GS tranny in a GT750 box

Suzukidave · Post by **Suzukidave** » Mon Sep 28, 2009 5:49 am

Suzsmokeyallan wrote: the only thing left to do is to cross drill a hole for 1st gear in the shaft but its hardened so that may be a bit difficult with common tools.

Allan , there already is a oil feed hole for the 1st gear in the output shaft . The only oil feed hole missing on the GS shaft is for the clutch basket support bearing , maybe they felt with the upgraded needle bearing in the clutch basket a oil feed wasnt needed ?

Suzukidave · Post by **Suzukidave** » Mon Sep 28, 2009 4:06 pm

Ta Da .. one GS750 tranny in a GT750 case , now that was easy wasnt it

tz375 · Post by **tz375** » Mon Sep 28, 2009 7:02 pm

Dave, that's neat. I'll drop the shafts off tomorrow at the tool and die machine guy to modify.

Some of us are more equipment challenged than others. I'm sure that's what my ex was saying too

How long is that sprocket spacer/oil seal sleeve on the ouput shaft and what's the OD?

Post by **Suzsmokeyallan** » Mon Sep 28, 2009 7:22 pm

Dave you will be happy to know in my quest to gather up all and sundry in small parts for cad clear refinishing i dragged out the 73 motor i got from you and pulled off some of those small parts bolted to it to add to the plating pile.
While all of this was happening i took the g/box out and was looking at the design more closely.
Now ive got it on the floor im going to pull one of those two GS750 boxes i have and start looking at the ends and what upcoming lathe work i'll have to perform.
What did you do for the sloppy 1st gear bushing, did you swap it out for the one from the GT gear??

tz375 · Post by **tz375** » Mon Sep 28, 2009 8:12 pm

Allan, a lot of that slop typically comes from too much side play. I have a GT trans here with a sloppy fifth gear on teh input shaft. I had second pressed off and checked it out and the actual wear is negligible but second had not been pressed on far enough.

First gear on the output shaft is the largest diameter gear in the box and yet it rides on the tiniest diameter on the shaft - what an odd design. If yours is still loose after machining the shafts, try shimming it.

Or check the amount you need to machine off. Maybe less than 1.6mm would work better for your components. Just make sure that none of the dogs are too close to their respective gears. If there is any clicking, the dogs must be shortened to provide adequate clearance.

Two gears engaged at once can create significant pain and suffering to your bike, your body and your wallet. As with any modification, you proceed at your own risk.

Suzukidave · Post by **Suzukidave** » Mon Sep 28, 2009 8:54 pm

tz375 wrote:Dave,
How long is that sprocket spacer/oil seal sleeve on the ouput shaft and what's the OD?

Richard , the OD appears to be the same as the stock GT750 as it fits perfectly and it 18mm long .

Suzukidave · Post by **Suzukidave** » Mon Sep 28, 2009 9:01 pm

Suzsmokeyallan wrote:Dave
What did you do for the sloppy 1st gear bushing, did you swap it out for the one from the GT gear??

I picked the best gear from the 2 GS sets i had and like Richard posted once it was between the bearings in the case the slop in the gear is much less so i went with it . If i would have swapped it out with a GT gear it would have messed up the better GS ratio i was looking for .

Post by **Suzsmokeyallan** » Mon Sep 28, 2009 9:39 pm

No not change the gear,, change the bushing thats pressed into it to the one from the GT.

Suzukidave · Post by **Suzukidave** » Mon Sep 28, 2009 9:52 pm

No i didnt , but the small bearing on that end of the shaft slides off easy so its not too late to make a bearing swap on that gear .

diamondj · Post by **diamondj** » Mon Sep 28, 2009 10:12 pm

Dave,

Very neat! One thing I was wondering about is why you used the helical primary gear (from the GT?) instead of the straight cut primary that came on the GS? I know the straight cut gears were a popular swap for some of the GS1000 racers back in the day...

Jim

Suzukidave · Post by **Suzukidave** » Mon Sep 28, 2009 10:21 pm

I was a money thing Jim , to do this gear cluster swap only cost me about 30$ for the ebay gear set but to also add the GS primary gears would have run the bill way up as it requires the straight cut gear also on the crank .

Post by **Suzsmokeyallan** » Mon Sep 28, 2009 10:21 pm

You cant just swap out the helical gears as the other one is the main gear stub assy on the crank between the RH and middle cylinder. If someone made a straight cut crank gear assy it would be possible, expensive but possible.

diamondj · Post by **diamondj** » Mon Sep 28, 2009 10:45 pm

I guess the question I should really ask then is if anyone knows if the straight cut crank gear off the GS would work on the GT crank? The 750 cranks turn up on ebay often for not a lot of money although shipping is a killer:

http://cgi.ebay.com/ebaymotors/CRANK-SH ... ccessories

tz375 · Post by **tz375** » Mon Sep 28, 2009 11:21 pm

Jim,
The better solution is a TR style straight cut primary gear set which will also speed up the transmission and take some of the load off.

Suzukidave · Post by **Suzukidave** » Tue Sep 29, 2009 9:43 am

This GS tranny swap will help in several ways besides the ratio's and thats i can now use the current sprockets to use any of the 520 , 525 , 530 chain sizes and it spaces the sprocket out better to fit around wider rear tires and there will be no problems with the wider O and X ring chains dragging on the output shaft seal holder .