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Discussion Starter · #1 ·
I am new to the Harley world so please excuse my limited experience and request for help.

There was a thread started my me on quieting a Thunderheader system on my 98 FXD and from that plus some experimenting I concluded it was a non-starter. Soooo - I have replaced the Thunderheader system with a White Brothers 2 into 1 e-series tunable system. Now my question is how do I go about tuning it? The 98 FXD has a Crane cam, SE Breather kit and the White Bros. exhaust. The previous owner had the dealer re-jet the system for the Thunderheader/cam/breather setup, but I do not know the jet size used. My experience with the Thunderheader was that the bike was rather cold blooded for a while after starting even with the enricher on full. It smoothed out after a couple of miles of warmup. Now with the White Bros system, it was even more cold blooded (almost impossible to drive in traffic) with the full open set of baffles (12) that came installed on the muffler. When I reduced it back to 5 (4 being the minium recommended in the literature that came with the pipes), it was very smoothe when cold and pulled from low RPM rather nicely. I am assuming that it is showing signs of over rich mixture because of this. As soon as it warms up outside a bit I plan to play with the number of baffles (i.e. exhaust opening size) but am not too sure how to judge when I get it right. Any advice would be appreciated.

Also if anyone wants a black Thunderheader system, please let me know.

Stan
 

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It really is whole lot of trial and error. It sounds like you are looking at making it as quiet as possible. In that situation, I would set it up for the maximum noise level you can stand (as many disks as it takes to reach that level). Then I would take it to a dyno and have the carb jetted to get the performance. Take it somewhere that has a sniffer with the dyno, so you get the air/fuel ratio dialed in. If you don't want to pay for the dyno tune, you can do it the old school way and adjust the jet size based on how your spark plugs look.

I have the e-seires pipe on mine and it really makes a big difference in the performance of the bike (about 8HP). I'm running 16 disks and it really isn't too loud, but I sppose it may be to some people. It's definitely way more quiet than the drag pipes that were on it before.

So are you giving away the thunderheader? :brows:
 

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Discussion Starter · #3 ·
The muffler came with 12 disks and that is the way I installed it and ran it at first. Was quite a bit quieter than the thunderheader, but also felt like it was running much more lean when cold. Right now I have 5 disks in and it runs very smoothly when cold (50 degrees outside). Don't know if the cold performance is an issue or if I need to worry more about the situation when fully warmed up. It did feel OK with the 12 spacers in there on first install when the engine had warmed up.

Stan
 

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FXR
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Sounds like you need to put it back to 12 disks and increase the jet size.
 

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n3hs said:
I am new to the Harley world so please excuse my limited experience and request for help.

My experience with the Thunderheader was that the bike was rather cold blooded for a while after starting even with the enricher on full. It smoothed out after a couple of miles of warmup.

Typical, hardly anyone ever adjusts the fuel screw or changes the pilot/slow jet.


Now with the White Bros system, it was even more cold blooded (almost impossible to drive in traffic) with the full open set of baffles (12) that came installed on the muffler.

Hard to believe that the WB flows MORE than the T-Header with 12 discs..hmmm

When I reduced it back to 5 (4 being the minium recommended in the literature that came with the pipes), it was very smoothe when cold and pulled from low RPM rather nicely.

Decreasing flow will make it a tad RICHER (that fuel screw/pilot slow jet range of the carb.

I am assuming that it is showing signs of over rich mixture because of this.

Nope LEAN. decreasing flow RICHENED the mixture..as it were thus made it seem better..

As soon as it warms up outside a bit I plan to play with the number of baffles (i.e. exhaust opening size) but am not too sure how to judge when I get it right. Any advice would be appreciated.


Get the adjustable fuel screw knob, this will make adjusting the slow speed circuit a snap for changing ambient conditions. It (the fuel screw) will also tell you where you need to be on the pilot/slow jet.
HOW?
The fuel screws range of adjustability is from 1.5 turns out to 3.5 turns out, IN = LEAN out = RICH.
That known, IF you lightly bottom the fuel screw, back it out 2 turns then while the machine is running and in the conditions it will be ridden in turn the fuel screw in or out till you get the highest smoothest idle counting the number of turns from the 2.0 initial out setting.
IF that high smooth idle comes at say 3.0 the fuel screw is telling you that the pilot/slow jet is too lean (the fuel screw is almost at it's max RICH setting) and you need to go to the next richer size pilot/slow jet.
IF the high smooth idle is at say 1.5 the fuel screw is telling you that the pilot/slow jet is too rich (the fuel screw is almost at its max LEAN setting) and you would need to go to the next leaner pilot/slow jet.
Optimum fuel screw setting is 2.0~2.5 turns out, thus leaving you adjustment for changing ambient temperature and humidity with the fuel screw.

Typical too lean fuel screw/pilot slow jet symptoms are:
Spitting back through the carb, poor low speed throttle response when cold, gets better if the choke is pulled on.

Hope this helps.

It's easy once you know what is going on in the carb and how to make the changes.
 

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Baffle exhaust tuning...

The best bet is to dyno tune w/ your current setup and if the noise is what you are able to tolerate then jet for that. Performance wise, trying 9/10 baffles may give you what you are looking for (OK, I know 'do not end a sentenace with a prepesition)... but dyno tune to your liking. I have baffled Super-Trapps and tune by allowable noise and heat (duals).
 

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Discussion Starter · #7 ·
Curious based on some comments here, but the White Bros with all spacers is considerably quieter than the Thunderheader.

Where do I get the fuel screw add-on mentioned. Sounds like after market so I presume I can't get it rom the Harley Dealor. And by the way the dealor here is very easy to work with and very helpful. Remember making something for my 48 merc when I was in high school so that I could do a similar thing. (Boy was that a long time ago.)

Stan
 

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What carb are you using?
 

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Discussion Starter · #9 ·
Stock carb that previous owner had re-jetted/dyno tuned for thunderheader, SE breather and Crane cam.

Stan
 

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n3hs said:
Curious based on some comments here, but the White Bros with all spacers is considerably quieter than the Thunderheader.

Where do I get the fuel screw add-on mentioned. Sounds like after market so I presume I can't get it rom the Harley Dealor. And by the way the dealor here is very easy to work with and very helpful. Remember making something for my 48 merc when I was in high school so that I could do a similar thing. (Boy was that a long time ago.)

Stan

Here you go, your dealer can get this for you.
http://www.dragspecialties.com/fatbook/1723/288/2383464
 
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