CB550 rejet for 4to 1 exhaust and pods?

[BNR34RB26DETT]

well im looking to rejet my cb.
I have done some research and according to this

1 jet size for custom 4 into 2 exhaust

2 jet sizes for 4 into 1 exhaust

1 jet size for K&N filter (single inside airbox)

1 jet size for drilling out the bottom of the airbox

2 jet sizes for both single K&N and drilled airbox

2 jet sizes for individual filters

2 jet sizes for no muffler (open header)

1 pilot jet size for every 3 main jet size increase

Add up all the jet size increases and subtract one. (Remember they go in steps of 2.5 for each jet size)


It seems that i will be needing
2+2-1= 3 size jet larger for main
and 1 size larger for pilot.

Stock jets on cb550 are 100 for main and 38 for slow

according to JetsRUS website, that puts me to

Keihin slow jet size 38 $10.99
Keihin slow jet size 40 $10.99
Keihin slow jet size 42 $10.99
Keihin slow jet size 45 $10.99

40 for slow jet and

main jet size 100 $5.99
main jet size 105 $5.99
main jet size 110 $5.99
main jet size 115 $5.99

115 for main jet.

Now i plan on buying 110 as well just so i can play with it.

But is this the correct understanding when it comes to rejetting? Did i pick the right jet numbers for my 4 to 1 and pod filter setup?

any comments would be appreciated

Thanks!

 

[focusinprogress]

it will get you in the ballpark....are you working with the early (74-75) carbs or the 77-78 carbs? for custom exhaust and pods I was at 117.5 mains and 40 pilots, but really struggled to get good rideability out of it, possibly needed different taper needles....I gave up on it and started gathering parts for the cb650/750 hybrid motor and got cbr600rr throttle bodies to convert to EFI. the later carbs are MUCH easier to tune on the 550.

 

[BNR34RB26DETT]

Hmm really. I had no idea about this. Thanks for the good info.
I'm running 75 so that would be the hard to the carb according to your information.

Should I consider swapping other parts such as taper needles (stock size?)

What is the edi you mentioned here?

 

[Hot500]

On my 500 I'm running stock carbs with velocity stacks & Bills B racing filters and 4 into 1 exhaust. My carb setup is 130 mains with 42 slows, stock needle on third clip.

The bike has good power pretty much everywhere. A slight dip as the needle comes in just before half throttle, then pulls nicely all the way to about 95% throttle with an extra kick at 9000rpm. At 95% the motor stutters and wont pull all the way to WOT.

My take on this is; with the stacks I'm pulling a lot of air. The stutter at 95% needs to go up to 135 mains. My plug chops show I should richen up all of the carb circuits, so I'll go lift the needle one clip as well.

 

[blackbuddha1]

set timing and valves first, do compression test to make sure cylinders are all real close.....buy a box of plugs so you can change them each time you change jets....not every cylinder may have same size jet....I'm running 2 different sizes on my cb650 4 into 2 almost straight exhaust and V stacks with wire screen....carb sync. at the end

 

[BNR34RB26DETT]

Thanks for the amazing replies. I ended up busing the best 115 and 40. I will update the thread after it's installed.

 

[leetmeat]

any updates?

 

[BNR34RB26DETT]

any updates?

well the bike dies out when i give it gas with throttle. however, when i open up the choke, bike seems to have no problem revving up high.
I have tried this with stock jets as well as jets 4 sizes larger and i experience the same issue...

Im not sure if its the jets or some other issues causing this problem...

 

[crazypj]

I did my 550 in 1978. when there were a lot less parts available
Drop needle at least 1 clip (nearer top)
Raise float level 1mm
Stock pilot jet works OK
Use genuine K&N filter.
The CB650 probably has way LESS airflow than stock with the covers on bellmouths, plus, they do nothing to smooth airflow with the crappy rubber ring on them