Remove Airbox and Install Pod Filters

[ezridermn]

I have a CB750c that I made into a Cafe Racer a couple of years ago. It looks good as is but I am going to rework it some this winter. The first thing I have done is remove the airbox and put on some K&N pod filters. I have a question about the hoses that ran from the airbox back to the engine. I am assuming, which means I don't know for sure, that they facilitated some sort of pollution control system. Am I correct in that assumption? If not what are the hoses for?

Can I just eliminate the hoses and block off the holes in the engine? If yes what have you done to block off the holes? If not what should I do with these hoses?

Thanks in advance for your help!

 

[Sonreir]

Hard to say without looking at the hoses and where they connect, but my guess is that they're engine breather tube(s). They're pretty necessary.

DWMS makes a great looking breather filter if you're looking to clean things up a bit, though.

http://www.dwmsracing.com/emporium/products.php?2&sid=b2297e0076917c8b2e4e857862686a7f

 

[teazer]

Don't know if you heard but those bikes are a complete PIA to jet without an airbox. If the top and bottom end are jetted right, they go massively rich in the midrange and need a back bleed to change float bowl air pressure.

 

[crazypj]

Yep, you have to drill holes in the carbs , plus, if you get it wrong, carbs will be scrap

 

[noexit]

I think it looks dam good as it is. The chrome airbox cover keeps the lines clean. Pods will mess that up. Unless you really like jetting carbs, I wouldn't touch it.

 

[YogiBear]

you can use breather filters to clean things up where the hoses were.

 

[NcMike]

Yep, you have to drill holes in the carbs , plus, if you get it wrong, carbs will be scrap

Where / why would you need to drill holes? Is this specific to 750's?

 

[crazypj]

Nope,the 900's need it as well.
Never done one so not exactly sure where some things get drilled and others get plugged.
It's a lot of work though and was only used for racing when stock carbs HAD to be used.
Realistically, if you want to fit K&N filters, spring for CR carbs or Mikuni smooth bores
Stock Kei-Hin will never be better than mediocre unless you really know what your doing and have a bunch of dyno time (with full EGA)
That's the reason everyone says stick with stock airbox

 

[NcMike]

Nope,the 900's need it as well.
Never done one so not exactly sure where some things get drilled and others get plugged.
It's a lot of work though and was only used for racing when stock carbs HAD to be used.
Realistically, if you want to fit K&N filters, spring for CR carbs or Mikuni smooth bores
Stock Kei-Hin will never be better than mediocre unless you really know what your doing and have a bunch of dyno time (with full EGA)
That's the reason everyone says stick with stock airbox

Oh, got it. I have a 550 and have never heard about it. Good to know though. I was thinking of possibly building a 750 down the road.

 

[surffly]

DOHC and SOHC Hondas have very different carbs so its important to know what model you are talking about when talking 750s
But both hate pods.

 

[crazypj]

You can make the sohc 750 work pretty good.
The dohc 750 -no way

 

[ezridermn]

OK guys. Thanks for the feedback. First a comment to clarify the motor. An 81 Honda CB750c is a DOHC motor.

I have attached a picture of the two hoses I am talking about. I would appreciate it if someone would clarify what the purpose of these two hoses are.

As always, thanks in advance for your help!

 

[crazypj]

One on right is clutch breather, you get condensation in there
Left one looks like airbox or cylinder head breather (or drain?)