Topic: Incredible shrinking airbox - CB350F

[Steve_NZ]

Hmmmmm... bought a '72 CB350F a couple of weeks ago. Put it into the local Honda shop for a once-over.
A number of things to address... Including airbox chamber assembly (plastic boxy bit between air filter and carbs) that has shrunk with age and heat - so much so that it doesn't connect properly any more.
Is this common?
Can anyone tell me if new ones are available?
Cheers!
Steve in NZ.

[troppo]

Dont know about the 350 boxes but from what i`ve heard its the rubber tubes that connect the airbox to the carbs that harden and shrink not the airbox itself.
I could be totally wrong, it has been known to happen lol.
I`m sure you`ll get a knowledgable response from one of our resident 350 experts.
Cheers
Troppo

[Steve_NZ]

Thanks Troppo,
You might well be right... all I saw was the gap the mechanic showed me between airbox and air filter.
Maybe I should ditch it all and go for K & Ns? (Are they still around?)

[troppo]

You can get the pods easy enough, K&N are one brand but the consensus in here is rejetting is needed to run right with pods.
Does the 350 have seperate boots between the airbox and the carbs?
Theres Honda mechanics that dont know anything  about these bikes, i went to one of the local honda shops and the pimply faced mechanic asked me what control module they used on my 750 when i asked him about some coils lol. He gave me a very strange look when i told him there is none, its points activated, almost as if to say i dont know about dinosaurs.
Cheers
Troppo

[Steve_NZ]

Yep - seperate boots.
Mechanic seemed up on these things - owned a few (+CB400s) himself... and took the time to show me all the bits of concern.
He found (and repaired) some other bits that needed attention too.
Glad I put my bike in for a once-over!

[troppo]

Your a lucky man to find a knowledgable mechanic, they are getting scarcer and scarcer here in aus, seems if it dont have computers in it they dont want to know it.
Wish i could find an older honda mechanic to check over my bike, i`m learning but still a little unconfident in my abilities

[Steve_NZ]

Great mechanic that talks sense.
He also worked on my TL1000 - fitted Honda fork seals to it... work great!

[dpen]

It's a pity you live near all those churches Troppo
  whist I do all my own work (mech by trade), there is a small honda shop in sydney where the old bloke who runs it is a walking microfiche on 750/4 parts
  the mechanic is a young asian bloke who's eyes light up when he sees an old bike

[Hush]

There's an older guy in Hastings (about 12k's away) and he lives and breathes old Hondas.
My local wrecker was a trained Honda apprentice under the old school too and he is very reasonable when it comes to parts for my old CB650, he even split a set of carbs the other week to give me a float!!!
If that is only a plastic air box (they were used to give the carbs still air to breath instead of forced stuff) then why not just plastic weld or even silicone snot it up?
Quick spray of flat black from a can would make it almost invisible behind the side covers.
I had to do that on my Nissan Silvia as the air intake box system pulled away from the air filter hoses and it might not look the flashest but it works!

[mattcb350f]

Thanks Troppo,
... all I saw was the gap the mechanic showed me between airbox and air filter.

Hmmm. Sounds like you might be missing a piece to me.

There is a metal tube (part #5 in pic) that connects the airbox to the filter box with hose clamps. The part is a little longer than needed and should be able to accomodate for any shrinkage.

Also, you could be refering to a gap between the air filter and the tube in the filter box, in which case there is a metal spring thingy (#3) which holds the filter tight in the box which you could be missing too.



 Matt.

[strangedaze39]

Yep Matt sounds right to me, check your airbox and filter assembly (like Matts post shows) and make sure you have all the correct parts. Your bike will run significantly different if your missing any of the boots or pieces that cause even the smallest gap.

Also all these boots do shrink with age, so it will be really hard to slide them onto there correct area. I found spraying the boots with carb cleaner will expand the boots enough to fit them on tightly. Make sure the boot clamps are slid all the way forward and completely loosened before attaching, I used to loosen them so they could obviously slide back, and forth on the boot but then when the boot needs to expand for attachment it totally stops it because it's not loose enough.

Hope that helps, let us know how it goes.

[Steve_NZ]

Gave it a good look over and all parts are present and correct. And can't see any sign of gaps now... which has me wondering if the mechanic (who told me the airbox had shrunk) pointed out the gap before he'd reinstated the oval duct between filter and airbox. 

 

[mattcb350f]

pointed out the gap before he'd reinstated the oval duct between filter and airbox.

That's probably what happened. Good to hear it's sorted out.

 Matt.

[bender01]

If you do have to take it apart again. Ive found that if you heat the air box with a small Electric space heater it will soften up and go back together much easier.

[fishman_Phil]

Steve ... we are fortunate to have one of the most knowledgeable Honda restorers and mechanics around, living right here in Waitara. His name is Graeme Duckett and currently has a great lineup of Honda Dreams from 1959 thru covering the 150, 250, 305 and 450 models. These are immaculate. Prior to doing these bikes he was into restoring all the 4 cyc from the 70s and the twins. I will introduce you to him sometime. He goes by the name hondanutz and runs the Yahoo Group called Dreamscene which I helped him setup initially.
Cheers ... Phil in NZ