[hoglar]

First, a little history: I purchased a used ’96 Fatboy HD a few years ago and inherited a D&D 2:2 slash cut exhaust. The only other thing done to the bike was a Dynojet kit. In the past couple of years I’ve added an EV-46 cam, 10:1pistons, and SE single fire ignition. The bike is making about 80 HP and 90 ft/lbs of torque.

Problem 1: I have always noted a tendency to surge and run rough at steady throttle or on compression when traveling around town (20-35 mph). Give it a little throttle and it was fine. It wasn’t bad, but noticeable. As I’ve made changes (especially after adding the cam) this has worsened to where I usually drive around town with my enrichner partially out, This helps but does not completely alleviate the problem. It’s worse in the winter.

I’ve had the bike into a couple of shops and it’s been dyno’d several times as I’ve made changes. They tell me it’s tuned correctly and the air fuel mixture is correct although there's a big dip at the low end. The dyno/shop folks tell me that's normal with the CV carb. The folks at Andrew’s cams suggested I get a better exhaust like Vance & Hines, Hooker, etc.

I’ve researched those exhausts and I do not see where they will improve my performance over the D&D exhaust I have now.

Do you have any recommendations?

Any help you can be with these questions will be appreciated. Thank you.

H-man

 

[Otto]

loose the dyno jet kit sounds like the intermediate is lean along with mixture screw out of wack

 

[hoglar]

Loose the Dynojet

Thanks for the reply.

You suggest dumping the Dynojet kit. I always thought adding the Dynojet kit along with new pipes was SOP for a new Harley. I haven't seen anything regarding Dynojet kits being a problem. Can you steer me to some info regarding this?

I also thought it might be the mixture screw. I've adjusted it and a shop has adjusted it. My next step was to take a look at the needle and adjust it down one notch (raising the needle). Concur?

 

[Otto]

most of the dynojet kits turn the main jet on to early due to the change in the emulsion tube thus causing people to run to lean of a intermediete jet and incorrectly adjust mixture screw changing the clip position might help but will decrease mpg and will generally just cover up the original problem

now if the carb was stock to begin with 48-51 intermediate 190-200 main stock needle shimed .015 or replaced with 1200 needle mixture screw 1-3/4 2 full revs. from litely seated. the dyno jet spring or trimming the stock one the oem slide air hole can be drilled per dyno jet or 1/8" drill bit with a ev46 this carb should be close to 90hp at 10:1 and still deliver about 40-45 mpg on the road

the 46 is one of my favorite bolt in cams for the evo with the right head work and springs i have seen it rev to 7k and make over 90hp

 

[hoglar]

Rejetting

I'm getting 80 HP and 90 ft/lbs torque with the current setup. It may take headwork to get to 90 hp.

Regading your suggestions. Let's see if I've got it right.

1. Replace the Dynojet Emulsion tube with stock
2. Change the Intermediate Jet to 48-51 (I believe you are referring to the Slow Jet)
3. Change the Main Jet to 190-200
4. Keep the Dynojet spring
5. Replace Dynojet needle with stock or 1200 EVO needle
6. Shim the stock needle .015” / don’t shim 1200 EVO needle
7. Set mixture screw to 1.75-2 turns from lightly seated
8. Drill out the slide air hole per Dynojet instructions or 1/8”

Is the drilling you suggest the same alteration discussed at the Nighttrain and other web sites? I’m guessing this allows vacuum to build in the valve slide chamber quicker for better throttle response.

http://www.nightrider.com/biketech/hd_cv_mods.htm#slide_detail

Once again, thanks for the help.
h-man

 

[Otto]

sounds right if the dynojet kit has beeen installed the slide should be drilled already so you shouldn't have to worry about that but yes it alows the slide to respond quiker

 

[rlpos]

You may also want to check for vaccum leaks