Topic: Sooooooo confused!

[Texasstave]

Whats goin on fellas?( or ladies if thats the case!)
  I'm not new to this forum, just don't post much cuz you guy's have so much awesome information i never have to! This one has me stumped. I'll start by saying that i HAVE NOT done a vacuum sync yet. Only a bench sync after carb rebuild.I have a 1974 CB750. Air pods and 4 into 2 exhaust. I went with 112.5 mains and moved my needle clips down (in the richer direction)one notch from center on the advice of the guy from the parts house. I gotta say the bike runs excellent! Really quick and responsive throughout throttle! The problem i have is as follows,I was getting pops through the carbs. Like an intake leak or a lean running motor.I checked for leaks and found none. It also had a slight stumble on take off which would generally produce one of these pops.Thinking my mains weren't big enough I kept adjusting on the richer side.Eventualy bottoming out the mixture screw and then going for choke to further richen the mixture.I then "stumbled"(haha) on a post that said that described a stumble being a rich condition.I figured i would give it a go, since i tried a half dozen other fixes, and started adjusting my mixture screws out. I have them at about 2 turns out.Stumble is gone and it still runs great throughout driving range. Here's the deal. At idle if i turn the throttle it will still pop through the carbs.It also seems to hover at around 2000rpm's for a few seconds then drops back down.(i have it idling at around a grand)There also doesn't seem to be any in between on my throttle positioner. I it's either 1000 rpm's or 2000 or higher.Anyone following me?
Can this just be a carb vacuum sync issue? Somebody tell me yes so I can go to sleep tonight!
I purchased this bike and a 70 a few months ago for dirt cheap and completely rebuilt the 74. I will post pictures in this thread of what it looked klike when i bought it and what it looks like now.Sorry I didn't take progress pictures.That's just how I am when I work on something.I don't have time to take silly pictures.Anybody else?
OK.I will now leave this in you guy's capable hands!
Steve

[Retro Rocket]

Welcome to the wonderful world of pods......

If the bikes standard or even slightly worked go back to the stock airbox and leave these troubles behind... Pods are a compromise and extremely hard to get a perfect set up because they don't have velocity stacks to smooth out  aiirflow going to the intake ports, also they get disturbances from cross winds and rain, tried them 30 years ago, never used them since.....Plenty of threads on here about them.
Member Tintop is making an aftermarket filter system using velocity stacks, it is being tested now but should be way better than pods....

Mick

[dave500]

sync it or get it synced then try again,a bench sync is good enough to start running but not really spot on,the pods are no help either,im guessing the igniton is spot on,have you got a timing light?

[seaweb11]

The 78K is really the only bike pods work on

[Texasstave]

Do have a timing light. Thats all done. Rebuilt carbs, bench sync, cam chain, valves and points gap and timing.So check it out. I had the stock air box and stuck it back on.It definately sounds different. didnt have a chance to get her really warmed up though.The pops seem to get worse the warmer the bike gets.

[Texasstave]

do the pods work on the 78 because of the addition of accelerator pumps?

[DYSKORD]

My helpful would be double check timing. If the plugs are firing while the intake valves are still partially open you could get this detonation. I have experienced this on a muscle car when the timing was 180deg. out. Not sure if it is the same on these CBs. Mine pops through the carbs a little when the bike hasnt warmed up completely but goes away as it comes to temp. It got better with a halfass carb sync as did the idle problem you are describing. When you are syncing the carbs you will notice you will have to constantly adust the idle adjuster throught the process. As the carbs become more synced the more you will need to adjust your idle down. I have a new ignition in the mail and a thorough carb sync will be done once installed. I am anticipating this will clear up my poppin prob.
Also check valve adjustment before any of the other stuff then cam chain. Not doing so will mess with timing. Make sure cam chain adjuster is adjusting.

[Duke McDukiedook]

112.5 sounds lean with your setup. Plugs will tell the tale.

Was it running properly before you slapped them wonderful pods on there?

[Retro Rocket]

do the pods work on the 78 because of the addition of accelerator pumps?

Notice the smiley's...

Pods will worl on any bike, just not perfectly, they are a compromise at best and a royal pain in the arse at worst. Your jet size does sound a bit small, try 120's

Mick

[Texasstave]

It was running like total hell before! The carbs were really bad and it only had the top of the box.

[Retro Rocket]

The airbox supplies relatively still air to the velocity stacks, which in turn feed a constant supply of air for fuel mix into the ports, pods do none of this and are generally a pain to tune, some guys love them but i have found most guys persevere because they like the look as well, i actually hate the induction "sucking sound" as well, i would prefer to hear an uninterrupted 4 into 1 myself....
Flick through this thread, you may find it helpful...
http://forums.sohc4.net/index.php?topic=79491.0


Mick

[IHWillys]

As others and yourself have pointed/alluded to, stumbling off idle with popping through the carburetor(s) is often times the result of an overly lean condition.  I've seen it multiple times in dealing with tuning of a single carb in cars and trucks.

Ken