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Discussion Starter #1
Hey I was just wondering what the wall thickness of most fiberglass seats are. I know some of you guys have them so if you could measure and let me know that would be very helpful. Thanks for the help in advance.
 

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while we are on the topic of fiberglass seats, how are you planning on mounting yours? I need some ideas before I drill a bunch of holes.
 

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Yeah, the one I purchased is 1/8"-3/16" thick. It's way too heavy. I made a seat that was 1/16" in most places. If you're making one, you can do a lot better than the crap CSM seats sold on ebay.

--Chris
 

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by tank i mean an army tank... my fuel tanks are paper thin too

gotta keep my bikes light so i can drink more beer
 

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Discussion Starter #7
good point monkey but I dont know how i am going to mount it yet as i havent even begun to building or really design it still kinda in the brain storming part on functionality, cost, time, etc. but ill post it up when the design is all done.
 

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that is the cool thing about doing things yourself... make something.. if you don't like it ... make the next one better.

we all started somewhere.
 

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I know its off-topic a bit, but I dont need to start another thread. I want to keep my cb750k6(5?) a two seater for the ladies :). I cant seem to find anygood setups with two seats w/ out having the rear fender on. I was thinking about geting the 78+ rear seat and tail and puting it on my 75, would that be easy to do? Has anyone seen it done or any nice twin seat setup?
 

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ok, let's clear up what you are asking here....

you want to keep the bike a two seater but you don't want to run a rear fender. I am not sure if this means you want a tail section or not.

the easiest way to keep the bike a two seater without a rear fender is to just keep the stock seat and make a taillight/plate holder to fit in between the frame rails and tuck under the seat. Another solution is to cut the rear fender down to just the bare minimum you need to mount a plate and a light. You could also have an upolstry shop mount a taillight in the back of your seat itself (maybe even a plate bracket as well) but that will cost and you will need to recover.

If you want have a dual seat and also a fiberglass tail, well then you are into custom territory. You said you wanted to use 78+ seat well that is actually two different seats. 1975 to 1978 cb750F supersports use one kind of plastic tail section seat and 1979 to 1982 supersports use another (whale tail style).

The 1975-1978 will fit your frame. The mounts are different but the supersports have a bolt on hinge, which means you might be able to drill and bolt the hinge to your frame and have the seat function as intended. These have a metal pan and will support a passenger's weight.

the 1979-1982 supersport seats do not lift, they bolt on to the bike with two side brackets. While this may make it easier to adapt, the problem is the bottom of the pan is a different shape and will not sit properly on the frame or give adiquate support to a passenger. The fact that the seat pan is plastic does not help.
 

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Geeto, Yes, no rear fender. I hate the look of the tail like bracket. I was planning or making a custom one to hold the plate/light. Easiest way I figured. I am looking to have a tail of some sort and still have room for two. the 75'-78' supersport seat sounds like the most logical. I definatly like to function of the hinged seat. If not drilling, i could cut and weld the old hinges onto the new pan? Now to find a supersport seat :) ... thanks very much for the all the info.
 

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quote:Originally posted by 75SevenFityFo

Geeto, Yes, no rear fender. I hate the look of the tail like bracket. I was planning or making a custom one to hold the plate/light. Easiest way I figured. I am looking to have a tail of some sort and still have room for two. the 75'-78' supersport seat sounds like the most logical. I definatly like to function of the hinged seat. If not drilling, i could cut and weld the old hinges onto the new pan? Now to find a supersport seat :) ... thanks very much for the all the info.
the frame hinge unbolts for the SOHC supersport seat so just use that, if you absolutley need to weld then weld it insetad of bolt it to the frame. If you try to weld an assembled seat you will catch it on fire (ask me how I know). Supersport seats open opposite of 69-76 K seats so you really can't reuse the hinges anyway (although they both fit the frame - the shape of the pans are different. Also I don't know what you are going to do about a lock (not that you need it, several of my bikes have not had seat locks for years), the lock bosses are welded to the frame.

The cb750F tanks are longer than the cb750k tanks so the seat may still come up short if you bolt her in the stock position. May guys have their seats reupolstered to make up the difference (it is like 2 inches) or you could mount the seat forward and see if it fits.

if you look at this auction - this 1978 seat has the hinge still attached (second picture - the one of the seat upside down - at the top of the pic). You see those two bolt holes? that is what you bolt to the frame and the bike has a hinged seat again.

the nice part about the F seats tail is that it has a molded lip on the back of it that you can use to make a mount for your taillight and plate with some basic sheet aluminum and not have to worry about tire interference.

Personally I feel that cafe bikes are solo bikes, and that if you really want to ride two up you should ditch the idea of a fiberglass tail, or make a removable one like the biposto ducati sport 1000 or triumph thruxton have. also the weight of two riders can be a lot of stress on a seat pan so if you keep the stock seat and just clean up the fender area it would make a difference.

one idea you should consider is the old sparto "limp dick" taillights:

http://cgi.ebay.com/ebaymotors/CUST...VQQcmdZViewItemQQ_trksidZp1638Q2em118Q2el1247

takes care of your light mount and plate bracket all in one. Looks hella vintage and has a small footprint. You can mount it high up on the rear fender and cut off the rest.

here are 2 pics of cb750s. the frist has a chopped rear fender and a generic british lucas style taillight and plate mount. the second has a stock rear fender and sparto. If you remove the grap rail on the second you can move the sparto up and cut the rear fender like the first pic bike has.

http://gallery.sohc4.net/main.php?g2_itemId=20

http://gallery.sohc4.net/main.php?g2_itemId=2718
 
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