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Discussion Starter #1
.....who just shakes his head when folks buy a bike and the first thing they do is cut off the back of the frame, knowing that in two weeks to two months they will be shoddily tacking bits of bed rail back there to hold a light and tag?
 

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No you aren't. You know you aren't because you have seen us kick the shit out of people here for it all the time.
 

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No you aren't. You know you aren't because you have seen us kick the shit out of people here for it all the time.
 

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when i was M.O.T'ing bikes in the 80's & 90's i saw some horrific modifications, the worst was a guy with a Honda CB550, he wanted to fit a custom tank, a sporster type tank, he removed the original tank then mixed a gallon of filler (bondo) and slapped it on the toptube, he built it up , and up, and up, and while the filler was still wet he pushed the custom tank onto it thinking that when the filler set it would hold the tank in place. I could tell you a hundred similar stories, including the gut that greased up his discs on his bike because the discs were made of steel and were always rusting..
 

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when i was M.O.T'ing bikes in the 80's & 90's i saw some horrific modifications, the worst was a guy with a Honda CB550, he wanted to fit a custom tank, a sporster type tank, he removed the original tank then mixed a gallon of filler (bondo) and slapped it on the toptube, he built it up , and up, and up, and while the filler was still wet he pushed the custom tank onto it thinking that when the filler set it would hold the tank in place. I could tell you a hundred similar stories, including the gut that greased up his discs on his bike because the discs were made of steel and were always rusting..
 

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Discussion Starter #8
on my projects I try to do as few frame modifications as possible, and only if they make sense. And think about all the loads that will be placed on the structure

This project:

http://forums.sohc4.net/index.php?topic=81000.25

Is an example... If you look a little ways down you see where they modified the frame to ditch the cruiser look (good) but lobbed off the back of the frame in the process (bad) and incorporated a piece of what appears to be angle iron where what could be termed the subframe meets the backbone of the frame. My issues are A) they could have pie cut and pinched the rear frame rails to form a support hoop for the seat and B) the load from the shocks will be attempting to deform the triangle of the subframe, which now has the piece of angle iron in it. That entire structure will probably flex with eventual failure of either the tubes leading up to the shock mount, or somewhere in the angle iron meeting tube structure.

I didn't just pick this bike as someone to rip on. I was looking at what people have done with the kz250 single as it is the same engine as I am working on for my air cooled KLR300/335 project. I thought that I might want a road going non dualsport bike if the engine turns out stout and saw this in my searches.

Later in the thread caferacer.net gets an honorable mention [}:)]
 

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Discussion Starter #9
on my projects I try to do as few frame modifications as possible, and only if they make sense. And think about all the loads that will be placed on the structure

This project:

http://forums.sohc4.net/index.php?topic=81000.25

Is an example... If you look a little ways down you see where they modified the frame to ditch the cruiser look (good) but lobbed off the back of the frame in the process (bad) and incorporated a piece of what appears to be angle iron where what could be termed the subframe meets the backbone of the frame. My issues are A) they could have pie cut and pinched the rear frame rails to form a support hoop for the seat and B) the load from the shocks will be attempting to deform the triangle of the subframe, which now has the piece of angle iron in it. That entire structure will probably flex with eventual failure of either the tubes leading up to the shock mount, or somewhere in the angle iron meeting tube structure.

I didn't just pick this bike as someone to rip on. I was looking at what people have done with the kz250 single as it is the same engine as I am working on for my air cooled KLR300/335 project. I thought that I might want a road going non dualsport bike if the engine turns out stout and saw this in my searches.

Later in the thread caferacer.net gets an honorable mention [}:)]
 

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Discussion Starter #10
The more i look at it, the more that angle iron truly bothers me.
 

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Discussion Starter #11
The more i look at it, the more that angle iron truly bothers me.
 

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I do not have a problem with removing the rear part of the frame if you can justify it. Which is obvious since I did that to my bike (which I believe Raven was somewhat critical of in another thread). But I agree that the running the top frame tubes into that piece of angle is dumbfounding. There's a whole bunch of ways that could have been done better. And what gets me is that it does not even seem like they are using that space for anything. Maybe that is where the toolkit will go....

The other thing I think is funny is that it looks like they added as much material on as they cut off. If you are not shedding weight it seems like you are missing the point of removing pieces of the frame.
 

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I do not have a problem with removing the rear part of the frame if you can justify it. Which is obvious since I did that to my bike (which I believe Raven was somewhat critical of in another thread). But I agree that the running the top frame tubes into that piece of angle is dumbfounding. There's a whole bunch of ways that could have been done better. And what gets me is that it does not even seem like they are using that space for anything. Maybe that is where the toolkit will go....

The other thing I think is funny is that it looks like they added as much material on as they cut off. If you are not shedding weight it seems like you are missing the point of removing pieces of the frame.
 

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I just realized there were more pages to that thread. Have you guys read through all of them? Did you see the rearset mounting! This is my favorite part:

"We also had a change of plans on the rear set mounts. We made up some brackets using these templates, but they were just WAY too thin. Even doubled up, they flexed and bent."
"So we made some plates out of MUCH thicker metal and welded them on."

And the final product...
 

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I just realized there were more pages to that thread. Have you guys read through all of them? Did you see the rearset mounting! This is my favorite part:

"We also had a change of plans on the rear set mounts. We made up some brackets using these templates, but they were just WAY too thin. Even doubled up, they flexed and bent."
"So we made some plates out of MUCH thicker metal and welded them on."

And the final product...
 

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All i know is that carpy's father invented the cafe racer in the 50s using cb750s in CA, and thats how he did it.
Latter his cousin benjie found a old storage locker filled with traditional hoops, since then everyone building a custom motorcycle turns to these parts.
I also watched a TV show that has experts on how to build a cafe racer. They hacked the whole back off a CB750 and said that as long as the wheels line up its really easy to replace the frame....

Problem that I have is that there are ways to do this right.
I dont mind the rear hoop thing to clean up the back and mate it with the seat. Fine, but putting the battery up there?
The problem comes with this idea that everything should be done for zero money and with what ever you can find on the floor.
So thats where stupid metal choices come into play and poor welding.
 

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All i know is that carpy's father invented the cafe racer in the 50s using cb750s in CA, and thats how he did it.
Latter his cousin benjie found a old storage locker filled with traditional hoops, since then everyone building a custom motorcycle turns to these parts.
I also watched a TV show that has experts on how to build a cafe racer. They hacked the whole back off a CB750 and said that as long as the wheels line up its really easy to replace the frame....

Problem that I have is that there are ways to do this right.
I dont mind the rear hoop thing to clean up the back and mate it with the seat. Fine, but putting the battery up there?
The problem comes with this idea that everything should be done for zero money and with what ever you can find on the floor.
So thats where stupid metal choices come into play and poor welding.
 

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Discussion Starter #20
I saw those....[:0] Unfortunately there isnt much you can do if he is truly having the ergonomic problems he described. If I find and build one, its gonna be midcontrols and dirtbike bars.

Why oh why didn't they drill and tap the plates?


I would have run the tubes all the way to the spine. Of course I would have also turned little inserts and pressed into the tubes as alignment/strengthening aids and made liberal use of gusseting on the outside of the tubes. There is a tube butt joint in there someplace just waiting to surface. The angle iron continues to baffle. Its setup like a little L shaped spring in the frame. Gives new meaning to the old saying "hinged in the middle" eh?
 
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