GS 1000 engine in GSXR 1100 first gen frame?

[John Kat]

I got to see the GSXR 1100 1st gen frame for sale today.
It wont be quite as easy as I thought because the top frame beams are not parallel...
This would mean having to insert extension adapters on eitheir side of the split beam in such a way that they would join on parallel longitudinal planes.
I suppose a drawing would better explain what I mean.
The good news is that I believe the extension should be around 50 mm maximum as one can see from the picture where I placed a GS 1000 engine upper case on top of a GSXR lower case.
Here are a few pictures:

[ozman]

keep us informed of progress john

[John Kat]

I did a quick drawing of the beam inserts that would be needed to extend the upper part of the frame.
It doesn't appear to be too difficult to have these made?
In fact as GregT mentionned, the most difficult will be to build the jig to hold the parts in place while welding them.
This design however would allow the use of two "half" jigs: one for the frontend to the insert reference holes, the other from the swingarm axle to the same insert reference holes.
We are almost done...
Here's the drawing:



Of course I could go the other way around and fit a GSXR engine in a GS 1000 frame like this one:

[John Kat]

Good news, I crossed the Rubicon today and bought a GSXR 1st gen frame
My plan is to get it on some wheels and pedal it down a slope to determine if the frame is straight...
Next I'll make a jig to retain the current settings of the swingarm axle versus the headstock.
It should then be easy to extend the jig by the required 50 mm to ensure the frame inserts are correctly welded in place.

[posplayr]

Of course I could go the other way around and fit a GSXR engine in a GS 1000 frame like this one:

This one def looks more Resto than Retro

[John Kat]

I stripped my GSXR frame today and...I got second thoughts about modifying it.
It's really beautifull engineering that went into it!
In fact it was clearly based on the XR 41 but on top of an aluminum frame it also got a lighter and more powerfull engine.
So why reverse engineer all that by putting an old GS 1000 engine in it???
Here's what it looks like:

[John Kat]

After cleaning up the frame a little, I positioned the GS 1000 cylinder head as close as possible to where it should go if the complete engine was in place.
In particular, I wanted to check the exhaust spacing and the overall height of the engine in the frame.
The conclusions are that there should be no issue on the exhaust side nor on the height side.
The only problem(?) seems related to the lower frame downtubes that will interfere with the lower engine case.
If this is really the case, it would considerably simplify fitting the engine as we would no longer have to extend the frame's top rails!
It would even be tempting to run an open craddle type of frame with the engine acting as a stressed member...
As there seems to be no 3D model of the GSXR first gen frame, I would greatly appreciate if someone had a GS 1000 lower engine case lying around that I could purchase?
I already have an upper case.
Here are the pictures and a link to a thread where a frenchman did the complete 3D model of the 2nd gen GSXR!

http://www.zimagez.com/zimage/1100gsxrkeyshot196.php

http://forum.airhuile.com/topic19462-1320.html

[John Kat]

Good news, today I positionned the upper engine case in the GSXR frame and it seems to fit like a glove.
One might have to grind away the small extension that's on the front right side of the upper case but else it's OK.
On the pictures you will see that the frame is tilted slightly forward with respect to the engine upper case to clear that extension.
If it had to remain in that position, the exhaut pipes would have to be (un)bent accordingly.
A small issue for the moment.
I checked the clearance for the cylinder head and it's OK.
For the lower engine case it's OK for the rear part but I need to check further for any interference with the front downtubes.
The other unknow is whether the lower case will fit into the existing frame mounting tabs???
Here are some pictures of the future XR 41...

[John Kat]

I finally got to the conclusion about getting the GS 1000 engine in the GSXR 1st gen frame: the frame is too short!
In fact you can get the engine in the frame by tilting it upwards in the front as you will see in the pictures but then the carbs will no longer fit...
Lowering the front of the engine in the frame requires an extension of 5 or 6 cm.
It's too bad because I believe the lower engine case would fit right into the frame's lower rear mounting lugs.
I will put the project on hold for the moment.

[Fjbj40]

Bummer! I had dreams of doing the same thing. I remember seeing a xr69 done using a bandit 1200.

[dorkburger]

........throttle bodies are smaller then carbs....far beyond my scope of knowledge, and not necessarily in the theme, but.......

[John Kat]

I finally gathered the courage to cut a GSXR 1100 G/H frame into two.
In fact, I found another frame without title to run this experiment.
Here are the two halves attached with a few strings just to get a feeling of what it would look like.
In one of the pictures, you will see the engine top case in place: it seems almost right?
The next question is to determine if I extend the top rails in a straight line ( that would help for carb spacing) or if I bend it slightly downwards to decrease the rake angle a little?
Any opinions?
PS: I'm still chasing for a lower engine case to complete the mock-up...

[steve murdoch]

This project is entirely out of my mechanical ability but i enjoy following along.
Keep at it, John.

[John Kat]

This project is entirely out of my mechanical ability but i enjoy following along.
Keep at it, John.

Thanks Steve!
This is what it looks like with the cylinder and head in place.
Tight but plenty of space for the carbs.
No issue with the exhaust port spacing.
Still missing the lower engine case...

[JTGS850GL]

Should be interesting once the lower case arrives. I'm betting that there's going to be some changes as a result. Looks to me like the engine is going to be raised slightly to clear the lower case on each side. Hard to tell but just going by the pictures. Interesting build.