Pro's and cons of velocity stacks ?

[Kyle Rossouw]

Hi guys, my 78 CBX when I bought it did not have its original air box but some really nasty K&N style air filters. I have done a complete carb restoration and would like to put velocity stacks on the carbs. I would just like to get some advice on this. Thanks. Kyle

[EMS]

Hello Kyle, welcome to the ICOA forum!

Not even considering proper tuning for velocity stacks, my main concern would be the intake of unfiltered air with all the particles it contains like dust, grit and sand. There is a reason, engineers put air filters on internal combustion engines.

[daves79x]

In addition to what Mike advises, what did your carb rebuild involve as far as jetting goes? If they were jetted for the K&Ns, and you kept that jetting, they might be OK, but if they have stock jetting, you'll be way off. Research the threads on the subject here - then seriously consider finding the stock airbox and go back to that.

Dave

[Jeff Bennetts]

Kyle what is your goal for your CBX?

Do you want to run the stacks just because you don't have the air box and your looking for options other than individual filters?

[Kyle Rossouw]

Thank you Mike. Hi guys, the reason I would like the stacks is to eliminate the air box, I am also going to reposition the battery and electrics, so that you will have an unadulterated view of the motor and carburetors ! The bike was a basket case when I bought it and not worth restoring so I have decided rather to showcase the engineering side of the CBX. Dave I kept the existing jets, this was the first time I worked on carbs of any sort so I am a complete novice and still have a lot to learn.

[steve murdoch icoa #5322]

Welcome to the site, Kyle.
Melchiro a member from the CB1100F.com site used #80 primary and #120 main jets with velocity stacks with good results.
This was on his track bike and like the others i think the stock airbox would be the best option for a street bike.

[EMS]

If you don't really ride the X much and use it for "Show and Display" or for maximum performance outings only, you will be fine with the velocity stacks. You need to rejet, however.
Steve's reference regarding jet sizes will be a good starting point.

[Kyle Rossouw]

The bike will be used for Sunday rides and the odd café racer/classic bike get togethers. I will need to import the stacks as there is nothing locally available in South Africa. Could you guys maybe point me in the right direction. Thanks Steve, Mike.

[EMS]

It's a little difficult to recommend any velocity stacks for the CBX, as most need some modifications. Once you find the stacks with the correct throat diameter, which should not be too difficult, fitting is the issue.
Putting the stacks on, the inlets for Nos 3 and 4 carbs will interfere due to the angle of the carb bank. Usually, the stacks need to be shortened to unequal lengths and some time, depending on the outer rim diameter, slightly trimmed in order to make them sit next to each other.

[steve murdoch icoa #5322]

Only $180.00 plus shipping for those ones.
http://www.ebay.com/itm/billet-aluminum ... 63?vxp=mtr

[Jeff Bennetts]

Kyle there is an alternative to the stacks you might be interested in, it won't look as kool but will work better and might be less expensive than the custom stacks.

Back in the day, 15 yrs ago maybe, a past ICOA member (James Elliot) had a setup that worked very well on an 80 CBX.

What he did was separate the airbox from the plenum, he then split the plenum (the plenum consists of two pieces) and discarded the rear housing. That leaves the intake horns intact, so they mount to the carb throats the normal way, you also have the OEM engineered unequal length intake horns on the backside of the plenum. What you must provide are the individuals filters for each intake horn, James used inexpensive, individual foam UNI filters.

This is actually a pretty stealthy way of running individual filters while maintaining the stock look and it may be cheaper overall compared to the custom stacks depending on what you pay for the OEM plenum.

[Kyle Rossouw]

Hi guys, wow those stacks look wicked. That's exactly what I'm looking for to show off the carbs. Jeff, thanks, I will keep that in my memory bank. I'm sure I will have many more questions as my build continues. I will post some pic's of the bike for you guys as my build progresses. Thanks again.

[Kyle Rossouw]

Hi Guys, where would I be able to purchase the jets needed? Thanks

[daves79x]

Here's where I get my jets: http://pjmotorsports.com/ They carry genuine Keihin jets. With open stacks, you should be somewhere in the 80/120 range as has been mentioned before. Stock is 65/98 to compare. You obviously need to see what yours are, but someone may have installed a Dynajet stage 1 or 3 kit, in which case the needles will be adjustable and the jet sizes won't equate to stock sizes. Stage 3 kit is OK properly set up.

Dave

[Kyle Rossouw]

Dave, thanks so much !