I posted this in the electrical / ignition section and so far the thought is carb related."Supposedly" my independant cleaned and rebuilt the carb. I know the jets are ok. Anyone think this could be an ignition problem. Any suggestions??


I have a 94Fatboy that I bought used about 1yr ago. idle and bottom end performance was rough. I pulled the idle jet and realized that it still had the stock 42 in it. Went to a 45 and cured about 80 of the rough idle and hesitation. I have tried to go to a 48 and that did not help. I think it is something in the ignition system. Looks like the module is stock. Anything else to try before dumping over $100 on a new one? I do not think I have any intake leaks at the filter or the manifold. The coil and plug wires are new ( stock coil and SE wires ) By the way, she runs great from 30 MPH and up. Any suggestions would be great!!

Current set up is:
andrews ev-27 cam
K&N filter
V&H big shots
thunder monster baffles
stock cv carb with 175 main and 45 idle jet

thanks

 

It is next to immpossible to diagnose a bike without seeing it.That CV carb could still need tweaking.The only way to check the module is on a machine that can watch the timing.Try another module if you have access to one.Of course you will have to own it.

 

Mine's a little older, but have had the same problem. Mine's an '87, with an 80 in bored to ? It has an S&S Super E carb. I rebuilt the carb last summer, still had low rpm hesitation, but ran great over 1500 rpm and up. I tried changing main jet to leaner size, but still had problem. An old EVO rider/wrencher told me to go back to orig jet, it was running too lean, so I changed it, still no help. He said he thinks it's just a characteristic of EVO's. Thay will run bad at low rpm and great at highway speed, or vice-versa. You pick which you want. I don't know the answer, I've adapted to rough running at low speed. If you find the answer, please post it.

 

I found the VOES (Vacuum Operated Electrical Switch) has some effect at low speed and idle as it senses a high vacuum and closes, which sends the signal to the ignition to advance the timing for a better idle and throttle response. I read the VOES does not do much past 2500 rpm. A simple way to check it is to unhook the VOES ( located on the horn bracket just above the horn) ground from the wire during idle to see if it there are any changes in idle. It defaults to open and will not advance the timing if it is defective or has a vacuum leak etc. which will allow the bike to run OK, but not at it's best.

 

I just fixed the same problem in my 87 Evo. First make sure your pilot and main jet are correct. Ride in thet powerband and chop the ignition and examine the plug. If both jets are good, move the needle down. I don't know S&S carbs but they should be adjustable. I have a cv carb, got my two jets correct and then moved the needle clip up which moved the needle lower in the carb. This helped with the transition from pilot to main jet.

 

Check the air/fuel mixture screw (assuming it is a CV carb)...I can't recall the setting for sure but 2 1/2 turns from seated rings a bell...check the manual.

 

I agree, mine is right at 3 turns for the sweet spot.

MikeyB