Who's tuned a carb around here?
#1
10-24-2015, 01:53 PM
Who's tuned a carb around here?
I'm getting ready to install S&S quiet tour slip-ons and a Fuel Moto stage one air cleaner on my carbureted '03 Road King. I'm figuring that the carb will need to be "tuned" in some way to compensate for the increased air flow in/out of the motor. I searched around and ordered the CV tuning kit from CV performance based on reviews I've read around the inter web.
Has anyone tuned/jetted their carbs before, with a similar setup as mine? I've never messed with carbs before. Or motorcycles in general for that matter. I'm a pretty decent shade tree mechanic, I just did the timing belt on my wife's van.
Has anyone tuned/jetted their carbs before, with a similar setup as mine? I've never messed with carbs before. Or motorcycles in general for that matter. I'm a pretty decent shade tree mechanic, I just did the timing belt on my wife's van.
#2
10-24-2015, 01:59 PM
most of the "carb kits" on the market are crap ( incl. dynojet, yost).
beware of anything that replaces the slide with plastic.
nightrider.com has a bike tech section and a piece on modding the CV carb, and a 2nd piece on evaluating the tuning of the CV carb
( the stock keihin CV carb is awesome and has also been used by KZ, triumph and honda- who own keihin)
the CV carb mods listed at nightrider are essentially the same mods we've been doing since the CV was introduced on big twins in 1990- with the addition of chamfering the leading edge of the slide- about $20 in parts from the dealer
at first go it is important to ensure that the float bowl diaphram is not leaking, nor the slide diaphragm...and check the float for proper float bowl level. all easy
swapping the needle for a slimmer taper N65 ( sporty needle) and changing the low speed and high speed jets.
baseline jets for an 88 might be 45 or 48 and 180/ 185.
once the bike is running reasonably well, then the jets may be altered to get best power and economy-
on my carbs the 4 x 4mm float bowl screws are replaced with allen heads so that I could swap jets roadside when tuning- using a mirror to see . that way the carb stays on the bike...of course you close the petcock first and open the float bowl drain
the Cv carb has the 4 circuits each of which affects the other above it:
idle circuit ( remove the aluminum plug- put LOCKTITE on the adjusting screw! whether stock or the EZ-just)
low speed jet
midrange is affected by the needle taper moving in and out of the high speed jet.
and the high speed jet which at full throttle may have the needle almost full out
add the accelerator pump which shoots in raw gas any time the throttle is opened quickly
tuning requires patience and paying attention to changes resulting from your actions- but once you have an idea what you are looking for you'll find it easier
mike
beware of anything that replaces the slide with plastic.
nightrider.com has a bike tech section and a piece on modding the CV carb, and a 2nd piece on evaluating the tuning of the CV carb
( the stock keihin CV carb is awesome and has also been used by KZ, triumph and honda- who own keihin)
the CV carb mods listed at nightrider are essentially the same mods we've been doing since the CV was introduced on big twins in 1990- with the addition of chamfering the leading edge of the slide- about $20 in parts from the dealer
at first go it is important to ensure that the float bowl diaphram is not leaking, nor the slide diaphragm...and check the float for proper float bowl level. all easy
swapping the needle for a slimmer taper N65 ( sporty needle) and changing the low speed and high speed jets.
baseline jets for an 88 might be 45 or 48 and 180/ 185.
once the bike is running reasonably well, then the jets may be altered to get best power and economy-
on my carbs the 4 x 4mm float bowl screws are replaced with allen heads so that I could swap jets roadside when tuning- using a mirror to see . that way the carb stays on the bike...of course you close the petcock first and open the float bowl drain
the Cv carb has the 4 circuits each of which affects the other above it:
idle circuit ( remove the aluminum plug- put LOCKTITE on the adjusting screw! whether stock or the EZ-just)
low speed jet
midrange is affected by the needle taper moving in and out of the high speed jet.
and the high speed jet which at full throttle may have the needle almost full out
add the accelerator pump which shoots in raw gas any time the throttle is opened quickly
tuning requires patience and paying attention to changes resulting from your actions- but once you have an idea what you are looking for you'll find it easier
mike
Last edited by mkguitar; 10-24-2015 at 02:55 PM.
#4
10-24-2015, 07:32 PM
Grand HDF Member
#5
10-24-2015, 07:47 PM
Thanks for the replies. The kit came in the mail today. It came with 46 and 48 low jets, the new needle, 190 and 195 mains, a thumb screw to replace the mixture screw with and a different diaphragm spring. I'm gonna get out there in the next week or so and mess with it once it's back from getting the frame fixed.
#6
10-25-2015, 07:39 AM
Seasoned HDF Member
I used to use a 1988 Sportster needle. That was the only year they didn't have an accelerator pump. A 48 slow jet and 195 main. Took the plug out of where the idle jet is and screwed the screw all the way in very gently and then backed out 1/2 + turns until the idle suited me. I also cut 1 coil off of the slide return spring.
This was with 80 inchers running stage 1 with an Andrews EV13 cam.
Bill
This was with 80 inchers running stage 1 with an Andrews EV13 cam.
Bill
#7
10-25-2015, 07:46 AM
Stellar HDF Member
Trending Topics
#8
10-25-2015, 10:59 AM
Road Warrior
most of the "carb kits" on the market are crap ( incl. dynojet, yost).
beware of anything that replaces the slide with plastic.
nightrider.com has a bike tech section and a piece on modding the CV carb, and a 2nd piece on evaluating the tuning of the CV carb
( the stock keihin CV carb is awesome and has also been used by KZ, triumph and honda- who own keihin)
the CV carb mods listed at nightrider are essentially the same mods we've been doing since the CV was introduced on big twins in 1990- with the addition of chamfering the leading edge of the slide- about $20 in parts from the dealer
at first go it is important to ensure that the float bowl diaphram is not leaking, nor the slide diaphragm...and check the float for proper float bowl level. all easy
swapping the needle for a slimmer taper N65 ( sporty needle) and changing the low speed and high speed jets.
baseline jets for an 88 might be 45 or 48 and 180/ 185.
once the bike is running reasonably well, then the jets may be altered to get best power and economy-
on my carbs the 4 x 4mm float bowl screws are replaced with allen heads so that I could swap jets roadside when tuning- using a mirror to see . that way the carb stays on the bike...of course you close the petcock first and open the float bowl drain
the Cv carb has the 4 circuits each of which affects the other above it:
idle circuit ( remove the aluminum plug- put LOCKTITE on the adjusting screw! whether stock or the EZ-just)
low speed jet
midrange is affected by the needle taper moving in and out of the high speed jet.
and the high speed jet which at full throttle may have the needle almost full out
add the accelerator pump which shoots in raw gas any time the throttle is opened quickly
tuning requires patience and paying attention to changes resulting from your actions- but once you have an idea what you are looking for you'll find it easier
mike
beware of anything that replaces the slide with plastic.
nightrider.com has a bike tech section and a piece on modding the CV carb, and a 2nd piece on evaluating the tuning of the CV carb
( the stock keihin CV carb is awesome and has also been used by KZ, triumph and honda- who own keihin)
the CV carb mods listed at nightrider are essentially the same mods we've been doing since the CV was introduced on big twins in 1990- with the addition of chamfering the leading edge of the slide- about $20 in parts from the dealer
at first go it is important to ensure that the float bowl diaphram is not leaking, nor the slide diaphragm...and check the float for proper float bowl level. all easy
swapping the needle for a slimmer taper N65 ( sporty needle) and changing the low speed and high speed jets.
baseline jets for an 88 might be 45 or 48 and 180/ 185.
once the bike is running reasonably well, then the jets may be altered to get best power and economy-
on my carbs the 4 x 4mm float bowl screws are replaced with allen heads so that I could swap jets roadside when tuning- using a mirror to see . that way the carb stays on the bike...of course you close the petcock first and open the float bowl drain
the Cv carb has the 4 circuits each of which affects the other above it:
idle circuit ( remove the aluminum plug- put LOCKTITE on the adjusting screw! whether stock or the EZ-just)
low speed jet
midrange is affected by the needle taper moving in and out of the high speed jet.
and the high speed jet which at full throttle may have the needle almost full out
add the accelerator pump which shoots in raw gas any time the throttle is opened quickly
tuning requires patience and paying attention to changes resulting from your actions- but once you have an idea what you are looking for you'll find it easier
mike
The following users liked this post:
Moe horowetz (05-02-2019)
#9
10-25-2015, 01:19 PM
Join Date: Jan 2007
Location: along the shore of Mishigami
Posts: 15,674
Received 4,298 Likes
on
2,353 Posts
The following users liked this post:
Moe horowetz (05-02-2019)
#10
10-25-2015, 05:57 PM
