GS tranny in a GT750 box
Moderators: oldjapanesebikes, H2RICK, diamondj, Suzsmokeyallan
- Suzukidave
- Moto GP
- Posts: 3980
- Joined: Fri Oct 24, 2008 5:55 pm
- Country: US
- Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
- Location: Lancaster Pa.
GS tranny in a GT750 box
I have been doing a bit of talking with several other list guys about this swap over , so i pulled out a 77~79 GS750 gear set and a GT750 lower case just to see what would be involved i could see there isnt a whole lot different between the 2 sets ( besides the better gear ratio of the GS gears ) the output shaft of the GS is longer that would allow spaceing the sprocket out for wider rear tires easier and also its splined for the later model front sprockets like come on also the GSXR and that will allow you to use there 520 and 525 and 530 chains . the biggest problem is on the clutch output end of the gear set , the GS shaft is longer ( about 7mm ) as the GS and GT use different methods to disengage the clutch . The GS uses the shaft thru the engine from the left side to push the pressure plate off where the GT uses the lever on the right side to pull the clutch pressure plate off the clutch pack so i dont know if the longer GS shaft will interfere with the GT clutch release http://suzukidave.myphotos.cc/suzukidav ... T%20Gears/ has anyone done this swap before ? .. Dave
Last edited by Suzukidave on Tue Jun 15, 2010 7:08 am, edited 1 time in total.
the older i get the faster i was
- Suzukidave
- Moto GP
- Posts: 3980
- Joined: Fri Oct 24, 2008 5:55 pm
- Country: US
- Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
- Location: Lancaster Pa.
This is a surprise that no one here has done this swap
Last edited by Suzukidave on Sun Mar 29, 2009 8:57 pm, edited 1 time in total.
the older i get the faster i was
- Suzsmokeyallan
- Moto GP
- Posts: 4326
- Joined: Fri Oct 24, 2008 9:11 am
- Location: Mostly Barbados, sometimes Florida and western Canada
- Contact:
Dont worry Dave, i'm backing you up on this one 100%.
Two strokes, its just that simple.
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
- Suzukidave
- Moto GP
- Posts: 3980
- Joined: Fri Oct 24, 2008 5:55 pm
- Country: US
- Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
- Location: Lancaster Pa.
-
- On the main road
- Posts: 131
- Joined: Thu Oct 16, 2008 4:26 pm
I have always wondered if this would work. But, I wouldn't know what to look for to determine it.
It would definitely help when it comes time to replace the sprocket. IIRC it cost me over $200 to have Kosman make the offset sprocket for me. So, every time I do a chain and sprocket replacement, it is going to be a major expenditure. If one of his standard Suzuki sprockets could be used, it would only cost $85 each time the sprocket needed changed.
My mechanical knowledge is limited, so keep that in mind as you consider this...
What if one were to replace the gearing on the buffalo clutch output shaft with the GS gears and use the GS output shaft for the sprocket? This way the GT clutch could be used and still have the benefit of the GS gearing and the longer output shaft. Would this work?
It would definitely help when it comes time to replace the sprocket. IIRC it cost me over $200 to have Kosman make the offset sprocket for me. So, every time I do a chain and sprocket replacement, it is going to be a major expenditure. If one of his standard Suzuki sprockets could be used, it would only cost $85 each time the sprocket needed changed.
My mechanical knowledge is limited, so keep that in mind as you consider this...
What if one were to replace the gearing on the buffalo clutch output shaft with the GS gears and use the GS output shaft for the sprocket? This way the GT clutch could be used and still have the benefit of the GS gearing and the longer output shaft. Would this work?
Last edited by Ogri on Mon Mar 30, 2009 11:30 am, edited 1 time in total.
-
- AMA Superbike
- Posts: 1769
- Joined: Tue Oct 14, 2008 6:47 pm
- Location: Blythewood, SC, USA
There's a blank plug on the left case of the GT where a clutch pushrod might have gone. I figure they planned it that way, but changed to the other type during development. Maybe a hydraulic actuator on the left??
Lane
Lane
If you stroke it more than twice; you're playing with it.
Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
Too many bikes, too much time, ENOUGH SPACE, FINALLY! Never enough money.........
- Suzsmokeyallan
- Moto GP
- Posts: 4326
- Joined: Fri Oct 24, 2008 9:11 am
- Location: Mostly Barbados, sometimes Florida and western Canada
- Contact:
Having some conversations with Dave proved to be rather interesting with regards to the swap over of the shafts.
He was lucky to have both transmissions to hand for direct comparison, thats always a big benefit..
From his detailed pics and what was discussed, the actual transplant is looking pretty straight forward so far. Once Dave gets the shaft bearings swapped over from the GTs shafts to the GSs so they can actually drop into the GT cases he will know better just what further adjustments are to be done.
You will also need the GS clutch inner basket for the upgrade too because the splines on the end of the GS clutch shaft are different than the GTs.
THEN theres the main issue of the slightly longer clutch shaft threaded end thats going to need some minor reworking to shorten it a bit.
The big benefits here are the longer and better designed drive sprocket splines on the output shaft and of course the better shifting and closer ratios between 1st and 2nd.
Gearboxes for the first generation GS750s show up on ebay for about $40.00 including shipping, so its not an expensive retrofit.
He was lucky to have both transmissions to hand for direct comparison, thats always a big benefit..
From his detailed pics and what was discussed, the actual transplant is looking pretty straight forward so far. Once Dave gets the shaft bearings swapped over from the GTs shafts to the GSs so they can actually drop into the GT cases he will know better just what further adjustments are to be done.
You will also need the GS clutch inner basket for the upgrade too because the splines on the end of the GS clutch shaft are different than the GTs.
THEN theres the main issue of the slightly longer clutch shaft threaded end thats going to need some minor reworking to shorten it a bit.
The big benefits here are the longer and better designed drive sprocket splines on the output shaft and of course the better shifting and closer ratios between 1st and 2nd.
Gearboxes for the first generation GS750s show up on ebay for about $40.00 including shipping, so its not an expensive retrofit.
Two strokes, its just that simple.
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
- tz375
- Moto GP
- Posts: 6204
- Joined: Mon Nov 03, 2008 10:47 am
- Location: Illinois
Dave has it in hand. As long as the width across the gears is the same, it will fit. The input shaft should not be hard to modify to use a GT lifter and GS hub. As lane suggested, it may be possible to fit a hydraulic lifter, but I couldn't work out an elegant fit for the one I have here.
It's a lot easier than trying to squeeze a 2001 GSXR 6 speed transmission into a set of GT cases. Shafts are good, input end is fine. Shafts in fact are the same diameter as a GT, so the bearings can be swapped. BUT the damn thing is 7mm to wide to fit in the cases and the selector mechanism is in completely the wrong place and would end up outside a set of GT cases!
Dave, I forgot about the oil pump. Will the GS gear drive that OK or will you have to swap over one pair of GT cogs?
It's a lot easier than trying to squeeze a 2001 GSXR 6 speed transmission into a set of GT cases. Shafts are good, input end is fine. Shafts in fact are the same diameter as a GT, so the bearings can be swapped. BUT the damn thing is 7mm to wide to fit in the cases and the selector mechanism is in completely the wrong place and would end up outside a set of GT cases!
Dave, I forgot about the oil pump. Will the GS gear drive that OK or will you have to swap over one pair of GT cogs?
- Suzsmokeyallan
- Moto GP
- Posts: 4326
- Joined: Fri Oct 24, 2008 9:11 am
- Location: Mostly Barbados, sometimes Florida and western Canada
- Contact:
Richard lets see that 6 speed transmission in the GT cases and where the selector will fall, do you have pics?????
Two strokes, its just that simple.
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
- tz375
- Moto GP
- Posts: 6204
- Joined: Mon Nov 03, 2008 10:47 am
- Location: Illinois
Allan,
It's about 2 inches below the GT cases. The GSXR gears are stacked and not on the same plane as a GT, and that makes the whole thing shorter. Later designs are even shorter by placing one shaft above the other.
But to fit a GSXR tranny in, needs fairly extensive machining, welding and then more machining to move the left wall of the transmission out. If the GSXR had a proper (casette) trans, it would be much easier.
And there's still the oil pump issue to resolve. Water pump is easy to replace with an electric pulse pump from world leaders Davis Craig in Australia, but the oil pump would be slightly more difficult to arrange. I already looked at Polaris triple oil pumps which are cheap and available, but not so easy to arrange the drive.
I think Ogri Tim has the right answer if the Gt input shaft will work.
It's about 2 inches below the GT cases. The GSXR gears are stacked and not on the same plane as a GT, and that makes the whole thing shorter. Later designs are even shorter by placing one shaft above the other.
But to fit a GSXR tranny in, needs fairly extensive machining, welding and then more machining to move the left wall of the transmission out. If the GSXR had a proper (casette) trans, it would be much easier.
And there's still the oil pump issue to resolve. Water pump is easy to replace with an electric pulse pump from world leaders Davis Craig in Australia, but the oil pump would be slightly more difficult to arrange. I already looked at Polaris triple oil pumps which are cheap and available, but not so easy to arrange the drive.
I think Ogri Tim has the right answer if the Gt input shaft will work.
- tz375
- Moto GP
- Posts: 6204
- Joined: Mon Nov 03, 2008 10:47 am
- Location: Illinois
Overall the GS cluster is closer than any of the GT gear sets. GT has a 68.57% gap on early bikes and 66.22% on M/A/B)
First is taller and fifth is lower. 1-2 gap is reduced (30.96% v's 37.54% on late A's and 38.98% on JKLM), 2-3 and 3-4 are almost identical gaps on both bikes and 4-5 gap is smaller on the GS (7.56% v's 14.53%) .
The gear pairs are as follows:
GT750 L GT750A/B GS750
First 13:37 13:37 14:36
Second 19:33 18:32 13:32
Third 22:30 22:30 21:29
Fourth 24:27 24:27 24:27
Fifth 26:24 26:25 25:26
On the Gt750, top was changed from 26:24 to 26:25 with the M and late in the A production, seconds changed from 19:33 to 18:32.
A couple of years ago, I sat down and worked out an ideal set of ratios for a GT and they are the same as the GS except for 3rd where I chose 22:30 and Suzuki chose 21:29, a difference of less than 2%.
So Dave, I like the ratios and it looks like the oil pump will probably work with that 1 tooth larger first gear
First is taller and fifth is lower. 1-2 gap is reduced (30.96% v's 37.54% on late A's and 38.98% on JKLM), 2-3 and 3-4 are almost identical gaps on both bikes and 4-5 gap is smaller on the GS (7.56% v's 14.53%) .
The gear pairs are as follows:
GT750 L GT750A/B GS750
First 13:37 13:37 14:36
Second 19:33 18:32 13:32
Third 22:30 22:30 21:29
Fourth 24:27 24:27 24:27
Fifth 26:24 26:25 25:26
On the Gt750, top was changed from 26:24 to 26:25 with the M and late in the A production, seconds changed from 19:33 to 18:32.
A couple of years ago, I sat down and worked out an ideal set of ratios for a GT and they are the same as the GS except for 3rd where I chose 22:30 and Suzuki chose 21:29, a difference of less than 2%.
So Dave, I like the ratios and it looks like the oil pump will probably work with that 1 tooth larger first gear
- Suzsmokeyallan
- Moto GP
- Posts: 4326
- Joined: Fri Oct 24, 2008 9:11 am
- Location: Mostly Barbados, sometimes Florida and western Canada
- Contact:
Pardon my question here Richard but what other GS models from the same time period had a 6 speed transmission....
Two strokes, its just that simple.
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
- tz375
- Moto GP
- Posts: 6204
- Joined: Mon Nov 03, 2008 10:47 am
- Location: Illinois
Allan, are you trying to tell us that there's a large bore GS from the era that had a 6 speed box that we are all forgetting about?
The 250/400/425/500 series are most likely to be inadequate for the power/torque we're looking at here.
When did Suzuki introduce a 6 speed trans on the 750 and larger bikes?
85 Slabside GSXR750 had 6 speeds. GSX750F katana had 6 speeds in 88 I believe but I'm no expert on those. The GSX750E from 83 on had only 5 speeds. The 1100 had 5 speeds up to 97.
So are you thinking Katana perhaps?
I have never been good at guessing games.
The 250/400/425/500 series are most likely to be inadequate for the power/torque we're looking at here.
When did Suzuki introduce a 6 speed trans on the 750 and larger bikes?
85 Slabside GSXR750 had 6 speeds. GSX750F katana had 6 speeds in 88 I believe but I'm no expert on those. The GSX750E from 83 on had only 5 speeds. The 1100 had 5 speeds up to 97.
So are you thinking Katana perhaps?
I have never been good at guessing games.
- Suzukidave
- Moto GP
- Posts: 3980
- Joined: Fri Oct 24, 2008 5:55 pm
- Country: US
- Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
- Location: Lancaster Pa.
There is a post on Smokeriders from Gary who races a GT750 and this is his comment on this as he has the GS tranny in his racer " I am running a GS input shaft and 1st gear in my GT. From memory the main problem is that the splines on the GS shaft are relatively further outboard (because the shaft is longer) and this would force the clutch hub outboard unless you put a 1/4" counterbore in the back of the hub and I wasn't too happy about loosing that much spline.
In the end I used a combination of a smaller counterbore and a spacer with 3mm taken off the threaded end of the shaft and it's been working fine in the vintage race bike for 3 or 4 years now.
In the end I used a combination of a smaller counterbore and a spacer with 3mm taken off the threaded end of the shaft and it's been working fine in the vintage race bike for 3 or 4 years now.
the older i get the faster i was
- Suzsmokeyallan
- Moto GP
- Posts: 4326
- Joined: Fri Oct 24, 2008 9:11 am
- Location: Mostly Barbados, sometimes Florida and western Canada
- Contact:
Richard i was thinking along the lines of the GS550 transmission if it was a six speed.
It could take the power of a STOCK GT750 quite easily, unless it was designed poorly, but Suzuki always overbuilt these things anyways.
It could take the power of a STOCK GT750 quite easily, unless it was designed poorly, but Suzuki always overbuilt these things anyways.
Two strokes, its just that simple.
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2
69 Suz U70
69 Suz T500
72 Suz GT750 cafe
74 Suz TS250
74 Suz GTXVR project
75 Suz RE5
75 Suz GT750
76 Suz TS400
76 Suz GT750
81 Suz GSX1100
86 Suz RG500x2
88 Hon CR500
93 Hon CBR900RR
98 Suz GSF1200x3
15 Kaw Ninja H2