Any motorcycle mechanics here? I have a problem

I have a 2003 Harley-Davidson Road King that is fuel injected.
A medical condition has kept me from riding for about a year and a half so the bike has not been started during that time.
I am in the process of getting it running again, so I put in fresh gas, replaced the battery, took the plugs out and spun the motor over enough to slosh the oil around.
I put the plugs back in and it fired up but only the back cylinder is firing.
Any ideas what to check to see why the front cylinder is not firing? It has to be either spark or fuel. Thanks for any input

Quick way to test if it’s the plug is to pull it and plug it back into the plug wire and then lay the base against the cylinder to ground it. Crank it over a few times while observing the spark gap.

Things I would in the order I would do them.

  1. Pull the sparkplugs, clean them both, verify spark on both then swap them around. Did the problem move to the other cylinder?

0.5 Swap the plug wires. Did the problem move to the other cylinder?

  1. Listen to the injector on the cold cylinder with a mechanic’s stethoscope. Can you hear it clicking open?

  2. Pull the injector. Does it look clogged? Blast it with injector cleaner.

  3. Swap the injector with the good cylinder. Does the problem follow the injector?

If none of the above pan out, then diagnosing gets a little more involved.

  1. Check compression on the cold cylinder. If the rings are good, you should be looking at about 190 PSI.

  2. I believe that motor uses a single, dual-output coil so the chances of you having a cold-spark condition on one cylinder and not the other are exceedingly low. Still there’s a chance. If you’ve made it this far and nothing has panned out, then start looking for a donor coil that you can swap in and see if that changes anything.

Find someone local with one of the code readers you can borrow. Any sort of misfire will record the event with data that can be very helpful. That is that strange check engine-ish light that should display at intervals on the dash/speedo.

(one of my bikes is a 2004 RK ----- the almost famous Road Kow in case you want to Google image it)

Gasoline gone bad is nearly always the culprit if it had been running fine before you left it over a long stretch. Guaranteed you had some water that condensated over that time period too. Good that you drained old gas tank, but some water and bad gasoline still remained in the lines and fuel injectors unless you bled them out. I’m sure youtube has plenty of videos on this.

I’d agree with this as the most-likely culprit.

How long did you let it run on one cylinder? If you only ran it a few seconds, you may want to try it again. Be sure to activate the throttle and have the revs go up/down for a minute or two. In theory, we’re trying to flush old gas and goo out of the intake track for that errant cylinder.

Note, if you check the spark as mentioned above, be sure the plug is grounded. I’m not Harley-wise, but an ungrounded plug can cause damage in some machines.

good point. unlike cars, motorcycles aren’t (federally) required to have sealed fuel systems. California (and perhaps the other “CARB states”) do, but if your bike doesn’t have California emissions then the fuel in the tank can degrade fairly quickly.

I would find that very unlikely since he said one cylinder is firing. There’s only 1 fuel pickup and 1 fuel pump, so the only place for “different” fuel mixtures to accumulate would be in the runs off the fuel rail to the individual injectors. And if that’s truly the case, then this would resolve itself in seconds. Still it does beg the question, how long did he let it run?

There are fuel injectors for each cylinder, not one. It’s possible one injector got clogged, while the other didn’t.

Which is why, in my very first post, I suggested swapping the injectors to see if the problem followed them. That has nothing to do with your guess of bad gas which is what I addressing in my prior post.

Good suggestions everyone. I will work on it more tomorrow. I ran the bike for about 3 minutes several different times. It would idle without holding the throttle open but I could tell by the sound that something wasn’t right. I have Reinhardt true dual pipes (no crossover) so it was easy to determine which one was not working. I just put my hand over the end of each pipe while it was idling and one was hot the other not. There was also a marked difference in the pressure coming out of the pipes. I cautiously ran up the throttle some but not very much. Prior to trying to start the bike I removed the spark plugs and noticed the front plug was a little fouled…at least more than the back one. I bought two new plugs today and will probably pour in some sort of gas/injector cleaner stuff. I will report back. Thanks for the help!

That’s … slightly troubling. There will certainly be lower pressure coming out of the cold cylinder, but you should still feel significant airflow out of the pipe. A gasoline engine is after all an air pump, and will still move a lot of air as long as it’s turning over even if there is no combustion taking place.

Try this as a quick and dirty compression test. Pull the plug out of the “good” cylinder (be sure you lay it on top of the head though so it can still find a ground), then try to crank it over. Does it seem like the engine is just free-wheeling, and the starter motor isn’t really fighting against any compression?

Kinda sounds like a stuck valve, huh?

Possibly or maybe a wiped cam lobe :smack:

You’ve really brightened my day now. Thanks.

is there any abnormally loud ticking? could also be a stuck/collapsed lifter.

Haven’t noticed that or any other abnormal engine noises. I had planned on working on it today but rained all day and I didn’t want to hang out in the garage. I have a compression tester so I will do a compression check tomorrow.

If you have an inductive timing light you can save some time swapping plugs and wires and you can eyeball to see if it’s firing evenly. or test them with an ohm meter.