78 CB750 CARBS/AIRBOX QUESTION

[DAK750]

WILL THE BIKE RUN WITHOUT AIRBOX??? I CAN START IT AND IT WILL RUN WITH THE CHOKE. WILL IT RUN WITHOUT THE CHOKE WITH AIR BOX ON. iS IT GETTING TOO MUCH AIR WITHOUT THE AIR BOX??

[TuNguyen-2]

If you do not install airbox, the bike will not run good. I go that problem before. I start my CB750 without air box, the bike is dead when I take up to haft way off throught. So it is good thing to install airbox before adjust any thing.

[shabbabear]

NEVER run w/o the airbox...you will suck in a tiny rock or something and get major vavle damage and the moisture getting into the motor will destroy proper combustion...backt o the box or get the individual filetrs like the unis or the old k&n's...hope that helps....shabbabear

[Altdo]

Of course you can run it without the airbox, and depending on how the carbs are tuned it will run fine.  You do run the risk of sucking something into the carbs and totally ruining the valves and possibly engine, but it'll run... infact a few of the bikes i've built never had an airbox or filters, just carb covers.  
If you do get Pod filters to replace your airbox make sure you get ones that will clear the choke on the second pod, they're kinda hard to find.

[blackhawkrider]

It won't run right, these carbs need the vacuum created by airbox/ pod filters in order to lift the slides. There are carbs that do work without an airbox but not the ones you have. Without the box it will start and run but will go flat halfway through rev range.

[leboeuf]

hi my name is shannon
i have a 1978 cb750k and the airfilter box was broke bad and i put some air filter pods on and it runs ok except when a burst of wind hits from the side it bogs down
can this be adjusted r should i try to get another airfilter box

if any help that would be great

[Drew750]

Hi there,

No expert, but bike should run but will be very lumpy as the carbs would be set with airbox fitted. Not good practise according to manuals etc. Even a change of airbox/cone filters usually means a change up in main jet to allow for the extra air in the mixture.

[78cb750-2]

1978 Honda CB750 here

I took the airbox off and installed pods. They went on fine but the choke end cable catches between the pods. Any suggestions?

I'm thinking to just put the airbox back on but its such a tight fit, any hints if I want to install the airbox?

[Re-run]

The airbox can split in half, that should make installing a lot easier.

Another option with the pods is to modify or bend the choke cable holder and see if that gives enough clearance.

[Re-run]

The airbox has a few duties. It holds the filter of course but it also allows a uniform amount of air in and prevents what you are experiencing with the pods.

People have put on pods and noticed that even having their knees in certain spots and cause airflow issues.

You can still use the pods but the issue will crop up and there is not much to fix it.

You MIGHT be able to modify a box to allow the pods to fit inside but then you lose the "cool" factor of pods.

[Re-run]

Actually they do not. These are slide carbs and as such will operate anyways as long as there is air and fuel. the only vacuum needed is that made when the engine performs its intake stroke.

[dumbar]

1977 cb with cleaned carbs, runs fine as long as you leave the choke on. Responds to throtle, runs smooth.  As soon as you release the choke engine bogs and dies. This is without the airbox.  Is it necessary to install the box before the engine will run without the choke?

[Re-run]

Dug this one up!
Removing the airbox allows much more air. If you need choke to run, you might already be slightly lean
My 78 will run without choke and airbox but it is slightly rich right now.

[Lucky 1]

What really bothers me about this thread is that all of these problems with the correct jets for the pod filters was worked out a long time ago. 30 years of it.

So either the people that know do not have computers or they are sitting there reading all of this struggle you guys are going through and are to lazy to tell you what jets or adjustments will be made to make the pod filters run correctly.

An adjustment to the mixture may be necessary.
On carbs that have needles that are adjustable, the clip may need to be lowered one notch
to fix the midrange. (richer)
A different main jet may be helpful also. (richer)

But all of this has already been well worked through.
I went here...http://www.newmotorcycleparts.com/fuel_system_parts/air_filters/pod_air_filters.html
They sell you the right jets with your pod filter.

[Re-run]

Yes and no, if the engine were brand new or very little miles, then yes, a certain jet/mix combo might work. But you add years and miles on, not to mention different altitudes and suddenly there is no 1 combination that works for everyone. It is not just this forum but others that have endless debated this with no clear conclusion.
To add yet another factor, what type of pods are being used. Cheapo emgo pods are different from better k&n which are yet different from uni pods.

I can guarantee you that if you took 2 same year bikes, and put in the same jetting and screw and needles settings, they will run different. And it will be because the engines have worn differently from each other based on multiple factors.

[shinyribs]

Altdo wrote

 
If you do get Pod filters to replace your airbox make sure you get ones that will clear the choke on the second pod, they're kinda hard to find.

These fit just fine.If you want a set Call Wayne at Qwiktime Performance in Roanoke Virginia. 540-206-2597.Tell him you want the ones Eric got for his Honda and he will hook you up!I think the run about $15 a piece plus shipping!Call him,I'm a silent partner of QT Perf!HAHA  .But for real,they do fit just fine

[shinyribs]

dumbar wrote

1977 cb with cleaned carbs, runs fine as long as you leave the choke on. Responds to throtle, runs smooth.  As soon as you release the choke engine bogs and dies. This is without the airbox.  Is it necessary to install the box before the engine will run without the choke?

Mine started and idled fine with no box or pods.Never put box back on mine,went straight to pods.Does rev better/higher with pods.But did pretty well with nothing on it at all.Some difference,but not a huge difference.Off idle stumble went away with pods vs nothing.Revs above 4000 smoothed out to perfect in my opinion.

[TOOLS1]

But, you have round tops.

shinyribs wrote

dumbar wrote

1977 cb with cleaned carbs, runs fine as long as you leave the choke on. Responds to throtle, runs smooth.  As soon as you release the choke engine bogs and dies. This is without the airbox.  Is it necessary to install the box before the engine will run without the choke?

Mine started and idled fine with no box or pods.Never put box back on mine,went straight to pods.Does rev better/higher with pods.But did pretty well with nothing on it at all.Some difference,but not a huge difference.Off idle stumble went away with pods vs nothing.Revs above 4000 smoothed out to perfect in my opinion.

[Piute]

Those round tops have a return throttle cable ? notice a sping there mmm...Piute...

[shinyribs]

Return cable and spring on mine. Tools...right again!