Author Topic: Removing top two side frame rails, good/bad?  (Read 2875 times)

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Offline alfredo

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Removing top two side frame rails, good/bad?
« on: November 06, 2012, 07:28:11 PM »
So, I am new to the forum and to the tx500. I am wanting to strip the frame of the top two side rails (see the pink in the image below). I plan on connecting the top middle frame rail to the to rear sides via some strong welds.

I am thinking this won't really affect the safety as the xs650 has only the top middle rail. At first glance, there doesn't appear to be a real clear reason why they have to stay there if the restructure is done properly. Meaning, if I connect the real rails to the middle top in a proper fashion, trued and such.

Anyone think this is insane? Any tips? Must have been done before right?


Offline steve

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Re: Removing top two side frame rails, good/bad?
« Reply #1 on: November 06, 2012, 07:28:45 PM »
Hey, Alfredo.  Welcome to the forum. 

Good diagram, it clearly shows the tubes you want to remove.  But it is not clear to me from the diagram how you would join the "green" tubes together, or how you plan to reinforce them.  Maybe you could sketch in (in blue) the "connection" you have in mind for the green tubes, and any gussets you intend to add. 

Alll I know so far is that you want to severely weaken one area of the frame (by removing the "pink" tubes) and will try to compensate for that by somehow reinforcing the "green" tubes.  In other words, I can see how you will weaken the frame, but that's all.

Those "pink" tubes are designed to support the steering head and keep it from flexing.  Removing them will very likely result in unpredictable flex in the steering head area, especially under hard braking or acceleration.  Without extensive gusseting, you might get head-shake or wobble while turning, and your front tire might lose traction and lead to a crash.   

Which leads to the obvious question:  why are you doing this?  I can see the potential downside of this plan (lots of time spent cutting out tubes and welding in gussets; possibly resulting in a weaker and/or heavier frame), but what's the upside? 

Offline metalman

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Re: Removing top two side frame rails, good/bad?
« Reply #2 on: November 06, 2012, 07:30:58 PM »
It seems to me that removing those tubes would make it a lot easier to pull the motor. I was recently pondering the same idea while wrestling out the motor again. There are no motor mounts on the top. I do see the problem of weakening things if not done right. Being a welder and fabricator, I don't think it would be a big deal to make some stout gussets. Maybe at the point where to 3 tubes join eachother in the back and in the front where the top tube meets the neck (those factory gussets are quite thin). It would be a fun experiment. How would it would handle? Only one way to find out. And a gizillion 650 frames have been chopped without making any crashers. I don't see why a 500 frame would be that much different.
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Offline guylr

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Re: Removing top two side frame rails, good/bad?
« Reply #3 on: November 06, 2012, 07:31:46 PM »
I wouldn't do that. The XS frame is a twin loop design that doesn't use the engine as a stressed member. Taking away the tops of both of those loops will definitely weaken the frame. It may not break on you but the handling might get wiggly just at the moment you need it to be solid. How often do you plan on pulling the engine anyway?
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline TXRAT

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Re: Removing top two side frame rails, good/bad?
« Reply #4 on: September 13, 2014, 07:34:57 PM »
I agree if you remove those two pieces of the frame it could lead to a very serious uncontrollable condition. I would not do it. I have talked to a few old timers, and they say yamer made these frames as cheaply as they possibly could, so to remove those two pieces could cause a critical failure even with proper gusseting.

Offline guylr

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Re: Removing top two side frame rails, good/bad?
« Reply #5 on: September 13, 2014, 10:49:22 PM »
That's a two year old post Rat. Those old timers would be wrong. The 500 frame is essentially a scaled up RD350 frame which is derived from the TR3/TZ350 championship winning road racing frame. Now maybe they were remembering the Honda CB350 and 450 frames of that era. Those really were cheap.

Guy
« Last Edit: September 13, 2014, 10:53:33 PM by guylr »
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline steve

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Re: Removing top two side frame rails, good/bad?
« Reply #6 on: September 14, 2014, 02:13:18 AM »
Yeah, I have always wondered about those CB350 frames, with the pressed sheet metal backbone.  I don't know if they saved any money with that design, but it sure looked cheap.   

Offline TXRAT

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Re: Removing top two side frame rails, good/bad?
« Reply #7 on: September 14, 2014, 04:22:59 AM »
yup, got a 360 stamped frame "out back". yeah, wanna do it, im thinking about doing mine  1/4" gusetts with a good bevel on the frame edges of it.

Offline TXRAT

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Re: Removing top two side frame rails, good/bad?
« Reply #8 on: September 14, 2014, 04:25:39 AM »
A few inches on the pink part of it toward the back though we'll have to stay to join to this center, backbone of the frame. Mine anyways, the way I hard tailed it.  :)