Jetting

[Rusty McNeil]

I think there are a couple of carb gurus on here, this is for you

I just installed a UFO exhaust

The setup I've had all along is;

I'm running a Dyna ignition on curve 3

The Y is gone from the airbox

two coils cut out of the slide springs

needles shimmed .020

Stock jetting

Vboost open full time

I'm in the Houston area so about 25-75 feet above sea level, but I also REALLY want my bike to run right in the Hill Country rides we do which is usually from 1500-3000 above sea level.

It has always run outstandingly and still does with the new pipe if not better.

My A/F guage is showing me to be what I consider lean under wide open throttle which is about 14:1 but the thing runs great. I "think" that max power is usually made when A/F is as close to detonation as possible without actually going there. I am somewhat worried about detonation though.

My question:

I have a set of Dynojet 165 mains. Should I install them?

Sean, you did a writeup in the Vboost that seemed to indicate that when tuning on a dyno almost every bike y'all had across the dyno made more power when you leaned it out. what do you think?
Also, my experience with tuning by A/F is related to cars and cars only. Does the fact that the load factor on the engine due to the relative lightness of a bike make leaner mixtures less of a concern on a motorcycle.
I'm pretty sure 14:1 on my wifes car from a dead stop wot situation would instantly throw it into detonation.

Am I right in thinking the load on an engine is part of the equation of A/F, timing, air temp, etc when it comes to what causes detonation?

 

[maleko89]

I talked to another Vmax carb guru he recommended an air/fuel curve from 12.75 - 13.25:1.

DJ165's are a tad bigger than stock so if you do that you may have to un-shim your needles. Do the needle test and that'll tell you if your rich or lean.

Rusty, what's your email? I'll forward you a picture and write-up I have on how to tune main jet, floats, mixture screws, and needles all my looking at different parts of the spark plug. I have the needle test documented too in case you haven't heard of that.

Regards,

 

[Rusty McNeil]

I talked to another Vmax carb guru he recommended an air/fuel curve from 12.75 - 13.25:1.

DJ165's are a tad bigger than stock so if you do that you may have to un-shim your needles. Do the needle test and that'll tell you if your rich or lean.

Rusty, what's your email? I'll forward you a picture and write-up I have on how to tune main jet, floats, mixture screws, and needles all my looking at different parts of the spark plug. I have the needle test documented too in case you haven't heard of that.

Regards,

Thanks Mark,

My Email is [email protected]

I have heard of some of what you siad but not all and not sure I understand the parts I have heard of so any info would be helpful and I would love to read it.

I have a datalogging wideband A/F so if reading a sparkplug to correlate approximate A/F's I can read exactly what the A/F is at any given RPM by downloading the datalogger with my laptop.

What I'm not sure of still is when I'm at wide open throttle with rpm's coming up (as in nailing it from first gear at around 2500 rpm's) do the rules about what part of the carb does what still apply as opposed to a steady but rapid increase in rpm where each part of the carb transitions to the next,

I can also read the guage but things happen pretty quick when running the bike to try and actually read the damn thing while running thru the gears.

 

[Rusty McNeil]

I installed the 165's last night and it seems pretty much dead on under WOT. It's running about 13.0-13.6:1 at steady state cruise which is kinda rich for cruise I think.

If I unshim the needles to lean out the low-midrange how much affect will this have on top end A/F?

 

[maleko89]

For steady state cruise I would try leaning the mixture screws first. Small throttle openings affect pilot mixture, needle taper and how far needle is inside the needle jet. Lowering the needle will affect your a/f reading too, so you're right as well. It gets kind of tricky since the circuits overlap. I will forward you my notes I talked about after work today.

 

[shawn kloker]

Rusty,I think some adjustable needles would help you.What rpm are you cruising at?I would try unshimming the needles too.Lean the mixture screws down some.

 

[Rusty McNeil]

Thanks guys. My steady state cruise RPM is 5000.

 

[Rusty McNeil]

Rusty,I think some adjustable needles would help you.What rpm are you cruising at?I would try unshimming the needles too.Lean the mixture screws down some.

I'd like to go Stage 7 or Morley Muscle but don't wanna unass the money as I've dropped about $1500 on the bike in the last coupla months. Any more and I'm gonna be sleeping in the garage

Any body know How much a Muscle kit costs?

 

[maleko89]

I think around $200. That includes a couple of main jet sizes, modified airbox lid, dual crankcase breather setup, air correctors and slide springs. If you want the adjustable stage 7 needles that's an extra $50. You might be able to get by without the air correctors, drilling of the slides, and slide springs. The reason they're needed for the stage 7 is because that setup lacks velocity stacks and also because of the increase of air pressure when going to individual filters. I'm not totally sure a modified airbox requires those stage 7 components. I'm making a set of 3 inch velocity stacks for my spare set of individual air filters. Eric Harnish did some research on velocity stack lengths and found that 3 inch stacks worked the best. I'm also adding an ignition advance circuit. According to people who have done the stacks and ITAM 4 ft/lbs of torque was gained compared to traditional stage 7. I'm going to compare this setup with Morley's kit.

 

[maleko89]

I forgot to mention that you need to give Sean your airbox lid and oil filler cap.