I am thinking of putting a Mikuni hsr 42 on my 06 Fat Boy. The motor has the SE 95" kit, SE 211 cams and the heads were ported and polished. The bike is also running an se air cleaner and Samson BG3 street sweepers. Can anyone tell me what a good starting point would be in regards to jetting? Those of you with the Mikuni, do you notice a difference over the stock CV carb performance wise?
Thanks in advance.

 

Start with a 165 main jet. The Mikuni is a great carb you can do so much with them Low jet you might play with jet needle. or go up one size on jet. You can go to Mikunis web site it has all the info you need. you can down load it.

 

thanks fot the info.

 

Like Dragos said, you can start with a 165 and see what happens.. More than likely I think you'll end up in the 175-185 range on the main jet... I wouldn't mess with needle height until you've done everything else... Also, look at using a 22.5 or 25 low end jet to begin with and adjust your fuel air mixture as dictated by throttle response.. The HSR's a real good and super easy to tune.. Jets run about $4 each so you won't spend a lot of money getting the right one... The manual is very easy to follow as well..

The difference over the CV carb is pretty big... The adjustable accelerator pump on the HSR is a big plus also..

 

Mikuni, is a great carb. The Mikuni 42mm though may be a touch small for a 95" setup. You will get really snappy throttle response with it, but around 4000k it will start to peter out a bit. The Mikuni 45mm is actually a slightly better fit. Low end throttle response/snappiness wont suffer, but it will breath out to your redline much better.

 

A good starting point would be 165 main (160 is standard) as already suggested, 98 needle (97 is standard) with clip in the middle, 50 pump nozzle (70 is standard), 20 pilot jet (25 is standard). Set the accelerator pump up as suggested in the tuning manual, you can change it later real easy if you want. The Mikuni tuning manual is pretty good for getting you dialed in real close.
Make sure you reroute your throttle/idle cables per the manual or you can put the carb in a bind and get a vacuum leak. Also check to see if the carb hits the cylinder fins when it's fully seated, some do-some don't. If it hits, you can file/grind a little off a fin or two.

 

Thanks for all the info. Its a great help.