Dead miss at high RPM's

[Bad-dragon]

Hi, My names Talan, and I have a Valkyrie problem. 

Purchased my 97 valk with 72k miles 2 months ago, had a couple minor problems which I have been able to fix (mostly as a result of a dyna 3000) but 1 left I can't nail down.  At WOT or slow roll on, I have a dead miss at high RPM's (~5500+).  This limits me to about 90 mph and takes alot of fun out of racing harley's light to light. I feel like its electrical based on how it stumbles.  I thought it may have been a coil, but after replacing all three, I was wrong.  Any thoughts?

A couple things about the "Bad-dragon": pingel petcock & in-line filter, 6degree trigger wheel, 90# springs, thunder headers, de-smog, airbox mod (no foam dividers and back half removed).

First post, help would be greatly appreciated!

[Michvalk]

I have never heard of anyone getting a Valk to run right after doing an airbox mod.

[Chrisj CMA]

are you sure about the rpm....there is a rev limiter at somewhere around 7K and going through the gears racing its not thta hard to hit it

[Bad-dragon]

I have never heard of anyone getting a Valk to run right after doing an airbox mod.

Dad has a valk and said the same thing. 

However, this is not a lack of power or a consistent issue at high RPM's but more of a violent jerk every .5 seconds (albeit random), which is why I was leaning to electrical...

Not rev limiter either it is a problem from 5000 (or so) through red line.

I should add it will run smoothly to rev limiter without issue when in neutral.

[salty1]

What condition are the plug wires? Higher revs will create more vibration, I wonder if you have a loose /broken ignition wire? Have you serviced the kill switch? Just ideas. I think your suspicion of this being an electrical issue is good thinking. 

[John U.]

It could also be  spark plug. They are more likely to miss under load so the fact that it doesn't miss when in neutral might indicate a bad plug.

[RP#62]

I've heard of some fuel filters limiting flow at high rpm.  I'd pull it out and see if it makes a difference.
-RP

[custom1]

A violent jerk every .5 seconds only under load?     Sounds more like the pinion cup teeth may be about gone.? Have you looked in there lately?

[Bad-dragon]

Have the rear wheel and drive assembly apart now for unrelated reasons, I will check the pinion cup while I have it off.

Spark plugs are new but the wires appear original. OEM good enough or is there an aftermarket recommendation? I'd like to take the "Tim the Toolman" approach if its available...

Thanks for the input!

[Blackduck]

   If you have opened up the air box then you are lucky to even get to 5000 rpm.
Just removing the foam pad requires a couple of size larger main jets (been there and seen what happens, a big flat spot on acceleration). Any additional enlargement of the intake tract will require even larger jets. If you have opend the airbox up try using some duct tape to blank of the extra opening and see how it performs.  
The mods to this airbox required 130 mains to get it running right.
Cheers Steve

[JaysGone]

I too tried opening up the air box.
Not a good thing.
PinWall on Ebay has tons of used ones for $10 plus shipping.
Id replace it and leave it stock.

[crazydago]

  Is it possible that you have too much advance with a trigger wheel and a DYNA 3000? Put your stock ECM back and try it to see if it  makes a diff.  BERT

[salty1]

I concur with the idea of getting that air box back to stock. Make sure what you have for carb jets and adjust accordingly to compliment that stock box. I would use OEM plug wires. FWIW.  

[Bad-dragon]

Any additional enlargement of the intake tract will require even larger jets. If you have opend the airbox up try using some duct tape to blank of the extra opening and see how it performs. 
The mods to this airbox required 130 mains to get it running right.
Cheers Steve

Dyna 3000 failed (same ol same ol from what I've read ) so I have the stock ECM on there,  I was told the jets were 103's, but not verified.  for some reason I didn't think about getting the airbox on ebay. I'll get it on order.

God bless Pinwall....

[Patrick]

I'm not aware of anyone that really had the airbox modifications work as they expected.. Huge jets were required,, a whole bigger than 103s,, and the engines still would run terrible..
Honda got it right,, and all the standard issue stuff works well.. The IS ECM, 100 mains and a regular airbox should fix your problem..

[MP]

Step one:  And sounds like you are doing it, is get another airbox from pinwall.  Do NOT do ANYTHING else until you get that back to OEM.  EVERY airbox mod I have heard of really messes things up.

MP

[Blackduck]

Messing with the airbox does cause problems and takes some sorting.
Have mine running right and the pic above is the current configuration.
Gets reasonable mileage and runs fine.
Each to thgeir own.
Cheers Steve

[Bad-dragon]

Fixed! Thank you for all your input!

It was 98% airbox! I just can't believe it! runs like a bat out of hell.
 
Thanks for your help!

[salty1]

Fixed! Thank you for all your input!

It was 98% airbox! I just can't believe it! runs like a bat out of hell.
 
Thanks for your help!

Glad your dragon is hauling ash again! 

[Blackduck]

As a matter of interest what did you do to sort this problem?
Cheers Steve

[HayHauler]

Well, 98% was the airbox.  I don't know what the other 2% was.

Hay 
Jimmyt

[Bad-dragon]

Well, 98% was the airbox.  I don't know what the other 2% was.

Hay 
Jimmyt

Well...the other 2% was the somewhat embarrassing part I was going to leave out. My U-joint was coming apart, which was providing extra symptoms. I guess I couldn't hear it "clunk" over the pipes.

anyway it blew apart at 60 mph, which was exciting.

[HayHauler]

Hmmmm.  Not embarrassing at all.  It has happened to others somewhat close to me. 

Hope it didn't take out anything else on its way out. 

Hay
Jimmyt