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Thread: 1977 GS750B - my long awaited first bike!

  1. #1
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    Default 1977 GS750B - my long awaited first bike!

    I've been poking around on here for a few years for info on bikes I had been working on for friends, but finally I have my own to enjoy!

    I had been wanting a bike for 12 years since my two good buddies and I walked past a really great looking 1970's CB750 with slight chopper/bobber leanings (& a $1200 for sale sign!). We all instantly decided we needed bikes... Years went by, classic Camaros came and went through my garage, my body decided that wrenching on things with engines and riding road bicycles was much less of a health risk than a decade of freestyle BMX bicycling. Still wanting a motorcycle, but three houses that I totally remodeled while living in got in the way... an old Royal Enfield 750cc Interceptor (sort of Cafe Racer style but built 25 yrs ago like this) in the back of a pickup truck with a for sale in about 2005 for $1000 almost hooked me in, but I never saw the guy again to buy it! Milled over it for months!

    When I met my now wife (6 weeks married!) 3 years ago, she and a bunch of my BMX and punk rocker buddies all had mostly old Japanese bikes, and she had just traded her Honda SilverWing that was too tall for her for a 77 GS550B that was a total basketcase! Luckily my bicycle and car mechanic skills (and advice from my former motocross race team mechanic and car restoration enthusiast father) really helped win her heart over when I was the third person to clean and rebuild her carbs, and the only one to do it right and get the thing running like a real beast!
    Well, after 2-1/2 years of wrenching on her bike (and others) and bringing it back from being almost un-rideable, and our roommate (one of the CB750 admirer buddies from a decade before) getting a great deal on a 1982 Kawasaki KZ650CSR at AMA Vintage Days swap meet and races, I am now the proud owner of a really fast $725 1977 GS750 project! Lots of plans for it. Once I finish remodeling this giant 5000 sq ft 122 year old Victorian house this winter, I will be posting a (re)build thread of my bike! Been trying to ride it as much as possible before winter with just enough work to keep it safely on the road. More details to come. Hopefully by the time spring is just around the corner, I will have the house more complete and can dedicate lots of time to the bike! My 1962 GMC panel truck (like a Suburban but no side windows, delivery/work truck style) is still waiting to see it's full glory, but now has been delegated as a motorcycle and construction supplies hauler until I get to finish restoring that...

    I will hopefully be posting a few things here and there about my bike, but I wanted to give you all an official "hello" and introduction!

    Now I gotta find another bike for the third buddy of ours that was in awe over that CB750 over a decade ago! Looking for a nice GS850 for him! He actually had an 80's GS550 at one point, but looking for a bike now so that the three of us can all ride together finally! Also inspired another buddy to get a really great $850 78 GS550E project bike recently! Another friend happened upon a $400 GS650G that I almost bought, without knowing how into GS's we were! Very excited about these old bikes... Thanks for all the inspiration that I've gotten from this website and forums!
    Last edited by Chuck78; 10-02-2012 at 10:20 PM.

  2. #2
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    House, bike, and truck restorations along with a new wife?
    I'm tired just thinking about all work. lol.
    Good intro, Chuck.
    2@ \'78 GS1000

  3. #3
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    Here is is, as it arrived home in the back of my 1982 VW rabbit turbodiesel pickup!
    Last edited by Chuck78; 05-08-2013 at 12:18 AM.

  4. #4
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    The previous owner said he rode it less than 200 miles in 2 years, and he acquired it as a repayment of debt from a friend who lost his license to a DUI. He said his friend had the cylinders bored out and engine work done. Not in too bad of shape, good chrome on the wheels and not much rust! Wiring has been hacked at here and there, almost new looking rear tire is almost bald (I was surprised at the ability to do rolling burnouts from coasting about 5-7mph while rolling on the throttle pretty hard! - I keep hoping "my buddy had it bored out" means that it has a big bore 850cc kit in it!). Rear disc brake is also a little too powerful, which could also lead to the tire problem!

    The gear indicator and neutral light didn't work after PO replaced the original gauges that had cracked glass. low headlight burnt out. battery was shot. Kickstarts the first kick 9 out of 10 times, but idles pretty poorly until engine is warmed up (vacuum leaks or carbs just need cleaned and rebuilt).

    It has what I think is a MAC 4-into-1 exhaust. I liked duals far better, but I think I will stick with this setup for some time. One exhaust bolt is broken off in the cylinder head unfortunately, and the header's black paint has mostly burnt off and it's rusty, but I figure a sandblasting and some good quality BBQ paint or POR-20 exhaust paint will be far cheaper than new exhaust. I wanted an EMGO turnout muffler, as the MAC chambered baffle wasn't as loud as I cared, and sounded just like a slightly louder version of stock. Well, the baffle was stuck in there with no bolt, and I wasn't in a hurry to do much to it but ride, so I left it. Well, one day when I was cruising down my favorite stretch of road with no houses or intersections, I cranked the throttle really hard from 20mph and the baffle launched out of the muffler shell like a canon! I really loved the way the shorty megaphone shell and 4-1 header sounded completely open, but it was just far too loud (my ringing right ear after every ride told me so, as the original baffle was a bit mangled from the rocket launch and possibly getting bumped by some cars before I retrieved it. What to do?

  5. #5
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    Well, my eardrums (and probably neighbors!) motivated me to make my own glasspack, since I absolutely loved the great raspy deep tone of Reda's GS550B with EMGO Dunstall mufflers that I fitted onto the stock headers.

    I polished up the MAC shorty shell, and went to the local car parts store and purchased a 2-1/4"x2" o.d. exhaust reducer and a section of 2" pipe. I then proceeded to go crazy on the drill press for several hours, drilling approximately 250-400 holes, some of them twice as I wanted to enlarge them when I first tested the sound (not loud enough!).
    Last edited by Chuck78; 12-08-2012 at 08:11 PM.

  6. #6
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    I had found a spaghetti sauce can that was the exact size of the ID of my muffler. using that as a template, I cut ground a piece of stainless steel to the same diameter, welded it to the can bottom, and then proceeded to weld an inside rim around it. The can remains are still there, but will probably rust away from the rest of the metal as it was just there as a guide to help me form this piece. I puddled up the weld in one spot on the rim and then drilled and tapped it for a retaining bolt.
    Last edited by Chuck78; 12-08-2012 at 08:11 PM.

  7. #7
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    I ground out a slot several inches into the perforations, and put a flat piece of metal in the middle of the tube to block about 40% of the exhaust flow to force it through the perforations and into the outer chamber, and then back into the core, where it could then be dampened by the fiberglass insulation that I wrapped around the core and secured in place with a coat hanger bent around in a spiral with hooks on the ends securing it through the holes in the baffle.

    Last edited by Chuck78; 12-08-2012 at 08:12 PM.

  8. #8
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    I rode it with 9" of fiberglass, and I was amazed at HOW LOUD THAT IT WASN'T, for a shorty glasspack! Wow! that internal deflector really must have quieted it down a lot! So I took all the 'glass out. Still doesn't have that awesome aggressive raspy deep idle tone of the open exhaust, but under healthy acceleration, it sounds really awesome still, almost like the open exhaust but at an almost respectable (and not deafening) volume. Rode with Reda and Shawn (KZ650CSR) 160 miles with camping gear to a wedding, so I decided to try 7" of fiberglass. So much quiter, and really softened the tone substantially (more so softening than volume reduction). Not as loud as the 19" long EMGO Dunstall glasspacks on Reda's GS550 though. I think the amount of holes I drilled really helped reduce the volume. Less holes, smaller or no deflector, and 2-1/4" o.d. pipe all the way if I wanted it louder. Went down to 6" of 'glass after that, getting closer. Well, I ripped it out again the other night, sounds cool but of course probably too loud. maybe 4" or 5" of stainless steel wool might do it if I can track some down...

  9. #9
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    Thought I should throw in a photo of my homemade differential manometer! I was just going to use some cheap PVC fittings and some pegboard, but then I saw this scrap of aluminum diamond plate u-channel that I salvaged from work, a restaurant walk-in cooler wall support that was holding the bottom of the door frame together during shipping! took some 3/4" copper air conditioning fittings and some tubing, some 1/4" copper stubs, and fired up the acetylene torch to braze this thing together! drilled a buncha holes and used a lot of small zip ties to hold the tubing down. made my own carb adapters with some leftover main jets and o-rings from rebuilding Reda's carbs, and soldered the screwdriver slot end of the jets carefully into some 3/8" copper tubing. Filled with automatic transmission fluid to dampen vibrations and pulses from the engine breathing (the only thing I had to pay for!). The small holes in the #80 main jets used for this helped slow the response of the fluid as much as the thickness of the ATF.

    The only downfall of this is that the clear poly tubing, even with a furnace fan blowing on the front of the bike, got to be a sloppy fit quickly as the engine got to operating temps. some rubber hose for the first few feet, spliced by a stub of 3/8" copper tube will be my only revision. I used colored electrical tape at the top of the gauge and corresponding at the carb end of the tubing to help keep the cylinders in order.

    Last edited by Chuck78; 12-08-2012 at 08:13 PM.

  10. #10
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    By spring I hope to have some of those cool chrome mini-gauges with neutral brights turn and oil pressure indicator lights to replace the (imo) ugly plastic stock dashboard setup on the older GS's... I think the 2.25" or so mini gauges will add to the sleek look I am going for. I was always very envious of the Kawasaki KZ guages. They look like an aftermarket gauge, but stock! The GS I always thought looked big, bulky, and tacky.

    After the first 60 mile portion of the 160 mile weekend following speed demon wifey trying to beat the rain to the wedding, following her at 80-97+ mph made me really want to get lower than these slight riser bars, and I had considered clip-ons for a minute, but undecided... may leave as is. New grips and a pair of round mirrors are in order, has the goofy 80's rectangular mirror, left side only. Largely I don't like the Cafe Racer look, but some elements of the cafe & bobber/chopper stylings I do like. I absolutely despise the fiberglass trunk flat board single seat cafe look, and think the inverted bars and clip-ons that drop down real low look very silly and impractical. I like the raw, stripped down, sleek, all business looks... smaller flat seat, remove current trunk, round lights, no farings and maybe stock side covers or flat aluminum plate to replace side covers, cool looking minimal gauges, the beautiful air cooled finned big inline four, & hopefully a cool looking set of leather saddlebags &/or handlebar bag. Classic style doesn't get any better than all of this in my vision!

    I'd like to put in new fork seals and much stiffer shock oil, as it dives harder than I'd like under braking. Rear feels perfect as is. I had wanted a dual disc up front, but may hold off on that, don't really need to ride that aggressively anyways! May be nice, but extra weight and a lot of extra work finding parts!

    I would really like to get a GS1100 aluminum swing arm to swap on, but those are pricey and hard to find! toyed around with cutting off the muffler mount/pass. foot peg mounts from the frame AGAIN (PO's terrible re-weld job) and condensing them to much shorter dimensions to show off the aluminum swinger if I ever get one. Considered welding passenger footpeg mounts to the steel swing arm, but not sure how that'd fare with the passenger's knees bending with every bump. Well, I probably won't have a passenger usually since Reda has been riding motorcycles longer than I have!

    I really wanted the flat seat, spoked wheels, round lights, and finned air cooled engine look for the vintage style I was after, and this bike was the best shot I had at it. The high riser seats are so hideous, makes me think of old grandpa cruisers (old grandpas, please don't take offense!). The slight riser stock seat has some minor tears in it and is very bulky, so I got a custom made 77-79 GS550/750 etc seat cover with 1" of foam padding off of ebay for $30 and plan to remove the original cover and reshape the foam gently with a handheld 4" grinder, and maybe put a gel bicycle cruiser seat insert recessed in the foam for the driver's position. I considered cutting and welding hte seat pan to narrow it slightly in the back and lower it by cutting/moving the hinges, and trimming down the rubber bumpstops. Maybe too much work for now, so I'll probably stick with the reshape/gel insert/recover idea for the time being, and make it a much more compact seat for better looks.

    Over the winter, a carb rebuild and re-jet is DEFINITELY in order. new o-rings and gaskets, multiple dips and blown out with air compressor, cleaned with tiny guitar strings in the smallest passages... I think 102.5-110 were the stock Mikuni VM jet sizes through 77-79 on the GS750's, and with intake and exhaust mods, I'll probably be going to the 112.2-120 range and leaving the pilot jets stock for now. Reda's 550 has pods and 102.5's and is WAAAAYYY faster than stock now! Wow...

    Points look new-ish, but eventually I would like to upgrade to electronic ignition. I might get the PAMCO setup http://www.gsignition.com/ after Reda's 14 month old Dyna S 1-4 pickup crapped out on her... that was half of the misfiring at idle problems her bike had! People swear by Dyna for reliability, but I am skeptical after reading a few similar stories. looking back on it, low voltage (11.9v) supplied to the ignition may have played a part it it, as well as lots of heat sitting in rush hour traffic. The heat is why I thought of a different idea. I liked the loudGPZ Chevy Cavalier HEI module custom ignition build, so I thought I may get an 81 or so GS ignition pickup that worked with a factory ignition module, and install it on my bike and make my own loudGPZ setup with a heat sink, two Cavalier automotive HEI modules, plus the diodes etc in that design for about $60-70 or so I estimate in parts. Still up in the air, and the points work great for now.

    I will probably be de-rusting and repainting the MAC header for now and pulling two dents out of the bottom (from truck loading I assume). I may see if I can find some used headers somewhere though that are cleaner and have more ground clearance, as cutting and shortening the height of the MAC seems a bit much, as it doesn't hug the oil pan very tight. I doubt I'll be cornering that hard to where it would scrape, but you never know...

    I also just went through and found that my stator seems good but the diode test on my replacement regulator/rectifier failed, and this is probably the cause of my max of 12.7 volts @ 5000rpm+ with lights off! I snatched up a slightly used "series" style Shindengen SH775 35A r/r off of a parted out 2011 Polaris RZR 800 (ATV?), as the series style is new and state of the art, and does not let the stator constantly run insanely hot like 99.5% of regulator/rectifiers on bikes do (the shunt style that shorts the excess voltage to ground at 1000 cycles/second). The series style just simply shuts off the voltage at 1000 cycles/second to keep the stator from running at full load nonstop regardless of electrical load. Pretty genius concept, right? See the recent thread in the electrical/ignition forum for two others who already were on this tip when I read it up on it.

    I will be trying to replace Reda's with the same or at least a Shindengen MOSFET style regulator, as well as adding a waterproof relay from Parts Express to do the ignition coil relay mod to bypass the excess wiring and ignition switch and kill switch to get full power to the ignition. Some Bosch Iridium spark plugs may go in as well, but on a healthy carb/ignition setup, probably not necessary. Those help with low voltage problems for sure, however.
    Last edited by Chuck78; 10-02-2012 at 10:09 PM.

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