Lost Power

[04rkryder]

95 Heritage Softtail, Mikuni, HSR42 Crane HI-4 Ignition. Bike was running fine and then lost power. Needed  WOT to get through intersection and sounded like a old model T. Made it home and checked that both cylinders are firing. Bike sat for several weeks while I was on roadtrip. Got back home and drained tank thinking maybe bad gas, filled with fresh gas and started right up and ran fine for 3 miles till it warmed up and back to lost power. Seems like it isn't getting fuel but don't know why it only happens after bike is warmed up. Don't know Mikuni carbs, always had S&S so before I pull carb apart and mess it up, any other things to check first. Could it be the Ignition module?

[Rugby_fxdwg]

Is it a HI-4E? Or a nose cone HI-4? If its a nose cone, it could be, how is the coil? Do you have a cover on the coil?

[04rkryder]

It's a nose cone HI-4 and yes there is a cover on the coil. I was going to try it with the nose cone cover off, maybe I'll pull the coil cover also.

[Hossamania]

A friends Fatboy had the coil cover vibrate and move enough to short out the coil. Removed cover, problem solved.
Check gas tank venting, gas cap vent as well. Try opening a gas cap when it acts up to see if that solves the problem, may hear a "whoosh" when you open the cap. Indicates lack of venting.

[04rkryder]

Thanks, I'll try opening the gas cap next time I take it out. It's a project bike so I don't use it much. My luck it's something more expensive and money is a little tight right now.

[04rkryder]

Original statement "Made it home and checked that both cylinders are firing" was in error. I assumed that because I could feel exhaust pulses from both pipes that both cylinders were firing. Further investigating today revealed that the pipes have a equalizer(power chamber) between pipes. Found rear cylinder not firing after warmup. Coil tests show same readings front and rear cylinder. Guess it's time for a new ignition module. Ordered Dyna2000i today.

[04rkryder]

Installed new Dyna2000i, bike is running fine again.

[Hossamania]

Thanks for posting follow-up results.

[Oclaf]

Original statement "Made it home and checked that both cylinders are firing" was in error. I assumed that because I could feel exhaust pulses from both pipes that both cylinders were firing. Further investigating today revealed that the pipes have a equalizer(power chamber) between pipes. Found rear cylinder not firing after warmup. Coil tests show same readings front and rear cylinder. Guess it's time for a new ignition module. Ordered Dyna2000i today.

sell it...