Topic: 75 CB750 Cafe Racer - Fine Tunning

[tango911]

Have a question guys.  Im mainly a stocker guy however,  Im jetting this cafe for a customer.   He bought this bike from someone that did a very nice build but did not jet the carbs for pods and 4-1's.     It was running very very lean and #4 didnt even run well.   I cleaned the carbs and drilled out the mains to about 115.5 .    I did not move the needles or change the pilots which are 40's.      Until i get the kill switch wired correctly i can not do proper plug chops but as of now its running ever so slightly rich.  Which to me is a good starting point.    Its a v & H  4-1.   

i guess my question is,  if at idle and am running rich, i dont really need to bump the idle jet up. right?   Typically with pods and a 4-1 you would think the pilot would need to be up about 2 from 40 to 42??   

thanks
Steve

[bjbuchanan]

gonna need atleast a 42 pilot jet. You are gonna be forced to be slightly rich at idle due to the limited tunability of stock carbs. Not pig rich but definitely not tan plugs if you let it sit and idle. If I was gonna tune for the pods I would shoot for the idle jet that keeps me happy around one turn out. With that you get adjustment in either range to fine tune for weather changes and other little perfection factors

Raise the needle/lower the needle clip one notch to start out with and try 120 main, probably need a 125. Leave the main for last because WOT is used least anyway and driveability there isn't as important. A dynoman jet kit could be useful because a dynoman 116 jet is the keihin equivalent to 122 if you can't find a 122.5 jet easily, just a thought

Killswitch is black power from a switched ignition source to KS. Black/white out of KS to the coil leads.

[tango911]

thanks!   i can get the kill switch eventually didnt have time to dig into his nest of wires.

[Davez134]

Also, not sure if you've seen this, but it helped me get a good starting point. http://www.hondachopper.com/garage/carb_specs/carb_specs.html

I too have 4-1, pods, casting number 657B with 40 pilot and 120 main with needle clip in 4th position from top. Have screws turned just a touch less than 1 turn out.  Little rich after idling for a while as previous post stated but proper plug chop showed ideal plugs.

[tango911]

very helpfull guys,   I was very close, but def need to go up more on the jet and move the needs.   thanks again.

Steve