I have a 2000 xlh1200 c i have had for about 2 months. It seems like the back cylinder is missing intermittently. The dealer said it runs fine but I don't think so. I put a volt meter on the input side of the coil (+on wire and - to rocker cover) while it's running. The front cylinder side shows 12.5-13 volt and the vm needle is steady as a rock. On the rear cylinder side it reads 12 volts and the needle bounces slightly when the rear cylinder misses. What i want to know is has anyone else noticed this same problem and if so did you find a solution? I have listened to a few other sportsters and they sound the same, but that still don't make it right. Help would be appreciated.

 

BTW I have hooker step tuned pipes, big sucker stage 2 and re-jet with yost tube. I had it dyno tuned yesterday and it didn't help the problem. the first run was 61.74 hp 64 tq and the last run was 70.04 hp and 69.97 tq. The re-jet was a master kit 40mm cv c. Had the comp test done and it was 180 psi front and 175 psi rear.

 

What kind of ignition is that? The bike came with a waste spark coil, where both plugs fire at the same time of of a single coil. How many low voltage connections are on the coil?

 

stock ignition and it has 2 in 2 out.

 

Then what you are reading with your meter is +12v and the ground through the ignition module for both cylinders. They both fire at the same time. If the rear cylinder is missing and the front is not, then check your spark plug, plug wire, and maybe the coil. If you grab it while it's running and it throws you across the garage, that part is bad.

As far as the needle bouncing when it's missing, if that's the cause, then the module itself may be bad, but that's a far stretch. I've never heard of a OEM module not working for one cylinder. More often, there is an intake leak or the carb isn't jetted right, or plugs or wires.

 

Well it work for both it's just the back one runs rough and the front runs perfect.

 

I also tried switching the low voltage inputs and spark plug wire to opposite sides of the coil and it was the same. That's why I thought it was the ignition module. The tech also checked the intake seal and it was ok.

 

OK so I just switched the inputs to the coil and left the spark plug wires alone. Now the fluctuation on the vm is on the front side and the rear is steady. The front cyl is running perfect and the rear is still stuttering, so that's not it. Also when i put my hand over the front pipe it always pushes out on my hand but on the rear pipe it i feels like it pushes out but in between puffs it sucks my hand up to the pipe. What can cause that?

 

I don't think your problem is ignition. If it was, you could swap the front and rear spark plug wires and the problem would move. You have some type of mechanical issue, or no issue at all. What did the guy at the dyno shop say? I would say your HP numbers look pretty good to me. I'd leave it alone or let a professional look at it.

 

The guy at the dyno shop said it was fine but the first dyno run was at12:21 pm and the last was at 2:04pm ,and i've read you can't do a good dyno tune in less than 4 hrs. So i don't know how much faith I have in him. I'm thinking about going to a different HD dealer to check his work, cause after the dyno and re-jet it is hard to start now. Today it was about 70 and besides choking I had to twist the throttle 2 times for it to start, before i only had to do that when it was cold out.