Help w/ Suzuki '72 GT750J 4LS Hub

[sandersg]

I'm working on a cafe project based on an '82 Heritage Special. I found a complete '72 GT750J hub in pretty good condition for cheap locally. First thing I noticed is that the hub appears to wider than my stock forks.

1. What's the easiest fix for the fork width. I will need more than 6 inches clear between the forks.

2. I don't plan on using the Heritage wheels. The hub like a standard 36-spoke pattern. Should I antcipate any problems lacing this to a stock 19 inch standard 36 spoke rim?

Thanks

 

[5twins]

You will probably need a drum brake front rim because the spoke holes are angled different than the disc front rim. You can ream the spoke holes and correct the spoke angle on the disc rim if need be. I've never done it but it's supposed to be pretty easy.

 

[sandersg]

You will probably need a drum brake front rim because the spoke holes are angled different than the disc front rim. You can ream the spoke holes and correct the spoke angle on the disc rim if need be. I've never done it but it's supposed to be pretty easy.

Thanks - the GT750J hub came with a 19 inch steel rim, but it's somewhat pitted and seems to have an unusual "bump" on the inner side in one spot. Doesn't seem to be due to impact. Looks almost like it was made this way, but never seen this before.

Any thoughts on the fork width??

 

[bbillington]

Thanks - the GT750J hub came with a 19 inch steel rim, but it's somewhat pitted and seems to have an unusual "bump" on the inner side in one spot. Doesn't seem to be due to impact. Looks almost like it was made this way, but never seen this before.

Any thoughts on the fork width??

Find a tree that is spaced correctly for the width you need.

 

[sandersg]

Update:
The concensus seems to be that it's pretty easy to remove material from the gt750j 4ls drum hub to fit the xs650 fork width. I'm assuming the axle will need some mods too. I've found NOS set of Suzuki rims and plan to lace the Suzuki 4ls drum hub to the 19 inch hub up front and lace the Suzuki 18 inch rear rim to my xs650 rear drum. Have ordered the spokes from Buchanan's and they say "no problem."
Will report back soon.

 

[prmurat]

You could make google search with Norton 4ls Suzuki and see what's done... I have one in the garage but I am waiting for a friend to lighten it, it's heavy as a dead monkey. He will make holes and turn down the inside but I will need thicker brake shoes. From stock they are not really good. My pal has one a Triumph but he had to work a lot to make it acceptable. Eons ago I had a GT750 and remember a lack of progressiveness (locked the front wheel and crashed) and quick fading.... But it looks good (and was still used on japan only single some years ago).
I have a Grimeca on my Egli... And ready to put a pair of discs!!!
Philippe

 

[sandersg]

You could make google search with Norton 4ls Suzuki and see what's done... I have one in the garage but I am waiting for a friend to lighten it, it's heavy as a dead monkey. He will make holes and turn down the inside but I will need thicker brake shoes. From stock they are not really good. My pal has one a Triumph but he had to work a lot to make it acceptable. Eons ago I had a GT750 and remember a lack of progressiveness (locked the front wheel and crashed) and quick fading.... But it looks good (and was still used on japan only single some years ago).
I have a Grimeca on my Egli... And ready to put a pair of discs!!!
Philippe

Update - I did respoke the 4LS hub to a NOS Suzuki GT750 drum rim. Rear XS650 hub has also been respoked to a new rim. Getting ready to go back to the shop to have the 4ls hub modified for the XS forks. If anyone out there has actual experience with this, I'd like to hear from them.

Also, I was wondering if it would make sense to swith the forks from side to side, leaving the disc brake mounts in the front to use one disc mount for a stay to the 4LS drum. Any thoughts on this? Seems this would allow for a shorter stay and looks like the alignment would be OK.

 

[sandersg]

You could make google search with Norton 4ls Suzuki and see what's done... I have one in the garage but I am waiting for a friend to lighten it, it's heavy as a dead monkey. He will make holes and turn down the inside but I will need thicker brake shoes. From stock they are not really good. My pal has one a Triumph but he had to work a lot to make it acceptable. Eons ago I had a GT750 and remember a lack of progressiveness (locked the front wheel and crashed) and quick fading.... But it looks good (and was still used on japan only single some years ago).
I have a Grimeca on my Egli... And ready to put a pair of discs!!!
Philippe

FYI - I'm moving along with the project. I was hoping for some "coaching" from folks who had adapted the GT750 4LS hub, but no luck. I figured out that the easiest fix for the axle is to have it machined to the same diameter as the GT750 axle. This is ~17mm to ~15mm. The XS650 axle body had a larger diameter than the threaded end, so the threaded are not affected. This way I have only to put a spacer in the non-clamping end of the lower forks to make up for now smaller diameter, narrow the GT750 outers and fabricate stays. Should have it done in another week or so.

 

[sandersg]

Interesting that I found much discussion about the '72 Suzuki GT750 4LS front brake hub on the XS650 forum, but didn't find any "how to" discussion. So, for others:
- I considered swapping the triple trees or changing the front forks for a slightly wider front fork to accomodate the GT750 4LS front hub. But, it all got too complicated. Plus I had purchased a fork brace that would not work with the wider triple tree/fork.
- The front hub side plates were narrowed by ~1/8" or ~3mm each side plate from the outside raised face. Make sure to measure yours and do the math.
- Easiest solution was to have the stock XS650 front axle turned to ~15 to fit the GT750 hub/bearings. There is enough material on the body of the stock axle that it can be turned down without inpacting the threads. So, the stock axle nut can be be used. A spacer is require inside the non-clamped end of the fork to make up for the 2mm that has been removed.
- My stock XS650 forks have mounting tabs for disk brake calipers on the rear of the lower forks on both sides. Techncially, I think they could be left on the lower forks. But leaving them clutters up the look. So, I'm removing them.
- The stock GT750 brake stay is a little short to position the side plate properly (vent forward) from the front fender mount to the hub. I plan to fabricate a new brake stay that will look like the stock GT750 stay, but will connect to both fender mounting holes.

That's pretty much it. It all makes sense when you do it. But, would have been useful if I had found someone who had already been through it.