'77 GS750 Cafe Build

[GS750cafe]

Greetings everyone! I've been researching quite a bit on here and finally decided to post some pics of my build. I've owned motorcycles my whole life (mostly dirt bikes and sport bikes) but am a total noob when it comes to really wrenching on them.
Here's what I picked up several weeks ago as the start of my cafe racer build. Its a '77 GS750 with only 12,000 miles on it. It needs some work and few parts but I think it's a good foundation.

I replaced a leaky petcock, striped the signals and mirrors, put on some clubmans and pods, chopped the rearend and picked up an older Kerker 4-1 exhaust. Now I'm working on the tail/seat section and plan on using the original seat, pan and cowling. I've cut it down and plan on welding it back together. I'm also thinking of using the original foam and cutting that down too to fit the shortened pan. Anyone have any experience with this type of seat mod?

A couple questions I have: 1) I'm contemplating chopping the exhaust at the first elbow bend from the end and adding a baffle. What do you think? Will I get enough back pressure? 2) Now that I have eliminated the airbox, what should I do about the intake hose to the motor? 3) I rerouted the throttle and clutch cables when I installed the clubmans but there still seems to be an excess of cables packed behind the headlight. Any suggestions? Oh, and the little bracket on the front brake line... where does that attach?

Thanks everyone! I'll keep you posted as things develop...

 

[crazypj]

They look like original lines, get new ones (may as well get custom length stainless braided or aircraft Kevlar lines)
You probably need the exhaust that length to work properly, shorter will push power higher in rev range.
Getting back pressure isn't a problem the correct amount and tuned length is

 

[Makr]

Alright, another GS to join the fray.

 

[IndieSol]

Cool bike, man. I've got a bid on a '79 GS 750 on fleabay right now. I'm doing the same kind of seat pan mod on my Honda 360 right now, but I'm going into it green as well. Interested to see what you come up with.

 

[Swapmeet Louie]

Man... That thing is clean! would be nice to start off with something in such good shape. I say do what ever you want to the exhaust...

Google Apollo Cone. I'd copy there design. I don't think anything your going to do to the exhaust (with in reason) is going to effect performance +/- enough for you tell the difference. My only advice is, loud can be exciting,. but, only for a few days... then it gets fucking old.

Other than that, get crazy... exhaust makes a bike. And is one of my favorite parts of a project.

Louie

 

[Qckslvr]

Re: '77 GS750 Café Build

Nice looking build, your post is what prompted me to post my 78.

On the brake line bracket I carefully cut it off with a hack saw.

The GS will run with a straight pipe, but you will loose torque. I repacked my Kirker with some space age crap I got from PG & E (our local utility). The baffle ID is the same ID as the collector pipe, so you aren't loosing much restriction. It is still loud, and my neighbors know every morning when I leave for work. I think my neighbors are signing a petition to have me lynched now.

If you removed the air box you are going to need to rejet. My GS ran extremely lean when I removed the air box with the Kirker. On the VM carbs I went 2 turns out on the idle fuel screw, installed 115 mains, and used needles set to the highest clip from a GS1000. My bike runs pretty good now, and will even lift the wheel a little.

Another big improvement was I got rid of the 630 tractor chain, and put a 530 chain on it. I also dropped a tooth on the drive sprocket which gave the bike a nice off the line launch. Lot of rotating mass in that big 630.

Hope that helps, and look forward to more pics

 

[GS750cafe]

Hey Guys, thanks for the input! I'm still undecided on the exhaust. I really like the old Yoshimura exhausts that Carpy is replicating, but I can't find anything for a GS. I'm wondering if I can modify the Kerker to look something like that.

Qckslver- I say your build as well. Great to see another GS on here! This will be good to bounce ideas off each other. I know I'm going to need to rejet, but haven't commited to it yet. I've got time, there's snow on the ground and it's ski season! I'm not sure what to do though, because I live at 6000' and ride up to 9000', so the pods and Kerker pipe let 'er breath but then the altitude has to factor in to that too... what did you do with the breather tube for the motor? I've seen some guys put a little pod filter on that. That's good advice on the chain too. I was thinking of replacing that. So what are the teeth your running now? You say you've got a bit more bottom end, but can you still do the ton? That important too right? Cool, I'm gonna work on the bike this afternoon. I'll shoot some more pics.

Cheers!

 

[Qckslvr]

My breather is a $4 little K&N I got at Kragens zip tied to the upper frame. It works good.

as for the sprocket I can't say it any better than Z-1's conversion chart.
"630 chain is 3/4" pitch (or think of it as 6/8"), 530 chain is 5/8" pitch - so the simple conversion in teeth is divide the 630 sprocket teeth count by 5 and multiply by 6."

the stock rear is 41 teeth, so in a 530 that would be a 49
the stock front is 15 tooth, and in a 530 is 18, but I dropped to a 17 tooth.

the bike will do a buck forty, but from 120-140 it takes a little effort. But I am 6'2", 250 lb monkey on its back.

I want to change out my Kerker to something better as well, but like you said we are very limited to systems for our bikes.

 

[thralldad]

Awesome!! ANOTHER GS!!

 

[trackfiend]

Yes another Zuk! I recently tried to pick up a blue '78 for my next project after I finish my 450. Definitely will be watching to see how this turns out.

 

[Big R]

Awesome!! ANOTHER GS!!

These things are popping up a lot on here lately - was there some sort of system crash at GSResources or something?

Great bike to start with. And FYI, a slotted rotor from a later GS will bolt right on.

 

[GS750cafe]

That's good to know Rich. I was thinking of drilling these out, but if I don't have to, why would I? Now I just have to find some...

I think more and more of these GSs are popping up as cafe builds because CBs are in high demand. I looked for a while for a CB, but either the price was too high or they sold really fast. Picked this up for $600, which isn't bad considering the low mileage and how clean it is.

I did a bit more work last night on the subframe. I had previously chopped it and cut many of the tabs off that I wouldn't be using, but then my grinder died on me. I picked up another grinder from my Dad (Dads are great to borrow tools from!) and a few discs at the store and spent some time smoothing out the excess metal where the tabs where. I also pulled a tape on the subframe and cut it to equal lengths (previously I was just getting crazy with the sawzall - nothing was measured). While hacksawing one tube of the sub frame, I was surprised to see how much things flexed! It'll stiffen up when I weld a bracket on for the rear cowling. My plan is to use one of the existing hinges on the seat pan, and bolt the cowling to the subframe so that the seat can be raised with the key and the cowling stays on the frame (like the stock set up, just chopped).

Next I'd like to tackle the rearsets. There is a triangle of tubing that comes off the subframe that holds the passenger pegs, exhaust and the rider pegs. I'd like to get rid of this triangle to clean up the look, then weld on a bracket for the rearsets. I've been contemplating trying the budget rearsets, using the 3 piece clamps but question how rigid they are. Any experience out there with that set up? I know from riding sportbikes that rigid rearsets made a big difference in handling, but I doubt I'll be riding this bike like that. Also, I need to resolve my exhaust issues first before I go chopping anymore off the frame.

Overall I'm happy with how she's coming along. My idea with the bike is to build something functional yet have that garage built look. I really like the look of Miob's and Swapmeet Louie's bikes. If I was aiming, that's the aesthetic I'd be shooting for. (Please suggest other builds with a similar look.) Performance wise I want it to be solid, but I'm not prepared (time, space, experience) to strip it to the ground and build it back up polishing everything as I go. I don't have a bunch of money to dump into it, and even though it's winter, I don't have a huge excess of time... Originally my lady and I bought this bike together with the idea that we would "share it" She rides and has had a few sportbikes and a cruiser, but after tooling around the block a few times she said it felt a little big. So, for Christmas I have picked up a '73 CB350 for her. It's a surprise, so don't tell her! It was advertised as a CB, but after I picked it up and did a little research I've discovered its a CL350 with CB pipes on it. No biggie, but its not as clean as the GS. Now i'll have two projects going. I'll start another thread for that one after the holidays. Thanks for looking and keep the advice coming!
Cheers

 

[Qckslvr]

These things are popping up a lot on here lately - was there some sort of system crash at GSResources or something?

Great bike to start with. And FYI, a slotted rotor from a later GS will bolt right on.

GSR is a great place for the GS owners. But some of them would have kittens if they saw a nice GS cut up.


As for the rear sets I can understand saving money. But you might want to just buy em. Tarozzi and Raask both make make rear sets for our GS. But they are $250 - $350

 

[GS750cafe]

I've been browsing GSR forums, trying to learn a bit more about the bikes. So far folks have been really helpful. It's funny though, I wouldn't even think of owning a stock GS without modding it - there are so many other stock bikes out there that so much cooler! Just MO though.

I find it hard to cough up $300 for rearsets when the bike was only $600! I didn't have any problem paying that on Gixxer, but that was $6500 and fuel injected and topped out at 175 mph! I've looked at the universal rearsets (http://www.tcbroschoppers.com/store/index.php?main_page=product_info&cPath=9&products_id=14) and seem like they are an option. I've also been looking at the Dan Moto ones which look like they might do the trick. The Dan Moto SS exhaust looks kinda cool too!

Qckslvr, what's your plan for rearsets?

 

[RedRocket]

I was able to pick up some cbr f3 rear sets off ebay for $50 to put on my 82 gs650. i went for sport bike rear sets rather then universal ones just because they have the mounted rear brake master cylinder. Just have to weld on some mounting brackets and i'll be set.

 

[NoobZooki]

Out with the Honda CB and in with the Suzuki GS LOL! Just kidding.

Looks like a good start. Keep it up.

 

[boingk]

Lookin' good there, Red. I had a GS850 that I was cafeing but ended up selling it so I could get the GSX-1100. Kinda wish I didn't, now, but it did have a few problems. Other than that it was an awesome bike.

If you get really keen you can search for a GS850 engine and slot the barrels, pistons and camshafts over into your 750. That way you'll be rockin' 843cc and around 80hp, as the 850's has a GS1000 camshaft. Mine sure went like hell haha.

Anyway, cool build and keep us in the know.

Cheers - boingk

 

[GS750cafe]

I began working on modifying the exhaust yesterday. I had a 2003 gsx-r pipe laying around from my sportbike days and cut the mid pipe out of that.

To my surprise, there is some baffling inside of the mid pipe. Next I cut the older Kerker exhaust in half, just below the 4 - 1 joint. The point of no return!

Then I taped the mid pipe to the 4-1 for a mock up. It looks pretty good. I'll have work out the angle of the joint a bit to get it just right, but this is more what I'm shooting for. Also I'll have to decide if I need a muffler on it or if it'll run as is... Here's a pic on the bike.

I started the bike up to run some fuel stabilizer through the carbs. At first the mid pipe wasn't attached. After it ran for a bit I shut 'er off and then taped the mid pipe on and fired 'er up again. It was amazing how much the sound changed with just a 10" section of pipe taped on! It sounded great. I would attribute this to the baffling on the interior walls of the mid pipe. I'm not set up for welding yet, but hope to be soon. I'll have to figure out the angle of the joint and clearance for rearsets, then tack it on. I'll also need to decide of if the overall pipe length is enough or if I need to add a muffler. If not I'll need to finish the end of the pipe where it was cut. An end cap maybe? Any suggestions?
When I had the pipes off I took a little steel wool to the collars to remove some of the rust.

Before

After
The plan is to wrap the headers in black, so the pitted pipes would be so unsightly.
Thanks for looking! Happy Holidays!

 

[boingk]

Lookin' good there, and smart idea on using the old pipe... although you probably could have sold that for a reasonable amount.

An

end cap maybe? Any suggestions?

This can be as simple (flat plate with a hole) or as complex (multi-faceted inverse cone w/tapered exit & reamed edges) as you like, and its part of the fun of it all. I would recommend a half-sphere with a central hole, purely because I reckon it'd look neat, and I havent ever seen a setup like that before. It should also give you a reasonable exhaust note, decent volume (slightly quieter note), and be easy to manufacture and fit - all you need to do is find a half-sphere the same external diameter as your pipe and then weld it on and make a hole in it (dills & files). As I said before, though, its totally up to you.

Cheers - boingk

 

[GS750cafe]

Well it's been ages since I posted an update... summer was so busy that it seemed to slip away! Now that riding season is pretty gone for another six months, I'm hustling to get this thing on the road!


I dicked around with several rearset options. First I tried the 3 piece clamps and cheap Thai rearsets. I actually liked the look of the Thai rearsets and quality seemed reasonable, but I could't get the clamps, rearsets and MC ('03 gixxer off ebay) to work...

Finally I bought a pair of Vortex gsxr rearsets for $80 off ebay. And settled on welding some tabs to the frame. The welds aren't the prettiest, but I'm learning... I'm pretty happy with the result and the riding position.

Next I'll prime and paint the tabs, order some steel braided lines and hook up the rear brake. Are folks running a rear break light on their cafes?


I also chopped the stock seat pan and welded it up in it's shortened form. It's not pretty, but it'll be covered in foam and leather and will allow me to use the stock tail cowling and seat hinge.

While I had the welder out, I worked on the exhaust. I tacked the mid pipe to the headers, removed the exhaust and welded that up. It cam pretty good. Again, not the prettiest welds, but as you can see, I wrapped it up anyways.

I read a bit about the exhaust wrap and I'm curious how many folks seal it after it's wrapped? Seems like a good idea - that stuff is not cheap and wrapping a 4-1 is kind of a pain... would hate to have to do it again! I fired her up to smoke the wrap and she sounds great! Maybe a touch loud, but I still could fab up some sort of end cap and baffle.


The other thing I've done is rebuild the front forks with new seals and oil. I also swapped out the rotor for a newer slotted one. The rear will get swapped out too.


I've also drilled some speed holes in the sprocket cover, but don't have any pics of that yet. I'll get them up one of these days. I replaces the stock drivetrain with a 520 chain and sprockets. I've ordered new, low profile gauges but haven't decided what to do about signals and brake lights yet - thinking of not running signals at this time... I also ordered a shorter clutch cable and was going to do the same for the throttle but am having a hard time finding the dual throttle cable that's on this year GS. I hope to get the tail section wrapped up soon and get the rear cowling attached. I'll keep posting pics if there is interest.


Thanks for looking.


Cheers