I have a softail chopper with a 2000 Evo engine, low mileage, S&S Super E carb, and straight pipes. I’m having what I believe is an electrical issue. The bike starts easily, and when I gently roll on the throttle, it usually responds as it should. But when I give it a quick twist of the throttle, it cuts out. I originally thought it was a fuel issue, but I’ve checked that entire system, rebuilt the accelerator pump, and that doesn’t seem to be the problem.

When I switch it on before starting, the speedometer light flickers. When I’m riding, the headlight surges as I rev the engine. I’ve checked the battery, battery connections, and other wiring to ensure I don’t have a short. The bike is very low mileage, and the Dyna S ignition is very new. Can anyone give me some things to check? Thanks in advance for you help.

 

First, check the voltage at the battery (running) to verify the regulator isn't over charging.

Second, drag pipes - straight pipes are for one thing only - wide open and though you can tinker and tune till you're blue in the face, you'll always have driveability problems at some rpm range. So until you're willing to insert some sort of baffle, even a simple one that won't necessarily make it quiet, live with it...

 

thanks... I'll check the battery while running.

Any suggestions on how to make a baffle or point me in the right direction?

 

Yes, do that. And overcharging system can be caused by a bad battery, or more correctly, one going bad. But either way overvoltage can cause all kinds of weird problems on a bike. And do straighten that out first, possible it could take care of your cutting out.

There's lots of trick baffles and ideas out there. One I really liked was to use a copper pipe connector that is near the id of your pipes. Takes some measuring to get right... or simply (much cheaper and easy to work with for me) is to buy a couple exhaust pipe connectors that have close to the correct od to fit well into the id of the pipe. If they are close or a little tight, you can split it with a hacksaw or grinder and tap them into the pipes.

You need to weld or somehow attach a round washer into the homemade baffle tube to reduce sonic inversion. It's not always a lack of backpressure thing that causes problems. And just because you may add some backpressure by way of the most simple baffle, it doesn't mean it'll be quieter - often it's the opposite and they will definitly pull better through out the RPM range.

One more thing (or 2) the further you put them up into the pipes, the better (less tinny) the sound and they need to be close to the same distance from the head or the tip, either one easiest to measure. And I always make mine cheap for testing. That way if they blow out no biggie. And when I'm happy with the arrangement, then figure how I want to fix them so the don't blow out or rattle.

 

I have a 99 Softail Custom with 1-3/4" drag pipes. I put 1" thumb screws about 4" from the tail ends. I tried turning them from crossways, to in line with the pipe, and found in line with the pipe worked the best. Between doing that, and opening up the idle mixture a little, it runs very consistantly, all the way from idle to top end. No hesitation anywhere, and just runs real great. Still getting 48 mpg with both city and highway riding. I do think it quieted it down just a smidgen, but not very much.

 

anymore ideas, guys?

 

Plug wires, plugs, and ignition circuit breaker. You have probably already checked this stuff, but, just in case.

 

Double check all of your grounds, they can be a source of electrical problems.

 

Here's a shot in the dark...
The Dyna S uses flyweights like the older bikers with points. I've not had hands-on with but a couple, but do remember reading (somewhere on here) about problems with the advance weights binding and read about the causes and remedies but it's been a long time ago. That causes issues with timing which is extremely important on these engines. May be worth investigation as well as the timing setting itself.

As others mention, grounds are as important as the hot wires - they carry the same load. And since this is a "custom" bike, without seeing it in person, it'd be difficult to offer many ideas beyond ensuring it has proper grounds to the frame, the engine, and between the 2.

 

Did you turn the accelerator pump screw all the way closed CW then come out CCW 1 turn Now when you twist the throttle you won't be shooting lots of gas into the intake Just a thought