djl - I think that I understand what you are saying, but the AFR on the chart shows a near ideal reading from 5200-6000. Wouldn't going down on the main jet take that the wrong way (lean)?

 

Actually I did a 5th and 6th gear pull on my 98 and the numbers went down and they also came in later in rpm...... so I can only imagine that a 4th gear pull would be inflated....

 

Ramps are steep, but it do work.
We have a NIB 1999-2006 296-2 on the shelf, if anyone is interested.
Client in Rome, NY, 107"/296/our big heads/55 HPI/Bassani, that WAXES his bud's 600 RR in a drag race.
R&R cam is an S&S .585 with a 1.725 rocker from what we see, and it too works, as Target64's bike runs that combo.
Scott

 

Maybe but you have to make the call on whether you want to run rich every where else, i.e., where you ride or run close to stoich at 6200rpms where you don't ride. Bring your chart with you and see what Mike thinks but I would drop the main maybe a half size and see what the dyno tells you. Remember, when the operator whacks the throttle, the only thing determining AFR is the main.

 

Sometimes but, as I stated, as a general rule and in theory, the parasitic losses of input to output via the drive gear to another gear to the countershaft would indicate a loss of power but not in every case and obviously not in yours. The OP is planning to visit a tuner's shop in my area for a monthly "dyno" day and that tuner charts fifth gear pulls so we may have an opportunity to see the results. Different dynos and different ambient conditions so I know there will be a difference. Additionally, my tuner's dyno is not a "happy" dyno, might even be a little stingy but you can believe the numbers are pretty much spot on.

 

DJL is right, I don't know what I was thinkin...The huge dip after roll-on is the accel pump shot. You probably have the stock 70cc pump jet in there, I would at least swap that to the 50cc jet before the dyno and go up one size on the main. It's pretty lean up top, you can see the plateau in the power graph, it wants to make more power but doesn't have the fueling to support.

 

I went back and looked at the OPs graph again and, for the first time, noticed that the dashed AFR line is at 14. I am used to reading graphs where that line is drawn, in red, at 13 as in the attached chart, so my judgment of lean vs rich was skewed a bit. Additionally, as I stated in previous post, that I am not familiar with tuning Mikuni carbs; CVs yes but not Mikunis. So, I can't comment on jetmech's suggestion regarding the accelerator pump but the logic is sound. However, I don't know if I would go up a size on the main but it won't hurt anything to do that as the OP can make adjustments on dyno day.

 

Good info, Scott. I have seen the graphs on Target64's build and they are very impressive. Do you remember what the numbers were for that 107 build?

 

[QUOTE=jetmech74;13766792]DJL is right, I don't know what I was thinkin...The huge dip after roll-on is the accel pump shot. You probably have the stock 70cc pump jet in there, I would at least swap that to the 50cc jet before the dyno and go up one size on the main. It's pretty lean up top, you can see the plateau in the power graph, it wants to make more power but doesn't have the fueling to support.[/QUOTE

Based on prior recommendations, I ordered a 165 main jet (one size down) today. Also ordered a 162.5 (two sizes down). Now I need a smaller accel pump nozzle and a BIGGER main jet. Knew that I should have bought a complete tuners kit.

I now recall that when assisting my dyno-operator buddy 12 years ago, he would sometimes temporarily disable the accelerate pump before a pull when determining main jet size. I should have thought of that sooner.

 

I would drop the main jet one size lower. You are way to rich from 3000 to 4000 rpm. Did they do any cruising AFR reading at various RPMs & MPHs? That is more important than your WOT for now until you get it tuned.

You could potentially get your WOT AFR perfect & be way too lean or rich at your cruising/partial throttle positions which is where you normally ride.

For most builds the Mikuni is known to be pretty close out of the box as far as jetting. You can download the Mikuni tuning manual if you don't have one already. As was mentioned before I would also drop the accellerator pump from the stock #70 to a #50. You can also adjust when the acc. pump comes on & turns off.