Topic: Needles all the way down and still too lean...

[Blitzburgh207]

I've done a few searches and I cant seem to find anything on this.  I have a '78 750k8 and I'm too lean from about 1/4 to 5/8-3/4 throttle.  I shimmed the needles this morning (just to be clear that I wasn't mis-diagnosing) and it ran way worse - so I returned them to stock, but I have no way to lower the needles further than stock (because they're not adjustable).

So, is my lack of power through the mid-range being caused by something else?

-I want to add that it still pulls through the mid-range, but not like it does at 1/4 or WOT, and there's a loud, sort of hollow or empty resonance coming from the motor when I roll onto mid-range throttle.
Is there no solution to this because I'm running my pods or what? What else will richen my mid-range throttle besides lowering the needles?

Thanks guys,
Adam

P.S. 1978 cb750K8 w/ pods and mac 4-2.  120 mains and stock slows (35's)

[dave500]

if you are lowering the needle(raising the clip)its going leaner than it was.

[Blitzburgh207]

I thought lowering the needle makes it run richer?  I raised it this morning and it ran like sh%#.... way too lean

[Bob Wessner]

The needle, being tapered, is thinner at the bottom and wider at the top. If you raise the clip (lower the needle) more of the 'thicker' part is going down into the jet tube leaving less space for fuel to be drawn up which translates into leaner. If you lowered the clip (raising the needle) and it ran worse or poorly by comparison, you may have other issues.

[Retro Rocket]

you may have other issues.

Yep, PODS......good luck on the tuning while you use pods. A stock airbox will go a long way in helping the bike run properly...

[Blitzburgh207]

uh oh Do you think I need to raise them more than I did?  (I used two M2.5 washers to shim - following instructions per another thread)  Or maybe half that? (Just one washer)

Thanks for helping guys.  This forum is my lifeline haha 

...I can't bring myself to put the stock box back on but I'm thinking of making my own "bread box" type box.  It's like KONG said on another thread one time: "The sock airbox is about as sexy as a plastic picnic basket" lol
...I loved that

[Bob Wessner]

"The stock airbox is about as sexy as a plastic picnic basket"

But if you are hungry enough, you will eat out of it, right? 

[Retro Rocket]

I suppose the "ugly" comment is subjective, i think it looks ok, the point is, if you do a search of this site you will find only a small amount guys that are really happy with pods { and i think they are bull#$%*ting anyway }, most guys fiddle with pods for months before putting the stock box back on and finding that it is a piece of cake to tune, doesn't really surprise me as these bikes were engineered to run well with the airbox { with its velocity stacks} and they do. If you want less problems, the airbox is the go, if you want looks then be prepared to suffer the side effects of pods. Forum member Tintop has an alternative to the pods that uses the stock stacks and works well.....

http://forums.sohc4.net/index.php?topic=79491.500

[Terry in Australia]

+1 on TinTops "Ram Charger", I've been testing one on my CB750K1 with a "worked" 836cc engine for the last few months and with 130 mains and no other adjustments in the stock K1 carbs, the thing absolutely flies, much better than when I was using 29mm CR's with K&N pods.

One thing to keep in mind that no-one else here has mentioned is that your PD carbs were designed to run lean to make the EPA happy, but were fitted with accellerator pumps to give the engine an instant shot of gas once you crack the throttle. If your bike is running too lean in the mid-range, check to make sure the diaphragm isn't cracked, and that the pump is squirting raw fuel when you crank the throttle open.

Here's a gratuitous pic of my K1 with Tinny's Ram Charger installed, he does them for your PD's too, and they are way better than the stock airbox or pods, etc. Cheers, Terry.

 

[TwoTired]

Just to reinforce what's been said. Lowering the needles deeper into the jet orifice further restricts fuel flow making it leaner.
You may not be able to shim those needles enough to totally correct the operational alterations made with pods. 

As to ugly... So then, looking at the bike with pods on it is more important than having the machine actually work right?  Interesting priorities.    And, I don't think a gold picnic basket makes the contents taste any better than a plastic one, but both will work better than the cheapest paper bag on a rainy day.

Pods are cheap, which is the only reason why they are popular.  Real racers don't use them at all.  (But, they also rebuild engines after every race.)  I see bikes with pods and see the entire bike cheapened to the same level as the kludged on components.

As a comparison; all that duct work in front of a jet engine is what enables the jet engine to make the power that it does.  How many supersonic fighter jets have you seen with the engine fan blades out in the breeze?  Duct and inlet design is about far more than just the entrance hole diameter.

Good luck!

[Blitzburgh207]

  I didn't say the stock box was ugly... I can really appreciate a really well kept stock bike for the classic that it is 

To me, pods just have the appearance of being more powerful and sporty - I just like the modified look really.  But I agree with you twotired.  Even the prettiest bike looks like a big turd if it's sputtering and backfiring it's way down the road. 

It's not that it runs too badly right now... Just that hollow resonance makes me think that something is wrong - and I feel like there should be a little more power in its place  .  Do you guys think I should try shimming more than I initially tried?

The reason I thought it was running leaner when I shimmed the needles is becuase there was an awful lot of backfiring going on in the carbs. Especially on deceleration.  And acceleration was spotty and numb.  Timing? The plugs are clean and it seems like my headers are a little darker blue than they were.  Maybe that's just my mind tho.

Thanks for the help guys 

[Retro Rocket]

To me, pods just have the appearance of being more powerful and sporty

Not so my friend. To be honest, if i were trying to run pods, or going to run pods {i WON'T} i would start by tuning my bike with the airbox on , that would give a good tuned baseline to start from and would be generally easier, knowing that there is nothing else effecting the tune of the bike. Then put the pods on and jet the carbs to suit. The pods will NEVER run as good as the airbox....