Weasel's 1978 GS750 cafe racer project

[Chuck78]

Chris' GS1100E package would be correct for your bike, but contacting him for a request on a 330mm or 340mm shock would be best.
At 200 lbs rider + 500 lb bike with full tank, jacket, helmet, etc, you really will want to consider 1.0kg/mm Sonic Springs from Rich Desmond here on the GS forums or his Sonic Suspension /Springs website.

Stock length rear shock and fork will ride fine but steering will not be terribly sporty, but as a result will be very stable at hi g speeds. Tight quick turns will not feel easy however, much more effort will be required.
A 10-20mm raise in rear or drop in front will REALLY pep up the steering response. 25-30mm is pushing it with a stiffer rear shock (rear won't sag as much, stays pretty steep on the rake especially with weak factory springs, but 15-25 mm taller is the best range to shoot for.

The best you'll get out of the factory fork springs is .83kg/mm. I'm running this, not too soft, but a very smooth compliant ride, but at 155 lbs and 483lb bike, I find it could be stiffer still for better handling yet still be far from harsh. I'd go for .90kg/mm or .95 kg/mm myself for my bike and rider weight. 1.0kg/mm is a pretty definite YES based on what info you've given.
If you use the stockers, use a lot of preload. Set up static sag as best as you can. Top out the suspension, measure front ride height. Then with proper spacers to set static sag, with all of your weight on the bike and balancing it, the suspension should compress from topped out down to 1/2 inch for a very sporty ride or up to 1 inch for a more comfortable ride. 3/4" is a good bet.
it really helps to have an assistant to help measure this, or use the zip tie method of loosely placing a zip tie just taught around the fork leg at the dust boot, sit on the bike, the zip tie will slide up to the limit of the travel, do not bounce the bike at all, gently put all your weight on it and then gently get off. then you need to measure the difference as you lift up on the handlebars and take all of the weight off of the front of the bike to top out the suspension.

[Chuck78]

EDIT - memory failed me, I just unbolted one off the 78 GS750 parts bike, & it is 325mm long. My Fox Factory Shox specifically made for the GS1000 are 335mm - as they must've realized the benefit on a race bike to decrease the rake & trail slightly through a longer rear shock.


So I would say a 340mm would be the best bet if they come 320/330/340. If 325/335/345, it'd be a toss up between 335mm & 345mm depending on what you want to do with the bike, riding style wise. If lots of long trips, , 335. If solo seat or sporty handling is what I suspect you want, 345mm. +25 mm max. Steering will be very quick at that, and needs upgraded fork springs and cartridge emulators. No drop in fork height if running +25mm, you would get all sorts of speed wobbles and maybe tank slappers without a steering damper/stabilizer.
350mm in a rebuilt/revised RFY is pushing it because they just throw some long extenders on those shocks and keep everything from the lower perch & up universal. Too long of extenders is bad, too much leverage against the threaded joint on Chinese quality alloys and thread cutting tolerances.

AllBalls steering stem tapered bearing conversion is a must if quickening the steering with 20-25 mm longer shocks. As are great wheel bearings and fresh swingarm bearings and races. People neglect these (grease fitting on yours? My '77 750 arm has 1) all too often, and wonder why they get funny quirky handling problems. At least check em out and clean/blow out with solvent and compressed air a bunch, inspect the races, & re-pack. Yours is all torn down, right?

[Chuck78]

I would still consider a YSS E-302's as the #1 best entry level upgrade. Yes, the $210 Hagon/Progressive/YSS offerings are a big upgrade over stock and over the crap $100 generic "stiff spring holders" - but the E302 is probably the first best good upgrade to get drastically better than Chinese quality machine work, advanced emulsion shock dampening, excellent tech support and manufacturer support, and a fully rebuildable shock with full replacement parts availability. It is in an aluminum alloy body with steel cylinder I believe, with threaded preload collars as well. you can also get it in whatever length you want, and request springs specifically for your bike weight, rider plus gear weight, and riding style.

http://www.yssusa.com/series-eco.html

E-302 Twin — Gas Shock Absorber
Price: $349.00 per Pair
Available Lengths: 280 mm, 300 mm, 310 mm, 320 mm, 330 mm, 340 mm, 350 mm, 360 mm
Type: Self Adjusting Gas Emulsion Shock
Features: Pre-Load Adjustment — Fork Fittings for Honda, Suzuki and all Scooters — Eyelets and Springrates Model specific or customised —



The RFY stuff has not the greatest quality machine work, but will do. There have been reports of the clevis mounts breaking, so the quality is slightly suspect, but I believe the origins of that are mainly where people take the wider clevis mount and fail to shim it with proper washers, and then clamp it down on a narrower swing arm clevis type shock mount and bend the aluminum in, compromising it, and causing it to break in half while riding down the road somewhere far from home.

Chris Livengood knows these things better than anyone, & give them a proper assembly, basically doing a full rebuild on a brand new shock and replacing the top out springs with something shorter, to give this a shot closer to the proper amount of travel that we really need. With a name brand shock, you do get slightly longer travel than what the Chinese rfy shock will give you. Some will tell you this is quite critical. Chris' CL MotoTech versions will have proper oil, proper assembly, & longer travel. He has also tested the spring rates. the last I recall, it was basically a fairly soft spring for small bikes, and then a progressive rate spring that was moderate spring rate until 55% or 60% through the travel range, then bumps up to a very stiff 140 pounds per inch if I recall correctly. that is the one with the very tightly wound or rather closely spaced upper coils and then standard wider spacing on the rest.


The RFY is a more advanced design very similar to very high end shocks, but if the dampening is not set up as you need it, that may be all you get... copycat design of high end, yes. Engineered dampening stack researched & set up for a bike and rider needing the spring rate the shock is equipped with, hmmm...????
not trying to sway you from them, they will be a huge improvement over stock and will likely give you a very pleasing ride, but just trying to shed light on the downfalls of buying a generic Chinese copy of a good shock that has been gone through and improved upon by a motorcycle enthusiast tech wizard.

[Weasel]

Thanks again Chuck. You confirmed the same research I learned about Chris. I know I keep repeating it but I say again, I'm going for "good" upgrades when things need replaced over stock. But I'm not putting top of the line items on a pleasure bike that won't be worth very much. I'll never race this thing or honestly ride it very aggressively. The stock rear shocks are in poor condition and rather than replace with OEM, I'm willing to make a slight upgrade. By saving a hundred dollars here and there n upgrades, this build budget goes a long way. And I'm not trying to cut corners completely, but the reality is the bike will be worth $1500 whether I put $3000 or $5000 into it.

if I decide to go with Chris, do I want the 3, 7 or 10w oil?

[Chuck78]

Well I was going to mention that these may perhaps still be the best riding shock for they money by far after Chris is done upgrading them.

Here ya go:


Thats a darn fine price right there!
I added the spherical eye bearings because I'm pretty certain that the quality of the upper eyelet bushing rubber is such that in two years, the bushings will be disintegrating and cracking apart, and in three years, there will be nothing left of them.

I can't comment on the shock oil without knowing more about the valving of the shock. Only Chris would be able to really give you a good recommendation as far as I can tell.if you recommend those three options, the middle of the road is probably good,and he has probably done some testing to know that this is the proper range of shock fluids to use, but I would message him and tell him your bike weight and set up, and ridng style, then see what he suggests.

lastly, I would not buy any of those until you ask him what the approximate spring rates are or which springs he uses on the options you select, so that you can refer to his spring dyno chart linked elsewhere on his site. there aren't many options for springs, but I think that heavier spring will do good for you.
by the way, no matter what, you want that top out spring replacement, as it gives you longer travel. That is very critical.

If you're redoing the whole bike as it seems, and changing out the seat/tail or reupholstering it to look more racer-ish, redoing turn signals, etc, in a big city market like Pittsburgh, I bet you could easily fetch $2000-2400 out of your bike since you are making it look more racer-ish, upgraded, & mechanically restored. Springtime bike fever time and nice photos/finishing toughest on the bike and it'd sell really quick here.
Most vintage bikes people know will need a lot of typical repairs etc... marketing it as totally dismantled & gone through makes its real worth to interested smart buyers quite high.

[Chuck78]

he mentioned having a new spring rate calculator, might want to check with him on the current interpretation of spring rates, this is his old chart. The 8 millimeters spring looks too stiff for all but a 540 lb stock supebike and heavy rider. better to go on the soft side and add as much preload as possible, rather than have too harsh of a spring. Consult with Chris, but I thought that what we wanted for comfort and decent sport was around 110 pounds per inch, upwards of 115 - 130 in a straight rate spring for aggressive cornering. 110-115/140 in a progressive rate.

if you were to use the heavier 8 millimeter spring, it looks like I would try with basically the most minimal amount of preload just to keep the spring from bouncing around when topped out, not much at all. Consult Chris on rates and oil weights. He is a rad dude.

[Weasel]

Thanks Chuck. Ok so my $3-5K project will be worth 2K LOL But seriously, I could never sell it after all this work anyway. Even still, I have to honor my budget and be realistic for the pleasure bike goals I have.

[Chuck78]

Thanks Chuck. Ok so my $3-5K project will be worth 2K LOL But seriously, I could never sell it after all this work anyway.

Notice I did say "Easily sell...Really quickly"

I see guys here in Columbus selling similar GS's & CB's all modded out with more of an emphasis on form and cosmetics than high performance parts, and they are asking $3,500 to $4,700! The $4700 was a GS550 or GS750 just recently! if you make it your bike without any regards to what the current cafe racer or retro modded tracker Cafe brat whatever style look is, then it is your bike truly one of a kind, but not always marketable for resale to get out what you have in it. If you go with similar to the trends but done tastefully with your own touches, you can get a whole lot of money out of it if needed, & have a really great bike with your touches, & the reassurance that you have had your hand on every part of it and you know it inside and out and have faith in it. unlike unknown bikes from hack mechanics and cosmetic resto-modders. I was just saying it certainly wouldn't sell for any less than that.

I did end up with more than entire spare bike worth of parts, but honestly I probably have $4,500+ wrapped up in mine not including the VM29 smoothbore carbs that got stolen off of it. 920cc high performance head work all suspension and brakes upgraded substantially, wider alloy rims, the works. No rear sets or fork conversion, but may do a fork conversion still and resell my previous upgraded setup to cover the cost of the custom machined parts for the fork conversion.

the only things left on my bike that came on it are the frame and wiring harness and rear inner fender basically!!!! old seat was rusted up, tail section snapped a bold, had a spare of both, upgraded to gs650 dual disc forks then dented the gas tank and tweaked the triples and 1 fork tube colliding with a deer at 57 mph,built up an entire spare engine while I still had one in the bike, then swapped it, the list goes on and on. It's a sickness! I have so many spare GS parts now but I won't get rid of most of them!

[Chuck78]

Thanks...Even still, I have to honor my budget and be realistic for the pleasure bike goals I have.

well that leaves future upgrades still to be determined, you are just getting it built now, there's always room to make changes in the future to suit your needs or adjust what you are getting out of the bike if you decide some of your original choices need revised. best of luck, glad to have you on board the forum while you do your build.

[Zagg]

Hey man, just stoppin' by to say great progress!

[Weasel]

Fair enough Chuck.

Thanks Zagg. How's things going on yours?

Seat pan arrived today. I think the longer pan looks great with the stock tank. Not overly impressed with the quality, the plastic is a little thinner than I expected. I'll probably have to reinforce it underneath, which shouldn't be too hard.

My hope of not altering the frame won't happen now. At 29.5 inches long, this is the longest pan I have been able to find. The good news is it will only be a small alteration to the very ends of the frame beyond the support cross member.

[Chuck78]

Seat pan arrived today. I think the longer pan looks great with the stock tank. Not overly impressed with the quality, the plastic is a little thinner than I expected. I'll probably have to reinforce it underneath, which shouldn't be too hard.

My hope of not altering the frame won't happen now.
good news is it will only be a small alteration to the very ends of the frame beyond the support cross member.

Good looking seat pan for a GS appearance upgrade, I like the long look quite a lot. Just 'glass the underside a bunch to stiffen it after cleaning any mold release agents etc off of it, that'll reinforce it quite a lot.

I'd continue the gas tank striping around the bottom perimeter of the rear hump of that tail section!

Did it come with a matching seat pad pan to upholster??? Or do you have to do that from scratch?

Glad you won't have to chop much off the frame!

[Chuck78]

Wow didn't realize you were going for a full refinish-EVERYTHING job!

I think you mentioned you were getting the rims powder coated, but if you haven't yet and have some extra cash, I would absolutely consider upgrading rims to 1 size wider each in polished aluminum 18"ers. 120/90-18 & 100/90-18 make for a very nice suspension geometry and performance grip upgrade, plus the bonus of a more appropriate looking wider width fatter tire.

http://japan.webike.net/products/21724568.html

$423 rims $137 GS400 18" wheel spokes ( I believe our hubs are all same diameter so this should be the ticket). Free shipping to the USA if you spend over $430... a lot to spend but that's a great deal on the wider rim upgrade, especially for polished aluminum vintage shouldered style rims

Of course powder coating what you have is going to be much cheaper!

Keep up the great work man, bring it completed to AMA Vintage Motorcycle Days weekend, camp out at the racetrack if you can! July 8-10th 2016 I believe, 3.5 hours or so from Pittsburgh west if I recall.

On re-lacing, don't forget that the inside spoke and outsides both have a different end bend angle on them. And also make sure that you start the spokes at the right spot so that your valve stem ends up in a large easy access opening area in between spokes, and not trapped in the middle of a tight triangle where you can't get a pump hose on the valve stem. It's easiest to refer to a built wheel to make sure you get the right starting point.

[Weasel]

Yes, it did come with a separate seat pan for upholstering. I was wondering if glassing the bottom was an option, wasn't sure if it was compatible with the plastic pan.

Yeah the original plan was to clean up and/or refinish anything that is serviceable and to replace/upgrade the parts that are past service. I wish I had the budget for all your suggestions Chuck but I just don't. But do keep them coming for future reference! I found a powder coater with fair prices so I can re-use a lot of this stuff. He's doing the rims & hubs for $30 per wheel. I'll probably need new spokes as mine are pretty crusty.

[Weasel]

I'd continue the gas tank striping around the bottom perimeter of the rear hump of that tail section!

That's still the rattle can paint job that was on the bike when I got it. It will be professionally painted eventually. I'd like to do something like this except the red more burgundy (original color of bike)