Hi Guys -

This is going to be a long post but want you to have as much info as possible.

I recently finished a 103" build (did it myself) on my 2009 Street Bob. The rear cylinder will not fire - only the front cylinder will fire. When the front cylinder fires, the rear cylinder area can be heard knocking or whatever the word for it is a bit. It made a similar sound if you ran the bike with one cylinder before I did this build so I'm crossing my fingers I haven't bent/broken anything. When I crank the engine with the starter and no plugs, it sounds completely normal. I have the right oil pressure at this point and no oil light and via the crude thumb test I have significant compression on both cylinders. I'm not throwing any codes on my ThunderMax other than the rear O2 sensor because it's not getting any exhaust (it's at 19.36).

Here's my build specs:
- 103" bored cylinders matched to the pistons
- Ross Racing flat top pistons
- Ported/polished/decked heads (I: 1.900/E: 1.610/D: .005")
- .030 head gasket
- SE Tapered Adjustable Pushrods
- Fueling 574 cam
- Ported/polished OEM throttle body
- SE 4.89 injectors
- NGK Iridium spark plugs
- S&S Super intake
- ThunderMax Autotune ECU
- 10:1 compression
- Relocated coil to horn location

I ran the bike with the Fueling cams prior to this build and I know that they are timed correctly (timing marks and so forth). I also ran the ThunderMax prior to this build. I also relocated the coil and of course had to extend the wiring and wanted it clean so I dismantled the Delphi connector for new wiring. In doing so, I forgot to take a picture of the wire orientations on that plug so I used the manual for wire color codes. I later found out that the manual is either wrong or all Dynas were wired improperly (I checked the Dynas at the motorcycle show in town). As you can see in the attachment, the two yellow wires are on opposite ends but in the manual it states the blue wire (which looks orange because of the color code strip in the photo) and yellow wire next to it should be switched. I've tried both ways and still the rear cylinder won't fire. I checked the plugs for spark grounding them against the cylinder and both spark. (My coil is single fire.) Both plugs smell like gas but only the front plug (obviously) looks like it was part of combustion.

This is the first time I've installed adjustable pushrods. I installed per directions that Harley gave (which were next to useless because there are no pictures) and multiple forum posts and YouTube videos so I'm hoping I installed correctly. I did 2.5 rotations per the directions and of course waited for bleed down before rotating to the next cylinder. I did the front cylinder first, rear cylinder second, rotating the engine as necessary (hopefully) in order to get it set for the front and then rear install. I suppose I could have installed them improperly or switched the exhaust/intake rods on the rear cylinder, but I was very, very meticulous so I'm betting not. They're clearly labeled. Regardless, I haven't had the time to tear down enough and lift the bike up to get to them, tear apart the rear cylinder for inspection, etc. I was doing this in my condo which meant I had to take the bike up the elevator at 3AM so nobody would know... I'm hoping to avoid having to do that again as I made a huge mess in my condo when bleeding the brakes (my Mityvac blew up everywhere) and, let's say, I've been yelled at.

Clearly I'm going to have to take it apart but I'm hoping I could get some advice here on what possibly could be wrong. If I crank the motor without the plugs attached, some white steam-looking smoke comes from the exhaust - just sort of floats out for a second - and smells a little like gasoline and car exhaust mixed together. If I spin the throttle a bit with plug wires detached I get a popping (like a "bmmph") sound from the intake while cranking. I have no popped fuses and tried the OEM/H-D spark plugs (which only had 2,000 miles on them) and still a no go. Again, my ThunderMax isn't registering any relevant codes. Plugs smell like gasoline in both cylinders so I don't think my new rear injector is dead. It is installed properly and wired up.

Would really appreciate you guys running throw what I wrote here and offering any advice. Yes, I do have the manual. Trying to avoid going to the mechanic because I've already overstretched my budget. Once I had everything apart I figured, "Why not a crapload of powdercoating? And, wow, might as will improve my suspension! And this. And that. And $$$!"

I'm freaking out here so be nice to me.

Thanks,
Nick

 

Ok Nick I am going to ask this and I figure you have checked this but here goes. Pull the plug wire loose and check to see if you are getting an arc between the plug wire and the plug. 2 if there is an arc look at the color, if it is orange it could be the plug, plug wire or the coil. Also check to make sure that the coil is getting the proper amount of amps to and thru if not this could cause a weak spark but if after checking all this might want to check the plug wire which might be bad

 

@wyldspirit - Thanks for the reply. Not sure what you mean by this. I checked the plug by butting it up against the head bolt and they spark. You're saying check the connection of the plug wire to the plug itself visually? So essentially pull the plug wire boot back and look at the connection? Sorry... I'm confused.

The plug wires are new Sumaxx 8.2's. For what it's worth, when I extended the wiring for the coil, I soldered the wires very cleanly and rebuilt the Delphi plug (a new one, actually) with new crimp connections and so forth. I've moved coils before so I wasn't nervous about it or anything. I almost completely rewired the coil wires from the elec. box to the coil to minimize resistance but realized how locked up the OEM wires were and didn't want to fight that.

Another person suggested to me that I may have set the rear adjustable pushrods wrong and that my valves are both opening at the same time on that rear cylinder. I don't know the symptoms of that other than it just not firing... but wouldn't it at least have a little bit of explosion or fire a bit? The bike backfired once with a sort of "poof" sound so I figure maybe that gas in that cylinder ignited and "fireballed" out. Always a good sign, right?

 

1. Take the spark plugs out. Crank the engine and make sure there is a spark across both plugs.
2. Make sure the plug wires are going to the correct cylinder.
3. Make sure you are getting fuel to both cylinders.
4. Take the aftermarket fuel controller out of the equation or at least check to see if it is giving you any malfunction codes.
5. Make sure your pushrods are adjusted correctly. If your engine is trying to open valves at the wrong time, you aren't going to get it started.

Basic general idea of what to do. This comes from years of engine building. Stick with the basics first.

If you put in new cams, are you positive you indexed them correctly?

Most of the time backfiring is a symptom of incorrect timing. Your pushrods may be adjusted incorrectly, your cam may be indexed wrong or your controller may not be doing what it should be when it should be. When you say "backfire" did fire actually shoot out of the pipe? If so, there is a good chance that you are getting decent fire in the cylinder-but not necessarily at the right time(which could be ignition, timing).

 

Yeah, the flame poofed out of my ridiculously huge exhaust megaphone (Rinehart 2:1). Was just a quick poof and made a funny sound - made me laugh, actually. Ever have one of those farts? There you go...

I'm not going to get to it until the weekend but will update you all after pushrod adjustment. Everyone in my circle is saying I must have goofed the rear pushrods - I did install those rods second so maybe I got them switched.

My cam timing/indexing is on point. I installed the cam a long while before and that was my first bit of engine work so I paid an indy to walk me through my work and make sure I covered it. Alignment circles are lined up. I actually fixed a misalignment on the oil pump when I installed those. Never had oil pressure issue at all, but someone lined that up improperly relative to how it's supposed to be. Never had an issue with the cam.

The big thing that changed in valve train OPERATION: adjustable pushrods. Hoping that's it. If not... tearing down that rear cylinder again and taking up heavy drinking. Any suggestions on a Whiskey? Haha.

Transparently, I'm not happy with the ThunderMax so I intend to switch back to my Delphi and get my SERT (or whatever the top end tuner from HD is) tuned by a guy up here who does a great deal of road riding in addition to a dyno: $500. But I wanted to have control over the map and RPM at start up - heat cycles can be done almost automatically on a ThunderMax - and I can watch the engine myself during initial break in (and understand what I'm looking at). But the ThunderMax hasn't been much of an improvement for me I don't like how you manage timing in it. I like tables. But the power was always consistent regardless of weather and so forth so I attribute that to the Autotune. I usually guessed a tune close enough it never made too many adjustments. Just something not right about it... I figured I would have gotten more power from it. Smoothed things out and really took a tone of heat out of the engine even beyond my original Stage 1 SERT tune job I had done on a dyno (not download). But ran a bit rich for my tastes...

 

If it's a 2 into 1 pipe, then you can't tell for sure fire is coming out of the rear cylinder. It may be a surplus of gas in the front cylinder because of the rear not firing. Good luck.

 

You wired the coil wrong.if you turned the coil upside down .you either have to cross the plug wires or re wire,look at the plug case from your harness and make sure the colors are right,it has to fire in order,simple solution,i hope that is your problem