Topic: 1970 CB 750 Airbox Boondoggle

[major domo]

I'm having lots of problems fitting the airbox on my '70 CB 750 KO. This is the early-style airbox used only on the 1969/70 KO's. The boots of the airbox are all the way on the carb throats, except for a small gap at the top part of the boot, which appears to be correct if one compares it to a photo in several Honda restoration books. But, I cannot get the top two upper mounting brackets to line up with the frame mounts. I'm off by about 3/16 inch off  to the rear of the frame brackets. Plus, the rear of the airbox is jammed right against the frame tubes. It would almost seem that the cartbs are not fully seated in their cylinder head boots, but I've checked that, and they are fully seated, and the boots are fully seated on the intake runners, right up the to "hex" nut on the runners. I've also made sure that the airbox rubber boots are oriented the right way, with the wider part of the grove at the bottom of the airbox opening.

This is an aftermarket reproduction airbox, from Yamiya in Japan, and supposedly an accurate repro.

I have noticed that there are two styles of this early airbox offered: One with a 2-bolt upper mounting bracket, and the other with a 3-bolt mounting bracket. Mine is a 2-bolt type, as shown in the original Honda parts manual. What is the difference between these two?

Any help appreciated!

[754]

Do you have original head,later have longer spigots,moves the rubbers further back.
Not if there are two lengths of intake rubber, would have to search thru the parts books.
 I dont thnk the box should touch the frame.

[greenjeans]

There are 2 different size rubber carb insulators.  The early bikes have the shorter ones. 

[major domo]

 Thhanks greenjeans. That is one thing that was begining to cross my mind is that the rubber carb holders may be of a different length. I'll have to try and get some measurements and/or more info from the likes of David Silver Spares.

[major domo]

Thanks for the reply, 754. I'll have to contact previous owner and ask if that is the original cylinder head. I'm also looking into the possibilty the the carb holders/insulators may be longer than they are supposed to be. Apparently, the early 750's (1969/70 and others??) had shorter insulators. If in fact my insulators are too long, that would go a long way to solving the  problem!