I rebuilt and rejetted my carb off a 96 fatboy for the new pipes an ac because it was chocking in mid range

now its poping like back fire out the carb at start up when its cold

was thinking of just changing it out with a s&s



Ild be thankful for any help

 

In my opinion, the s&s is a briggs and stratton carb....total junk, ill prolly get lynched for that one.., needless to say, the keihin is one of the best carbs for a harley, very tunable and very simple, couple things you need to look at if its popping, usually popping is caused from a lean condtion, when you rebuilt it, did you put the diaphragm in correctly? and what did you jet it at?? it also could be a intake leak, did you check and or change the carb mounting rubber?

 

After checking for intake air leaks I would replace the jet needle with a 1988 sportster 1200 needle HD P/N 27094-88 and change the slow jet to a 45 and a 165 main Be careful when re-installing the rubber diaphragm on the slider assembly back into the carb body Make sure you get that rubber in position before you replace the top plastic cap or you'll lose top end and make sure that the voes hose is reinstalled if you still run a voes

 

The stock CV carb is probably the best carb for your bike. I hear of guys changing out for Mikuni's and other carbs. But, the CV is bullet proof. Sounds like your slow jet is a little small. Or as others have suggested, it could be a seal leaking around the intake. You want the slow jet and main jet to be as close together in number as possible for smoother running of the bike.Hope that helps..

 

I got the jet kit from keihin the set up it recommended was a 45/180 with a needle to replace the factory one with

also changed all the gaskets and I also changed the seal on the intake that came with the rebuild kit

I checked for vacuum leak in the vacuum lines and intake seal

made some adjustments to the fuel air mixtures seems better now has 1 3/4 turns on it

what would a lighter or shorter sping on the slider do for preformance

 

thanx for the advice on where and what to check

 

The CV is a great carb. At 40mm, properly tuned, it will perform very well up to about a 100" motor. At that point, it just isn't big enough to move enough air to support a motor of that size.

Sounds to me like it might need to be fattened up a bit.
Might want to try a 48 pilot jet, and shim the needle.

 

i dont play with the springs on the slide, but if you feel its slow to open, you can open the vaccum hole on the slide to .100 ,not .125 like they give you in most jet kits. also 45 is lean if you got a good air cleaner set up, it should be a min of 46, period. I like my bikes to run just a bit fat simply because it deters detonation and the bike runs so much cooler. I just jetted a stock road king, it left my garage with 46/185 and one shim under a stock needle, she purred like a kitten...lol hope that helps.

 

Im running a hyper charger on it and vance an hines hi low shot gun 2 1\4 I also put a set of cones in the exhust. the kit also came with a 48 and a 185 it said to use with ac pipes an a cam it seems to be alot more cold natured sense i rebuilt an rejetted is that norm for these cv carb to do that but it has been prtty dang cold here lately

Il try the other jets and see how that goes thanx for the tips s&s carbs I know more about but I figured from what Ive heard these cv can be good carbs so with the help Il get it right thank you guys alot for the help

 

When the bike is jetted fatter than stock, they are very cold natured, espically in weather we have had lately, the stock jetting is crazy lean, i cant imagine more engines valves and pistons werent burnt up, just experiment and play with what you got, your on the right track, and your bike may like a 46/180 or even 175, its all in altitude and all that scientific stuff...lol. good luck man.