Add group to favorites
Back to post list
Send new message to group Search:
Post Subject:
Throttle pickup from idle
Throttle pickup from idle
I have a 1996 Honda CBR1000F. I am very happy with it, except for one
little annoyance: When I want to add power after having it completely
closed, it is very difficult to avoid a jerk just as the throttle
opens.
Earlier, it was impossible to avoid the jerk. Since then, I have
replaced the drive chain, adjusted the valves, synched the carbs and
lubed and adjusted the throttle cables and throttle grip. It helped
somewhat, but it is till not right. I have to be extremely careful if
I want to avoid the jerky transition.
Running at a very high gear more or less eliminates the problem, but
that is just masking the symptom, not solving the problem.
The engine runs, as far is I can tell, perfectly otherwise.
This can't be normal? How to I troubleshoot this?
--
RoRo
I have a 1996 Honda CBR1000F. I am very happy with it, except for one
little annoyance: When I want to add power after having it completely
closed, it is very difficult to avoid a jerk just as the throttle
opens.
Earlier, it was impossible to avoid the jerk. Since then, I have
replaced the drive chain, adjusted the valves, synched the carbs and
lubed and adjusted the throttle cables and throttle grip. It helped
somewhat, but it is till not right. I have to be extremely careful if
I want to avoid the jerky transition.
Running at a very high gear more or less eliminates the problem, but
that is just masking the symptom, not solving the problem.
The engine runs, as far is I can tell, perfectly otherwise.
This can't be normal? How to I troubleshoot this?
--
RoRo
Re: Throttle pickup from idle
Robert Roland <fake@ddress.no> writes
>I have a 1996 Honda CBR1000F. I am very happy with it, except for one
>little annoyance: When I want to add power after having it completely
>closed, it is very difficult to avoid a jerk just as the throttle
>opens.
>
>Earlier, it was impossible to avoid the jerk. Since then, I have
>replaced the drive chain, adjusted the valves, synched the carbs and
>lubed and adjusted the throttle cables and throttle grip. It helped
>somewhat, but it is till not right. I have to be extremely careful if
>I want to avoid the jerky transition.
>
>Running at a very high gear more or less eliminates the problem, but
>that is just masking the symptom, not solving the problem.
>
>The engine runs, as far is I can tell, perfectly otherwise.
>
>This can't be normal? How to I troubleshoot this?
My last VFR did that when I bought it. I think I just learned to ride
around it as I didn't do anything to cure it beyond replacing the worn
out chain & sprockets - the bike had sat in a barn for 5 years before I
bought it.
What you might want to try is replacing the cush drive rubbers in the
rear sprocket carrier. I intended to do that with the VFR but there was
always something more useful to spend the money on - usually petrol :-)
--
Bob Scott
Robert Roland <fake@ddress.no> writes
>I have a 1996 Honda CBR1000F. I am very happy with it, except for one
>little annoyance: When I want to add power after having it completely
>closed, it is very difficult to avoid a jerk just as the throttle
>opens.
>
>Earlier, it was impossible to avoid the jerk. Since then, I have
>replaced the drive chain, adjusted the valves, synched the carbs and
>lubed and adjusted the throttle cables and throttle grip. It helped
>somewhat, but it is till not right. I have to be extremely careful if
>I want to avoid the jerky transition.
>
>Running at a very high gear more or less eliminates the problem, but
>that is just masking the symptom, not solving the problem.
>
>The engine runs, as far is I can tell, perfectly otherwise.
>
>This can't be normal? How to I troubleshoot this?
My last VFR did that when I bought it. I think I just learned to ride
around it as I didn't do anything to cure it beyond replacing the worn
out chain & sprockets - the bike had sat in a barn for 5 years before I
bought it.
What you might want to try is replacing the cush drive rubbers in the
rear sprocket carrier. I intended to do that with the VFR but there was
always something more useful to spend the money on - usually petrol :-)
--
Bob Scott
Re: Throttle pickup from idle
"Robert Roland" <fake@ddress.no> wrote
> Earlier, it was impossible to avoid the jerk. Since then, I have
> replaced the drive chain, adjusted the valves, synched the carbs and
> lubed and adjusted the throttle cables and throttle grip. It helped
> somewhat, but it is till not right. I have to be extremely careful if
> I want to avoid the jerky transition.
>
Something sticking slightly in the throttle mechanism ???? Hand grip,
cable, cable connection near carbs, butterfly(s)........,it would only take
a tiny bit of sticking. No (or not enough) slack in the throttle cables?
Too MUCH slack in the cables? Throttle return spring(s) too strong?
Just some wild guesses. FWIW.
"Robert Roland" <fake@ddress.no> wrote
> Earlier, it was impossible to avoid the jerk. Since then, I have
> replaced the drive chain, adjusted the valves, synched the carbs and
> lubed and adjusted the throttle cables and throttle grip. It helped
> somewhat, but it is till not right. I have to be extremely careful if
> I want to avoid the jerky transition.
>
Something sticking slightly in the throttle mechanism ???? Hand grip,
cable, cable connection near carbs, butterfly(s)........,it would only take
a tiny bit of sticking. No (or not enough) slack in the throttle cables?
Too MUCH slack in the cables? Throttle return spring(s) too strong?
Just some wild guesses. FWIW.
Re: Throttle pickup from idle
Robert Roland wrote:
> When I want to add power after having it completely
>closed, it is very difficult to avoid a jerk just as the throttle
>opens.
Hello, RoRo. Are you in Norway?
Motorcycle drive trains have a lot of slop in them. You would have a hard
time
shifting gears if the slots in the freewheeling gears weren't larger than the
dogs on the pinion gears.
So, once you're in a gear, any time you change throttle position, the
motorcycle
will jerk a little bit.
And this jerking is aggravated by the constant vacuum (diaphragm) carburetors
that act like they have a mind of their own. If you change throttle position
the vacuum slide drops and leans up the mixture.
When you open the throttle, the CV carb is also slow to respond to the need
for more gasoline as engine vacuum drops off, especially if the idle circuit
and the acceleration transition ports are gummed up.
There is nothing that responds quite as well as a set of radial flat slide
Keihin carburetors, but that's an expensive solution to the CV carburetor
problem.
Although you've synched the carbs, you still may have a problem with dirty,
gummed up idle ports and passages. CV carburetors are famous for getting all
gummed up and the mechanic$ are eager to get your bike into the $hop and
$ynch your carb$ for you.
But, I recommend that you pour about 4 or 5 ounces of a clear carburetor
cleaner into a full tank of gasoline and then go for a slow ride to clean the
ilde circuits out.
I don't know what is available where you are, but a mixture of xylene,
toulene, acetone and methyl alcohol works very well to clean gum and varnish
out of the jets and passages.
In the USA, I recommend Berryman B12 Chemtool Choke and Carburetor Cleaner in
the liquid form.
If the throttle response is still jerky after cleaning the idle circuit, you
can adjust all the idle mixture screws counterclockwise about 1/4th of a turn.
http :// www .bikebandit,com /partsbandit/showschematic.asp?dept_id=195205
6: SCREW SET is the idle mixture screw.
Don't go too far CCW with those screws, the idle jet is about a #40, which is
fairly large.
If you open the idle mixture screws too far, the idle speed will slow down
and the exhaust sound may become dull and thudding.
The mistake the amateur mechanic makes is in turning the idle speed knob
clockwise,
This uncovers a pattern of three acceleration transition ports which
shouldn't be uncovered at idle. They are NOT controlled by the idle mixture
screws, they are controlled by the bottom edge of the butterfly.
When the amateur mechanic blips the throttle to check for response, the
engine won't idle back down.
So, don't go too far with opening up the idle mixture screws. Just a little
bit to help the throttle response.
--
Message posted via MotorcycleKB,com
http :// www .motorcyclekb,com /Uwe/Forums.aspx/tech/200708/1
Robert Roland wrote:
> When I want to add power after having it completely
>closed, it is very difficult to avoid a jerk just as the throttle
>opens.
Hello, RoRo. Are you in Norway?
Motorcycle drive trains have a lot of slop in them. You would have a hard
time
shifting gears if the slots in the freewheeling gears weren't larger than the
dogs on the pinion gears.
So, once you're in a gear, any time you change throttle position, the
motorcycle
will jerk a little bit.
And this jerking is aggravated by the constant vacuum (diaphragm) carburetors
that act like they have a mind of their own. If you change throttle position
the vacuum slide drops and leans up the mixture.
When you open the throttle, the CV carb is also slow to respond to the need
for more gasoline as engine vacuum drops off, especially if the idle circuit
and the acceleration transition ports are gummed up.
There is nothing that responds quite as well as a set of radial flat slide
Keihin carburetors, but that's an expensive solution to the CV carburetor
problem.
Although you've synched the carbs, you still may have a problem with dirty,
gummed up idle ports and passages. CV carburetors are famous for getting all
gummed up and the mechanic$ are eager to get your bike into the $hop and
$ynch your carb$ for you.
But, I recommend that you pour about 4 or 5 ounces of a clear carburetor
cleaner into a full tank of gasoline and then go for a slow ride to clean the
ilde circuits out.
I don't know what is available where you are, but a mixture of xylene,
toulene, acetone and methyl alcohol works very well to clean gum and varnish
out of the jets and passages.
In the USA, I recommend Berryman B12 Chemtool Choke and Carburetor Cleaner in
the liquid form.
If the throttle response is still jerky after cleaning the idle circuit, you
can adjust all the idle mixture screws counterclockwise about 1/4th of a turn.
http :// www .bikebandit,com /partsbandit/showschematic.asp?dept_id=195205
6: SCREW SET is the idle mixture screw.
Don't go too far CCW with those screws, the idle jet is about a #40, which is
fairly large.
If you open the idle mixture screws too far, the idle speed will slow down
and the exhaust sound may become dull and thudding.
The mistake the amateur mechanic makes is in turning the idle speed knob
clockwise,
This uncovers a pattern of three acceleration transition ports which
shouldn't be uncovered at idle. They are NOT controlled by the idle mixture
screws, they are controlled by the bottom edge of the butterfly.
When the amateur mechanic blips the throttle to check for response, the
engine won't idle back down.
So, don't go too far with opening up the idle mixture screws. Just a little
bit to help the throttle response.
--
Message posted via MotorcycleKB,com
http :// www .motorcyclekb,com /Uwe/Forums.aspx/tech/200708/1
Re: Throttle pickup from idle
On Wed, 08 Aug 2007 17:54:50 GMT, "Albrecht via MotorcycleKB,com "
<u33665@uwe> wrote:
>Hello, RoRo. Are you in Norway?
Yes, I am.
>Motorcycle drive trains have a lot of slop in them. You would have a hard
>time
>shifting gears if the slots in the freewheeling gears weren't larger than the
>dogs on the pinion gears.
>
>So, once you're in a gear, any time you change throttle position, the
>motorcycle
>will jerk a little bit.
Yes, even cars have plenty of slop. The point is that if the rider (or
driver) is able to take out the slack gently, the jerk will be small,
maybe even not noticeable.
>Although you've synched the carbs, you still may have a problem with dirty,
>gummed up idle ports and passages. CV carburetors are famous for getting all
>gummed up and the mechanic$ are eager to get your bike into the $hop and
>$ynch your carb$ for you.
>
>But, I recommend that you pour about 4 or 5 ounces of a clear carburetor
>cleaner into a full tank of gasoline and then go for a slow ride to clean the
>ilde circuits out.
>
>I don't know what is available where you are, but a mixture of xylene,
>toulene, acetone and methyl alcohol works very well to clean gum and varnish
>out of the jets and passages.
I'll see what I can find. If that does not solve the problem, I'll
take the carbs apart and clean them manually.
>If the throttle response is still jerky after cleaning the idle circuit, you
>can adjust all the idle mixture screws counterclockwise about 1/4th of a turn.
>
> http :// www .bikebandit,com /partsbandit/showschematic.asp?dept_id=195205
>
> 6: SCREW SET is the idle mixture screw.
It seems I have to remove the carbs to get to them. They seem to be
located on the underside of the carb. Can it be that stupidly made?
>The mistake the amateur mechanic makes is in turning the idle speed knob
>clockwise,
I just remembered: The idle speed knob is very sensitive. It is
difficult to get the right idle speed. Even the slightest twist will
be too much one way or the other. Of course, the rubber connection
between the knob and the actual screw does not help.
>So, don't go too far with opening up the idle mixture screws. Just a little
>bit to help the throttle response.
I will. It may be spring before I get to it, though. Winter is coming,
and we haven't even had a summer yet.
Thanks to you and everyone else for your suggestions.
--
RoRo
On Wed, 08 Aug 2007 17:54:50 GMT, "Albrecht via MotorcycleKB,com "
<u33665@uwe> wrote:
>Hello, RoRo. Are you in Norway?
Yes, I am.
>Motorcycle drive trains have a lot of slop in them. You would have a hard
>time
>shifting gears if the slots in the freewheeling gears weren't larger than the
>dogs on the pinion gears.
>
>So, once you're in a gear, any time you change throttle position, the
>motorcycle
>will jerk a little bit.
Yes, even cars have plenty of slop. The point is that if the rider (or
driver) is able to take out the slack gently, the jerk will be small,
maybe even not noticeable.
>Although you've synched the carbs, you still may have a problem with dirty,
>gummed up idle ports and passages. CV carburetors are famous for getting all
>gummed up and the mechanic$ are eager to get your bike into the $hop and
>$ynch your carb$ for you.
>
>But, I recommend that you pour about 4 or 5 ounces of a clear carburetor
>cleaner into a full tank of gasoline and then go for a slow ride to clean the
>ilde circuits out.
>
>I don't know what is available where you are, but a mixture of xylene,
>toulene, acetone and methyl alcohol works very well to clean gum and varnish
>out of the jets and passages.
I'll see what I can find. If that does not solve the problem, I'll
take the carbs apart and clean them manually.
>If the throttle response is still jerky after cleaning the idle circuit, you
>can adjust all the idle mixture screws counterclockwise about 1/4th of a turn.
>
> http :// www .bikebandit,com /partsbandit/showschematic.asp?dept_id=195205
>
> 6: SCREW SET is the idle mixture screw.
It seems I have to remove the carbs to get to them. They seem to be
located on the underside of the carb. Can it be that stupidly made?
>The mistake the amateur mechanic makes is in turning the idle speed knob
>clockwise,
I just remembered: The idle speed knob is very sensitive. It is
difficult to get the right idle speed. Even the slightest twist will
be too much one way or the other. Of course, the rubber connection
between the knob and the actual screw does not help.
>So, don't go too far with opening up the idle mixture screws. Just a little
>bit to help the throttle response.
I will. It may be spring before I get to it, though. Winter is coming,
and we haven't even had a summer yet.
Thanks to you and everyone else for your suggestions.
--
RoRo
Re: Throttle pickup from idle
>On Thu, 30 Aug 2007 19:40:05 +0200, Robert Roland <fake@ddress.no> wrote:
>On Wed, 08 Aug 2007 17:54:50 GMT, "Albrecht via MotorcycleKB,com "
><u33665@uwe> wrote:
>
>>Hello, RoRo. Are you in Norway?
>
>Yes, I am.
>
>>Motorcycle drive trains have a lot of slop in them. You would have a hard
>>time
>>shifting gears if the slots in the freewheeling gears weren't larger than the
>>dogs on the pinion gears.
>>
>>So, once you're in a gear, any time you change throttle position, the
>>motorcycle
>>will jerk a little bit.
>
>Yes, even cars have plenty of slop. The point is that if the rider (or
>driver) is able to take out the slack gently, the jerk will be small,
>maybe even not noticeable.
>
>>Although you've synched the carbs, you still may have a problem with dirty,
>>gummed up idle ports and passages. CV carburetors are famous for getting all
>>gummed up and the mechanic$ are eager to get your bike into the $hop and
>>$ynch your carb$ for you.
>>
>>But, I recommend that you pour about 4 or 5 ounces of a clear carburetor
>>cleaner into a full tank of gasoline and then go for a slow ride to clean the
>>ilde circuits out.
>>
>>I don't know what is available where you are, but a mixture of xylene,
>>toulene, acetone and methyl alcohol works very well to clean gum and varnish
>>out of the jets and passages.
>
>I'll see what I can find. If that does not solve the problem, I'll
>take the carbs apart and clean them manually.
>
>>If the throttle response is still jerky after cleaning the idle circuit, you
>>can adjust all the idle mixture screws counterclockwise about 1/4th of a turn.
>>
>> http :// www .bikebandit,com /partsbandit/showschematic.asp?dept_id=195205
>>
>> 6: SCREW SET is the idle mixture screw.
>
>It seems I have to remove the carbs to get to them. They seem to be
>located on the underside of the carb. Can it be that stupidly made?
>
>>The mistake the amateur mechanic makes is in turning the idle speed knob
>>clockwise,
>
>I just remembered: The idle speed knob is very sensitive. It is
>difficult to get the right idle speed. Even the slightest twist will
>be too much one way or the other. Of course, the rubber connection
>between the knob and the actual screw does not help.
>
>>So, don't go too far with opening up the idle mixture screws. Just a little
>>bit to help the throttle response.
>
>I will. It may be spring before I get to it, though. Winter is coming,
>and we haven't even had a summer yet.
>
>Thanks to you and everyone else for your suggestions.
***************************************
I have one of these for 4-stroke carb adjustment for atvs and
motorcycles:
http :// www .motionpro,com /motorcycle/tools/pilot_screw_adjusting_tool/
I've found it to be extremely handy, No more burned fingers, and no
more removing the carbs from atvs, just to adjust the idle fuel screw.
It might help you.
Good Riding and Good Wrenching to You!
Wudsracer/Jim Cook
Smackover Racing
'06 Gas Gas DE300
'82 Husqvarna XC250
Team LAGNAF
>On Thu, 30 Aug 2007 19:40:05 +0200, Robert Roland <fake@ddress.no> wrote:
>On Wed, 08 Aug 2007 17:54:50 GMT, "Albrecht via MotorcycleKB,com "
><u33665@uwe> wrote:
>
>>Hello, RoRo. Are you in Norway?
>
>Yes, I am.
>
>>Motorcycle drive trains have a lot of slop in them. You would have a hard
>>time
>>shifting gears if the slots in the freewheeling gears weren't larger than the
>>dogs on the pinion gears.
>>
>>So, once you're in a gear, any time you change throttle position, the
>>motorcycle
>>will jerk a little bit.
>
>Yes, even cars have plenty of slop. The point is that if the rider (or
>driver) is able to take out the slack gently, the jerk will be small,
>maybe even not noticeable.
>
>>Although you've synched the carbs, you still may have a problem with dirty,
>>gummed up idle ports and passages. CV carburetors are famous for getting all
>>gummed up and the mechanic$ are eager to get your bike into the $hop and
>>$ynch your carb$ for you.
>>
>>But, I recommend that you pour about 4 or 5 ounces of a clear carburetor
>>cleaner into a full tank of gasoline and then go for a slow ride to clean the
>>ilde circuits out.
>>
>>I don't know what is available where you are, but a mixture of xylene,
>>toulene, acetone and methyl alcohol works very well to clean gum and varnish
>>out of the jets and passages.
>
>I'll see what I can find. If that does not solve the problem, I'll
>take the carbs apart and clean them manually.
>
>>If the throttle response is still jerky after cleaning the idle circuit, you
>>can adjust all the idle mixture screws counterclockwise about 1/4th of a turn.
>>
>> http :// www .bikebandit,com /partsbandit/showschematic.asp?dept_id=195205
>>
>> 6: SCREW SET is the idle mixture screw.
>
>It seems I have to remove the carbs to get to them. They seem to be
>located on the underside of the carb. Can it be that stupidly made?
>
>>The mistake the amateur mechanic makes is in turning the idle speed knob
>>clockwise,
>
>I just remembered: The idle speed knob is very sensitive. It is
>difficult to get the right idle speed. Even the slightest twist will
>be too much one way or the other. Of course, the rubber connection
>between the knob and the actual screw does not help.
>
>>So, don't go too far with opening up the idle mixture screws. Just a little
>>bit to help the throttle response.
>
>I will. It may be spring before I get to it, though. Winter is coming,
>and we haven't even had a summer yet.
>
>Thanks to you and everyone else for your suggestions.
***************************************
I have one of these for 4-stroke carb adjustment for atvs and
motorcycles:
http :// www .motionpro,com /motorcycle/tools/pilot_screw_adjusting_tool/
I've found it to be extremely handy, No more burned fingers, and no
more removing the carbs from atvs, just to adjust the idle fuel screw.
It might help you.
Good Riding and Good Wrenching to You!
Wudsracer/Jim Cook
Smackover Racing
'06 Gas Gas DE300
'82 Husqvarna XC250
Team LAGNAF
Re: Throttle pickup from idle
Wudsracer wrote:
>I have one of these for 4-stroke carb adjustment for atvs and
>motorcycles:
> http :// www .motionpro,com /motorcycle/tools/pilot_screw_adjusting_tool/
>I've found it to be extremely handy, No more burned fingers, and no
>more removing the carbs from atvs, just to adjust the idle fuel screw.
I just use the 1-inch long slot head tip from a set that fits in a 1/4 inch
socket.
--
Message posted via MotorcycleKB,com
http :// www .motorcyclekb,com /Uwe/Forums.aspx/tech/200708/1
Wudsracer wrote:
>I have one of these for 4-stroke carb adjustment for atvs and
>motorcycles:
> http :// www .motionpro,com /motorcycle/tools/pilot_screw_adjusting_tool/
>I've found it to be extremely handy, No more burned fingers, and no
>more removing the carbs from atvs, just to adjust the idle fuel screw.
I just use the 1-inch long slot head tip from a set that fits in a 1/4 inch
socket.
--
Message posted via MotorcycleKB,com
http :// www .motorcyclekb,com /Uwe/Forums.aspx/tech/200708/1
Re: Throttle pickup from idle
Robert Roland wrote:
>> 6: SCREW SET is the idle mixture screw.
>
>It seems I have to remove the carbs to get to them. They seem to be
>located on the underside of the carb. Can it be that stupidly made?
Unfortunately, yes.
Idle mixture screws have been placed on top, underneath, and on the sides of
CV carbs.
They don't have to be adjusted very often, they are usually set at the
factory and sealed with an anti-tamper plug.
But, if you need to do a thorough cleaning of the carbs, you have to remove
them and drill out the plug. Shop manuals recommend using an exhaust gas
analyzer to return the mixture to factory specs and then a new plug is
installed.
--
Message posted via http :// www .motorcyclekb,com
Robert Roland wrote:
>> 6: SCREW SET is the idle mixture screw.
>
>It seems I have to remove the carbs to get to them. They seem to be
>located on the underside of the carb. Can it be that stupidly made?
Unfortunately, yes.
Idle mixture screws have been placed on top, underneath, and on the sides of
CV carbs.
They don't have to be adjusted very often, they are usually set at the
factory and sealed with an anti-tamper plug.
But, if you need to do a thorough cleaning of the carbs, you have to remove
them and drill out the plug. Shop manuals recommend using an exhaust gas
analyzer to return the mixture to factory specs and then a new plug is
installed.
--
Message posted via http :// www .motorcyclekb,com
Re: Throttle pickup from idle
What you describe is fairly common on modern bikes with CV carbs. The
short story is that the idle mixture is set very lean from the factory
in order to meet smog standards. When you open the throttle, the
mixture momentarily leans out even more, until the slide moves enough
to properly enrichen the mixture. The engine catches suddenly and you
get a sudden burst of power.
The simple fix is to adjust the idle mixture screws for best idle,
rather than best emissions. Turn each of the mixture screws out
(counterclockwise) 1/4 of a turn at a time. The idle speed will pick
up initially, then stop increasing as the mixture reaches proper air-
to-fuel ratio. You might want to then try turning each screw back in
1/4 of a turn at a time until the idle speed drops off, then open each
back up by 1/4 turn.
This should help. Good luck.
What you describe is fairly common on modern bikes with CV carbs. The
short story is that the idle mixture is set very lean from the factory
in order to meet smog standards. When you open the throttle, the
mixture momentarily leans out even more, until the slide moves enough
to properly enrichen the mixture. The engine catches suddenly and you
get a sudden burst of power.
The simple fix is to adjust the idle mixture screws for best idle,
rather than best emissions. Turn each of the mixture screws out
(counterclockwise) 1/4 of a turn at a time. The idle speed will pick
up initially, then stop increasing as the mixture reaches proper air-
to-fuel ratio. You might want to then try turning each screw back in
1/4 of a turn at a time until the idle speed drops off, then open each
back up by 1/4 turn.
This should help. Good luck.
