When I choke my bike and start to ride it, it feels like it pulls better in the lower rpm range. Does this mean it needs a larger pilot jet, or slow jet?

Do Harley dealers carry different sizes?

 

the stock CV carb does not use a conventional choke- it uses an enricher circuit.
which pulling out that **** opens.

tuning and modding the CV carb is easy- but you need to understand how the 5 circuits work and interact.

( enricher, idle needle, low speed jet, needle taper, high speed jet--- there is also the accelerator pump)-

nightrider.com has a biketech section with info on modding and tuning the CV carb

the same carb was used in some triumph and kawasaki models, jets and needles are available from a number of sources including HD as well as the yost and dynojet tuning kits ( DO NOT use the slides or springs with these kits- they do not work very well).

if you are not the original owner, you can tell if a CV carb has been worked on if the idle adjust screw seal has been drilled out

the CV carb is a really really good design and will provide good power, tunability, with economy - is is self adjusting for altitude, a huge advantage over most other brands

on the evos, the stock jetting for the CV would often make the bike backfire or sneeze through the carb at about 1500~1800 rpms- this was easily remedied by adjusting teh idle circuit.


mike

 

Many "old timers" would replace the needle with one from a sportster and be done with it

 

yes- the sportster N65 needle affects the range from about 2500 to 4300 rpms.
so would do nothing for OP's thoughts about low end.
the needle interacts with the high speed jet

the 5 circuits in the carb can interact with each other...


and because tuning a motor is not simple; the spark advance plays a part.
The carbed bike may use a voes which will help get the correct spark advance for the load on the motor and the throttle position....if the hose is off or busted.

or even an intake leak

Mike

 

================

Maybe maybe not.

When the motor's cold or not up to full op temp it will normally feel a bit more snappy/trqy because when the the motor is up to norm op temp esp in simmer time temp it get all heat soaked with reudces pwr/trq making throttle response less crisp & more musHy down below.

But easy way to chk if thats case or not to see if its truely running lean enough coming off idle and or when at low throttle position to loose umph when the motor hot add a little choke (1/8-1/4) to fatten up fuel a little bit.

If it picks up being more spunky then its in fact running a bit lean & its time to relaibrate the carb,but if richening up duel mix a bit a with a little choke doesnt make any diff then i'd say its not running too lean and its more of an issue with not motor loosing some umph.

So if thats the case if you have an oil temp gauge whats the oil temp vs outside airtemp when the motor seems to have lost some low end umph?

I ask this because i recently installed wards elec cooling fans & an ultracool oil cooler with dual elec cooling fans which collectively working together reduced oil temp on an 89 deg deg day anywhere from 30-50 deg + depeding on traffic cond and or when at cruise which made a big diff in how the motor perf/felt.

The oil & motor running much cooler on my bike resulted in:

BTW - (MY BIKE'S A STOCK 09 WITH TWC 96")

* MOTOR RETAINING BETTER CRISPER THROTTLE RESPONSE.

* MOTOR RETAINED MORE POWER.

* MOTOR STOPPED DETONATING ON THE REC 91 OCTANE FUEL.

* VALVETRAIN WAS QUIETER.

* OIL PRESSURE IMPROVED QUITE A LOT NOW HOLDING STEADY AT 16-17LBS @ 950-1K RPM IDLE & 45-50LBS AT CRUISE @ APPROX 2500RPM IN 89 DEG HEAT .

PRIOR TO INSTALLING THE 2 COOLING SYSTEMS OIL PRESSURE USED TO RUN QUITE A BIT LOWER BEING 8-10LBS AT HOT IDLE & 35-37 LBS AT HOT CRUISE IN SAME 85-89 DEG OUTSIDE TEMP.

NOTE: ABOVE STATED OIL PRESSURES ARE WITH SPECTRO HVY DTY 20W-50 STD DINO .

EVEN WITH THE 2 COOLING SYSTEMS ON MY BIKE IF I WAS TO RUN SYN 20W-50 BIKE OIL HOT OIL PRESSURE RUNS QUITE A BIT LOWER THEN IT DOES WITH THE STD DINO WITH BOTH BEING SAME 20W-50 GRADE BIKE OIL.

So bottom line is if richening up fuel mix for a bit with choke at 1/8-1/4 on doesnt help lower end perf when motors up to its normal op temp then maybe its running hot enough to cause it to loose some umph like my bike did prior to installing the 2 cooling systems
that lowered my motors oil temp a lot (lowered motor temp too but dont know by how much) allowing the cooler running motor to not heat soak & loose some pwr/trq/perf in the process which is something you should consider.

1 more thing ,are you sure that maybe the clutch isnt slipping just a tad when the motors hot too that could also make it feel its loosing some power/perf?

SCOTT

 

Tuning needs cannot be determined until the engine is at full operating temp. Basing your needs on how the bike handles when cold with enricher (choke) applied is not recommended. Question OP : using your logic, how does the bike run after it is warmed up, and you pull the "choke" **** out?

 

Don't remember for sure as it has been a long time since I tuned a CV carb, but as I recall we used to go with a 45 slow jet, 165 to 175 main jet, 1988 Sportster needle and cut 1 coil off of the slide spring. Pull the idle screw plug and set it at about 1/4 turn out.


Bill

 

I run a 46 slow and a 195 main on my cammed 2002. You should at least start there. You can buy jets here. http://www.cv-performance.com/

 

I just had my 2003 Fatboy tuned after adding a Propipe and SE heavy breather. I "think" I damaged something during the dyno because now I hear noise in the cam chest at 25k miles. I am upgrading to S&S 509 cams, hopefully gear drive. I know my main jet is 195 and currently borderline rich. Is it possible to not have to re-dyno after I change the cams? Wasting the $$$ on previous dyno i my biggest hearburn with my current situation. Thanks in advance for any input.

 

Tuning a carb on a cold bike is like giving CPR to a corpse. What's the damn point?