883L Spark Knock

[Ssawahl]

Good evening all.

I have an 08 883L that I bought new and now has 113,388 miles on her original motor. I've done alot of cosmetic work but motorwise I've swapped the pipes numerous times changed the airfilter to a smaller one and relocated the coil. Over the years I've had to replace the rocker top gaskets three times, the clutch pack once, the throw out bearing twice and the clutch cable once. Besides that regular fulid changes.

Anyway about 2 months ago I was heading somewhere and started hearing what sounds like little rocks hitting metal as if you were driving down a dirt road. So not a constant sound but more randomly spaced "tinks".

First I was told to check my primary chain tension and look inside the case to see if the chain had been hitting the case. I did and tension seemed good and the inside of the case has no marks. Also everything on the primary side (which is where I hear the sound btw) looked like it was in great condition.

Next I had a Harley service manager take her for a ride. That's when he said it sounded like spark knock. He asked what kind of gas I ran, Always 93. He suggested I changed my plugs, did that didn't help. And tonight I flushed my tank and put new gas in her, still making the sound.

Any ideas as to what I could do next to find and solve this issue? My bike has been off the road for the last 2 months and it's driving me crazy not being able to ride her.

[Hossamania]

At what speed and rpm or conditions does this occur? When accelerating while cruising, or while accelerating thru the gears too? High rpm and low rpm? If happening  at 55 in 5th gear, does it stop if you downshift to 4th? Do you "lug" the motor on a regular basis?
It's possible that there is a buildup of carbon on the pistons. This can raise compression,  causing detonation like you are experiencing. You could get a bore scope and look thru the plug hole to examine the piston tops to see if it is excessive, if you'd like.
One way to remove it, or remove some of it, is to get the motor good and hot by riding it for a bit (not just idling it), remove the air cleaner, and spray water into the throttle body while working the throttle to keep it running. 4 or 5 sprays, then let the motor "catch up", repeat quite a few times. Change the oil, and take it for a ride, see if there is any improvement.

[Ssawahl]

At what speed and rpm or conditions does this occur? When accelerating while cruising, or while accelerating thru the gears too? High rpm and low rpm? If happening  at 55 in 5th gear, does it stop if you downshift to 4th? Do you "lug" the motor on a regular basis?
It's possible that there is a buildup of carbon on the pistons. This can raise compression,  causing detonation like you are experiencing. You could get a bore scope and look thru the plug hole to examine the piston tops to see if it is excessive, if you'd like.
One way to remove it, or remove some of it, is to get the motor good and hot by riding it for a bit (not just idling it), remove the air cleaner, and spray water into the throttle body while working the throttle to keep it running. 4 or 5 sprays, then let the motor "catch up", repeat quite a few times. Change the oil, and take it for a ride, see if there is any improvement.

Thanks for the response!


I do not have a tachometer so I can't tell you rpms. But it seems to happen little when throttling up hard or when crusing. I've heard it at around 45 briefly, 55 and 65 slightly more.

Also I do not lug the motor if it starts to lug I immediately shift down.

I talked to a mechanic friend and took a modified approach to your suggestion. I put Lucas high mileage fuel treatment into the tank and used Berryman intake valve and combustion chamber cleaner in place of water. 

As of yesterday afternoon it seems like maybe that is helping but I can still hear it. But I also do not know how long it would take to clear up.

I will be contacting the manufacturers of the tuner that I have in the bike to see if that might be causing the problem too.

[Hossamania]

Which tuner are you using? Was it modified as exhaust and air filters were changed? What and when was the last time something (exhaust, etc.) was changed? How soon after that did the problem start?
When was the last time the intake, throttle body had a good cleaning? Are your heads still venting into the intake, or modified to vent to atmosphere? If still vented to the intake, that can introduce oil mist over time, which needs to be cleaned out of the throttle body. Cleaning is a good idea even if vented to atmosphere. A good intake/carb cleaner sprayed in all the orifices, throat, linkage will help with better running, and possibly lean conditions caused by dirty intake.

[Hossamania]

Another round of carbon cleaning probably wouldn't hurt either.

[Ssawahl]

Which tuner are you using? Was it modified as exhaust and air filters were changed? What and when was the last time something (exhaust, etc.) was changed? How soon after that did the problem start?
When was the last time the intake, throttle body had a good cleaning? Are your heads still venting into the intake, or modified to vent to atmosphere? If still vented to the intake, that can introduce oil mist over time, which needs to be cleaned out of the throttle body. Cleaning is a good idea even if vented to atmosphere. A good intake/carb cleaner sprayed in all the orifices, throat, linkage will help with better running, and possibly lean conditions caused by dirty intake.

Thank you again for the response Hossamania.


I am using the Fuelmoto Mini EFI tuner. I has been updated since I changes the pipes and air cleaner. But I did message them again to make sure it is the right update. 

The problem didn't start untill over a month after the new exhaust was put on and over 2,500 miles later. In that time everything seemed fine.

Besides replacing the rocker top gaskets the top end of the motor has never been gone through or modified. 

I've run the intake and carb cleaner through twice now and plan to do it once more this weekend. After I went through the process last night I rode her for about 20 miles at various speeds and it appears that the sounds is almost gone. 

Thank you for all of the advice so far and any further advice!

[Ssawahl]

Also sorry for the delayed responses I don't always have time after work to get right home and do noisy things with my bike before having to stop to not annoy my neighbors.