Hi all,

I need some tips on how to diagnose a problem with my Sportster.

2012 XL1200C, 15000 miles
Mods:
V&H twin slash slip-ons
SE Stage 1 air cleaner kit
FuelMoto micro EFI tuner

I've had the bike for two years (I bought it used - had 800 miles) and haven't had any problems until recently.

The bike runs fine when cold, but after it warms up I get brief losses of power when accelerating from idle.

What I have tried...

I've run both Seafoam and Techron fuel injector cleaner (at different times) through full tanks of gas.

I replaced the plug wires (the rear cylinder tested out of spec with multimeter) and plugs.

Any help will be greatly appreciated.

 

You could always fix it with the gas cap repair.

Take the gas cap off.
Pull a softail under it.
Reinstall the gas cap.
Problem solved!!!

Have you checked your ignition pick up?

Do you have the FSM for your bike?

 

Check your battery connections at the battery and the starter. Doesn't sound electrical but I had a similar problem when my + cable had corroded and was disconnecting causing a brief power loss at times. I didn't fully recognize it until it started doing it every time i hit a bump.

Change your plugs as well if you haven't already and verify the gap.

I'm no mechanic, but those are an easy inexpensive fix that could resolve the issue.

 

You might want to ask a mod to change your username.

 

could be a coil failing. although you'd probably throw a code. Check out iRider's comment about battery cables - I had the same problem. Ended up having to put a lock washer on the negative bolt to hold it in.

 

A long read, but the similar problem I had with my wife's 2006 Sportster was ultimately solved with a new crank position sensor. That is nearly 10 years ago, ant the bike still performs flawlessly.

2006 Sportster 883L (carb)

The bike was purchased new in June 2006. From day 1, it had an intermittent problem. Occasionally, when it was ridden in warm weather and motor was warmed up, it would cough/fart thru the carb when trying to start up from a stop light. To keep the bike from dying at lights, you had to keep twisting the throttle. Accelerating hard, there was a flat-spot where the bike would just limp along for quite a while before taking off.

We took the bike back to the dealer and he explained that HD sets these bikes far too lean in order to meet EPA standards. He re-jetted the carb – replacing the low speed jet with a #48 jet. (Stock is a #42.) He did not drill out the plug for the mixture screw, so I know he did not adjust that.

The bike ran okay for a short time, but then the same intermittent issues started again. I installed the SE intake/breather in the spring of 2007. The bike ran fine all 2007, so I assumed installing the SE intake had solved the problem.

Fast forward to 2008, and the same intermittent cough/fart thru the carb starts again, and all the other symptoms. I took the carb apart and found no crud and no obvious problems. I put in a #45 low speed jet, drilled out the mixture plug, and set the mixture screw 2 ¾ turns out. This made no improvement and all the issues were still there.

I tore carb apart again. Replaced the needle and spring with the needle and spring from a Dynojet kit. (I did not drill out the hole in the slide.) I put the needle c-clip in the 4th slot from the top and put in 3 washers. I also replaced the breather washer that had come with the SE intake kit with a couple washers that were a little thinner. (The washers in the SE intake kit were slightly thicker than 1/8” - .137”. I replaced them with washer that were slightly thinner than 1/8”) I thought this would allow the carb to fit a little tighter in the gasket between carb and manifold, perhaps giving a better seal.

At the same time, I replaced the crank position sensor because I had heard of similar issues to mine being caused by a bad crank position sensor.

After all these changes, the bike appeared to be running absolutely flawlessly. Now the question was, did the mods to the carb solve the problem or was it a bad crank position sensor??? I ran the bike a few more days to make sure the intermittent problem is really gone. Then I put the original crank position sensor back in and ran it for a while. Sure enough, the intermittent problems returned when the bike was hot. I put the new sensor back in and it has run flawlessly all season. Conclusion – Crank Position Sensor was the culprit!

 

You may want to post this question in the Sportster forum https://www.hdforums.com/forum/sportster-models-10/
That way you won't have anyone tell you to trade a great motorcycle for a sloptail.

 

Could be your FM Micro TPS wire connection. I've had similar problems with it.
Re-tapp the Fuel Moto Micro TPS wire. The TPS bayonet is a long term poor design.
It's designed to puncture just a small piece of the TPS wire insulation, and doesn't make a good connection.
Remove the wire, strip the insulation, and reconnect the splice connection to the bare wire.

 

my tps was giving me problems like you describe replaced it. no more issuses.

pull your ecu/module codes
https://www.hdforums.com/forum/sport...des-dtc-s.html

if you bike has a "trip" button, use that instead of looking for a button behined the speedo.

 

Thanks all for the great info. I'll let you know what I find.