Airbox lid: on or off?

[Syscrush]

Hey all.

My '79 came with a Gary Wolf 6-2-1 header, K&N filter, and no airbox lid. The engine has been rebuilt (overbore with Honda pistons & rings, stock cams were degreed), but is mostly stock, and the carbs have been returned to stock parts/settings.

It needs a carb tune - it misses and hesitates at some RPM/throttle combos, and it has the rattling sound at idle that I've been told is characteristic of needing a sync. It also has some intake noise that's resonating at 5-6k RPM, and I'm not fond of - it drones and feels like it's drilling right into my ears.

Given all of this, my intention is to replace the airbox lid before proceeding with getting the carbs sorted out, because I know that will affect tuning.

I have a couple of questions:

1. Is the airbox the same across model years, or do I need a 79/80 lid?
2. Am I missing some benefit to leaving the lid off? I don't care about going up or down a few hp.
3. Is there a good source for a part like this, or should I just be watching ebay?

Thanks.

[daves79x]

Sorry - didn't see this post. Yes, you need an airbox lid. '79 lids were unique (without the tab for the hold-down spring), but all years will fit OK. Then throw away the K&N and get the stock mesh/oiled foam, or a stock late model paper filter. Your bike will never run quite right with the K&N. But none of these things sound like a total solution to your problem. Don't know about the 'missing' at some throttle settings being carb-related. Does the bike idle down perfectly and respond from idle smoothly? Can you lug down in top gear to less than 20mph and accelerate smoothly away?

This bike has had a lot of work done and hard to tell what might be slightly amiss elsewhere. Some more specifics on the exact symptoms as you ride it more would help.

Dave

[Syscrush]

Thanks very much, Dave.

I shouldn't have said "missing". It's really a hesitation at some revs - especially when launching.

Is this airbox assembly missing its lid?

[daves79x]

Phil:

Yes, lid is missing, but also missing something at the intake - the rubber does not look right, but hard to tell from the pic. The rubber might be backwards.

Dave

[cbx6ss]

Looks like the rubber seal is missing.
Here's mine

[Syscrush]

'79 lids were unique (without the tab for the hold-down spring), but all years will fit OK.

Other than being concours incorrect, are there any issues with running an '80 or later lid on a '79?

[daves79x]

No, any year works fine.

Dave

[Syscrush]

Hmmm... I went and had another look at my airbox, because it looked to me like the one from ebay that I posted earlier had a retaining clip that mine is missing. Now it looks to me like something may actually have been cut off my airbox and I probably need a whole new assembly:



Can I work with this, or do I need a replacement?

Any pointers on where I can get a replacement? I'm gonna call Honda on a whim, maybe just to hear them laughing at me. But you never know with Honda - I bought some new carb parts for my uncle's '81 GL from a Honda dealer and they actually had 'em in stock. Oh, but that was 10 years ago. We'll see.

[Syscrush]

No luck with Honda - unsurprisingly it's discontinued. I'm waiting to hear back from Zdeno - the biggest local source for used parts. We'll see.

[EMS]

Phil: Not sure what you mean. Your box seems to be an early unit without the metal clasp. You should be able to put a lid on and go.

[Syscrush]

Phil: Not sure what you mean. Your box seems to be an early unit without the metal clasp. You should be able to put a lid on and go.

That would be awesome. What I mean is that the rear lip shown highlighted here in red looks like it may have been cut down:



Is this something to worry about?

[daves79x]

No, that's the way they look. As Mike said, you just need a lid and the proper hold-down bolts and washers (still available from Honda).

[Syscrush]

Beauty. Louis has a lid that he sells with the hold-down bolts. Placing my order now.

[Syscrush]

Then throw away the K&N and get the stock mesh/oiled foam, or a stock late model paper filter. Your bike will never run quite right with the K&N.

Thanks again for all of the help and info. I want to ask about this specifically - I know about the perils of messing with the airbox from my experience with other bikes old and new, but have never heard an admonition against a K&N filter for tuning reasons before. Is this a CBX-specific issue? What's wrong with using a K&N on these bikes? What are the symptoms of trouble?

[Rick Pope]

I'll attempt to fill in until Dave gives you the correct answer.

Our CBXs tend to run pretty lean. The K&N simply doesn't provide enough restriction, therefore vacumm, to draw enough fuel into the carbs. Unless that K&N is pretty dirty.