Topic: CB750 k3 with pods

[adamalk3]

Hey, all.
I've come here because I've spent countless hours doing research and have finally given up and I'm now asking for your advice. Sorry for being that guy.

Bike:
- CB750 k3 SOHC
- 657a carbs, completely rebuilt and cleaned
- #42 pilot jets
- Pod filters
- New coils
- Electronic ignition, timed
- Valve clearance set
- Carbs synced
- Brand new carb holders, boots, manifolds, whatever you prefer to call them.
- 4 into 1, no name headers, no baffle

Not sure if it matters that much, but I'm in Detroit, MI, so whatever elevation that is.

I've attached an image of the brand/type of pod filters I'm running.


Symptoms:
- Comepletely dies when blipping throttle quickly, at idle or under load.
- Sputters a lot when giving it a bit of throttle, 1/4 all the way to WOT, while riding.
- Bike won't even go over 70mph, just sputters hard while trying to push further at WOT.

I've tried jets 115 thru 140. But haven't done ALL needle clip positions. I realize this will take a LOT of time going through all combinations of needle positions and jets.


Which brings me to my questions:

- What is a typical set up for my carbs with the pods I'm using?*
- Could there be other factors other than jet size and needle clip position playing into the issues I'm having?*


Before anyone suggests putting the stock airbox back on, I know. I've considered it, but I do not have a stock airbox and I would prefer to really TRY pods first. I've owned the bike for 4 years and I haven't been able to get it running properly.

[PeWe]

My CB750 with pods and rather open 4-1 that had a baffle inside.
- Pilot (stock 40)
- Needles 1 step richer wich is 4:th from top instead of 3:rd notch.
- Mains: Huge 147.5
This was in the 80's with real fuel and bike ran great. No issues at all with pods.
It had 836, ported head, cam.

Your description verify too use stock pilots. (sputter on low lift, too rich)
Needles too lean due to twisting throttle problems.

Completely wide open system will probably give less torque on lower rpms and problems to get it to work at all on low lifts.

[adamalk3]

Thanks for the response!

My bike is a 1973, stock engine other than pods and exhaust. Stock jets are #40  pilot and #110 main, needle clip stock at 4th from top (2nd from bottom).

I do understand what adjusting is to be done, but when I'm having troubles with is finding the right settings/jets. So I'm asking for what is typically done with my setup.

Thanks again!

[flybox1]

Run the engine to operating temps.  toss in a new set of D8EA plugs and fire it up.  let it idle under a box fan for 4-5 min.
Take out the plugs.....what do they look like?

check this...
http://forums.sohc4.net/index.php?topic=146178.0

[PeWe]

Change pilot to 40, mains to at least 125, minimum. 130 is better
My K6 had 115-120 with 4-1 and stock air box. Pods need more fuel since air will flow much more.

[Bankerdanny]

Thanks for the response!

My bike is a 1973, stock engine other than pods and exhaust. Stock jets are #40  pilot and #110 main, needle clip stock at 4th from top (2nd from bottom).

I do understand what adjusting is to be done, but when I'm having troubles with is finding the right settings/jets. So I'm asking for what is typically done with my setup.

Thanks again!

I think stock mains are 105 (I know that is stock for my '76 750F), so 110 isn't a very big jump considering the open exhaust and pods.

[flybox1]

Gotta get idle/IMS/Pilot jet dialed in first.   A plug chop gives you the starting point...otherwise its a shot in the dark.
Correct bowl fuel level.    Clean, known-good pilot jets.  Chop it.
Dial in the IMS for tan plugs.  If you reach the end of the usable adjustment range, change pilot jet.
Retest until its right.  Only then move to dialing in the needle clip position...