CV help
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Joined: Sep 2009
Posts: 22
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CV help
I'm looking for advise on my '03 FLHT, I have the factory CV carb, 1550 big bore kit, SE251 cams, SE high compression 10.25:1 pistons, SE 31775-01A 6200 rpm ignition,SE high performance air kit, Dyna jet kit, I'm running stock 190 main and 45 slow jets, and my air mixture is at 3 turns. It's been a few years but as far as I remember the needle E-clip is at groove #4 as recommended, and slip on drags.It runs like a raped ape in cool weather, gets sluggish above 80 degrees, and is only getting 30mpg. To me this means I'm too rich. What can I do to get my best performance and up my mpg's to where they should be without tearing the carb off and trying a bunch of different jet sizes? All advice welcome, Thanks
Cruiser
Joined: Nov 2009
Posts: 212
Likes: 5
From: Left Coast FL
I'm pretty happy with this tuner kit from CV Performance...
http://www.cv-performance.com/cvp-ha...um-tuners-kit/
I had it installed when I did my cam plate upgrade, cams, etc. been running it for about 2 months now and it's been working great.
http://www.cv-performance.com/cvp-ha...um-tuners-kit/
I had it installed when I did my cam plate upgrade, cams, etc. been running it for about 2 months now and it's been working great.
Tourer
Joined: Dec 2007
Posts: 377
Likes: 3
From: Canada
My build is similar to yours but with more Headquarters stuff (95", 10.25:1 SE cast domes, HQ 0034 cams, HQ ignition, Dynojet kit, SE air cleaner, slip ons from a SE Road King)
I get about 35 US MPG on a good day.
I asked about it over on the old HQ forum and it was highly recommended to ditch the dynojet kit (guessed to be the biggest factor in my bad mileage) and go back to stock carb configuration with a HQ jet kit (IIRC a sportster needle with a couple of spacers), a new slide, a stock spring, and a stock emulsion tube.
It was also recommended that I'd do better with the addition of a good 2-1 pipe.
So far I haven't done any of this stuff
as even if the MPGs aren't where they should be the bike runs so good I hate to mess with it. I've put around 25,000 miles on the build as is.
I do have a Supertrapp Supermeg 2-1 ready to go, and intend to change out the dynojet kit - but until I do its just advice given to me that I'm sharing with you. No first hand knowledge yet!
I get about 35 US MPG on a good day.
I asked about it over on the old HQ forum and it was highly recommended to ditch the dynojet kit (guessed to be the biggest factor in my bad mileage) and go back to stock carb configuration with a HQ jet kit (IIRC a sportster needle with a couple of spacers), a new slide, a stock spring, and a stock emulsion tube.
It was also recommended that I'd do better with the addition of a good 2-1 pipe.
So far I haven't done any of this stuff
as even if the MPGs aren't where they should be the bike runs so good I hate to mess with it. I've put around 25,000 miles on the build as is.I do have a Supertrapp Supermeg 2-1 ready to go, and intend to change out the dynojet kit - but until I do its just advice given to me that I'm sharing with you. No first hand knowledge yet!
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
I personally think the "tuner" kits are junk.
dynojet, yost, thunderslide...
since the CV was introduced on big twins ( 1990) the common mod has been to drill the slide air bleed to 1/8" and perhaps chamfer the slide.
sporty needle N65C and change the jets ( and your jet choice may be close)
my 80" bikes usually like 42 and 170...and get better than 45 MPG- your larger motor would likely need larger jets and get lower MPG
the tuning took some work, incorporating many test runs and an o2 sensor in my header, with a voltmeter taped to the handlebars
I suggest you get to basics and try to restore the carb to closer to stock.
check the gaskets and seals, check the float valve and the float level. check the intake manifold seal...all that stuff incl. the accel pump seal.
the CV ( "constant-velocity") carb is self compensating for changes in air density -whether caused by temperature or altitude- if all the basics are correct- then the slide and needle are not working correctly, or calibrated correctly.
the 4mm float bowl screws are easily replaced with allen heads for quick bowl drops- also a small mirror- easy to fiddle with mid-test run if you already know it's screwy
nightrider.com has a section on bike tech and tuning the cv carb...it gives tips where you can guess rich or lean by the throttle response under various conditions
mike
dynojet, yost, thunderslide...
since the CV was introduced on big twins ( 1990) the common mod has been to drill the slide air bleed to 1/8" and perhaps chamfer the slide.
sporty needle N65C and change the jets ( and your jet choice may be close)
my 80" bikes usually like 42 and 170...and get better than 45 MPG- your larger motor would likely need larger jets and get lower MPG
the tuning took some work, incorporating many test runs and an o2 sensor in my header, with a voltmeter taped to the handlebars
I suggest you get to basics and try to restore the carb to closer to stock.
check the gaskets and seals, check the float valve and the float level. check the intake manifold seal...all that stuff incl. the accel pump seal.
the CV ( "constant-velocity") carb is self compensating for changes in air density -whether caused by temperature or altitude- if all the basics are correct- then the slide and needle are not working correctly, or calibrated correctly.
the 4mm float bowl screws are easily replaced with allen heads for quick bowl drops- also a small mirror- easy to fiddle with mid-test run if you already know it's screwy
nightrider.com has a section on bike tech and tuning the cv carb...it gives tips where you can guess rich or lean by the throttle response under various conditions
mike
Last edited by mkguitar; May 18, 2013 at 04:37 PM.
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