T8's 750 Cafe Racer Project

[T8erbug]

Lookin good man, somewhat jealous of those shocks. I was hoping you would not put any gussets in between the bottom of the seat and the bottom portion of the hoop but still looks slick either way.

I had to put the gussets there because they are what will be holding my upper shock mounts after I drill through them. I wish I didn't have to but they are also they key piece of strength to bracing the whole rear of the bike especially with shock mounts soon to be going through them. I think you'll like the finished product. I did a shock mock up today and they looked great although I'll have to place the upper shock mount a bit lower than I would have liked ideally (creating more ride height in the rear) but I think with rider sag it will work out perfect. Only time will tell!

[AX2007]

Will those Supermoto wheels hold up under the weight of the 750? The GS has to be 250lbs heavier than any dirtbike....

[Chuck78]

Lookin' good T8! I hope you get to ride that thing this season! That's why I've been doing mine one project at a time and trying to keep it on the road. Finally getting pretty darn close on the carb settings. I LOVE the way my bike rides, and the power it has with the GS850 pistons. I highly recommend you tear yours down and bore it out for Wiseco 10.25:1 844cc pistons, it will be a real blast... Do all the brake/suspension/wheel/frame stuff first by all means, and ride the thing a good bit!

I'm not sure how far along you are with the frame and having the engine mounted in it, but when I pull my engine to swap in GS850 cylinders bored to 920cc and do a valve job etc, I plan to do some bracing and welding on the frame with this info that I got from the defunct oldskoolsuzuki.info website.


A. these tubes support the headstock against torsional movement. The plates B. support the frame tubes to prevent them from bending due to the load created by tubes A. The cross-bars D. stiffen the area above the swingarm pivots. The tube connecting both sided is placed at the same height as the engine mounts to keep the engine in place under acceleration. If we replace the cross-bars with a pyramid D1. we add even more stiffness to that area and prevent the swingarm pivots from moving back and forth in addition to up and down. It may look a bit awkward and I question if it adds anything as you must not underestimate the strength and function of the rear subframe.
The connecting rectangular tubes E. help to distribute loads from the swingarm pivots to the rear of the frame, as well as providing a mounting point for the rear brake amongst other things. F. There's very little room to triangulate the space in front of the cylinders because of the exhaust pipes but it is possible. You may need to dent the tubes a little to make them clear the exhaust pipes but this is better than making the V smaller. Tightening the two center exhaust clamps will prove difficult too.
Now that the headstock and swingarm pivot areas are beefed up the connecting tubes are supported by plates C.
You should also consider making B. and C. box sections, so placing a plate on both sides of the tube with a strip in between to close the box. Or use rectangular box-sextion like I did (60x20)
Tubes only need to be around 16mm in diameter with a 1mm wall thickness. Box sections need to have 1mm wall thickness and single gussets 3mm.

By all means take note when removing the engine as to how much clearance you need to the frame overhead to remove it, and don't make those box tube braces hang too low! A good place to start is tack weld in the front F braces with the header and engine in place, and then fit up the top C braces and make sure when you pull the engine that you have them sized good enough for engine removal. Sorry to dump more work on you! Just do it my way, ride the thing with the mods in the works now, and then pull the engine later for a big bore kit and freshening and weld in some cromoly tubing to stiffen the thing in the proper areas!

I might as well start a new thread on here with the entire article from the oldskoolsuzuki.info site. I saved that whole webpage when I realized no one had posted on those forums for a year. site owner lost interest after too much spam infiltrating the board.

[T8erbug]

Will those Supermoto wheels hold up under the weight of the 750? The GS has to be 250lbs heavier than any dirtbike....

These wheels are engineered with over 35 years of technologic advancement.. Kinda like using an old corded phone vs. a smartphone. It's practically unfair haha. I could probably get a hold of actual technical data that shows proof for those in disbelief. BUT for the average fella who doesn't care much for the techy data the hubs are still built from aluminum just as the originals were but beefed up in key areas and lightened by cutting away material anywhere that didn't translate to strength, the spokes are about 1-1/2x thicker which I'm only assuming will translate to strength as well as add rigidity where it may have been lost by using an aluminum rim, the nipples are beefier to handle the bigger spokes, and the rim is shaped to translate a load more efficiently than the old steel rim. All in all they're a heck of a lot lighter and a heck of a lot stronger. I will get with a couple applications engineers and talk about it with them and see what they think just to be sure. But yeah realistically my hope is to have my bike come to the scales at anywhere from 400-425lbs which is about 170lbs more than next year's YZ450F. Not quite 250lbs more

[T8erbug]

Lookin' good T8! I hope you get to ride that thing this season! That's why I've been doing mine one project at a time and trying to keep it on the road. Finally getting pretty darn close on the carb settings. I LOVE the way my bike rides, and the power it has with the GS850 pistons. I highly recommend you tear yours down and bore it out for Wiseco 10.25:1 844cc pistons, it will be a real blast... Do all the brake/suspension/wheel/frame stuff first by all means, and ride the thing a good bit!

I'm not sure how far along you are with the frame and having the engine mounted in it, but when I pull my engine to swap in GS850 cylinders bored to 920cc and do a valve job etc, I plan to do some bracing and welding on the frame with this info that I got from the defunct oldskoolsuzuki.info website.


A. these tubes support the headstock against torsional movement. The plates B. support the frame tubes to prevent them from bending due to the load created by tubes A. The cross-bars D. stiffen the area above the swingarm pivots. The tube connecting both sided is placed at the same height as the engine mounts to keep the engine in place under acceleration. If we replace the cross-bars with a pyramid D1. we add even more stiffness to that area and prevent the swingarm pivots from moving back and forth in addition to up and down. It may look a bit awkward and I question if it adds anything as you must not underestimate the strength and function of the rear subframe.
The connecting rectangular tubes E. help to distribute loads from the swingarm pivots to the rear of the frame, as well as providing a mounting point for the rear brake amongst other things. F. There's very little room to triangulate the space in front of the cylinders because of the exhaust pipes but it is possible. You may need to dent the tubes a little to make them clear the exhaust pipes but this is better than making the V smaller. Tightening the two center exhaust clamps will prove difficult too.
Now that the headstock and swingarm pivot areas are beefed up the connecting tubes are supported by plates C.
You should also consider making B. and C. box sections, so placing a plate on both sides of the tube with a strip in between to close the box. Or use rectangular box-sextion like I did (60x20)
Tubes only need to be around 16mm in diameter with a 1mm wall thickness. Box sections need to have 1mm wall thickness and single gussets 3mm.

By all means take note when removing the engine as to how much clearance you need to the frame overhead to remove it, and don't make those box tube braces hang too low! A good place to start is tack weld in the front F braces with the header and engine in place, and then fit up the top C braces and make sure when you pull the engine that you have them sized good enough for engine removal. Sorry to dump more work on you! Just do it my way, ride the thing with the mods in the works now, and then pull the engine later for a big bore kit and freshening and weld in some cromoly tubing to stiffen the thing in the proper areas!

I might as well start a new thread on here with the entire article from the oldskoolsuzuki.info site. I saved that whole webpage when I realized no one had posted on those forums for a year. site owner lost interest after too much spam infiltrating the board.

I'm kind of partial to the modifying of a frame's rigidity. . I'll be honest, I'm just not smart enough at this point to even say whether it's a good idea or bad idea. I sell fasteners for a living at the moment and can honestly say even while being in an engineering program at school I did not know a bolt was designed to stretch or in other words have elasticity until going through training at work (I'm sure I'll learn this at some point in school haha). I had no idea how over-torquing a bolt could completely ruin it's strength properties and how easily over tightening one can actually be (90% of us do it every time we wrench on something).. Once a fastener is improperly tightened it reaches a point of no return where it is no longer the same. In a critical application it's as good as trash. That being said, I just have no idea all the work motorcycle engineers put into designing a motorcycle frame. They are made to flex under load in certain areas and transfer loads to others. I'd just be worried to over strengthen an area even by a little bit. The load has to go somewhere and it WILL find a weak spot. Who really knows? Shoot, I just need to hurry up and get my degree so I actually know stuff! I do know one thing though and that is that a motorcycle is a fine machine that is designed entirely upon the concept of balance. You can't change anything on a motorcycle without having it affect something else. The intricacies of a motorcycle never cease to amaze me. I guess that's why I love it. Always a challenge

[Fjbj40]

If you are interested in frame bracing, which I did to my 1000 then this is a good read. You will find out that the only, or recommended , bracing is C, D(in red) and E.

http://www.thegsresources.com/_forum/showthread.php?t=142286&highlight=%22Frame+bracing%22

[AX2007]

These wheels are engineered with over 35 years of technologic advancement.. Kinda like using an old corded phone vs. a smartphone. It's practically unfair haha. I could probably get a hold of actual technical data that shows proof for those in disbelief. BUT for the average fella who doesn't care much for the techy data the hubs are still built from aluminum just as the originals were but beefed up in key areas and lightened by cutting away material anywhere that didn't translate to strength, the spokes are about 1-1/2x thicker which I'm only assuming will translate to strength as well as add rigidity where it may have been lost by using an aluminum rim, the nipples are beefier to handle the bigger spokes, and the rim is shaped to translate a load more efficiently than the old steel rim. All in all they're a heck of a lot lighter and a heck of a lot stronger. I will get with a couple applications engineers and talk about it with them and see what they think just to be sure. But yeah realistically my hope is to have my bike come to the scales at anywhere from 400-425lbs which is about 170lbs more than next year's YZ450F. Not quite 250lbs more

I was thinking of my piggish 750 for the weight... But what you said makes sense. It looks bad ass though. I'm jealous.

[GregT]

I'm kind of partial to the modifying of a frame's rigidity. . I'll be honest, I'm just not smart enough at this point to even say whether it's a good idea or bad idea. I sell fasteners for a living at the moment and can honestly say even while being in an engineering program at school I did not know a bolt was designed to stretch or in other words have elasticity until going through training at work (I'm sure I'll learn this at some point in school haha). I had no idea how over-torquing a bolt could completely ruin it's strength properties and how easily over tightening one can actually be (90% of us do it every time we wrench on something).. Once a fastener is improperly tightened it reaches a point of no return where it is no longer the same. In a critical application it's as good as trash. That being said, I just have no idea all the work motorcycle engineers put into designing a motorcycle frame. They are made to flex under load in certain areas and transfer loads to others. I'd just be worried to over strengthen an area even by a little bit. The load has to go somewhere and it WILL find a weak spot. Who really knows? Shoot, I just need to hurry up and get my degree so I actually know stuff! I do know one thing though and that is that a motorcycle is a fine machine that is designed entirely upon the concept of balance. You can't change anything on a motorcycle without having it affect something else. The intricacies of a motorcycle never cease to amaze me. I guess that's why I love it. Always a challenge

Relax - given the frame you've got and the power you're looking to put through it, you don't need to brace it. there are two 750 race bikes being built local to me and i've said the same to them. They've seen the bracing put into our 1000 frame and neither of them are ever likely to approach the power levels or sheer agression of riding that it sees...
I'll state again my very personal dislike of wire wheels on heavy bikes. yes, i know just what you've used and it's good stuff - no problems likely IMO.
BUT - wheel stiffness is a major part of achieving good handling. The effects of a lack of stiffness however will only show in any significant way at the outer edge of the performance envelope....road use, just watch spoke tension.

[T8erbug]

Relax - given the frame you've got and the power you're looking to put through it, you don't need to brace it. there are two 750 race bikes being built local to me and i've said the same to them. They've seen the bracing put into our 1000 frame and neither of them are ever likely to approach the power levels or sheer agression of riding that it sees...
I'll state again my very personal dislike of wire wheels on heavy bikes. yes, i know just what you've used and it's good stuff - no problems likely IMO.
BUT - wheel stiffness is a major part of achieving good handling. The effects of a lack of stiffness however will only show in any significant way at the outer edge of the performance envelope....road use, just watch spoke tension.

Nothing helps someone to relax like someone telling them to do it haha. And I'm not sure you followed what I said correctly. I'm NOT bracing my frame. It was just a suggestion given to me by one of my good buds on here. Thanks for the info though! I'll be sure to keep my spokes tight

[T8erbug]

I was thinking of my piggish 750 for the weight... But what you said makes sense. It looks bad ass though. I'm jealous.

Thanks man!

[T8erbug]

Wiring. . . . .

I just pulled the motor out for the second-to-last time before powdercoating and as I sat there and looked at it with all it's wiring I realized it's been so long I have forgotten where just about every wire goes haha. I'm a little overwhelmed. Has anyone found those wiring diagrams useful? I tried finding one but cannot locate my year and model. If anyone has a link to a 79' gs750 wiring diagram I'd GREATLY appreciate it.

I'll be welding this weekend so if all goes well I'll have the shocks mounted up and she'll be standing on her own legs and feet for the first time since the tear down. I'm very very very excited. I'll also finish fabbing the rear tank mount. Once I can get the tank mounted in a stationary position I can finish the seat plug and start the fiberglass work. Lots to be done but the end is near!!

[Brodie]

What do you need? I have one for the N & EN and one for the LN.

EDIT:Here is one for the N & EN. The only difference I can see is the fuel gauge.

[Bevo]

Guys

Having spent some time on a heavy supermoto DR400 trail riding and jumping it, the wheels stayed tight and I had no failures.
If you factor in the force of a jump with a plus 300lb pound bike plus rider on the wheels it stands to reason it will hold up on the road.

Great build and machine work!

[T8erbug]

I got some work done on the bike this weekend. I was able to weld most everything and get things mocked up. I decided to TIG weld because I suck at MIG. I know MIG is supposed to be easier but I guess it's just because I learned to TIG first it's just easier for me. My welds aren't all stacked nickels but they look good enough and I got good penetration.

Here is the part I had Ben make up for me on the lathe. It is both upper shock mounts connected. I'll mock it up as a unit to ensure proper alignment, tac it up in place, weld it, then cut out the center of it once they're in their final places.


The gussets and the rearset brackets fully welded in place



Holes for upper shock mounts drilled


Shock mounts installed and ends with fully cut threads



Quick mock-up of the shocks


Getting close!!


Now I just need to finish TIGing the shock mounts in place and work out a couple minor fitment issues and she'll be on her way to getting all put back together!

[boontonmike]

Man, that upper shock mount is a beauty. Also a great idea since that will tie everything together solidly. Good work.