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Advice needed for 1980 CB750 C- Seat/exhaust

tdxanthos

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Hi all,

I have recently purchased a 1980 CB750 C with the goal of converting it to a cafe racer. I am very new to working on bikes and have run into some minor issues that I was hoping that I could get some advice on.

First, I bought a brat style seat from Dime City Cycles and after I cut the frame and positioned the seat hoop (currently only taped into place) I realized that the way that the gas tank is shaped/connected creates a space between the seat and the frame. I am thinking that there may be a way of making it work, but I wanted to see if anyone else had any recommendations. I would also be open to returning the seat and purchasing another that may fit better. There are some photos below that illustrate what I am referring to below.

Also, I purchased an aftermarket muffler that I was hoping to connect to the existing exhaust system, but the size of the 2 to 1 pipe is much larger than the size of the muffler. Would I be able to use a exhaust reducer like THIS or would I need to purchase a whole new exhaust system?

I know that these are very basic questions, but I appreciate any advice that I can get.

Thanks!

FullSizeRender.jpgIMG_3663.jpgIMG_3665.jpgIMG_3668.jpgIMG_3670.jpg
 
You have to make a seat fit perfectly on your own, there will be none made that exact fit. When you get rid of the OEM part you have in essence chosen to be the engineer there.

Your exhaust is worn out, look at the rust, anything you do will only make that worse. And there is no way we can tell you if those reducers work, you have to know the exact pipe sizes to do that.
 
You might want to look into a new seat. That particular seat appears to be suited for a flat frame bike, not the C or SC frame which has all the curves to support fenders, plastic etc. I cannot provide exactly the year make and model, but that seat appears to be better for flat frame bike. Not saying it can't work, but you probably want to use parts that require less frame modification/cutting. I have also seen many custom seat pans etc to accommodate café seats. Just google DIY custom motorcycle seats and start collecting ideas.
 
amc49,

Thank you for your reply.

I have some ideas for accommodating the gas tank being in the way towards the front of the seat, do you have any recommendations as to how to engineer the seat or the frame to become more flush?

Regarding the exhaust, would you recommend purchasing a new exhaust system if I would like to add any sort of reducers?

Thanks!
 
If you decide to change seats, I would recommend eBay. I got my seat custom made by an ebay seller. He uses OEM seat pans, so no need for frame modifications. I know yours is a brat seat, but I'm sure the two of you can work something out since you have already made modifications to your frame. If you are interested I can search his eBay name and give it to you. He makes seats for almost every motorcycle out there and the quality is really good.
With the exhaust, you might be better off with a MAC header/muffler set.
242f270e607038d6ad0ae0b716af9bc1.jpg




 
That's killer. Using the OEM seat pan is so much of an advantage you can't ignore it.

I agree, when using the OEM seat pan, the edge lines up against the tank and the fender on the back seem to be cleaner most of the times. You have to be a pretty good seat maker to make it look good...and I'm not.

By the way amc, this was the project you and many others helped me with, so thank you. He bike is a blast to ride and it's pretty fun getting stopped by old farts when they realize it's a CB750 like the one they rode ages ago.


 
Anytime Bucko........................hope it didn't get too hot today..........krikey, all the Sasquatch be dyin'.
 
Sasquatch is definitely feeling the heat these days. Can't really complain, the winter sucked ballz and I'm sure the way coming is not going to be any better, so slap on some sun block and enjoy the sightseeing of tank tops and mini skirts. I'm sure Sasquatch doesn't mind that either.


 
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