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Discussion Starter · #1 ·
Well, If you didn't see my project thread, I am building a 92 gsxr 600 with an 03 gsxr 600 motor. Anyway, I am thinking about chopping up the frame a little bit. It seems to me like it would work, but I just want to get some thoughts on it before I move in this direction.

This is a picture of the stock frame:


This is a modified picture of what I have in mind with the engine in place. I am really good with photo editing, isn't that a really convincing job? It almost looks like it is meant to be there.


On the stock frame, the lower tubes triangulate the frame and give it its strength. The newer bikes and the engine I am using are designed for the engine to be a stressed part of the frame. I figure If I put a forwar upper mount like hte one I drew in the picture, it should give plenty of strength to the frame. What do you all think?

I guess I could always weld teh lower tubes back on if it doesn;t work!!
 

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the mad doctor
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3,399 Posts
i'm really surprised you got that motor in there at all!! i see you had to tilt the motor back quite a bit to get the throttle bodies to clear the frame. might want to look into a custom oil pan/pickup with the motor that far from where it's designed to run. i'd hate to see you smoke a perfectly good motor because it starved for oil.

but about the frame, i would either modify the stock lower rails, or build custom ones, and make sure that motor is bolted in on as many points as possible. that frame wasn't meant to have the motor just hanging like a newer bike does. i could forsee alot of flexing of the frame, and possibly some cracking at the mounts. i'd tie everything together as much as possible. you could make a custom cradle pretty easily out of steel. it'd weigh a bit more than aluminum, but it's easier to work with, and less likely to crack under load.
something like this, but set up for your motor/frame:



 

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Discussion Starter · #3 ·
The engine is not really leaned back very much. The oil pan flange is almost perfectly parallel with the lower frame rail. I am pretty happy with how it sits, I don;t think I will see any oil starvation in this bike.

The engine actually has no mounts on the bottom of it. That is why I was thinking about removing hte stock cradle/bottom frame tubes. It really seems to serve no purpose with this engine in place.

Now I am no engineer, but it seems that if I mount it as shown below, the tension and compression strenth of the engine will give the frame plenty of strength. I circled the 3 engine mount locations in red so you can better see what I am dealing with.

 

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Function IS Form
19 Z900, 88 Kat11
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I'd definitely leave the stock cradle.

On the 03 gsxr, the engine is a stressed member. The frame is designed around having the engine holding it together. Not so much with the old frame :)
 

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Discussion Starter · #5 ·
Yeah, that is what I am saying, the engine is designed to be used as a stressed member, so I think I should use it as one. What I am saying it that I will connect the front mount to the steering neck and the upper tube and then the engine will take the place of the cradle. As it is, the cradle will not connect to the motor in any place and it seems that it will be pretty redundant. Please continue to give me input on this, I am very hesitant to remove the lower tubes, but it would make my job very easy and it will save some weight, and it would be pretty cool!
 

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Function IS Form
19 Z900, 88 Kat11
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The engine is designed for it, but the frame isn't. The upper rails on a newer gixxer (and the whole frame itself) is designed to use the engine. That frame that you have is designed to have lower rails... the engine isn't going to be enough to keep it from flexing.
 

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The old 600 frame isnt designed around having the engine hold it together like the 03 600 frame is. If you put 2 pictures of the frames side by side youll notice how different they are...not to mention how much thicker the 03 frame is. Your probably thinking that once u got the forks on and the front wheel on the ground that it will hold together like an 03 frame with an 03 engine and it will probably seem like its holding together fine.
 

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Function IS Form
19 Z900, 88 Kat11
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emanaresi said:
you really think so? That would be pretty dissapointing. I guess I don't really see how the aluminum lower frame rails could supply more rigidity than the engine would...well, I guess I have some real thinking to do.

The shape and stress points are designed with the whole frame in mind (on sportbikes more than others). The shape of the box is designed a certain way for a certain reason by engineers with all sorts of letters after their names.

Technically, you -could- chop the frame the way you're saying. I'm just pointing out the potential risk factor, being that the frame might flex an awful lot with half of the box missing. The problem with sportbikes is that when the frame flexes, it's a very stiff thing flexing a very great deal on a very small area. This is where you see broken necks and mysteriously twisted forks.
 

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Discussion Starter · #10 ·
Yeah, I am not interested in running into any of those problems.

It just seems like with the way the engine mounts, and with its intigrel strength, the lower frame rails will really be just a redundency (is that a word?)

Now that I look further at it...I think it would might be a mistake to not build it the way I am proposing. The pic below whos the forces on the frame with red arrows. With no lower bracing, the frame would tend to bend in the direction of the green arrow (probably at the corner, I bet that is the weakest point). However, with the engine supplying forces in the directions of the blue arrows, it should be very strong. The triangular structure of it should work out great.


The picture below shows the mounts that would have been used on the stock motor. However, the new motor does not have a mount on the bottom or on the front of the motor where the stock mounts are indicated. Again, I am not an engineer, but I do have a little engineering training...I am gonna have to talk to a few engineers at work and see what they think...man, it will be so easy without those bars
 

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emanaresi said:
It just seems like with the way the engine mounts, and with its intigrel strength, the lower frame rails will really be just a redundency (is that a word?)
One definition for redundancy would be the provision of additional or duplicate systems, equipment, etc., that function in case an operating part or system fails. :LolLolLolLol: So like you just said....the lower frame rails are there to back up the top ones.:D
 

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British Bloke in Canada
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I think your going arround this the wrong way, why did you choose the GSXR 600 to start, ...if you had chose a bandit 6 or 12 the mods would of been so much easier.
the gsxr 600 is a through away ebay peice you can pick up for a few hundred bucks, and I think wont really have enough stomp for that chasis, not to mention chain alignment, water cooling, mounting, etc. I say sell the 600, and bolt in sothing that will work easy. hell a oil cooled gixer 750, or even the katana 750 is the same generation
 

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Eff Tee Pee
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bandit 12 motor would be badass! he does have a valid point. Im just concerned with the potential situations of a failing frame!!
 

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GURU
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dont cut it!!!!!!!!! dont there are so many more things at play here. Im a senior ME student so im not an engineer but ive done alot of research in this area and ive been a fabricator for almost 7 years now. You arent thinking about everything I can assure you because there are way more forces that act on a frame. Just like everyone said, the motor is designed as a stressed member but the Frame Is Not!. That doesnt mean you can bolt it to the motor and expect it to work without any additional bracing. you are connecting the mounting points with straight lines first of all which is an assumption. With all the internal casting ribs in the motor its designed to take loads at those points in certain directions and that frame will load it differently then an 03 600 frame. You might rip the motor apart! While your free body diagram was partially right you arent considering your suspension linage and shock point loads, frame twisting etc. The load you had there was what the bike would see if you were coming down from a wheelie. Think about braking forces pusing the stem backwards, twisting forces from leaning, shock load forces at the base of your tank, etc you have to remember the stock frame wasnt as strong in 92 as the newer ones as well. Id bet the 03 frame without the motor is stronger then the 92 frame.





The 03 frame is almost a straight shot from the steering head to the swingarm pivot. The 92 frame isnt and needs that additional cradle. Even though it doesnt bolt to the motor in any way it still is needed unless you want to get really crazy and start bracing the frame all over the place.
 

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the mad doctor
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shift1313 said:
oh yeah and that hawk frame with the cr motor is awesome!! is that a 500? or a 250. any more pics/info?
it's a 500. wish i could say it's mine, but it's not. i was talking to a guy about my hawk/cr and he sent me those pics. really clean install, but needs better mounts. the guy said he cracked most of the motor mounts in less than an hour. mine will have big ass urethane inserts in all the mounts.


and about the motor swap, that's a 93 frame, which is liquid cooled. getting an oil burner in there is NOT easy. but... you could stuff a water cooled 1100 motor in there pretty easily, or an RF900 motor.

but hey, if he's already got the 600 motor, why the hell not. it's not gonna be a simple swap, but it's doable.
 

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skr00zloose said:
or an RF900 motor.
:Stupid:

HOLY SHIT! Someone said something about/around my bike model!!!!
 
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