Topic: 78 CB750K air box rebuild.

[maxheadflow]

Well, I've been cleaning things up slowly. Just pick a part and start look at how screwed up it is.  Got the motor all cleaned, replaced side cover/ oil pan gaskets and some seals.  While the inside of the overs look pretty good clean, outside was incredibly dirty.

Started in on the air cleaner.  The rubbers for the stack and carb to head stuff look new and not OEM.  The carb to manifold has some serious steps that need to be matched.  The clamps on these look to be the ones you can get on Ebay and they seem to work even those there was a bunch of dried permatex black silicone on the cab and head spigots.  Got all that cleaned off with a small dremel and stainless steel wire wheel.

I cut the air horn off the bottom box and removed the head breather stuff.  The box looked pretty ratty but cleaned up with some 00 steel wool.  It's beginning to look better.

The stacks had come screw clamps on them and the last guy that worked on it kinda destroyed the rubber where they go to the heads so I figure to replace.  Can anyone make a suggestion as which way to go on replacement. One of the things I see is that the stacks are different between the 70-76 and the 77-78. One has a middle number of  341 and the other 405. Anyone know what the differences are?  I suspect that the end of the carb is a different diameter and the band clamp is too.. Where is the best place tho get this stuff?  Looks like the OEM stuff is still available.  What about the clamps? 

TIA Max




 

[maxheadflow]

Here are some more pics.

[seanbarney41]

you guessd it...pd carbs require different airbox boots cuz they are bigger diameter than earlier roundtops.  OEM clamps are getting scarce.  If you find some you can afford, better grab them up.  Many members have found non oem band clamps that fit and function well.  Personally, I try to re-condition originals as much as possible by replacing screws, bending them back into shape, and polishing with 0000 steel wool and wd40.

[HondaMan]

I also had success re-using the old clamps by re-shaping them like they were new, with the steps near the screws that collapse and stretch out to provide the tension.

[maxheadflow]

Thanks for the info guys.  I only have 2 if the original clamps and they look like the were run over by a forklift then straightened out.  The other 2 were narrow hose clamps.  You can see by the rubbers that the ends were over squeezed enough to distort the ends.  Looks like new clamps and boots/stacks.

[maxheadflow]

you guessd it...pd carbs require different airbox boots cuz they are bigger diameter than earlier roundtops.  OEM clamps are getting scarce.  If you find some you can afford, better grab them up.  Many members have found non oem band clamps that fit and function well.  Personally, I try to re-condition originals as much as possible by replacing screws, bending them back into shape, and polishing with 0000 steel wool and wd40.

Went down to a local Honda shop and they are pretty savvy about the ol' stuff.  Clamps according to them are still available. I ordered new OEM carb boots/stacks from them.

[Airborne 82nd]

Norma makes a very good clamp rolled edges on both sides and no worm gear notches.

https://www.normagroup.com/norma/en/products/

[70CB750]

Norma makes a very good clamp rolled edges on both sides and no worm gear notches.

https://www.normagroup.com/norma/en/products/

+1  You can find them on Amazon as Euro clamps, they work great.

[maxheadflow]

I not too hot on the narrow worm drives.   A previous owner did a good job of  screwing up the air cleaner tubes with screw clamps. Tightened them to point they were permanently distorted.  He also did not install them right in the box causing them to slip to the inside.  They would not line up or seat on the carbs.

[HondaMan]

I often use the aerospace type from Oetiker, but you must be careful to not overtighten them. They have enormous mechanical advantage on their high-quality worm drives, such that you can cut the hoses right off by tightening them enough.

...and don't ask how I know this, because I won't tell you...

[maxheadflow]

While I used the standard ear crimp type clamps, I'm not sure which clamp you are referencing.

This type?

https://www.oetiker.com/en/Products/Clamps-and-rings/Worm-Drive-and-Universal-Clamps/Stepless-Screw-Clamp-PG-178

[Dolomite]

Not sure if you need to replace this but when I did mine the gasket between the lower and upper box was completely shot. Narrow closed cell weather stripping foam worked great as a replacement.

[Jerry Rxman Griffin aka MuthaF'er]

https://www.amazon.com/gp/product/B0036R4UDC/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

[Dolomite]

https://www.amazon.com/gp/product/B0036R4UDC/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

So I used those the first time and had tons of issues with getting repro boots to seal, vacuum leaks for days. When i swapped them out for OE style ones, all my intake issues went away. Also if those are over tightened they WILL cut into the boot just like regular edges

[maxheadflow]

Some pics of it going back together.

First the original tubes, while soft, were squashed with hose clamps pretty good and not installed right.  The green line runs parallel  to where the box was sitting.    One red shows how the tube was nit installed completely to the box and the ridge that supposed to be in the box was rolled over.  Other line shows how the ends were squished with hose clamps.   

Second pic shows new tubes stuffed properly in the box.

BTW the center piece gasket was good.