91 GSXR750 swing arm on 83 GS750E question.

[djee]

Hi everyone,
So I searched to find some information on this swap with no good results.

Anybody performed that swap and would be ready to answer some of my questions ?

First of all, gixxer swing arm is about 1/4 to wide for the frame and don't believe I can modify the frame nicely.Should I work on the swing arm ?

Then, the position of suspension mount on frame is more of a headache for now. Any pics would be welcome.

First bike, first mod.....but won't let go until I have done it....ready to learn...

Thanks

[TheCafeKid]

Hi everyone,
So I searched to find some information on this swap with no good results.

Anybody performed that swap and would be ready to answer some of my questions ?

First of all, gixxer swing arm is about 1/4 to wide for the frame and don't believe I can modify the frame nicely.Should I work on the swing arm ?

Then, the position of suspension mount on frame is more of a headache for now. Any pics would be welcome.

First bike, first mod.....but won't let go until I have done it....ready to learn...

Thanks

Im not sure that you can stuff that swinger in there without some extensive frame work. You might be better off using a Bandit swinger, as it essentially the same, without the 'trappesing" braces.. You could have someone brace it too, but its already substantially stiffer than the stock swinger, and the frame is going to flex before it does..

I myself will be modding my 1100ES, and Im sticking with the STOCK swinger (for oringinality and ease of the projects sake, as well as looking nearly stock with the bonuses of the upgrade parts) and the GSXR wheels WILL fit in the stock swinger of both our bikes, up to 5" i think...

[tone]

Had the same problem here



Gsx 750 frame & late model gsxr swingarm in my case, your combination should be similar, what i had to do was remove some of the metal inside the swingarm mount on the frame, than machine the swingarm bearing stops a little to allow the bearings to sink in more then remove the exess material from the ends of the arm

Other problems you will find & need to check out before going too far into it are, problems with the arm catching the rear footrest mounts, i removed mine, chain alignment issues & the obvious linkage & top shock mount issues eg you need to get the shock mounted as if it was in the gsxr for it to work properly

Another option is something like this


again a gsx rather than a gs but stock but much messed about with arm with a 5.5 wheel & 180 tyre, this takes a hell of a lot more work & many hours of fabrication to achieve but the issues are similar to the above

hope it helps
tone

[posplayr]

tone

Very Nice craftsmanship

[djee]

Thanks for the answers

GSXR wheels WILL fit in the stock swinger of both our bikes, up to 5" i think...

Maybe I'll try this for this summer....althought my wheel is 5.5''....will see....
I aslo read about the bandit swinger, i'm trying to do it with what I have but in any case I have a plan B.

than machine the swingarm bearing stops a little to allow the bearings to sink in more then remove the exess material from the ends of the arm

I would only have to remove approx 5mm on each side so maybe i don't have to work on the frame with this option...besides the top shock mount of course.

problems with the arm catching the rear footrest mounts

Removed it....will be using gixxer controls w/o passenger footrest.

the obvious linkage & top shock mount issues eg you need to get the shock mounted as if it was in the gsxr for it to work properly

This is the headache ! Do you have a closer shot of your rear susp. set-up ? I can probably find on the web too...

Another option is something like this

very nice.....I'll miss one thing....talent !


Thanks guys....I'll try the original swinger to start with then the bearing solution + new top shock mount....worst come to worst the bandit swinger....As soon as I resolve this I'll post it here.

[tone]

Thanks for the answers

Do you have a closer shot of your rear susp. set-up ?

I sorry i dont have any more pics of that particular bike as i sold it on in pretty much the state you see it there

Its really not to much of a problem to figure out where the mounts for the linkage & top mount need to sit once you have fitted the swingarm tho, what i do is take pics of the shock etc in a stock gsxr this gives you a good idea of the shock angle & height you will need to mount everything at in your frame.

The swingarm should be around 12 degrees from the horizontal & once the shock & linkage are propped in place you will see where the mounts need to be, again i stress get it a close as poss to the same angle & height as i the gsxr for it to work properly, keep refering to your pics

Once that is sorted the rest is simple fabrication/welding, use good materials not rubbish from some scrap bin, you will need 5mm mild steel plate for both top & bottom mounts & something like cfs3nbk tube for the brace that takes the top mount, most of the other braceing can be erw in various profiles & sizes if you bother with it & i advise you do, particularly the common under tank brace & the usual one in the V each side of the frame as these are weak points in a stock gs frame & you will be putting forces into areas that they were never designed to take

tone

[djee]

progress of the day

Today fitted the gixxer swing arm in the bike.

Removed excess material on swing arm but no need to do on frame mount, also need to shave the bearing stops (which is a tube).

2 things:
- I figure the 2'' I am loosing on the lenght of the swingarm is no big deal ?
- As I was trying to figure the shock mounts......I was thinking why don't I convert to dual shocks ? To me it looks a lot easier. And is it lighter ?
I also prefer the look, I think it fit better the bike but in terms of performances (in the day to day) would it be same ?

But anyway, so far so good.....can't wait to see that 170 behind me !

Cheers

[posplayr]

Given where you are I would stick with the mono shock. The bike is originally monoshock right? Also it will be much easier to find a GSXR 2nd gen shock then trying to find some decent duals.

[djee]

Given where you are I would stick with the mono shock. The bike is originally monoshock right? Also it will be much easier to find a GSXR 2nd gen shock then trying to find some decent duals.

Yes the bike is originally monoshock. Should I expect the gsxr shock to be too soft given the bikes wheight difference ?

Note that I have also swap the 91 gsxr750 USD fork on the front.

CHeers

[posplayr]

Yes the bike is originally monoshock. Should I expect the gsxr shock to be too soft given the bikes wheight difference ?

Note that I have also swap the 91 gsxr750 USD fork on the front.

CHeers

I woudl guess it depends on how you mount and what dogleg you use (in other words what the mechancial advantange is). If you put everything on as if it was mounted on the GSXR, it is probably too soft. I know some of the 1st Gen GSXR guys put 1st Gen 1100 shocks and dog legs onto their 1st Gen 750's. You could ask over at gixxer.com about that mod.

Bottom line is you can always get a new spring, I would do some calculation as to what the lever arm is and what the spring rate is stock. How much weight difference we talking about.

All things otherwise being equal:

If your GS750 is 500 lbs
And the GSXR 750 is 400 lbs
Then it is a 100 lbs diff at 50% weight ratio is only 50 lbs difference.

Given total weight for rider of 200 lbs So total weight carried by the back is:
(400+200)/2 = 300 lbs v.s. (500/200)/2=350 lbs. This is a 16% difference (=>350/300-1)

[djee]

Moving slowly,

Thank you guys for the last replies.
So moving very slowly these days...work work and work...anyway.

So okay, I will stick to the mono.

Now I am centering the rear wheel with the front one and here's the set-up:


Gentely clamp on the rear wheel


And the result I have so far would be that I'm missing approx 1/8in right to be centered.
Right at front wheel


Left at front wheel



But I have also notice that I will be almost toucching frame right side


And have a much bigger gap on left side:



Base on your experience, does it make any sense ?

Cheers

[posplayr]

are those pieces of L bracket even straight? Check them with a string.

A.) Do you have any idea what your rear spacers needs to be. The front alighment can be changed all over the map if the rear wheel is not centered in the frame. Wheel offset in the swing arm is based on swing arm offset. The wheel needs to be in the center of the frame (+/- 1/8" if you are going to use a tape measure).

Here is a simple way to get close. Compare the distances from the left to the right and split the difference. That is the center of the forks. That is where the wheel goes . Be very careful to measure all distances with respect to the pivot bolt axis



B.) Did you see if the rear wheel is aligned with the swing arm pivot? Measure distance between rear axles and the swingarm pivots.

With A and B above you can do your measurement

[posplayr]

I posted in this thread a while back

http://www.thegsresources.com/_forum/showthread.php?p=1102275#post1102275

[djee]

A.) Do you have any idea what your rear spacers needs to be. The front alighment can be changed all over the map if the rear wheel is not centered in the frame. Wheel offset in the swing arm is based on swing arm offset. The wheel needs to be in the center of the frame (+/- 1/8" if you are going to use a tape measure).

B.) Did you see if the rear wheel is aligned with the swing arm pivot? Measure distance between rear axles and the swingarm pivots.

Ok good, I'll double check those things. I assume the rear wheel is centered as the swing arm and wheel come form the same donnor bike (GSXR 750 1991) and I have all the original parts on it. THks

[posplayr]

I went back and looked at the pics. Just judging from where your straight edges line up on the frame, it is saying the wheel is close to centered in the frame. This is not going to be accurate unless you get the rear axle parallel to the swing arm pivot.

I forgot is this an 1150? or 750/750? Regardless the GS pivot bosses are likely centered, but that GSXR swing arm may not be. IIRC, the Bandit is about 3/16" offset.

Also as you have probably surmised, it is going to be tough getting a rear brake push rod to fit between frame and swing arm on the rights side (is the 1150 set up that way?).

If you look at my thread, I was able to offset the whole swing arm to the left to give more space and changed the wheel spacers to compensate.

But before you go too far with this take a look at where you are with the chain. Are you even close? Most of these GSXR conversions retain the stock GS sprocket carrier. That means new spacers . You have the tread the chain between tire and frame. With my 4.5x18 and 170/60-18 I had about 4.5-5.0mm clearance on either side using a 530 chain. A 5.5x17 with 180/55-17 you are ususally down to 2.0 mm or so either side.

At this point you are not just doing an alignment between front and rear. You are tring to find the right combination to get the rear wheel centered and have the chain run straight up to the countersprocket. Basic steps are.

1.) Wheel has to be centered in the frame (within 1/8" (3mm) or better.

2.) Align the rear wheel axle with the swingarm pivots by measuring pivot center to axle center as best as possible ( to within 1/16" or 1.3mm)

3.) Check chain alignment and see if you are going to have to change sprocket carrier or swingarm to get chain alignment (to within 1/16" or 1.3mm).

If NOT go back to 1.) above.

Alignment between rear and front wheel is going to be a fine adjustment one the 3 items above are sorted.


BTW, to get to these accuricies with a tape measure you need to "burn and inch"