'78 GS750 Project

[MonkeyWrench]

Hello everyone,

I picked up this '78 GS750EC from $100.00 from a friends brother about a week ago. It had been sitting for about 2 years outside prior to be saving it. I have already dumped the old gas, cleaned and check gap on the plugs, added new fuel and got her started! Big win in my opinion. Now my issue is I've had it started 3 or 4 times only for about 2-3 minutes at a time. It seems to be putting out some white/grey smoke. I'm thinking it might need a valve job. I have a couple you tube clips up. Let me know what you think.

Part 1: First success start up after 2 years
https://youtu.be/PcYdVBpsVrc

Part 2: After spark plug cleaned and gaps checked
https://youtu.be/X5P61j1gdl0

 

[Guest]

Hard to tell could be just moisture in the exhaust. Do a compression and a leak down test. Go from there.

 

[moose]

Since it sat outside for so long there could be water contaminating the engine.Oil and filter should also be refreshed. Pay attention to the state of the oil as it will be pretty cruddy if water is present. Also be sure to check the air filter and the airbox for cleanliness. Could be some vermon holed up in there. There is a breather line to the airbox that vents from the cam cover. This line(hose) should be examined and the vent cover removed to get at the stainless mesh pack for a good clean as well. I would check those things as soon as possible. If it can't breath all the tlc in the world won't help.

 

[chuck hahn]

Heres what I think.

......its been setting for 2 years, so it may be a few things in combination. Rings a bit gunky and not moving well in the pistons grooves. And after that much time the valve stem seals may have let a little oil seep past and its burning off. Dont worry about it right now.
Do the valve adjustments, a full carb tear down and rebuild with all new orings and new orings in the intake manifolds as well.

Then run it like snot for a few weeks to get it through a bunch of fully heated and cooled cycles on the engine to shake things loose and clean the pipes out of any residual crap.

If it still smokes a little for a few minutes after a night in the garage but then dissipates the valve stem seals are for sure going south. If it still smoke constantly and never stops then it can be at least two things...valve stems seals are real bad and wont stop seepage at all or its time for a ring job.

Here are some invaluable links that will get the bike done quickly and right. On the cycleorings link youll find the intake orings on page 3. The kit does 1 full rack of carbs. you will NOT need any rebuild jet kits and all that urban myth crap. Berrymans dip the carbs for a full 24 hrs and rebuild them, bench sync, and put on the bike. gauge sync them once shes back up and running. And check the points condition and gaps per the manuals directions. Then check the timing as prescribed.

OH..replace the phillips heads that hold the intakes onto the head with allen head bolts. Life savers in the future..ask me how I know!!!
http://zeus.mtsac.edu/~cliff/storage/gs/GS750_Service_Manual_early8valve.pdf

http://members.dslextreme.com/users/bikecliff/images/vm_carb_rebuild.pdf

http://cycleorings.com/

 

[MonkeyWrench]

Thanks for the feedback guys. I had a small issue with some minor flooding in my basement over the weekend and didn't get to wrench on the bike much. However I do have a couple updates. I checked the oil condition and it didn't get any moister in it (as far as I can tell) viscosity is good, a little dark but not beyond anything I've dumped out of any other bike after a regular oil change. I've let the engine take a back seat for the moment while I get some parts ordered for the carbs and a gasket kit.

While I was waiting I decided to take a crack at the rear tire. It was a bear to turn and I mean BAD. I took the chain off earlier before I started the motor just in case it wasn't in neutral for some reason. Pull off the exhaust to get to the axel. Once I loosened up the left side tensioner the wheel spun freely. Only thing I can think of is over time the chain had not been adjusted and the axel wasn't aligned properly. Not that I have the whole rear end apart I have two questions:

1. Should I rebuild the caliper just to be safe??
2. Where to get new rotors?? I researched a while and found some replacements but they are pricey, $200+ a piece for them. The rear rotor is shot and needs replaced for sure due to metal on metal. I need to measure the front and see if they are salvageable.

 

[MonkeyWrench]

Since I can only post one picture at a time. I also removed the rear tail light, turn signals, and cowl.

 

[mikerophone]

Welcome MonkeyWrench, you're off to good start here. This site and it's members are a wealth of knowledge...read up, download the manual from BassCliff's site and ask the questions the search function doesn't solve for you.

I'm sure you can get a rear caliper from a member here in the parts wanted or parts for sale sections. Witttom and Posseux part out bikes like yours regularly and the 750 is a pretty common machine anyway. You may as well rebuild the calipers, I suppose they may just need some fresh fluid pumped through them so you could try several bleed and refill of the master cylinder cycles and see how it feels. Consider replacing with SS lines if you dig into them and/or they feel spongy. I think you have a good starting point for $100.

Does the oil smell like gas at all when you pull the fill cap and stick your nose up to it? If the petcock ever stuck on prime and/or the floats/needle seats stuck, you likely have gas in the crankcase. You'll want to change the oil soon enough anyway, just use Shell Rotella from Walmart, don't need fancy motorcycle oil for our bikes.

Do as Chuck says above and I bet you'll stop seeing the white smoke. Maybe some Marvel Mystery or light oil squirted down in the cylinders and rotated a few times by hand every few hours will free up the rings if they are sticking too. Oh and like Chuck says you don't need any parts for the carbs except the rings unless you strip a jet or feel grooves in your needle seats with your fingernail. The aftermarket kits are junk, and you only want Mikuni genuine jets if you bugger them up getting them out but they'll clean up nicely if not. The carb rebuild tutorial is your bible for this process. Get some good screwdrivers (note that the phillips on Suzuki's aren't phillips at all, they are JIS, and a phillips will do in a pinch, but can often strip or cam out) and replace all the screws with stainless steel hex head bolts on eBay or Dr. Bolts.com (Z1 Enterprises) once they come back online.

I'm guessing you'll probably pare the wiring harness down to a minimum, but make sure you do the quick charge test (search member posplayr out) and the revised stator tests too and clean all your electrical connections out with de-oxit and finish with dielectric grease. Go through and flow solder into your fuse box connections too if you intend to keep it. Get an AGM battery (I like the Chrome brand) unless you decide to go full Li-Ion and hide it under a humped tail section. Consider the single point ground scheme too, but at the very minimum, make sure your grounds are clean, tight and as short as possible. I'd also replace the R/R with a series type like the Polaris SH-775 and regardless of how good your tires look, I would replace them with some Shinko's before you do any real riding. They may have a date code on them.

Keep us posted and keep those pictures coming search youtube on how to use photobucket to post full size versions, and you can do more than one per post that way too.

 

[MonkeyWrench]

Thanks mikerophone, You packed a lot of good information into one post. I found a company by the name EBC Brakes that makes replacement rotors. With a little help from a local shop for the part number and eBay I was able to get a new right side rotor for under $100. I also got the part number for the front left side rotor as well. I'll get a set of pads this weekend and work on the caliper. Thanks again for all the help everyone!

 

[MonkeyWrench]

Looking at new brake lines. I'd like to go with braided lines. Anyone know where to get a set my 78 GS 750 E or do I have to get a kit and build them myself?

*I have dual calipers on the front. Is it possible to run two lines directly from the master cylinder instead of using a T connection.?

 

[8ball]

Looking at new brake lines. I'd like to go with braided lines. Anyone know where to get a set my 78 GS 750 E or do I have to get a kit and build them myself?

*I have dual calipers on the front. Is it possible to run two lines directly from the master cylinder instead of using a T connection.?

Yes. You can find brake line sources many places. You can order lines from some places in a custom length and choose the bends you need on the fittings. I got mine from this ebay seller:
http://www.ebay.com/itm/Custom-Suzu...929482?hash=item3ab8f15f4a:g:qW4AAOSwcOFWbOwx

If you have them custom made, you need to measure the length you need with the forks fully extended....and give yourself another inch, or so. Figure out what thread pitch you have... I don't recall if it is 1.0 coarse or 1.25 fine thread. You will need one double and two single banjo bolts

 

[MonkeyWrench]

Thanks 8Ball.

A couple updates. I decided to rebuild the calipers and master cylinders since I didn't spend much on the bike. I'm waiting on those rebuilt kits to be delivered but I did get the EBC right side rotor and it looks great. I didn't plan to replace the front rotors but I think I will now. I'll be ordering new brake lines (front and back) after the 1st of the year. I'm going to dig into the front brakes this weekend. She not much to look at yet so no new pictures. My office has started looking like a parts room with everything laid out on the floor.

On a side note one of the two rear bleed values was seized. I had to torch and cool it a few times to break it loose. Always have a propane/map torch if you're working on something old and rusty.

Happy Holidays all and be safe.

 

[mikerophone]

Always have a propane/map torch if you're working on something old and rusty.

Agreed - a little tip if you don't already know it too is to make your own soaking solution with a 50/50 mix of acetone and ATF. Don't use the fingernail polish grade acetone, get good hardware store in a can or lab grade acetone from a chemical supply. I mix it up and put it in an old spray bottle and use it to break seized bolts all the time. Soak, heat, soak, heat and tap a little with a screwdriver or chisel, soak again and they almost always break free. These bleeder bolts are notorious, as are some of the bottom case bolts since they are dissimilar metals subject to galvanic corrosion - steel bolts in aluminum threads.

Personally, I'd save the money you're going to spend on new rotors for something else, unless they are really warped or down to the minimum thickness tolerance. I'd just clean them up and paint the edges and centers if it were me. Many folks around here, myself included, riding around on 30+ year old rotors with 50k+ miles with no issues. You're going about the lines and calipers right, though. Those items, and even the master cylinder internals are the things to rebuild or replace in my opinion. With that said, it's your money, your safety and your peace of mind! :encouragement:

Happy Holidays to you and yours as well!

 

[Stahlgrau333]

Thanks 8Ball.

A couple updates. I decided to rebuild the calipers and master cylinders since I didn't spend much on the bike. I'm waiting on those rebuilt kits to be delivered but I did get the EBC right side rotor and it looks great. I didn't plan to replace the front rotors but I think I will now. I'll be ordering new brake lines (front and back) after the 1st of the year. I'm going to dig into the front brakes this weekend. She not much to look at yet so no new pictures. My office has started looking like a parts room with everything laid out on the floor.

On a side note one of the two rear bleed values was seized. I had to torch and cool it a few times to break it loose. Always have a propane/map torch if you're working on something old and rusty.

Happy Holidays all and be safe.

When you take the calipers apart, be sure to check the pistons for pitting. If you find any - and chances are, you will - they'll need to be replaced.

 

[MonkeyWrench]

Ok I always thought in the back of my head things were going TOO smooth. I got the rear caliper pucks out. They are in great shape so no need replace them. However. Once I got the rear master cylinder off I got found some bad news. It doesn't look like I'll be able to get mine apart to rebuild it due to the rust. I'm posting a picture of the damage.

If anyone has an idea of how to get mine apart let me know. Otherwise I'll be on the search for replacement.

 

[Guest]

Soak that piece in vinegar and it will eat off all of the rust. A little bit of heat from a propane torch and the acetone mixture mentioned above and you may be able to get it apart to salvage some pieces. It looks toasted though. Maybe put up a parts wanted add here.

 

[MonkeyWrench]

It has been a while since my last update on here. I've made some good progress on locating some of the parts I needed. I found a great guy on Ebay that was parting out a '79 GS750 that was in amazing condition. I bought the gas tank w/ petcock, original switches, aftermarket controls (clutch, break, and throttle), updated regulator rectifier, and rear master cylinder. ended up being a very good find and saved me a good chunk of money since we made a couple package deals for some of those parts.

Here are the things I still need to get. Any help or input on these would be appreciated.
Speedometer
Tachometer
Headlight
Tires - Front and Rear

 

[MonkeyWrench]

Did some work this weekend on the front end. Handlebars, controls, headlight, rear tire and related assembly have all been installed.
One thing I'm still fighting with is finding replacement bleeder and breather screws for the rear caliper. The old ones were pretty messed up already since I couldn't get a wrench on them. I had to use vice grips to get them out. I'd like to replace with a new set. Anyone know where to find those?

 

[MonkeyWrench]

I was able to track down the bleeder screws i need for the rear caliper on ebay. Spent the rest of the weekend replacing wheel bearings, front and back. Took some TCL to get the front ones out compared to the rear. Once that was all set I re-installed the wheels and other axle components. Rear caliper is on now, with a new full length brake line. Front brake lines are installed but not the calipers. I need to disassemble those and clean them up to see if they need rebuilt. I have new brake pads on the way. Once those get here I hope to have the front calipers ready install and bleed the breaks. It'll be nice to roll the bike around in the garage with breaks to stop.

Weather is getting warmer. I hope everyone is being safe out there, keep the rubber side down.