CV Carb problem
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Road Captain
Joined: Jun 2008
Posts: 502
Likes: 3
From: Sarasota, Florida
CV Carb problem
I am working on my friends Sportster that has the CV carb. Yes, I know this is the Touring Forum, but I am hoping someone has had this problem. (Tried the Sportster forum and got a few replies.
With the air cleaner off and keeping the engine at 1500 - 1800 rpm's, I have a VERY small stream of gas coming from the accelerator pump discharge nozzle.
The bike is running very rich, and has fouled the front cylinder plug.
It will seem fine, then I shut the bike off, restart in a minute and it will barley start. I have to hold the throttle nearly wide open to get it to start. Lots of black smoke.
Has anybody had this problem and discovered a fix.
BTW, I installed a new vacuum piston and Float and needle. Set the float at .450 and also set it at .480. Neither setting had much effect on the richness.
Installed the '88 sportster needle and 46 pilot a couple of years ago and the bike has run perfectly since.....Except just now.......
With the air cleaner off and keeping the engine at 1500 - 1800 rpm's, I have a VERY small stream of gas coming from the accelerator pump discharge nozzle.
The bike is running very rich, and has fouled the front cylinder plug.
It will seem fine, then I shut the bike off, restart in a minute and it will barley start. I have to hold the throttle nearly wide open to get it to start. Lots of black smoke.
Has anybody had this problem and discovered a fix.
BTW, I installed a new vacuum piston and Float and needle. Set the float at .450 and also set it at .480. Neither setting had much effect on the richness.
Installed the '88 sportster needle and 46 pilot a couple of years ago and the bike has run perfectly since.....Except just now.......
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
guessing the ethanol has eaten the accel pump diaphragm, there should not be fuel coming from there unless the pump is activated by the pushrod on the diaphragm
replace it, 3 screws, carb stays in place.
i can;t remember the float setting off the top of my head...I know the measurement i used was in MM( added spec in post below)
check that the idle adjustment needle hasn't fallen out- locktite it.
for my 80" bikes with modified slides and sportster N65 needle I was usually using a .42 or .45 low speed jet, and a .175 high speed- that with a modified slide ( .125" hole, chamfered leading edge.)
nightrider.com has good modding and tuning info in the biketech section
I love the CV
mike
replace it, 3 screws, carb stays in place.
i can;t remember the float setting off the top of my head...I know the measurement i used was in MM( added spec in post below)
check that the idle adjustment needle hasn't fallen out- locktite it.
for my 80" bikes with modified slides and sportster N65 needle I was usually using a .42 or .45 low speed jet, and a .175 high speed- that with a modified slide ( .125" hole, chamfered leading edge.)
nightrider.com has good modding and tuning info in the biketech section
I love the CV
mike
Last edited by mkguitar; Jun 16, 2014 at 07:22 PM.
Road Captain
Joined: Sep 2008
Posts: 727
Likes: 1
From: Silverdale, WA
Seems like there is a ball check in there to prevent this, may be stuck with dirt/corrosion. Sounds like time for a clean and inspect on accel pump. Had start is due to rich mixture on a hot restart. Probably starts right up when cold right?
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
ok, but your accel pump appears to be leaking into the carb... did you look at that?
mike
mike
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
float setting per 1990 manual is
.725~.730" or 18.4~18.5 mm
from flange face to float perimeter with carb inverted.
bend tab to adjust
4mm allen heads are a good replacement for the float bowl screws since you have it off.
makes for tuning roadside easier.
mike
.725~.730" or 18.4~18.5 mm
from flange face to float perimeter with carb inverted.
bend tab to adjust
4mm allen heads are a good replacement for the float bowl screws since you have it off.
makes for tuning roadside easier.
mike
Last edited by mkguitar; Jun 16, 2014 at 07:35 PM.
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Road Captain
Joined: Jun 2008
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From: Sarasota, Florida
Ok....Tested the petcock using my mighty vac - Gas comes out of the vacuum hose.
Naturally, both dealers do not have the petcock in stock - ordered - At least 4 days to wait.
I will reply in 4 or 5 days with the results.
Thanks for all the help and ideas.
Naturally, both dealers do not have the petcock in stock - ordered - At least 4 days to wait.
I will reply in 4 or 5 days with the results.
Thanks for all the help and ideas.
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Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
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From: Phoenix '53, '88, '09 Big Twins
you might consider replacing with a non vacuum petcock.
as owners are discovering, alot of the rubber parts on our bikes do not hold up to the additives packages in pump gas.
which is the end results in increased emissions from raw gas spills or over rich mixtures.
mike
as owners are discovering, alot of the rubber parts on our bikes do not hold up to the additives packages in pump gas.
which is the end results in increased emissions from raw gas spills or over rich mixtures.
mike
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