Honda CB750 Sandcast

The Restoration Shop => Fuel (gas - petrol) Tanks, Side Covers and Air Box => Topic started by: Steve Swan on October 20, 2011, 12:01:04 am

Title: Rubber gasket under carb cap
Post by: Steve Swan on October 20, 2011, 12:01:04 am

I'd like to hear your thoughts on the use/fitting of rubber gaskets under carbs caps.

Seems I'm interpreting Honda information as somewhat unclear about these gaskets.

The 69.4 Parts Book sketches show a rubber gasket fitted under the carb cap, pn 16171-275-0004, beginning Evin #1.  Ditto 71.2 Parts Book, specifying this gasket to be used beginning Evin #1 thru 44812.

The #15 Honda Service Bulletin, 3/16/70, is the bulletin calling for replacement of the #28 setup for the updated kit.  Page 4 of this bulletin explicitly states, quote, "Do not use gaskets under the carburetor caps !"

I'll spare you my logic as to the purpose of the gasket, BUT I would like to hear your opinions of fitment/use thereof.

Questions I have are:  1.  Why do the Parts Books show the gasket, give a pn, while the Service Bulletin explicity instructs to not use gaskets under the caps ?  2.  Should the gaskets be used or not ?

Thanks in advance for sharing.   :)

Title: Re: Rubber gasket under carb cap
Post by: Steve Swan on October 22, 2011, 12:20:37 pm

Honda showed these gaskets in their parts books and in their service bulletin said not to use them.  I've seen carbs with and without them.  Would like to hear your thoughts if these gaskets should be used or not.

Title: Re: Rubber gasket under carb cap
Post by: Steve Swan on December 19, 2011, 12:05:50 pm

Still hoping to hear a reply to this question  ;D

Title: Re: Rubber gasket under carb cap
Post by: Riccardo on December 19, 2011, 01:44:42 pm

I've ever seen the carbs with gaskets.

I've purchased 2 set of superior carb replacement (OEM Honda parts) with slides from DSS and they arrived with gaskets.

I think that HONDA, in the 1970, wanted to resolve the problems of carburation of the CB750.

At first it has modified the top part of the carburetors.

More large cables, longer registries and more large slides, all in order to render stabler and little sensitive the system carburetors to the temperatures.

In according to moment it has advised not to mount the gasket also in order to avoid the increase of the tolerances deriving from the heating.

It seems clearly that these were only of the temporary attempts, waiting for the new carburetors from the k1.

These are my suppositions.

I personally think that the carburetors make air without gaskets.

Title: Re: Rubber gasket under carb cap
Post by: Steve Swan on January 08, 2012, 11:58:45 am

Somehow i missed your post on this topic, Riccardo.... :(  Your logic makes good sense.   ;D  Thanks !