Help with missing/backfire-like issue?

[originalmc]

Hey El Loco, I registered just so I could reply to this thread...

I live in Portland too. Monster 620 ALSO recently had the Motocorsa 6000 mile service. Termignoni slip on exhaust.

EXACT SAME SYMPTOMS. Popping/loss of power on medium acceleration in 2K-4K RPM range. I just called Brad at Motocorsa and he described it as "popping in the airbox" and said he would take a look at it next week but didn't indicate strong confidence that they could make it go away with a simple fix.

Did anything work for you? I'm hoping to not spend major scratch on a problem that can't be entirely fixed.

[el_loco]

Hey mc,

I had the throttle bodies synced and that helped some, but it's still giving me the occasional hiccup.  The popping in the airbox always sounds and feels more like an electrical short, so it threw me at first.  I JUST purchased an OEM airfilter to use instead of the K&N that was in my bike when I bought it.  My theory is that with my Remus Ducati Performance pipes AND the K&N, my lean-from-the-factory motor is just too lean.  I had it dyno'd and the leanness isn't anyhting dangerous, but my Hp was also right where it should be on a stock 750, so the K&N is obviously not giving me any kind of HP gain, may as well take it out and see what the stock one does.

[TreyRiser]

Sucks that you havent figured out the solution because believe it or not I am having the exact same issue with my bike. I get a very infrequent pop/hesitation while riding at about 4000 RPMs, very intermittent and I cant replicate at will. I have a 99 M900 with FCR 41 Carbs and a termi slip ons...K&N Pod Filters...my first thought was too rich too but not 100% sure. Other than that occasional hesitation the bike runs perfect, sorry I don't have the answer...I hope somebody figures it out though. I was considering new plugs...and maybe new coils.

[battlecry]

I'm crossing my fingers, 'cuz I finally exorcised the miss/hickup in the 3K band.  The bike is a '03 M800S with hi-mount Remus cans and a holed airbox. 

It only took six years.  Did the following:

Throttles synch with homemade manometer.
Adjusted valve clearances, openers at 0.004 and 0.006, closers at zero, and cams at 107 deg @ 0.03 lift.
PC III USB with enriched fuel in the 2-4k band.  No dyno,  just added fuel in bands where the bike was not smooth, took a few months of riding but now I'm happy with the results.
TPS reset.
High temp sealant on exhaust joints.

After all of this, the bike was smoother, no hickups in the airbox, but it still missed a little in the 3k band.  Rode like that for two years, resigned to live with it.  To really kill it took the additional mods:

Replaced the main and fuel injection relays (I think they wear prematurely because of the vibes/heat on the bike).
New NGK wires with 5K resistor red caps.
New NGK resistor plugs, DPR8EA-9.

The bike runs great now right from idle to scare me silly.  Like Mr. Earl said, I do not think it is an easy fix.  I think the PC III or some similar fueling modifier is needed and was really surprised with the impact of the new resistor wires/spark plugs.  I was running hotter non-resistor small gap NGK plugs before.  Never again.   

[the_Journeyman]

Interesting.  I've got a 2000 900SS that pops through the airbox on medium/low/steady throttle just under 4K.  It's annoying, and I'm stock aside from Sil Moto mufflers  ~

JM