Airbox lid: on or off?

[Syscrush]

But couldn't that be corrected with jetting?

If it was causing excessive turbulence or a weak vacuum signal so that the slides don't lift, then I could see that as something more difficult to correct.

[bikeymikey748]

Phil, is it me, or does the filter look dry? These are washable, reusable bits, no? If it is dry,were you to apply the K&N oil to it, it might change your fuelling enough to help in a better diagnostic. The oiled/slightly more restrictive filter will make your mixture a bit richer, across the board.This might cure/shift some of your issues. Seems an easy way to go.The rubber bits look a bit dry too, have you verified all the clamps/ seals/joints ?
Your mention of, suspect, synchro seems another 'first move' sort of event. Proper sync affects throttle response at all engine speeds/loads. Looking past an apparent concern of this nature is like looking at new furniture when your house is on fire. One, small, step at a time, Cadet.
Your concern regarding intake drone seems linked to the missing top. Much R&D time is spent on airbox design. One of the components is lowering the intake noise. No top = more noise, among other things.
The exhaust system you're using might influence your fuelling enough to warrant rejetting, on its own. You might want to consider doing plug 'chops' at the affected RPMs.

[daves79x]

Rick is essentially correct. The K&N leans out the carbs enough that, especially with aftermarket exhaust, there is a flat spot at 5000-5500 rpm that cannot be jetted out. CV carbs do not respond well to intake changes like this, even more of a nightmare when using pods, although those can be made to work OK. Most guys with stock bikes really don't notice much difference with the K&N, but with especially 6-1 exhausts, it can be noticed.

Dave

[Syscrush]

Thanks everyone.

The plan is as follows:

1. Clean and oil the filter, check gaskets, boots, etc.
2. Sync the carbs.
3. Fit the lid.
4. Dyno with sniffer to get a good baseline and afr numbers.
5. Jetting by someone with CBX expertise, according to dyno/sniffer results.

I am aware of the midrange flat spot with 6-1 exhausts and stock carbs. The PO had a 6-1 for a while but removed it and replaced it with the Gary Wolf 6-2-1 for this reason. The exhaust was made by GW for the PO, with the express intention of flowing better and improving the midrange flat spot. I would like to keep it because of the provenance, but I'll have to decide for myself based on how well it works.

[bikeymikey748]

although those can be made to work

I have zero experience with the stock airbox setup. But as Dave mentions, jetting for pods can be made to work. In my case, at least, there's no hint of any fuelling iregularities at any engine speed/load.
Dave, why would pods respond more favourably to jetting over the stock box, especially given all the issues with their (pods ) use, and the noted 5,000rpm. 6-1 flat spot ?

[daves79x]

Seems you can just 'overwhelm' the carbs' circuits with massive rejetting with pods. Either with stock-type jets (up several sizes) or the Dyno Jet stage 3 system. There will always be some nagging issues with pods, but mostly they'll work OK. Upsize with stock type jets and gas mileage will not be affected much, but expect low to mid 20's with the stage 3. The trouble with a drop-in K&N seems much more subtile. CV carbs are not infinitely adjustable and the exact mid-range spot affected is near impossible to correct without going way too rich elsewhere. Remember - CV carbs do not respond to intake/jetting changes as others do. Just relating my experience with lots of them.

Dave

[Syscrush]

Thanks very much, Dave.

[EMS]

There is one other thing in favor of the stock airbox in combination with stock carbs.
As you know, the CBX carbs were angled towards the inside in order to provide clearance for the rider's knees. This resulted in different lengths of intake runners between outside and inside carbs.
And when tuning the stock set-up, supposedly the Honda engine engineers somehow compensated for this length difference inside the airbox. You can tell, when you take an airbox apart, that the plastic intake nozzles inside are different.
It may be one of these design fairytales that float around about classic bikes, but then again....

[bikeymikey748]

Yup, thanks Dave, makes sense. One issue I have is poor range. I've dropped my needles one groove, and dropped two teeth off the rear sprocket. My plugs indicated a bit of 'wiggle' room ( they were on the rich side of acceptable at a mid-range 'chop' ). Again, no fuelling issues, just trying for greater range.
Mike, fairy tales? I dunno, makes more good sense to me. Besides, I embrace those sorts of tales
Suitably chuffed that I've learnt something new, it's off the the garage for me.
Phil, baby. Keep those updates coming

[Syscrush]

I actually located another airbox lid closer to home. IF everything works out I'll have the bike back in the shop to take care of items 1-3 this weekend. FINGERS CROSSED!

[letxbruce]

I lost my internet connection in the middle of my reply, so I hope this is not a duplication. Let me throw in another comment on K&N filters. WAY back in the 1997 Winter CBX Express Tim Ware wrote an excellent article outling various modifications he made to his CBX along with the corresponding dyno charts. I based my rebuild based on his article. 1147 Weisco pistons, K&N Individual filters, Dyno Jet Stage III, Dyna S Ignition and high voltage coils, and Kerker 6 into 2 exhaust system. After talking with Tim a couple of times, I settled on 096 mains, 074 Primary and Dynojet needles in 3rd groove from the top. I also enlarged the 3 slide lift holes in the top of the slides with a 11/64 drill bit per K&N instructions. (K&N recommended 100 mains and needles in the top grooves)

It has run perfectly, with no hesitations or flat spots all the way to redline. The plug readings are perfect. This is one strong CBX. Fuel mileage is 25 around town, but will do in the 40's cruising. The point is, without someone like Tim and Dyno Jet doing extensive research backed up by dyno runs, this project could easily have been a big disaster. I would have never attempted it on my own because of all the variables.

[Syscrush]

I picked up my lid tonight - it came from James Elliot, who is apparently quite active in the CBX community (and has 7 CBX's back at home in London). Very nice guy and I'm sure a valuable resource going forward. Something he told me that I thought was funny is that he started out modifying CBX stuff almost 30 years ago, but now most of the demand is to take modified parts and return them to stock. :)

I am planning to take the bike with the new parts in to the shop tomorrow. Hopefully it gets taken care of this week sometime.

[NobleHops]

I picked up my lid tonight - it came from James Elliot, who is apparently quite active in the CBX community (and has 7 CBX's back at home in London). Very nice guy and I'm sure a valuable resource going forward. Something he told me that I thought was funny is that he started out modifying CBX stuff almost 30 years ago, but now most of the demand is to take modified parts and return them to stock. :)

I am planning to take the bike with the new parts in to the shop tomorrow. Hopefully it gets taken care of this week sometime.

IMO James is 100% correct from a monetary standpoint. Keep your stock parts Phil, I did .

N.

[Syscrush]

The airbox assembly I got from James did not have the screws/bolts/nuts or whatever you call the pointlessly Honda specific fasteners for the lid. I called Honda and sure enough they're still available for about a buck each.

They're supposed to arrive on Tue or Wed, I'll be taking the bike in for the clean & oil on the filter, the carb sync, fitting the lid, and doing the voltmeter wiring mod.

[daves79x]

As I said in a previous post, yes, the special bolts are available, but you need the special washers also to make a tight fit - make sure you get them.

Dave