I have a 2018 Limited, my first M8, my last 2 bikes have been the TC ... a 96 and an 88.

This one sounds a bit different from the last two ... but what bugs me is the knocking sound it makes when accelerating between 1800 and 2300 rpm. Not the same knock you get from using low grade gas in a car engine but what sounds like a knocking sound I believe coming from the heads. Yes I use quality premium gas.

I have no buddies with an M8 so I have no way to compare to see if it is "normal" or there is something not right.

I have progressed to stage 1 with HD stock Stg 1 tune but it did the same knock before when it was stock too ...

Any ideas?

 

I'm not an expert, and this is just my opinion, but......... I wouldn't be running my motor at that low of an RPM except maybe in my driveway. Get them R's up and see what it sounds like. I've always been told Harley's DO NOT like being lugged. Just a thought.....

 

my M8 cruises at lower rpms than previous engines for sure with all the torque of the big V Twin..2500 and even a little lower is a piece of cake, not lugging at all with no questionable engine noises to speak of ...I would say get to the dealership and ride another one along with them testing to compare, sounds like your warranty is intact so if there is an obvious difference they should do an investigation/inspection...btw, recently was at the Kelowna HOG rally and you have great riding up there, but you already know that!

 

Yeah I don't feel the bike is lugging at all at the lower rpms, just me onboard tho.

Yes we have some great riding here ... right now it is really smoky from all the fires we have but when it's clear it is beautiful for sure. Glad you enjoyed it.

 

Most my riding the M8 I'm around 2300-3000 rpms no lugging at all.

 

Both of mine would knock, just as described, if I aggressively rolled on the throttle at low rpm. They would do it even at highway speeds and higher rpm, just not as bad or noticeable. It happens for just a split second, then stops. It was explained to me by very trusted tech that it's spark knock and that the M8s factory timing is more aggressive, with the factory tune relying heavily on the new improved (whatever that means) knock sensors to make timing adjustments. Noticed the same thing on bikes I've taken on test rides.

 

Mine does it too.

 

 

I think you're experiencing the same issue that I have. My CVO makes the knocking sound at idle, both in gear and out of gear. The clunk, knock, clunk sound continues under low acceleration through 1,800 RPM or so.

I originally assumed it was a chain tension(er) issue, so I took it to my local dealer to try and have it resolved under warranty. After a few hours in the shop, the tech came out and said "it's normal".

BS! I didn't spend $40k on a new bike to have it go clunk, clunk, clunk. Try telling HD corporate that. They were zero help. Their only solution was "increase the idle speed to 1,050 RPM". I did that, using my FP3 tuner, but it didn't solve the problem.

There's less knocking at idle, but it's still there. So, I took things into my own hands and opened up the primary.

I measured the primary chain slack and it was a little loose. I fiddled with the auto chain tensioner and got it to kick up a notch. I ran the bike for 30 seconds, blipped the throttle a couple times, then shut it off the measure again. One notch put the chain lash exactly where it needed to be, so I put cover back on, refilled the primary, and went for a ride. There was a little less noise, but it was still there, so I went back inside again.

This time I over tightened the chain. WARNING, this is really BAD. A loose chain is a happy chain. A tight chain causes EXCESS WEAR and things start to BREAK. I wanted to see if the noise would go away. It did... completely. This lead me to believe that the problem has to be with the compensator, so I took it apart to check for an obvious defect. None found. I put everything back together, put a new gasket on ($32... ouch!) and buttoned it back up.

 

I think I know what knock you're talking about, OP, and it isn't ignition knock. Ignition knock is something else and sounds completely different. What OP hears, and what I also hear on my 2018 RGU, is a deeper knock more akin to wood blocks clacking together. It is most noticeable when under light throttle load while the motor is in the 2k to 3k rpm range. It isn't a pleasant noise, but it is a common motor noise. I've heard it before with other engines, including in-line fours, Goldwings, and Japanese V-twins.

How I experience this noise depends on whether or not I'm wearing earplugs (I almost always do wear earplugs), the traffic around me, my mood, distractions, and probably other ambient factors. Mostly, I don't notice it at all. I try not to. I do best when I keep my head in the ride and not pay attention to all the noises that big motor is making, while it works two feet away from my ears. I think earplugs make this noise more noticeable, because my foam earplugs tend to strip out clicky and windy noises but leave behind lower pitched clacky noises. Fairing type I think has a lot to do with how we hear the noises.