I have a problem dealing with spark knock when doing roll on's, mostly in high gear( 2500-3500 RPM) ,always with a hot engine,and I'm not quite sure what to do next.

Let me describe the build first,
2002 Classsic
Carb/ Re-jetted
bored to 95 in
screaming Eagle heads W/ flat top Pistons (compression ratio around 9.5/1)
cam is a S&S your drive 570
ignition module/ Daytona twin tech
mufflers: series E White Brothers, K&N air filter

Now with all that said I did have this bike to Dyno tuned (Dyno numbers were very respectable at the time and fuel air ratios seem to indicate a very good pattern ) successfully and everything seemed to be in order, but so far trying to eliminate high-speed or high rpm spark back is been a problem. Initially the tuner continues to tell me just to turn down the advance curve slope. The initial setting was number seven on the module, and now I've had it turned all the way down to number one! now as far as my tuner goes,he says it's not always possible to totally eliminate spark knock altogether,especially from a hot engine and hot weather! I was wondering if this is true? Is there anything else someone can think of, that I might myself start looking at next?

Thanks much!

 

I'm not sure if I agree with your tuner that there is no way to remove the knocks completely. I just had my '05 RG upgraded to 95" with cams. Since I have the EFI system, and was using the SERT, my dyno tune took a bit longer. But, at the end, no more knocks at any throttle range. So, this leads me to believe that it can be done! What are you using for fuel management and timing?

Also, have you pulled your spark plugs and inspected them? Depending on who you talk with, the HD plugs may not be the best choice. My tuner suggested I use the NGK plugs instead. No pings or knocks thus far. If your plugs are fouling, there is an issue! You need to make sure, also, that your rings are properly seated from the build. If you plugs are oil fouled, and you're consuming engine oil, your rings are not seated! These are just some troubleshooting items to check. Good luck!

 

please describe what spark plug knock is ????????? thank you

i ask because on m last trip i had vibration problems and the dealer told me that i had spark plug knock and he had to re-adjust my pc3 .

 

FFB,

There are several reasons why your engine knocks. Some of the reasons include low octane fuel, too much carbon on your pistons, lean fuel/air mixture, and the one you'd asked: spark plugs. Under normal (stock) condition and heat range, your OEM plugs work just fine. However, once you start to play with the fuel/air mixture, your spark plugs may now be too "hot" or "cold!" By changing to colder plugs, you can reduce the amount of detonation (pings, knocks, etc.). This method, however, is not a be-all and end-all solution.

It's always better to adjust the fuel/air mixture first. Instead of changing the plugs. By adjusting the PCIII, your dealer was doing just that.

 

If its a knock registered by the ECM and not one you have identified during riding..................

My question would be which type of plug are you running, the reason I ask is that (I could be wrong here, so check it out with someone who really knows), I believe that changing to some aftermarket plugs can fool the system into thinking that knocking is taking place, when in fact all is well.

Of course if you are running stock plugs you have just wasted several seconds of your life reading all this

WB

 

only a Harley owner would think 2500-3500 is high rpm

 

thank you kahuna ...........finally i got an answer . not one dealer could expalin it to me and i went to 5 of them.