Help Diagnosis Twin Cam

[N456SK]

2012 Flhtk, motor redone with 25k, dark horse crank, street port, new valves, bronze guides(reputable vendor here), pulled heads 15k later, had chambers opened up, valves lapped, new stem seals(guides still tight, etc). Bike now has another 15k ran perfect till a trip last fall, bike was running along at 60 accelerated and noticed a popping coming back through throttle body, rode it carefully home,100 miles, bike ran normal until you accelerated quickly! Fast forward to now, here is what I've changed, plugs, wires, coil, crank position sensor, map sensor, head temp sensor, fuel filter. I have done compression ck(185 F&R), leak down good, pulled rockers, checked valve springs, replace lifters, inspect cam, pull throttlebody, install intake seals, r&r pipe and heat shields, ck for cracks, replace ex gskts. Still does exact thing! Any ideas, could a defective ecm cause this without throwing code? (No codes)
Please any ideas!
Thx Steve

[kd]

Did you check your fuel pressure?  It sounds like it may be lean (running out of fuel).

[N456SK]

I thought about it but I figured since it will run to full throttle fine as long as you do it easy, but I will try and locate a gauge to check!
Thanks!

[Hillside Motorcycle]

Did you check your fuel pressure?  It sounds like it may be lean (running out of fuel).

May have nailed it.

[smoserx1]

Any ideas, could a defective ecm cause this without throwing code? (No codes)

I am going to say yes because it happened to me and replacement absolutely cured it but (and this is a big BUT), mine and yours are apples to oranges.  Mine's a 99 FLHT and is carbureted (meaning no ECM fuel management).  Here is what happened.  On my bike the check engine light comes on for a few seconds every time the ignition is activated and goes off if no issues.  The problem started with the light coming back on briefly while riding, often accompanied by a backfire.  At first it was every few months and got steadily worse for almost a year till it was doing it about every 5 minutes.  What I think was happening was the unit was briefly loosing then regaining power internally (IOW rebooting).  When I replaced it the problem went away and had never returned.  I think my situation was rare and I believe the ECM's are reliable and long lasting, but nothing lasts forever.  They are also expensive, but there again my problem would never have shown up on an ordinary diagnosis.

[N456SK]

Okay, couldn't locate fuel pressure gauge, so I pulled the gas tank from my brothers bike (same model which is running good) install his fuel tank on my bike, didn't fix it?? I'm stumped?
Steve

[Tynker]

2012 Flhtk, motor redone with 25k, dark horse crank, street port, new valves, bronze guides(reputable vendor here), pulled heads 15k later, had chambers opened up, valves lapped, new stem seals(guides still tight, etc). Bike now has another 15k ran perfect till a trip last fall, bike was running along at 60 accelerated and noticed a popping coming back through throttle body, rode it carefully home,100 miles, bike ran normal until you accelerated quickly! Fast forward to now, here is what I've changed, plugs, wires, coil, crank position sensor, map sensor, head temp sensor, fuel filter. I have done compression ck(185 F&R), leak down good, pulled rockers, checked valve springs, replace lifters, inspect cam, pull throttlebody, install intake seals, r&r pipe and heat shields, ck for cracks, replace ex gskts. Still does exact thing! Any ideas, could a defective ecm cause this without throwing code? (No codes)
Please any ideas!
Thx Steve

Sounds like a valve is too tight...

[Hossamania]

Would a compression test or leak down test identity a tight  valve?

[N456SK]

Tight valve as tight in guide, or to tight on lifter adjustment?
Steve

[barny7655]

three things to check , 1/ fuel , you have done , 2/ air , ,cleaner and air flow,  3/  exaust pressure , check for blockages , other things to check , check primary chain, check gearbox  fluid etc  ,restrictions, check wheel bearings ,tightness,  check brakes, rear belt , see if you can turn motor over by hand , rear wheel .id coast at 50mph , and see if bike coasts normal in neutral ,there is a few things that might be pulling the motor up , or pulling the bike up , cheers

[Hossamania]

Would a compression test or leak down test identity a tight  valve?

Me we mind, I see it was done.

[guydoc77]

I wager intake leak.

[N456SK]

New intake seals, no change!

[guydoc77]

Especially if the heads were milled, even with new seals they may still leak.
I had the same issue with one a few years back.
We thought sensors, we thought injector wires, we thought plugs, on and on.
I changed the intake seals multiple times after I finally figured out it/they was/were the problem.
Eventually talked to Jimmy at HPI and they made me a shortened (at the ends and at the shoulders) intake with custom O ring seals and the problem was fixed for good. I also think that the R&R Overflow air cleaner I ended up installing helped fix the thing. It does not require lining up a backing plate which causes issues with aligning the intake to the heads.

Maybe try the brake clean spray thing around the flanges before shooting more out of the parts cannon.

By the way, mine ran great for 5000 miles before the exact issue you describe developed.
At first we tried milling the flanges. I tried sanding the intake ends with a belt sander. I tried different brands of flanges and multiple new seals. I tried shims of various sizes when mounting and remounting the original HPI air cleaner/backing plate. Some of these "fixes" would last for a few hundred miles, some would last a few miles. Very frustrating at the time.

Good luck.

[N456SK]

Ok, so did another warm compression check, 185 F and R, sprayed carb cleaner around intake(no change in idle), carefully installed another set intake seals (no change), finally took ecm and sec module off brothers bike and installed on mine, again no change! Only thing I haven't changed is throttle body, could it cause the popping?
Thx, Steve

[Geezer_Glider]

What tuner are you using? Data log? You are going to have to start diagnostics to find the problem.
Just suggesting,
R Meyer

[N456SK]

Powervision, will do data logs tomorrow after putting everything back together, just checked all plugs on injector wiring, throttlebody, map sensor, and head temp! All checked good, gonna slip another set of injectors in while I got tank off.
Steve

[xlfan]

Does Powervision correct for lower ambient tempetature?

[wnogood]

Maybe apples to oranges, but I had an old evo softail with drag pipes (no baffles) that did exactly what you are describing. You could hit the rev limiter, but you had to be slow on the go fast grip to get there. If you ripped it quickly, it would spit, pop, buck, and nearly die unless you backed off the throttle. I added lolipops to the exhaust and it never did it again. Such are LAF drag pipes I guess....

[itsafatboy]

might be dumb but check your throttle blade , make sure not cracked HPI had issue at one time the post would break, also try adding accel fuel if there is a setting for quick throttle accel boost, TMAX has that setting, strand its not surging which would seem to mean lean, and that its popping from throttle body , 

[N456SK]

Well finally found the problem, loose head bolt on rear cylinder, bad news it pulled the stud? What's your suggestions?
Thanks, Steve

[Hillside Motorcycle]

Install a Full-Torque Permanent Thead insert.
Never worry after that.

[Pirsch Fire Wagon]

 

[N456SK]

Should I worry about the other ones?
Steve

[koko3052]

If I was tearing it apart to do one insert...I would them all & forget about.

[Armin]

Timesert is the way to go:

http://www.timesert.com/html/hd.html

Armin.

[baggerpaul]

Back off push rods do a cylinder leak down .may be a bad valve not sealing and or head gasket issuie .had an issuie like this on a 124.

[baggerpaul]

Whoops never mind I see that you got it figured out might have been a better idea to check all the pages .lol dammit sucks to have to fix a pulled stud from the case .Good luck!

[Hillside Motorcycle]

Install all.
Needs to be done in a vertical mill.

[TorQuePimp]

Timesert is the way to go:

http://www.timesert.com/html/hd.html

Armin.

Agreed

If splitting the cases you are looking at $50-$75 in inserts and an hour- hour and a half labor

Cheap insurance.....can be done in a seat and guide machine.....and quick

[N456SK]

Thanks all! Steve