This is a bit lengthy but I sure could use some help with this one. I’ll start at the beginning.

The bike:
2007 Ultra Classic 96 CI Engine 6 speed transmission purchased new December 2006.

The original issue:
At around 5K miles on the bike the engine developed a ticking noise that would start right at 1.8K RPM and stop at 2.8K RPM. Sounded like a lifter out of adjustment in the front cylinder. At 13K miles the ticking had over time gotten louder and was driving me nuts so it was time to do something about it.

What was found?
Bad crank assembly. The right side flywheel half had a palm size outward lump in the casting on the inboard side. As you turn the crank assembly and load the rods to the right, the front rod (only) taps the lump as it goes past it. What we figured is the engine load was just right between 1.8K and 2.8K RPM to load the rods to the right and start the ticking noise. One other symptom the bike always had is a louder than normal overall engine noise to it. Hard to describe but when I road other Harleys (all were 88 CI engines) I would hear the exhaust not the engine. On mine you always heard the roar of the engine. I think the rod going past that high spot on the flywheel was causing a fan blade noise effect in the crank case. Basically it was making a wind turbulence noise.

The new build:
S&S 4.5” stroked crank assembly with their 106 piston kit (3.785 bore)
Andrews 54H cams
Open Close Duration Lift LSA Lift TDC
Intake 16 42 238 .555 103 .165
Exhaust 43 15 238 .555 104 .158

The heads were done to match this set up (stage 1 (stock valves)) by Bishop’s Performance in Redford Michigan
.040" Head gasket
Pistons are S&S 10.5 to 1 flat tops with .000 deck height
Corrected/calculated Compression @42 degree intake closing is 195 (9.37 to 1)
The CCP with the new engine before it was first started was 193 in the front and 198 in the rear (done with 2 different quality gauges)
Actual cold cranking compression after 500 miles and done with a hot motor is 196 both front and rear (after 7-8 puffs)

Other build parts that were already on the bike:
1) Thunder Max ECM with Auto Tune
2) Arlen Ness Big Sucker with K&N air filter
3) Vance & Hines True Duals with Monster Oval Mufflers
4) SE Compensator
5) 30 Tooth primary belt pulley
6) HD 145# clutch spring
7) Isolation Drive System

The new issue:
During the first ride the bike started great cold (only needs the compression releases when hot) and ran fantastic. The engine was kept under 3K RPM for the first 15 miles. At the 15 mile point the engine was brought up to 3.5K RPM and everything was good until lowering the throttle to a cruising speed of 3K. Once the engine RPM steadied at 3K RPM the detonation sounded like a machine gun going off inside of the engine. The detonation is loud and rapid. If I close the throttle or open it up more the detonation goes away. You can accelerate right through the 3K RPM range with no issues; the detonation starts when the engine settles down and cruising at 3K RPM.

What has been done so far to correct the detonation?
1. I tried 6 different calibration maps in the Thunder Max ECM, 103s, 110s, then even a 131 CI. No changes at all. Bike ran great on all of them except cruising at 3K RPM.
2. Set the AFR to 12 to 1 across the board to fatten it up and cool off the pistons. No changes at all.
3. My next thought was it might be bad gas. So I completely drained the tank of the 93 octane premium fuel and put in 2 gallons of fresh regular gas. No changes at all.
4. Drained the regular fuel out and put in 2 gallons of 110 race fuel. No changes at all.
5. I began pulling timing out 4 degrees at a time in the 3K RPM range. As I did this the detonation started up further below and above the 3K RPM range, where it didn’t before, which I thought was a bit strange. After removing 10-12 degrees in the 2K – 3.5K range the detonation was basically gone.

The original timing was at 25 degrees in the 2K-3.5K RPM range with the throttle input below 1/3.
Now the timing is at 10-12 degrees in the 2K-3.5K RPM range with the throttle input below 1/3.
Performance has suffered and the engine now has a huge single ka-bang out the exhaust on deceleration.

What to do now?
1. Replace the crank sensor. Possibly the crank sensor is putting out additional pulses at 3K RPM causing the detonation.
2. Replace the coil pack. Possibly there is cross firing between the coils causing the detonation.
3. Pull the primary cover and put timing marks on the Compensator to see exactly where the Thunder Max is firing the timing at.
4. Pull the heads and have them opened up from the stock 85 CC’s to 87-88? Too lower the compression?

Any suggestion?
Dave

 

this is a head scratcher. ( and I am not a builder- at the least this'll keep the thread on the 1st page)

my only comment is that #4 you could try a thicker head gasket to lower compression rather than machining.

but are you sure this is detonation/pinging as your efforts with ignition timing and fuel octane seems to have minimal effect.

detonation can be seen on a scope.

could it be another noise- torsional loads on bearings etc.


#3 I have timing marks on the motor sprocket on my pans and evos- easier than using the flywheel marks- but then I have the chain hole to look through


Mike

 

I think when you take out timing, it has to be gradual, not just at a set rpm.
As far as the decel problem, check your configuration and see if the decel box is active, I know you shouldnt have to have it marked, but that might eliminate the decel.
Are the timing marks on the cam lined up properly?

 

Mkguitar
The head gasket is a .040” so to go to the stock .045 would only take a little out of the compression. I don’t mind spending the money to CC the heads if it would help get rid of the detonation.
It definitely sounds like detonation and not mechanical. Pulling timing did get rid of it but took the power with it.
BLACK 3
I did curve the timing so it was as gradual as I could make it. I did try checking the decel box to active but it still does the one big bang on long deceleration.
The cam timing marks are positively lined up. I have 196 PSI in both cylinders (could not have this much PSI and equal amounts if they were not lined up) and I have a picture of it. That was also one of my first thoughts before doing the second compression test and finding the picture of them lined up.
Thanks for the help
Dave

 

I'm hoping someone with more on the ball will chime in here, but I'm wondering if a thinner head gasket, .030", would help by making a tighter squish band. I know it sounds counter intuitive because it will raise the compression slightly, but... You could have the heads cc'd to keep the ccp at 195 with the .030" head gasket.

 

Will the bike in it's current configuration start right off, or does it have to crank for a few seconds before it lights off?

 

Retrop
The bike fires right up hot or cold.

 

If you're 100% sure that it's not something rattling around inside your engine, then you need to make sure your cams are correctly indexed. Assuming they're timed correctly, check the flow rate of the injectors, and make sure you're not overtaxing them with your build. For reference, I had to up-size mine for my 103, the stock ones wouldn't flow enough.

Next step is change your plugs to one range colder. If your wires are stock, change them. Change your fuel filter and check the in-tank lines. Make sure your air filter is clean.

Once all those things are checked, changed, and done, go back to your tune. With stock cams, I was running 14.5 AFR, right around 40 degrees of advance at 50 MAP, and a VE in the mid-80s (front cylinder). Now granted, with your 54 cams, your fuel and timing needs will be different, but still....

I'm not a fan of the Thundermax, and I think you're running into one of its limitations. You need to get your VEs set to your target AFRs. This is a relatively simple process with a TTS or a PV, I don't know whether the T-Max has this capability. With pump gas, you can easily run 14.2-14.5 in your cruise range, and drop it to around 13.2 from about 2750 on up from 60 MAP and up. But you've got to get the VEs set first, then attack timing.

If none of this works, take it to a dyno tuner or consider investing in a tuner that offers a self-tuning interface.

Good luck.

 

From a lack of any real contribution to what's going on inside the engine, I'd suggest checking over the exhaust, heat shields, and anything else on the frame near the engine which might vibrate with a harmonic at the 3000 rpm range and make the sound. I have found that my heat shields need to be tightened periodically, my crash bar would make a cracking sound from flexing at the mounts and one rear crash bar did the same. All of the chirps and cracking noises would occur at certain rpm which caused vibration unique to that item. Had to go around the bike hitting various stuff with the heel of my hand or with a rubber hammer to locate the guilty items. A thin smear of anti-seize on the mating surfaces, not the threads of the bolts, seems to eliminate the noise. slightly re-orienting the heat shields and tightening the clamps quiets them. I also had to tighten the nuts on the header pipe/cylinder joints to recommended torque to quiet them. At various times I have been worried about piston slap and rod knock all of which turned out to be something else. Also had a knocking noise from the muffler clamps not being quite tight enough and they would move just enough at the joint.

 

That pretty much rules out crank sensor problems then.