 1/2 throttle then the AP will play less of a role and there are other things too.

But before we go down a rabbit hole.....confirm please.
You said the bike was working fine and did not bog doing the exact same thing, right before you installed the JD kit?

 

Hi sorry about that ill try and answer those questions now, thank you for the help

-the bike bogs at any speed, it only bogs if i go from closed to full throttle quickly,

-im not sure what needle was in it before, it was most likely a stock needle and yes on the 4th position

-my ac spray started after the slide was open and only sprayed for about half a second, since then today i have tried doing the "eddie mod" and now it sprays alot longer than 2 seconds. but now im not sure what i have done wrong but the bike will not run without choke and is all over the place in rpm, and is backfiring at idle...

and the bike had a slight bog before doing the jet kit, it was pretty unnoticable because of how underpowered it was from the restrictions on it.

 

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16 minutes ago, Wombat221 said:

Hi sorry about that ill try and answer those questions now, thank you for the help

-the bike bogs at any speed, it only bogs if i go from closed to full throttle quickly, 

-im not sure what needle was in it before, it was most likely a stock needle and yes on the 4th position

-my ac spray started after the slide was open and only sprayed for about half a second, since then today i have tried doing the "eddie mod" and now it sprays alot longer than 2 seconds. but now im not sure what i have done wrong but the bike will not run without choke and is all over the place in rpm, and is backfiring at idle... 

and the bike had a slight bog before doing the jet kit, it was pretty unnoticable because of how underpowered it was from the restrictions on it.

 

In what kind of riding situation do you ever go from closed to WOT??
Quantify the bog as well, how long, how bad,

The needle could have some writing or markings on it that would identify it....

If you change so many things at once it is a moving target and you are just setting yourself up for failure.

Now there is almost no way if telling what caused the issue as they are all interconnected.

I almost feel like suggesting you should undo everything you did and save yourself from going nuts.
Start at a baseline and then change one thing at a time, then you can be much more certain where the problem actually is.

Also change things with a plan - start with the main jet, then needle, then slow speed, then ap.

Assuming of course the carb is clean, float at 9mm, no air leaks, valves on motor within spec.....etc.

- the AP ( accelerator pump ) no idea what an "ac" is..... should only just miss the slide. spraying when it is open is not good enough.
  it has to be just as the slide starts to lift without actually hitting the slide.

- if it only runs WITH the choke then somehow you have made it very lean.
  Blocking or changing one of the air or fuel circuits.

  When you say "it will not run without" the choke. that is way too general, you have to be specific.

  So it won't start without the choke even when hot?
  It won't idle without the choke?
  It won't run even at high rpm and lets say half throttle without the choke?

  if this is just at idle then ...
  - is your idle actually set? can you get it to hold a steady 2000 with the throttle choke/no choke?
  - you never confirmed your pilot jet size or pilot air jet size ( we are just assuming its 45 )
  - what fuel screw are you using, and what setting?
  - have you checked/set your float level?

Also in regards to restrictions there are the snorkel, the restriction in the carb rubber between the engine and the carb and the throttle stop on the carb preventing WOT. The slide needs to clear the carb on WOT.

Have a great weekend!

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5 minutes ago, Chicane said:

In what kind of riding situation do you ever go from closed to WOT??
Quantify the bog as well, how long, how bad,

The needle could have some writing or markings on it that would identify it....

If you change so many things at once it is a moving target and you are just setting yourself up for failure.

Now there is almost no way if telling what caused the issue as they are all interconnected.

I almost feel like suggesting you should undo everything you did and save yourself from going nuts.
Start at a baseline and then change one thing at a time, then you can be much more certain where the problem actually is.

Also change things with a plan - start with the main jet, then needle, then slow speed, then ap.

Assuming of course the carb is clean, float at 9mm, no air leaks, valves on motor within spec.....etc.

- the AP ( accelerator pump ) no idea what an "ac" is..... should only just miss the slide. spraying when it is open is not good enough.
  it has to be just as the slide starts to lift without actually hitting the slide.

- if it only runs WITH the choke then somehow you have made it very lean.
  Blocking or changing one of the air or fuel circuits.

  When you say "it will not run without" the choke. that is way too general, you have to be specific.

  So it won't start without the choke even when hot?
  It won't idle without the choke?
  It won't run even at high rpm and lets say half throttle without the choke?

  if this is just at idle then ...
  - is your idle actually set? can you get it to hold a steady 2000 with the throttle choke/no choke?
  - you never confirmed your pilot jet size or pilot air jet size ( we are just assuming its 45 )
  - what fuel screw are you using, and what setting?
  - have you checked/set your float level?

Also in regards to restrictions there are the snorkel, the restriction in the carb rubber between the engine and the carb and the throttle stop on the carb preventing WOT. The slide needs to clear the carb on WOT.

Have a great weekend!

Hey mate sorry about the typo i did mean AP not ac.., the bog only lasts for maybe 3-4 seconds and nearly stalls the bike, the AP** starts spraying about half a second after the slide opens and lasts maybe 3-5 seconds.  is there a way to adjust the timing for the ap on the Slant Carbys?

it will not start without choke even when hot and wont idle without it either. the idle was fine and it started up and idled perfectly yesterday.

-45 pilot jet 

-stock fuel screw set to 2 turns out (have tried 2.5-1 and 1.5 turns aswell 2 seemed to be the best)

-i have not checked the float level is there a guide on how to do it? im fairly new to carbs

I have removed the snorkel and the restricker in the intake rubber, but i was not aware of the throttle stop. how do i remove that? thank you for your help 

 

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alright i got it to idle half decent again, but it sounds like it wants to stall with the choke but now it runs without choke again

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