When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey all,
I'm working my way through a project bike I picked up from a friend. It's a 2003 Heritage Softail Anniversary. He unloaded it cheap because he kept having issues with it, and one of them was a backfiring and power issue. I've been slowing working through this issue and think I made a nice breakthrough last night. I installed a new CPS and it was still doing it. I decided to remove the plug wire from the rear cylinder and it fired up and ran smoothly (for running on one cylinder that is) I then replaced the rear plug wire and removed the front. It didn't want to run for crap and backfired. So the issue is the rear cylinder for sure.
Here's what I've done so far.
1. replaced 1 fuel hose in gas tank and replaced fuel PSI regulator housing (it was cracked) I tested the unit outside of the tank to make sure it didn't have anymore leaks. I did use the proper hose clams, and tool to install.
2. I have Installed a new coil, plugs and plug wires. (installed a coil relocation kit)
3. I installed a new crank position sensor. (Old one wasn't putting out the proper amount of AC voltage when cranking)
4. Checked the compression and both cylinders read 150 psi in both.
5. I removed the rocker box covers and inspected the valve movement while cranking. All valves are moving properly and not sticking open.
6. It has a Fuel Pak on it. I've removed the Fuel Pak and tested with just the factory ECM, to eliminate the Fuel Pak as the possible problem.
So, I feel I'm down to either a bad fuel injector on the rear cylinder or a bad ECM (since it controls when the spark hits the cylinder.)
My plan next is to swap the injectors and see if the issue moves to the front cylinder.
Anyone have other ideas of things to look or check for?
Picture for $h!ts and Giggles.
I am sure you already know but backfiring through the carburetor is a sign of lean condition. If your cylinder problem doesn't move with the injector I would be looking at the intake manifold seals. Good luck
I've sprayed around the intake with carb cleaner while it was running, but it never made a difference. Is there a better way? I tried the smoke method years ago with my old Crossfire Injection 84 Vette, but don't have the equipment to do a smoke test now. I'm always open to learn and find better ways to diagnose things.
Another way is with a propane torch.... unlit of course....
As the bike is idling, with the propane torch gas on low (again, unlit), direct the flow of propane around the seals... If the idle increases, you found your intake leak..
I find the propane method less messy than the carb cleaner method.... Unless of course your intake manifold needs a good cleaning...
I use smoke for exhaust leaks.. I have several incense sticks in a drawer somewhere.. left over from the 60's.....
By the way, did I mention not to lite the propane torch...???
Last edited by hattitude; Jun 25, 2021 at 10:27 PM.
1. I leak tested the intake. It's good.
2. I swapped the injectors, but the issue didn't move. Front cylinder still ran fine, rear backfiring. That eliminated a bad injector and poor stream. Fuel pressure if fine.
3. I have all new coil, plugs and plug wires, but I did the primary and secondary tests again.
4. Checked for proper resistance on injectors. Also checked the wiring for injectors, using the tests in the HD electrical supplement service manual.
5. I put compressed air into the cylinder while holding at TDC and had no detectable air leaking out the intake or exhaust.
I know it's a long shot that the ECM could be defective, but I'm really running out of ideas. I just don't have an extra one lying around. LOL
Anyone in the Northwest Houston area want to loan me a early EFI softail ECM to test the bike? LOL
Well I figured out the problem today. I was taking it apart to install some Screaming Eagle cams my brother gave me for the bike. Pictures say a thousand words. This is why you can't put 95K miles on an early twin cam engine without doing some maintenance. Cam bearing apparently exploded and the cam destroyed the cam bearing opening. Now, either a used engine or rebuild it with new lower cases.
Anyone ever have the casing welded up, and machined out again?
Well I figured out the problem today. I was taking it apart to install some Screaming Eagle cams my brother gave me for the bike. Pictures say a thousand words. This is why you can't put 95K miles on an early twin cam engine without doing some maintenance. Cam bearing apparently exploded and the cam destroyed the cam bearing opening. Now, either a used engine or rebuild it with new lower cases.
Anyone ever have the casing welded up, and machined out again?
Wow....
Sorry for your problem... that is certainly something I didn't consider... I would have thought that would make some major noise...
Slideshow: From the troubled AMF years to modern misfires, these bikes earned reputations for reliability issues, questionable engineering, or disappointing performance.
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Slideshow: The Swiss custom shop has taken a Harley Softail and stretched it into something so long and low that it looks closer to a rolling sculpture than a conventional motorcycle.
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Slideshow: A standard cruiser becomes an intricate metal canvas in the hands of a Swiss custom house known for pushing Harley-Davidson platforms far beyond their factory brief.
Slideshow: Harley-Davidson's challenges aren't abstract; they show up in dropping shipments, shrinking dealer traffic, and strategic decisions that aren't yet translating into growth.
Backfire through throttle body.
