Topic: CB650Z POWER CONE AIR FILTER

[frenchalex]

hi everyone,

hope that you can help me on that one...

got cb650z 1979 UK and always wanted to fit some chrome power air filter cones for the sound of succion and performance. but obviously the original air box was very restrictive, so now the carbs are running very dry and can only drive with the choke on. what would you advice me to do? do i have to change the main jet? needle? the carbs are keihin PD51A with a 92 main jet. i have bought but not received yet some mac 4-2 turn out exhaust as i don't like the 4-1 from the previous owner, will it affect my carbs too?

best regards,

Alex

[ProTeal55]

Alex,

Whenever you change the amount of air going into to a motor, or the
amount of exhaust comming out of the motor, a jet change is usually in order.
Thats the beauty of the all mighty carb !

To what jet you need to change to I am unsure, as the Velocity stacks that are
on my bike now came with it, and I have yet to touch my carbs..

I am sure someone else will chime in to help...

[eldar]

Well throw on the 4-2 first and see where you are at. Then decide if you need to rejet. The 4-2 works a lot like the 4-4 systems and may help even out SOME of the lean running. you will still probably ahve to rejet but maybe not as much. Once you have the 4-2 on, I would say to try a 100 size to start with. You will need to reset your low speed screws too.

[frenchalex]

would you think i will have to change the jet neddle too?

[eldar]

the needle, no. just the main jet. the lows are pressed in (I think) and are hard to change since replaceable jets are threaded. You can however, tap threads into your jet seat. Just be VERY carefull.