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Author Topic: Got a free '78 GS 750! Gonna attempt a hardtail bobber (sort of..)  (Read 3547 times)

Offline villageidiott

  • Posts: 13
VonYinzer and Hilsy... thank you so much for the technical lesson. I am so glad I didn't chop the frame past the shock mounts when I was putting it in the back of the SUV!!

So I have been doing tons of research on other options. Brat-style, Cafe... they are both interesting but I think a Cafe style might be a bit more doable for my first build. I can still mess about and do some modding and playing around but can also keep from ending up in a ditch somewhere!

Something like these examples?


Offline hillsy

  • Posts: 2888
I think you should be first concentrating on getting your motor back together and just getting the bike functioning / running / on the road before you think about a style or other dress-ups.
 
That motor may well need a crank re-build if it's been sitting the best part of 20 years with the cylinders off, so that is going to empty your wallet real quick. Whilst the Suzuki roller bearing cranks are bulletproof in operation, they can get rust in the rollers a lot easier than plain bearings and this is their downfall if they are left sitting without oil - and you have to pretty much do ALL the bearings when you re-build these cranks (I spent over $3K re-building an 1100EF motor some years ago so I know how easily the costs can spiral).

Offline villageidiott

  • Posts: 13
So I am thinking about ordering some Bridgestone tires... but am I safe to order 130/90-18s for this bike?

As an aside, after some serious elbow grease... the rims have come out VERY clean. I imagined pitting etc. and there is virtually none.

Check out these pictures... ( i haven't polished the spokes yet)...


Offline Big Rich

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You need to find the rim width - it's normally stamped near the valve stem hole. Most likely, yours will say "2.15*18".........than a 120/90-18 is the largest tire you could fit.
Taking a break for a bit. So direct all pm's elsewhere please.

Offline villageidiott

  • Posts: 13
Well I hope not. The bike has only had the head off for about 2 years and I am hoping it doesn't need a bottom end rebuild. It was sitting in a dry shed and I will be opening it up with dad to take a look. Lord help me if the crank is in trouble.

I have the bike apart now which is why I am thinking about change. I will have to deal with the engine at some point regardless of what I do with the frame. I don't want to put it together just to take it apart again.

I first saw the GS when I was in my late teens. I absolutely hated the length of the bike. I was on a Yam RZ 350 at the time and couldn't believe my dad was driving this "limo" style bike. I have mellowed since then (now in my mid-30s) and have come to appreciate the older vintage bikes but i will never leave the bike as it was. It is an easy decision now esp as I have already chopped the frame just behind the shock mounts.

Today I used the grinder to remove the center stand mounts. The center stand was SO heavy. I also placed the tank and side covers on it to see if any inspiration came to me. Nothing yet!



Offline Big Rich

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  • Heaven is so far away.
I've left the centerstand mounts on every bike I own - it's easy to throw the stand back on for maintenance.
Taking a break for a bit. So direct all pm's elsewhere please.

Offline VonYinzer

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  • Oh, I got a helmet...
Don't bother ordering tires. You won't need them for a good while, so that's engine rebuild money tied up. As Hillsy said, build that motor first or at least determine if the motor can be rebuild in an economical fashion. Depending on the damage done from being improperly stored, you may be better off buying another motor all together. It happens all the time with half finished projects. Parts rust, pit, corrode...

That said, having a good idea of what you're trying achieve is also key. Find a "style" you want to shoot for and map out some sort of plan. You don't have to stick to it like a nun to the bible but try and stay focused. As a first time builder you're starting from the most difficult position possible. A pile of parts. With determination, money, a vision and a TON of focus you can achieve your goal but don't kid yourself into believing it will be easy.

As you stated, a "cafe" would be a somewhat simpler plan of attack. It requires minor frame modifications which is a plus. Use as many stock parts as possible, but make sure they'll function properly. Are your forks in good condition? What shape are your brake systems in? Is the fuel tank still safe and useable? Inspect all of your parts and determine what's worth using and what needs replaced.

Now...

You have a solid base to start with. Don't worry about paint colors, aesthetic modifications, etc just yet though. Put the bike together with what you have. Make it run, and run RIGHT. Make it safe. Make it perform as designed (or a close facsimile... haha). Now you can begin the modifications to form the custom motorcycle you're daydreaming about, but still... Have a plan and attempt to stick to it. At least tje basis of it. Remember though, this is the last set of steps.

Right off the bat you should be concerned with the things you can fix/upgrade to make your bike a better machine. Again, forget about the dreams of "cafe" stardom just yet. Some of the weak points on any of these vintage machines are suspension, and (depending on the model) electrical systems. I'll tell tough now that some of the best money to upgrade parts you'll buy are new rear shocks and fork internals. After that you should design a plan to upgrade the decades old wiring and electrical components. Technology has grown in leaps and bounds in both regards and you're doing yourself a major disservice if you don't take advantage of the latest available in both instances. That said, you're also not building a Moto GP bike. You don't need $1000 shocks and USD forks. Read, investigate and spend money wisely.

Now, back to the motor. You're machine is an expensive paperweight without a properly functioning lump. Yours in particular is a mess. Sorry, but thems the breaks. Not to say it can't be rebuilt, but there will be a lot of cash spent in this area for sure. This is where you need to really think long and hard about your true and honest plan. Do you juat want an functioning and dependable motor, or a fire breathing GSXR killer (if only in your own mind ;) )? No matter your decision, do it right. Don't cut corners and understand your limitations. Building a motor, especially a DOHC I4 can be daunting. Sometimes it's cheaper and simply easier to pay someone who knows what they're doing to make things right. The choice is yours obviously, and I'll never try to convince anyone to shy away from such a challenging endeavour, but again; know your limitations. And to beat a dead horse, having a solid plan of attack is fundamental to a successful engine build. Know what you want, how to achieve it, what parts/tools/knowledge is necessary and stay on course.

Anything can be accomplished in your situation, but you need to be honest with yourself and your abilities. Remember that safety, functionality, performance, and style should always come in that order. Most importantly perhaps though, remember that this is not your job. This is fun. This is a release and an exercise in learning and skill building. Let it stay all of those things and you'll love every second.
That shit's bananas.

Offline villageidiott

  • Posts: 13
Wow, thank you all for the ideas and advice.

I think then, here is my short-term game plan,

1. my little bro is bringing the sandblaster over tomorrow evening. The tank is fine as far as I can tell. No leaks, cracks, dents and the cap seals well. I can sandblast the frame as is b/c it will cost me nothing to do and I have done some of this work before. Blast the swing and the frame, the tank and some of the smaller metal parts. I know I won't need them for a while, but as I haven't decided for sure what to do with the frame yet, it won't hurt to have it cleaned up and waiting. My workshop is dry so no worries about rust.

2. as per your great advice, I will take stock of the condition and availability of as many parts as I can ID. this will include a good inspection of the engine. dad is a first-class mechanic and has rebuilt dozens of engines, he will be frank and honest with me I am sure. he wants to teach me how to do all this which is great and is all part of the reason i took on such a large project.

3. i will keep researching and reading build threads and looking at pictures. until yesterday i was sure i was going to duplicate most of what can be seen in that first set of pictures. now i realize that would have been foolish. i have to get a clearer picture of what i want. (at this point i think i would like something like the cafe style seen in the pictures above... the cb750 with yellow and black motif)

Thanks again for all the advice, please keep it coming. I am completely determined to see this project through. I just have to find time... too many court cases to read!!)

Matt (the villageidiott)

Offline villageidiott

  • Posts: 13
Hey guys, can anyone tell me where to go to get some excellent shocks for the rear of the bike? I would like to get something an inch lower, as I would like to also lower the front end about an inch.

Any help would be greatly appreciated. Not only has tech changed a lot since 1978 but my shocks are pretty pitted and in need of some cosmetic help.

Thanks.

Offline Big Rich

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Do a Google search for Hagon shocks. Their basic models are around $200, and could probably help you out if you contact them.
Taking a break for a bit. So direct all pm's elsewhere please.

Offline hillsy

  • Posts: 2888
You need to get the bike somewhere near running before you think about suspension IMO.
 
And for the record, lowering a bike has more handling repercussions than lowering a Civic.

Offline villageidiott

  • Posts: 13
Ya, I drive a Jetta TDI... hate Civics, lowered cars, loud car exhaust and loud car woofers. But I like the look of a lowered Cafe Racer. Speaking of which... I think I ought to see about getting this thread moved over to the Cafe Racer section/forum as I think it doesn't belong here anymore. Does anyone know how to get that done?

I am not looking to decrease the performance of my bike, and if that is the definite result I will not lower it, but lowering both the front end and the rear shouldn't do much to alter the geometry of the bike, should it? I am going to do my homework anyway, as the idea appeals to me. I do wonder about the issue of exhaust clearance and peg height.

As for not needing suspension work or new tires. I very respectfully disagree with the idea that I don't need to worry about these things. I am no pro of course and I have a great deal to learn and am willing to do so but it seems to me that a rolling chassis is indeed something to get working on. Worse case scenario, I have been led to understand that I can find another engine (either a 750 or 850) and bolt it in if need be. I would really rather not do that but I will if I need to. I have already found another '78 750 engine running for a couple hundred owned by a friend of mine.

My goal with this project to learn how just about everything works on a bike. I want to understand the way a bike is built, as much of the principled science as I am capable of comprehending, and I want to have fun. This is a project that can extend to several years if need be. So I really want to use this engine and rebuild it (keeping in mind that it may be an expensive project) in which case I may simply find another.

I have set for myself a pretty strict budget of $2000 dollars (plus a max of 10% if absolutely necessary). I paid nothing for the bike so I think will make a very cheap vehicle. I am aware that at least some of the electronics will need to be replaced, and am planning on a top-end rebuilt in the very least. I may be dreaming with that figure but its a goal nonetheless.

I have in the last week or so determined that the crank is not rusted and ruined, the engine freely moves, the front and rear calipers are not seized (as they looked to be when I first saw them!), and unfortunately that the front suspension is almost definitely going to need to be replaced as the 'shafts' (wrong term?) are really pitted. Not sure what to do about that yet.

I will post some pics this week. I am going to sand blast the tank and likely the frame as well. I have to decide what to do with the rear seat etc this week as well. I have sort of settled on something akin to the look of the picture I have included here. Of course, that is a different company, etc but its just something to look at and think about.

I do really appreciate any comments and advice... I have a great deal to learn but my goal is to keep at it until this box of parts is running and on the road.

Matt.

Offline Big Rich

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Good on you for taking it that way. We as a group just want you to build a safe and reliable bike first. Performance upgrades and aesthetics can always come later.

Speaking of performance - a GS850 motor won't bolt in and run. They are shaft drive bikes. I think you are thinking about the 850 top end though, which "should" bolt on (I haven't looked into it personally though). And there were some variations to the 750 motor I think in the later years. But they should be obvious upon inspection.
Taking a break for a bit. So direct all pm's elsewhere please.

Offline hillsy

  • Posts: 2888
Buy your friends 750 motor and slot it in (BTW - 850's are shaft drive, so they won't work). That way you will be lightyears closer to having a running bike for less $$$. Then you can re-build the original motor over the next few years if you wish / as funds allow.
 
I didn't say you "don't need" new shocks or tyres. I said there's little point in spending $$$ on this stuff if you are left with a box full of engine parts and no running bike. Cart before the horse and all that.....
 
You want to learn about bikes? Re-build this one to stock specs and THEN modifying it gradually into what you want. At least then you have a baseline of how the bike should function as opposed to starting off with a modified base that won't give you any point of reference to modify against.

Offline JordanCFH

  • Posts: 49
I was in the same boat you are Matt (minus the box of parts) my bike only had carb problems,which like hillsy and von said get the bike running first before doing any modding. I personally have had some experience working on this kinda stuff( helped rebuild my old mans Harley and the odd metal work / car engine rebuilds as a kid) but im no where near the pool of knowledge these guys are.

 I would suggest getting the manual for this bike to help yourself figure out the bike while its still a pile of parts. Always be the one doing the work as i find that having the knowledge of your dad ( i do the same thing) explain and show you how you gotta do things. when you do it you will remember it much easier and have a better grasp on it.

I'm looking forward to seeing the progress on your build, and yes please be safe, if your not sure don't do it. this will save you money and most importantly keep your heart beating.