You most likely will need to change your idle jets to a size bigger like I tried. I went from a #45 to #50. Dynojet doesn't give you idle jets.

I'm experiencing the exact phenomenon right now. That's why I'm switching back to a standard jetting and a stock filter. I'm beginning to seriuosly doubt the K&N as a performance booster. I have a track day coming up this weekend, and I can't have any unpredictability, especially in the low rev range.

Here's what my bike is doing specifically:

Idle is jumping like crazy, and I can't get a good synch, because the idle keeps moving. Revving the throttle throws the whole balance off.

Strange quirk, but after doing a stoppie, something adverse happens with my bike and it runs like total **** for the next 10 minutes. This hasn't happened with any other superhawk, but it'll bog down hardcore in the 5k range, backfiring and threatening to stall. Really sucks because that's the main power range, especially for getting on the highway, not the place to stall.

I pulled up to an empty intersection today, so I revved my bike all the way to 10k just to check for stumbles. Did this twice with no problems, felt great. Then I leave the intersection and the bike bogs down at 3k and again at around 5.5k. It was at this point I became furious and decided to just go back to the stock setup, because if this happens at the track I could die, literally. Not worth it.

 

Loco,

Don't think your performance issues are kit related. Dynojet doesn't provide low speed jets for a reason, (ie; 2 1/2 turns out on the F/A mix screw). Fools the carbs into believeing they have a bigger slow jet, to a point. I think, based on your description of problems you're experiencing, you may have several issues. Could be vacum related, leaks, pinched lines, cut slide diaphram, binding slide or possibly a fuel starvation problem? Sticking float/needle and seat?

Free reving and reving under a load are two entirely different measures of engine performance capability.

Whether you decide to work with what you have, or remove and replace everything back to stock, closely inspect everything as you disassemble it. You're right....No sense getting killed if you don't have to...

I've decided my Dynojet kit installation is right. I plan to remove the K&N filter, replace with the stock one, which will richen the mixture back up a bit, warm the bike up and recheck the carb sync, road test and evaluate the results. If necessary, remove the K&N block-offs to try and better understand their effect on carb vac. signal, (ie; actuation speed of the faster, lighter Thunderslides), which could also be causing a momentary lean condition. I see this quite often in Harley CV carbs when I install these kits. TQ/HP dips on the Dyno. Quite often the fix is to reinstall the stock spring, or mod the kit provided spring until acceptable results are achieved.

Good luck with your bike. Let me know what you find. I'll post what I find out about mine and what it took to get it right.

Ride safe.

 

Loco: have you checked the diaphragm in the fuel petcock? Mine was acting this way when I discovered a tear in the said diaphragm (both times!) Good luck

Mikstr

 

I will replace the petcock assembly just for good measure.. I have already checked the choke cable to make sure its fully disengaged, and jets are back to stage 1. Stock filter will go on, then carb sync.

You can carb sync without the airbox correct?

 

Whilst I am no expert in such matters, I am inclined to think that your new combo is not set right yet.

I reckon some dyno time will have it sorted for you. Too many people run this combination with success. I think it will be some minor factor in the whole show that is not quite right.

I cannot see how the airfilter is responsible. Everyone seems to agree that they flow more air. As an airfilter will flow air at a linear rate, you just need to get the various carby zones to match the ariflow, and then you should be right. If fuel is matched to the airflow I cannot understand how an airfilter that flows more air will reduce power. Most evidence that the K&N does not work does not seem to be backed up by a proper tuning session. Those that dyno tune their bike after fitment seem happy. Obviously if you don't re-tune post fitment, it will not work.

Oh, and I think synching the carbs without the airbox should be fine.

 

Loco,

I would suggest you simply pull off the diaphragm cover plate on the petcock assembly first. A tear, if there is one, will be readily apparent. Why spend money for nothing?

Best of luck in finding the source of your problems

cheers
Mikstr

 

I have 4 other petcock assemblies sitting around, that I know work, so I will cross-check them against what I pull off my bike. I know these changes seem drastic, but I don't have the freedom to try each little mod, put the bike back together, and ride it for 10 min. Also, I can't really afford a few hours on the Dyno, plus I don't have all the pieces I need.

Basically, I know that K&Ns are shaky to begin with, in terms of reliability. Compound this with the fact that I don't have the blockoff plates and I think its no wonder my carbs are acting off. I'm going back to what I know works, maybe after the track day I'll try to figure out a sweet power mod using the bigger jets and airflow.

 

BY the way.. anyone else tend to start these tank-type mod's right as they fill up their tank? This is the 3rd time in a row I've had to adjust something in my tank with a decently full supply and it's a pain in the *** lugging a 25-lb tank around the garage.

 

nothing a syphon hose can't fix

Mikstr

 

Re-synced the carbs, adjusted idle to 1250-1300, road tested. Bike performs awesome. Smooth, noticable seat of the pants improvement. Hot and cold starts are fast/effortless, (better than stock config.) At this point I've left the K&N filter / block-offs in the box. Motor sounds throatier, smoother idle.

I think I was being a little too hard on the off idle stumble, (Free reving it.) Realistically, an on the road launch or roll-on doesn't indicate a noticable hesitation at all, (all rpm ranges). I would say that what I was experiencing was the normal expected reaction time of the carbs. Will monitor pipe / plug burn color to confirm an acceptable jetting setup.

Can't nail down the effect of the 500 ohm adjustment to the TPS, but overall performance seems great.

I would rate this Dynojet kit install a success. Some seat time will prove this out, but yesterday's test ride was impressive.

 

Congrats Happy to see that all is well.

In regards to your comment about the TPS adjustment, that is why a good friend once told me to only try one change at at time, makes it easier to isolate the effects of everything. That being said, I also know that the desire to not go through the whole dance of removing the tank,... can lead one to circumvent this rule for the sake of expediency.

Getting back to the mod itself, I realize that many swear by the "TPS mod" but in my experience, it actually dulled engine response with no discernible benefit. After riding around with the bike in the 500 ohm setting for about two weeks, I ended up going back to the pre-adj setting (@800 or so if I recall) and noticed a substantial improvement in throttle response and roll-on acceleration. If you are feeling ambitious, it may be worth trying to un-do the adj. just to see how it works.

cheers
Mikstr