Raising the Jet Needle

My spark plugs appear to be slightly rich, and a riding friend tells me the exhaust smells of unburned fuel.

My KZ1100 engine is completely stock, except for a V&H header with the street baffle (no glass wrap), and Dynatek 2000/mini-coil ignition.

I've opted to use the stock air box with a K&N washable filter, rather than convert to pods.
Here is the BS34 carburetor set up: main jets 125 (stock spec is 120) with the original jet needles raised 1mm, and the pilot jets 37.5 (stock spec)

The modifications are confined to the main jets (two steps up) and raised needles. I'm planing to change the main jets to 122.5, and am wondering...


Is it necessary to raise the needles?

NO, not necessary to raise the needles.

+1.
When you go larger on the main, it has the effect of raising the needle already due to the larger diameter opening at any point you are on the needle. No need to do it twice.

Pay attention to where your throttle is mostly when you're riding. Do you ride at 3/4+ throttle a lot? Most likely you're rich in the 1/4-1/2 range if you ride like most people on the street. Here's a good reference for what circuit is in play at different throttle positions.

www.Sudco.com/Carburetor02.html

Alan

Alan...super-helpful info! THANKS!

koolaid_kid & baldy110

I dropped the needles back down to the (non-adjustable?) stock position, and put in the 122.5 main jets. All it needed was to up one size on the main jet...and that's it!

Thanks a Trillion for the push!

koolaid_kid wrote: +1.
When you go larger on the main, it has the effect of raising the needle already due to the larger diameter opening at any point you are on the needle. No need to do it twice.

Must be referring to the Needle Jet/ Emulsion tube, not the Main Jet there. The Needle goes into the Needle Jet. Changing the main will have the most effect on 3/4 throttle and up, although it can map across more of the throttle opening.

Motor Head wrote:

koolaid_kid wrote: +1.
When you go larger on the main, it has the effect of raising the needle already due to the larger diameter opening at any point you are on the needle. No need to do it twice.

Must be referring to the Needle Jet/ Emulsion tube, not the Main Jet there. The Needle goes into the Needle Jet. Changing the main will have the most effect on 3/4 throttle and up, although it can map across more of the throttle opening.

On a Mikuni BS34? The main has a direct effect on the needle, which is why you tune the main first, then the needle.