frame modification...

[gerwintown]

Hey,

This is a question for those who have experience with frame modification, more specifically, the cutting of the rear frame, just beyond the shock mounts. I see alot of cafe racer style bikes that do this, referenced with this photo:

http://farm1.static.flickr.com/89/236063968_4f57b3bffd_o.jpg

Notice how the subframe ends right after the rear suspension. Obviously, this would be as short as it could go, and its a honda, not a gs550. Anyways, what, if any, additional modifications would an act such as hacking off the end of the frame like this require? Anything to be especially careful of? what am I gaining from doing this? what am i losing?

Thanks to anybody with some information on this, sorry if this is covered somewhere else, just trying to learn. see ya.

w

[rapidray]

All you have to be concerned with is adding something back to mount your rear bodywork & taillight. If you never carry a passenger there is nothing to worry about structurally after the shock mounts so I say "Go for it!" Ray.

[jimcor]

You lose:
The additional bracing provided by the subframe.
The ability to carry a passenger or anything on the rear seat. In other words you don't even have a bike you can ride to the store for a sixer, much less take touring gear on. Guess how many bikes showed up in Brown County with chopped aft ends...0.
All the classic value of your bike.

You gain:
A wobbly ride.
A great way for water and moisture to enter the frame.
A bike that looks like it was unfinished and is missing something.

[runrx02]

you would probably want to tie the two shock mounts together with a cross brace just to be on the safe side, also cap the ends so they are not open

[oldschoolorange]

I did the same thing to my bike and then just welded some steel tubing between the frame rails at the back. then just cap them off with some bar ends

[gerwintown]

i was thinking that i would only hack (love using that word) the frame up to the flat metal crossbar that currently exists and cap off the ends somehow, or weld a new cross bar connecting the shock mounts together.

I would think that if i did any of the above I wouldnt really have any problems with wobbles....at least i dont understand the physics of it...seems like it should work. what kind of wobbly performance are we talking about?

also, as for the six pack thing....its called a backpack, and i never drink alone, so it might be called a friend with a car....haha thanks!

what is brown county?

[jimcor]

what is brown county?

Look in the Meeting Place, ya can't miss it. Oh well, maybe ya can, here ya go:

http://www.thegsresources.com/_forum/showthread.php?t=101242

http://bwringer.com/gs/browncounty/

Hey! Just noticed Gerwintown you're in Cincity! Are you gonna make it to the Cincinnati Rally? It's comin up this weekend weather permitting. The info is also in the meeting place! Or right here:

http://www.thegsresources.com/_forum/showthread.php?t=101143

[Ogri]

i was thinking that i would only hack (love using that word) the frame up to the flat metal crossbar that currently exists and cap off the ends somehow, or weld a new cross bar connecting the shock mounts together.

I would think that if i did any of the above I wouldnt really have any problems with wobbles....at least i dont understand the physics of it...seems like it should work. what kind of wobbly performance are we talking about?

Don't worry, you will not have "a wobbly ride". Racers have been doing this for years. Do some research on vintage race bikes. Don't rely on the advise of someone on a forum on the internet.
Do some searching around on this site. There are many others who have made many modifications to these bikes with great success. There are always naysayers that will try to talk you out of modifying your bike. Do the smart thing and do some digging.

http://www.sundialmotosport.com/

http://www.motorcycleshopper.com/articles/hondacb350/chapter1.htm

http://www.ozebook.com/compendium/t500index.htm

http://www.caferacer.net/

Here are some places to start. much of these are twostroke related, but these guys have experience in what you are trying to accomplish.

[78gscafe]

I did it on my GS550 cafe bike. I did weld in a hoop to tie it all together and filled all of the gaps left in the frame. You can read about it in the build

http://www.thegsresources.com/_forum/showthread.php?t=106193

and see pictures of the hoop here

http://www.thegsresources.com/_forum/showthread.php?t=106193

Good luck with the build and if you have any other questions about chopping up the frame don't hesitate to ask. I don't think I left any of mine untouched.

[Commodus]

Hey,

This is a question for those who have experience with frame modification, more specifically, the cutting of the rear frame, just beyond the shock mounts. I see alot of cafe racer style bikes that do this, referenced with this photo:

http://farm1.static.flickr.com/89/236063968_4f57b3bffd_o.jpg

Notice how the subframe ends right after the rear suspension. Obviously, this would be as short as it could go, and its a honda, not a gs550. Anyways, what, if any, additional modifications would an act such as hacking off the end of the frame like this require? Anything to be especially careful of? what am I gaining from doing this? what am i losing?

Thanks to anybody with some information on this, sorry if this is covered somewhere else, just trying to learn. see ya.

w

Yep, very common modification. Ye olde racers did it to shave some weight, and the cafe guys do it, ostensibly, for the same reason. Likely the real reason is it looks bitchin. \\/

Do it! And post some pictures when yer done. Oh, and get a set of 4-4 pipes, too. Cuz they look great too :-D