Properly tuned, a Mikuni only needs a few finger turns in of the idle speed adjuster to fire right up when cold, no other choke/enrichment necessary, then turned back out immediately upon firing, and its AFR charts, again when optimally tuned, look as good as any FI charts I have seen. Plus, a carb can be tuned well by riding & wrenching, try that with FI. FI certainly has advantages in self-adjusting to radically different atmospheric conditions, but then there are the many threads about malfunctions in the FI electronics/sensors and the resulting downtime and cost of repair. Seems like a tie at best...

 

years ago when I had my sportster the guy at local independent bike shop said to put an S&S Carb on it, man what a difference. and it ran great and I did not have to mess with it.

 

Great old thread HD Tech, thanks to those who keep it alive for folks like me that haven't seen it.

 

Does anyone know if this is only FI TC's or it applies to Carb bikes as well?

 

On the FI bikes like my 04, they have a ECM that takes care of the fuel, ignition advance and such. Carb bikes of this era have separate systems. The ignition is a ICM. I do not see any ping control. Know the last carb bikes used the MAP sensor to retard timing. Some just had a vacuum sensor electrical switch (VOES on plate that choke pull is located) .

 

On the 2014 and Newer bikes ( at least the touring models) Harley changed the strategy for the ion sense or knock sense. They are actually trying to prevent any knocks. They will actually start to pull timing before a knock occurs. As they sense an increase in resistance they will actual pull timing to stop a knock. Then that value is stored and used every time you hit that area ( map pressure, RPM , throttle positions)

Think of it as a dynamic timing table. The timing will continue being pulled for x time if it doesn't sense a resistance change again.

My bike has never pinged but you can see it pulling timing and increasing the knock count. I turned off my knock sense and could see the knock counts increasing with no ping heard at all. ( using PV to see the data)

This is a very basic explanation and I may not be describing it 100% correct but this is my understanding from FM

 

^^^ That's how it works on modern cars too (except they have designated knock sensors).

When I scan my Corvette racing, that's the graph table I'm looking for, I want it flat as kansas. Any knock, particularly knock at torque peak, is very detrimental to the engine.

And you're right, knock sensors detect knock way before you hear it. When I had my old Evo, I could hear knock in certain situations - it was a sound I hadn't heard in years!

 

On my 2103 CVO you would hear a sound ( pre knock ) then a second ping and you would see the knock count increment and the timing being pulled. But it would not pull timing again until the next event.

On my 2015 going down the highway at 65 MPH 25-2700 RPM it can pull from .25 degrees up to 6-7 Degrees. after the first time it does it it will continue to do it even though you do not see the knock count increment. Then after a period of time it will just stop.

I have shut off the knock control on a day when I was seeing timing pulled like that got back on the highway and and road the same way and never heard a single ping or knock.

I do not like this new way of handling spark knocks but there is nothing I can do other than turn of the knock control until I start actually hearing a knock

 

I remember back in the eighties when Oldsmobile first started using knock sensors. It really didn't work all that well and any abnormal engine noise would knock the **** out of the timing and those 231 v6 motors didn't have any power to begin with. I can remember just tapping on the motor would be enough to activate it. That's when the EPA standards had all motors running wicked lean. So what we would do to compensate was to drill out the carbs and increase the jet size on the 02 solenoid. I'm sure they work a little better today. You gotta remember they didn't have ecm's then...

 

Yes those were dark days for cars...

Modern knock sensors are great, loose exhaust pipes hitting the frame will trigger them but otherwise they are fool proof. Modern computers are so good now... I personally love scanning my Vette during drag strip runs, reading the AFR and timing and if there is any knock, then adjust spark and fuel if I need to by a few keystrokes... no more spilling gas all over the engine pulling the fuel bowls to change jets (after I read the plugs for lean/rich which is dubious information at best...lol).