CB 750 seat design issues

[saltybirdman]

So I just picked up a '76 CB750 and have been looking at different seat designs. I have been lurking around checking out other people's seat designs and haven't quite found what I'm looking for. I really like the look of the flat two-up seats on a few of the Wrenchmonkees builds, but I admit to being a newb when it comes to these bikes. Now I want a seat design similar to one of these as a basic starting point-

Now my only question is what kind of modifications would need to be done to the tail? It appears that they chopped the rear raised part of the frame where the stock fender would mount, shortened the rear rails, and added U shaped piping to connect the ends. Is this all that is really needed to tie the rear end together? Sorry if it's a stupid question, but I don't want to overlook anything. I'm still in the planning phase and don't want to get too far ahead of myself.

Another thing I noticed was that on a couple of their CBs they aren't running an oil tank, or at least not visibly. How is that the case on these bikes? Wouldn't it be detrimental to the oil temp and longevity of oil life? On the bike in the first picture I didn't see an oil tank or a battery under the seat.

I know this is a later model, but I love the look of the center frame section and how clean it is.

What are some other options as far as the oil tank goes?

School me on these designs and whether they are modern innovations on classic designs or if they're just fashion over function type shit. If anyone can shoot me links to any threads that I may have overlooked that contain useful info, that would be awesome. Thanks in advance.

 

[drummershoes]

love that last pic and would def love to have that seat on my 81 cb750F'er. :

 

[jampoel]

This is a picute of how I did my modifications to my 76CB500T. I cut off all the seat brackets except the lock I ran out of disks. And cut out the center brace, it stuck up two high, then welded in some left over tubing from the hoop and added two tabs to screw the new seat pan to. I welded the hoop on and mounted the fender and found out it sat too low to the tire so I had to make a cut in both sides and pulled it up to give a little more clearance. Its pretty easy once you get going!

 

[the architect]

I was also set on keeping my CB750 2-up. This is what I came up with:

My seat pan is 1/2" water-resistant hardwood plywood. The foam is a medium-firm density, closed cell. The seat pan slips beneath the gas tank, on each side of the gas tank rubber. The pan has (4) permanantly mounted studs that then slide down into tube-shaped bosses (you can see two of them in the last photo, on the frame ahead of the tire). From there, (4) knurled brass thumb screws (nuts) hold it in place.

I was inspired by the Wrenchmonkees work, too. As far as the oil tanks, they're either craftily hidden away or it's not a CB750. Some of those that you referenced don't have tanks because they're indoor display pieces rather than ridable machines.

Cheers! There's a million ways to skin this cat - just figure out your top (3) priorities and move forward from there.

 

[Ogri]

Nice work Architect! Very clean and classy.

 

[the architect]

Nice work Architect! Very clean and classy.

Thank you, my friend ;D

I have a build thread up over on the SOHC Honda forum, but I've been meaning to post it over here, too. I'll get around to it one of these days

 

[saltybirdman]

Very cool work jampoel and architect. It really is as simple as it looks, just a little daunting until I actually dive in. Thank you for the detailed pics guys.

 

[7zark7]

... As far as the oil tanks, they're either craftily hidden away or it's not a CB750. Some of those that you referenced don't have tanks because they're indoor display pieces rather than ridable machines.

Cheers! There's a million ways to skin this cat - just figure out your top (3) priorities and move forward from there.

I don't think that's right. I'm pretty sure the DOHC CB750s didn't have external oil tanks. Only the SOHC ones were dry sump.

You can see that last picture is a DOHC.

 

[Basement rat]

Both of my DOHC 1979 CB 750's and every CB750/ Nighthawk made after 1979 I have EVER seen has a wet sump oil system. No oil tanks.

An old trick to clean up the oil tank situation was to make an extension of your stock gas tank with a bulkhead between the two. In the same steel "gas tank" frame you have both your gas tank and oil tank.

 

[uphoto]

I don't think that's right. I'm pretty sure the DOHC CB750s didn't have external oil tanks. Only the SOHC ones were dry sump.

You can see that last picture is a DOHC.

At the same time he is right too. The top bike is a CB750F which usually has an oil tank but that series of bikes they made were not running bikes.

The one at the bottom is a DOHC bike so yes it doesn't have an oil tank.

 

[bradwsm]

Love the tank and seat color combo. Nice work

 

[mothgils]

To the PO, I am not sure how your 750 frame is designed in the rear but my 550 frame had to be cut about 1" behind where the rear shocks mount. I then formed, bent and welded on my rear hoop. You can look in my build thread (check my sig). I need to update it with more pics.


Off topic: Architect, beautiful man! If the bike is done (I am assuming it is), make a post in show n shine!