What size jets to use?
Thread Starter
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Novice
Joined: Aug 2014
Posts: 16
Likes: 4
From: UK
What size jets to use?
Hi
I'm having some issues with my Road King, it's running too rich and I'm not sure what the cause is.
I replaced the diaphragm this week (as the old one had torn) and fuel was dripping out of the carb. The main jet was loose, so I tightened it back up.
SETUP
SYMPTONS
//
Before I pay Ł250 and get the bike dyno'd and the carb setup, I would like to try and resolve this myself.
I'm having some issues with my Road King, it's running too rich and I'm not sure what the cause is.
I replaced the diaphragm this week (as the old one had torn) and fuel was dripping out of the carb. The main jet was loose, so I tightened it back up.
SETUP
- 2005 Road King with stock CV carb, 48 and 195 jets.
- 95" engine with S&S ported heads.
- Carb is clean with nothing sticking.
SYMPTONS
- When out on a run today, the bike would occasionally stutter when I went from 3/4 to WOT. Not every time, but usually around 60mph and 3500-4000ish rpm.
- The plugs are sooty and when I start the bike from cold, soot and water comes out of the exhaust.
- Bike starts and idles fine.
- Idle mix screw makes no difference to idle drop.
//
Before I pay Ł250 and get the bike dyno'd and the carb setup, I would like to try and resolve this myself.
- What size jets do you recommend?
- What else can I do to lean out the bike?
Road Warrior
Joined: May 2005
Posts: 1,301
Likes: 24
From: Minden LA
Hi
I'm having some issues with my Road King, it's running too rich and I'm not sure what the cause is.
I replaced the diaphragm this week (as the old one had torn) and fuel was dripping out of the carb. The main jet was loose, so I tightened it back up.
SETUP
SYMPTONS
//
Before I pay Ł250 and get the bike dyno'd and the carb setup, I would like to try and resolve this myself.
I'm having some issues with my Road King, it's running too rich and I'm not sure what the cause is.
I replaced the diaphragm this week (as the old one had torn) and fuel was dripping out of the carb. The main jet was loose, so I tightened it back up.
SETUP
- 2005 Road King with stock CV carb, 48 and 195 jets.
- 95" engine with S&S ported heads.
- Carb is clean with nothing sticking.
SYMPTONS
- When out on a run today, the bike would occasionally stutter when I went from 3/4 to WOT. Not every time, but usually around 60mph and 3500-4000ish rpm.
- The plugs are sooty and when I start the bike from cold, soot and water comes out of the exhaust.
- Bike starts and idles fine.
- Idle mix screw makes no difference to idle drop.
//
Before I pay Ł250 and get the bike dyno'd and the carb setup, I would like to try and resolve this myself.
- What size jets do you recommend?
- What else can I do to lean out the bike?
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
you will find some good carb modding & tuning info at nightrider.com
biketech
cv carb
ensure that the accel pump diaphragm is good, all the seals etc.
it is easy to go too rich.
the idle mixture controls idle but affects mixture at rpms above idle
the low speed affects low speed mixture, but affects mixture at rpms above
the needle controls midrange speed ( along with high speed) but affects mixture at rpms above
the high speed control mixture in about the last 7/8 of throttle...but this is affected by all the other settings
for example my stage 1 evo bagger 45/175 and N65 needle worked great with a modded slide ( drilled and chamfered) ...this gave a reliable 45 MPG at 65 MPH and good power throughout the rpm range
my cammed and hi-comp FXR has same carb mods but 42/180/N65
it has overdrive, ignition and a 2/1
I've tuned alot of cv carbs and the largest hi speed I have ever used is a 185...and that was with a stock needle.
read up and you'll be able to correlate what you are doing with the result. you can adjust the throttle position at speed and tell if you are rich or lean on teh high speed
going into a shop or dealer may not help much...the carbs are gone and shop kids don;t know where to plug in teh computer
strongly suggest you stay away from tuning kits, plastic slides from dyno or yost- good seals, set-up and $20 of HD parts will do it
mike
biketech
cv carb
ensure that the accel pump diaphragm is good, all the seals etc.
it is easy to go too rich.
the idle mixture controls idle but affects mixture at rpms above idle
the low speed affects low speed mixture, but affects mixture at rpms above
the needle controls midrange speed ( along with high speed) but affects mixture at rpms above
the high speed control mixture in about the last 7/8 of throttle...but this is affected by all the other settings
for example my stage 1 evo bagger 45/175 and N65 needle worked great with a modded slide ( drilled and chamfered) ...this gave a reliable 45 MPG at 65 MPH and good power throughout the rpm range
my cammed and hi-comp FXR has same carb mods but 42/180/N65
it has overdrive, ignition and a 2/1
I've tuned alot of cv carbs and the largest hi speed I have ever used is a 185...and that was with a stock needle.
read up and you'll be able to correlate what you are doing with the result. you can adjust the throttle position at speed and tell if you are rich or lean on teh high speed
going into a shop or dealer may not help much...the carbs are gone and shop kids don;t know where to plug in teh computer
strongly suggest you stay away from tuning kits, plastic slides from dyno or yost- good seals, set-up and $20 of HD parts will do it
mike
Last edited by mkguitar; Apr 2, 2016 at 04:23 PM.
Thread Starter
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Novice
Joined: Aug 2014
Posts: 16
Likes: 4
From: UK
Confused
I fitted a 46/185 set of jets today.
Cleaned the carb from top to bottom and blew compressed air through the holes.
Tried adjusting the idle mix again, no joy, idling completely unaffected by the EZ just screw.
Took it on a run, pulled fine. Seems a bit hotter, but to be expected. No stuttering any more.
My problem is "changing the jet sizes does not seem to affect performance" this can't be right surely?
The only other change I have made in the last month is to fit a baffle to the exhaust. Could this change in back pressure have anything to do with it?
Cleaned the carb from top to bottom and blew compressed air through the holes.
Tried adjusting the idle mix again, no joy, idling completely unaffected by the EZ just screw.
Took it on a run, pulled fine. Seems a bit hotter, but to be expected. No stuttering any more.
My problem is "changing the jet sizes does not seem to affect performance" this can't be right surely?
The only other change I have made in the last month is to fit a baffle to the exhaust. Could this change in back pressure have anything to do with it?
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