TOPIC:

First start today since installing the brass floats and setting the wet float level. While I was at it I replaced the 110 mains with 105's. The fuel level in all 3 carbs was too high previously using the stock floats and measuring them dry. It started right up and ran perfectly! So now this is my setup with the DG 6 into 1 pipe. 42.5 pilot jets, 105 main jets, air screws 3 1/4 turns out, jet needle raised one notch (lowered clip). Seems to work good. Thanks Scotch for the floats. Well worth it!!

fastpapaw wrote: First start today since installing the brass floats and setting the wet float level. While I was at it I replaced the 110 mains with 105's. The fuel level in all 3 carbs was too high previously using the stock floats and measuring them dry. It started right up and ran perfectly! So now this is my setup with the DG 6 into 1 pipe. 42.5 pilot jets, 105 main jets, air screws 3 1/4 turns out, jet needle raised one notch (lowered clip). Seems to work good. Thanks Scotch for the floats. Well worth it!!

Hi FPP,
I'm also working with a DG pipe. I currently have 96s as mains and I'm running in the sixth notch on the needles. Before spring I plan to change the mains to 100s and move the the third notch on the needles. 42.5 pilot jet is the stock jet. When you say you lowered the clip I'm thinking you mean to the forth notch. Am I correct?

Congratulations

Bill

OK I'm here strictly to learn, and this is asked in ignorance, but are the lower numbers on these jets smaller orifices? If so, I'm missing something on these carburetted sixes. Usually, if you go to a freer-flowing exhaust, you need to increase jet size for more fuel feed to increase the power. Of course, that goes along with, or before, raising the needle, too. Edumacate me on this please. I don't have any Kaw sixer carb experience! I only know the injection system on the ZN's!

What changes are happening on plug color when you guys make these jet changes?

Hey Trike Builder,

From some of the posts I've been reading regarding the jet size/ needle position, it would seem that most bikes out there are running really rich. Normally you have to go one jet larger than stock when running headers because the headers free flow more than stock but also the design of the header will cause a negative back pressure pulse in the pipe sucking more exhaust out of the cylinder which also make the valve overlap more effective. This effect tends to cause the mixture load in the cylinder to be slightly lean and therefore you usually have to go one size up on the main jet.

Normally, one would select the main jet based on full open throttle performance. Ideally you would determine this on a dinomometer. Once the correct main has been determined, you start adjusting the main needle to properly blend in the part throttle metering.

In the old days a header manufacturer would suggest that you start with a certain size main primarily to protect their name. No one wanted to be known for blowing up engines because of their headers, but there are a lot of factors which need to be considered when jetting. Compression ratio and camshaft duration are usually the primary considerations.

For those who have never come across this document it's excellent reading on selecting carbs and setting up. Most of what I'm stating here is based on my reading/understanding of the fundamentals in this document produce by Mikuni carbs.

www.mikuni.com/pdf/vmmanual.pdf

Another great read is a book called "Scientific design of Exhaust and Intake Systems" by Phillip H. Smith which is a Robert Bently Automotive Publishers book last reprint according to my copy was 1998.

I'm a motor head, what can I tell you. I've been reading this kind of stuff ever since I first smelled Klotz racing fuel and I can tell you that was a loooooooooooooooong time ago.

Enjoy
Kawboy

Correct, 4th from the top.

Hi Bruce,

According to DynoJet, the DG pipe wants smaller jets. The stock jets are 110s, DynoJet recommends 96s to start but also provided 100s in my kit.

Bill