"gasp" or pop upon accel?

[Bennie07]

Alright experts! (I'm hoping mac will chime in here, he seems to be a wealth of knowledge for this type of stuff)

Back again, with another small issue. Well, actually, not all that small. The other morning my bike stalled leaving me in the middle of a turn on a busy road as I was trying to enter the flow of traffic. Luckily for me, there was no one coming from either direction, but still....if there had been, it could have bad juju. I don't want it to happen again!

I have chuckster's single plate intake, V & H dual baggers, cobra fi2000r. I've been playing with the cobra settings a little, but for the most part, I've kept the range of pot 1 at 2 3/4 to 3, pot 2 at 4 1/2 to 5, pot 3 - zero. I've been running 89 octane lately since the temps here are finally getting warmer.

I've been playing with the idle to keep it at a level that seems, if anything, on the high side. Even though it sounds great when it's idling low, based on the recommendations here, the harley lope isn't good for the nomad. I don't have a tach so I can't say for sure what RPM's I'm idling at, but it's not set so low that it's "loping". That being said, I don't think these things are supposed to sound like they're running at 15 mph in first gear while at idle either.

Here are a couple of things I've been experiencing:
1.) I will get a "gasp" or minor "pop" at the intake when I roll on the throttle from a stop, it's almost like a small backfire through the throttle body. I've had it happen at speed as well, particularly after a quick release of the throttle, then a quick roll on of throttle to return to speed. This does not happen quite as often as it does when starting from a complete stop.

2.) I've found that sometimes after decel (even with downshifting) and coming to a stop with the clutch lever pulled that the idle won't settle down to where it should be. I cleaned the throttle body on Monday night after my stall in traffic happened with my train of thought being that maybe the idle problem I've been having had possibly caused me to set it too low when it does settle correctly.

Maybe these two things are related, maybe not. I'm just not sure.

Another possibility: I had a cap pop off one of my metal ICS pipes a while back so I re-installed and resealed those, but maybe a vacuum leak between the chuckster plate could be in play here? The cap popped off as I was trying to set up the cobra one day, got a pretty good backfire, and the idle went through the roof. That's when I found that the cap had popped off.

If it helps, I could make a video and try to recreate the issue I'm seeing.

TIA all!

[IntheWind]

Did Chuckster's intake include the reed valve coasters? Usually blocking the reed valves eliminates any deceleration popping.
__________
IntheWind
'08 Nomad

[tomm]

The symptoms you're experiencing are exactly the same as what I saw when I installed the Cobra fuel processor. Took me a lot of tweaking to finally get it right. Just the slightest movement on pot 1 made a big difference. But I was eventually able to tune it in and all those problems went away. Note that with the Cobra, you have to increase the idle for pot 1 to have an effect. That's why most folks prefer the Dobeck. Much easier to tune at idle.

Do a search for one of Mac's write-ups on tuning a fuel processor. He's done it several times.

Oh, and do a real thorough check for vacuum leaks as well. I think Mac would tell you to replace all the vacuum hoses and caps every couple of years just to be on the safe side.

[Bennie07]

tomm, yeah, I actually found that thread where you were asking about how to set the cobra. I actually was trying to set mine up when it blew off the ICS cap from the backfire. I just re-read that thread and it sounds like you had to crank up the idle merely to be able to tell when the engine missed a beat, correct?

wild, chuckster's kit came with a plug to block off the tube going to the coasters, but I haven't removed them. I do get a "spatter" (for lack of a better term) sound on decel, but not true all-out backfiring or discernable individual "popping". I'm not particularly concerned with that at this point, but will likely order the coasters soon, just to clean up the area around the jugs.

[tomm]

Originally Posted by Bennie07

tomm, yeah, I actually found that thread where you were asking about how to set the cobra. I actually was trying to set mine up when it blew off the ICS cap from the backfire. I just re-read that thread and it sounds like you had to crank up the idle merely to be able to tell when the engine missed a beat, correct?

wild, chuckster's kit came with a plug to block off the tube going to the coasters, but I haven't removed them. I do get a "spatter" (for lack of a better term) sound on decel, but not true all-out backfiring or discernable individual "popping". I'm not particularly concerned with that at this point, but will likely order the coasters soon, just to clean up the area around the jugs.

That's right. If I remember correctly, I had to crank the idle up to around 2K before changing pot 1 had an effect. You have to go really slow and let the engine settle down between each adjustment, but it does work.

Once you get pots 1 and 2 dialed in, I believe Mac said that opening up pot 3 to about 0.5 may get rid of the popping on decel.