Hello, I'll try to keep this consise:
2003 1200 Sportster Custom w/stock cam/carbs. About 2weeks ago ridden home w/no troubles. Left ON for two days [oops] this drained 1yr old battery. Push started and rode 20 mi keeping RPM high hoping to recharge. Ran steadily worse on this ride until back home--guages (tach & speedo)acting totally crazy during this ride. (I guess because the batter was DEAD) Have since removed, recharged and had battery load tested by Interstate store...passes with high grades. At this time, bike would no longer start. Replaced fouled plugs and bike will start faithfully, but runs POORLY. Trouble codes on speedo all report 'clr'. Blubblers/black smoke etc not able to rev up with fast or slow throttle action. Replaced ign coil and bike ran for 1 min perfectly (thought I had it fixed) then went back to blubblering like before. Have since replaced wires/ign module unplugged headlight & tore down carb & blown out passages. Checked for vac leaks -found none. Set & reset float. Still when cold will run perfectly for almost 1 min then blubber. Shows 13.8-14.2 volts across battery when running, timing adjustment has no affect. Stator and reg test OK with ohm meter. No diff behavior if reg and stator are unplugged. (Thought here was that the charging system would heat up after 1 min & cause power problems resulting in poor ignition -not true it behaved the same running from battery alone). This bike runs OK for 1min when cold no matter what is done to it but for no more than that length of time!!! Two weeks no riding is BAD THING. I don't know what else to consider...all engine internals must be OK because it sounds great for that first minute, but I don't know what else to focus on now!

 

WOW, that a lot of replaced parts. Lets go back to where the problem started with the dead (drained) battery. After the bike has set overnight, with no charger on the battery, what voltage do you measure across the battery with the ignition OFF, and then again with it ON without starting the motor?

 

+1 with charley. start at the beginning. I would also re check those vac lines. a crack is hard to see.

 

I've not measured the static battery voltage after an overnight off-charger sit. I will do that and report back. (ign off then on -two values to report)

I expect that it'll show just over 12v -my reasoning being that it cranks strong. Nevertheless, I'm glad to have new ideas/advice on this problem, and will make these measurements.

Am I right to understand that there is only one vac line involved here...that being between the intake manifold and the VOES?

Also, I've not considered the ride angle switch as a possible problem source here because I understand that should it 'fire', it would just kill the ignition. True?

thanks, and I'll get back to you all shortly....

 

My son in law had a very similar issue on his Fat Boy (which he just resolved a couple of days ago after a very frustrating 3 weeks). Bike would start and idle, but couldn't rev it past maybe 1300 rpm. Turned out that one of the batt cables - I'm not sure which one - got dorked up when he had taken out, then replaced the battery. Check connections at both ends as well as try wiggling them to see if perhaps there is significant strand breakage somewhere under the insulation.

 

I had the exact same problem on a '03 that belonged to a friend. Replaced the VOES switch and it was cured. I think it was like 40 bucks.

 

The VOES has nothing to do with idling and I think up to about half throttle. It only comes into play when you aggressively get on the throttle and there is enough vacuum pressure to engage it. I would hold off replacing it till you go over whats already been said.

 

I agree it has nothing to do with idle, but it has everything to do with off idle performance if it is at fault.

My buds scoot had been to the dealer twice and every indy where none found the problem.....It would start just fine and idle all day, but as soon as you twisted the grip to take off it would sputter and die or if you babied it, it would continue to run but exhibit the same sputtering and lack of power he describes.

I ain't saying it's the problem, just contributing what I finally figured out on one particular scoot acted exactly like his.

Oh, by the way, water in the gas will cause the exact same...if he has a little water in the tank, it will idle all day but fall on it's face when twisted.....Scooters left outside exposed to sunlight and cooler nights will form water in the tank and then the water beads will block the cruise jet when you twist it. Water beads will fall away at idle and allow sips of gas to enter the idle jet, but a higher velocity flow of gas will lift the water beads and block the cruise jet when the grip is cranked.

I don't think his problem is related to the battery episode. I'm thinking he has either a fuel or spark issue.....The VOES switch effects spark advance where if the switch is faulty, the engine won't accell when off idle vac falls as you twist the throttle(falling manifold vac triggers VOES), fuel blockage from water does same....two different problems with the same result.

His job is to split the problem by the process of elimination. Our job is to give him our experience. Your job is to allow all that to happen.

 

Just as quick note regarding the voes switch.....it can give you a real crappy idle....if it's switched to the 2nd timing curve. I played around with my voes the other year with a vacuume pump on the bike while running, so I can tell you that it does affect running across the idle to middle throttler range..... that is if it's not working. Simple to test it statically though, vacum pump and an ohm meter......if I remember the stock voes setting is between 3.5-4.5in-mercury vacuum to trigger the switch. Best of luck, hope you get it figured out.

 

I stand corrected. Good advice from both.