I have a 09 FLHX with 12K miles that is knocking from the rear cylinder. The knock started someplace around 2 K miles. The knock is louder when cold and is barley noticeable after warm up. The noise is loudest right at 2500 rpm and sounds like the rear cylinder piston is slapping. The motor has always had synthetic 20w50 in it and was broken in conservatively, well as conservative as can be always riding two up with a pack of riders that ride like scolded dogs in Florida’s midday sun! The oil has been changed at 1K and then every 3 K miles because it always appeared and smelled somewhat burned.

I took these measurements at idle after pulling in from a 100 mile. Albeit not a controlled environment, but being able to measure many other bikes under the same relative conditions, I have a good idea that my engine is running hotter temps than their engines.

- The oil at every 3 K interval is really black in comparison to oil changes from the same kind of motors I see regularly for oil changes and was down about 20 oz measuring the removed oil.
- The rear cylinder breather tube and stock air filter is wet with blow by while the front is not
- Oil temp measured at the filter neck is about 265 deg
- Plug temp at the base of the spark plug – front 250 deg, rear 350
- Exhaust port temp at the end of the upper exhaust flange bolt – front 350 deg, rear 550 deg

My very narrow experience and listening to the engine components with a mechanical listening device, I believe I have worn or damaged rings and a worn, slapping piston in rear cylinder. Based on the oil being burned and very dirty on a motor of this age, I would like to get the opinions of some more experience mechanics that possibly have witnessed the sound of the tail tale piston slap on a late model.

Regards,
Barry (streetglide)

 

Still under warrenty?
I ask a seemingly stupid question about a 09 cause my 08 went out of warrenty about 2 months after I bought it.,when I took it apart.
If it is warrenty I would get to a good Dealer and get this all documented. Documented in case they argue. Cover the bases. You are probably right.
Something wrong at the rear cilinder. Sooner or later you will find out whats up.
Actually the burning oil is terrible and I don't see how anybody can argue with that.

Good Luck with this.

 

Thank you Gunny.

 

sounds like piston slap...possibley an out of round cylinder or ring failure...

 

The bike is under warranty and the dealer has agreed to lend me a bike for a week. The only concern is the noise wasnt something they have heard before. Thats a problem to me. If its a worn out piston and ring for whatever reason, I would think this would be something a seasoned mechanic would be familiar with in a late model TC. Its only a stock motor for crying out loud!. I was out at bike night tonight at the local haunt and had an opportunity for another mechanic to listen to it at 2500 rpm, he said the same thing, he had not ever heard that sort of noise. He did agree that based on my information only, the symptoms sound like a worn piston / rings. I want to tear it apart so bad right now! Anyway, I have an appointment in the morning to go see "the guy".

 

I know the feeling. As soon as I saw this I wanted to start taking the rear cilinder apart. Urge to grab tools.
Good Luck.

HD is where the Auto dealers were, 30 years ago.
Some were good, some affected your mind negatively for the rest of your life.
I have a deep distrust for most Dealers. But they are getting better. Somewhat.

 

To my fortune there is a good friend at the service desk, my service visit was quick, painless and an excepted response, sounds like both valve train noise and yes a little piston rattle. So it’s documented now and if it gets louder or uses more oil, they want to take it apart. It was my preferred resolution anyway, the path of least resistance!

I will wait patiently as well since if they go into the cylinder, I will have those parts replaced with the screaming eagle roller lifters, adjustable push rods and roller valve lifters. To me it sounds like it’s a pretty safe bet that H-D will be getting into my motor!

An interesting comment from the engine tech, he runs the dyno there too, he preferred old dino h-d 20w50 to syn 3, more durable he said. That was a shocker to hear. He asked if I had tried non-synthetic blend, mentioning to him I have changed the oil every 3 K because of the noises. Last night, before bringing it to them to listen to today, I put in h-d 20w50 regular oil and a h-d filter. Just to be sure someone just didn’t suggest that the oil looked like I had overheated the motor or something.

 

I agree on the dino oil.

I know your symptoms, but maybe take a listen to the compensator area in addition to the rear cylinder. Just a thought, seen many compensators grow weak quick.

 

Something to think about if the oil is seeing 500 degrees. Seals and 'O' rings don't like things that hot.
Also that is close to the flash point for Dyno oil. If not above.
Have to say guys, I worked for an oil co for many years and here is the main difference between dyno oil and synthitic oil.

To make synthinic oil engineers take a real good Dyno base oil, with long and short and every which away, and run it through a big machine that lines up every molocule of the stuff to be exactly the same. Not long, not short. Exactly like they want it. Thicker or thiner. Then add additives.
Sythetic really is far superior to Dyno. Really ,think about it. Look at the spects. Fact.

 

I have an 2007 Ultra that I heard what seem like a piston slap noise shortly after I purchased it. The thing that found that was causing it was not the engine but, was the transmission gears. I noticed that it was more prevalent in the lower RPM range (under 3,000). Every time that the engine fires, it loads the trans. gears. So basically, the noise was from the back lash from the trans. gears. I replace the trans. oil with Redline 80/90. This quietened the noise where it is not as noticeable. You may want to give this inexpensive troubleshoot a try.