Topic: 1977 cb750 carb issues (pods + 4 into 1 free flowing)

[mibanez3]

hey this is my first post here, this is also my first carbureted bike so I'm trying to learn and figure out as much as I can from the internet.
the bike came with pod filters, i think they are emgo and are oiled. it also has Mac 4 into 1 free flowing exhaust un-baffled. I've read in several forums is very hard to tune this carbs to pod filters
Engine starts first kick and with no choke, it idles nicely and revs up like a champ on neutral. the problem I'm having with the bike is that I think it is running very lean at cruising speed; with the throttle between 1/4 and 1/2 the engine just bogs and if i give it more throttle it revs up nice again.

the current jets are
140 main
42 idle

with that being said I've done some research and tried moving the main jet needle clips up one position at the time with no success (they were in the top notch when i got the bike and are currently in the middle notch), when i moved it the first notch i didn't see any improvement but when i moved to the middle position i think it got worse.

since I'm going more for reliability than looks on this bike i don't really mind having the stock filter box and i ordered one from eBay for 17 bucks. I know the stock main jet is 115 and the PO went too large with the 140 trying to solve a problem he never sorted out. if i stick the stock filter box do i need to go back to the stock jetting #115? or should i go a little larger (#120) due to the larger 4 into 1 exhaust? also should i decrease the idle jets?

i know its a lot of questions but I'm a little lost and any info is greatly appreciated.

thank you

[Vinhead1957]

Do you have the carbs with accelerator pumps?  Non expert but the earlier models normally have that problem and pumps were added to correct it. 

[mibanez3]

Do you have the carbs with accelerator pumps?  Non expert but the earlier models normally have that problem and pumps were added to correct it.

Yes i have the model with the accelerator pumps and it is working correctly, although the #2 carb squirts a little bit more fuel than the others; i think it is because its the closest to the pump

[Supermex01]

It may be the opposite and you are running rich. Check spark plugs
Also check for any air leaks on the intakes.

[Black 750K8]

With no carb experience you are doing the best thing by going back to the stock air box. When you get it I would go back to all stock jets and settings. Then start doing your plug chops. This will tell you what way you need to go. I would pick up 2 or 3 new sets of plugs. I don't think the pipes alone will require much of a change but the plugs will tell the story.

[flybox1]

Yes i have the model with the accelerator pumps and it is working correctly, although the #2 carb squirts a little bit more fuel than the others; i think it is because its the closest to the pump

....also might be if you've replaced the fuel lines between carbs, you might have tossed out the tiny brass restrictor tubes inside the accel pump circuit tubes. they take up some of the volume in that circuit.  just a thought.