I.D. my bike & get a newbie started off right

[dardoonk]

Okay, I'm the proud owner of a 1977 GS750. This is my winter project that is obviously going to become a spring project. The good news, it runs & is all round, pretty solid & looks to be mostly stock. Since I am new to the forum, I will get my first stupid questions out of way.
1] What the heck version did I buy? I can't match it up to anything on the web. Single front disk brake & the high bars have thrown me off. The seat appears to be aftermarket, but is in real good shape.
2] I see references such as GS750 "C" or D or some other letter. What does the last letter stand for?
3] Where online can I find the orignal factory specs? Rake/ Trail/ HP /
4] I will be rebuilding the engine. What type of cylinder sleeves are factory? I guess I am assuming these motors have sleeves.
5] The fork tubes say they are air filled? Next to the triple tree on the right tube is a place to pressurize with air. What the heck is this? The other tube is capped (no nipple) but looks as though it can be installed.

I have a whole lot of questions, but I'll save a few.

 

[Guest]

I got this from suzukicycles.org. According to what I found, your model year there was just a GS750, no E,L,T,or S. Here are the stats they had listed.
By the way, nice bike. Ride safe.

GS 750 1977
Overall Length: 2 225 mm (87.6 in)
Overall Width: 855 mm (33.7 in)
Overall Height: 1 170 mm (46.0 in)
Ground Clearance: 150 mm (5.9 in)
Wheelbase: 1 490 mm (58.7 in)
Dry Weight: 223 kg (492 lbs)
Engine type: Air-cooled 748 cc inline-4, DOHC, 8 valves. 72 hp/ 8,500 rpm, 60 Nm/ 7,000 rpm.

 

[Commodus]

Last letter is sometimes a model code, in your case it would be a year code. Technically every Suzuki motorcycle has a year code, often people just don't mention it. For example, my 1982 Katana is technically a GSX750SZ. GSX for the family, 750 for displacement, S for model and Z for the 1982 model year. 1977 was B, so your bike is GS (family) 750 (obviously) B (model year code). No model cuz there was only one 1977 GS750. Well OK, technically there were probably market differences, but basically just one.

Nice bike, by the way.

Oh, and yes, the motor is sleeved. When did Suzuki start using coatings on four-strokes, I wonder...?

 

[dardoonk]

snark, thanks. So I bought a ba$t@rd bike? Hmm... Does the E, L, T or S from other model years. have any bearing on whether or not the parts will fit my bike? Parts interchangability may end up my biggest point of confusion.
​

 

[Guest]

You've got a good bike. Those letters are basically trim codes; cruiser, commuter, sport, or standard...your year just came in one trim, that's all. As for part interchange, it will really depend on the part. Seats and body work are where the biggest differences come in. The powertrain is mostly the same accross the model line...the main difference I've seen being in sprocket size and cable length)the handlebars on some models are different). From the looks of it, you shouldn't need much. Your local Suzuki dealer is a great reference point for these things...especially if they have been around long enough to sell that bike new.

 

[fgh]

Cylinder Sleeves

Cylinder Sleeves

As I understand there are no sleeves in most stock blocks. If you really want to replace the pistons then you'll pull the cylinders and have them measured. With that info you buy oversized pistons and get the cylinders honed to fit. You may be able to find pistons that can max out the available cylinders to boost displacement and hoursepower. If you're just looking for a reliable bike then its probably best to get a leak down test done on her. That will tell you if its in sound condition and will identify weather or not and leakage is at the pistons or either valve.

I don't know when they started but a long time ago manufacturers began to nickel plate cylinders. The nickle plating will prevent cylinder wear. As long as the PO's maintained her well you may have a block that is good to go for many miles.

 

[jonr]

Dardoonk,

You've got a real assemblage here.

1. You've got a 1977 GS750B. B stands for model year in this case. However, someone has put mag wheels and the step seat from a 1978(C) or 1979(N) "E" model. The letters in parentheses are for model year. The "E" means "chain & sport" model. EDIT: Only the B,C,N's had single disks up front; dual disks came on every EC and EN 750.

2. Answered in #1

3. I can give you the specs when I get home as I have the factory service manual. I'm not saying that all of it isn't online, but I know it's in the manual.

4. Already answered.

5. You've probably got replacement fork tubes on that bike. If you had a detail shot of the brake caliper, I could tell you. Air forks were not available on the 77,78 or 79 750's (79 750 L "cruiser" models used different forks/brakes, but did not have air forks). Sometimes if you had air forks, there would be a line that connected both forks to ensure equal pressure in both. There would be a single valve on that line to air them both up/down.

I've had my 78 GS750E for about 10 years now and know her well. They are fine machines!

-Jon

 

[rickt]

Interesting information

Interesting information

I was provided, free of charge, a 1978 GS750 a couple of months ago. The bike came from the original owner, has 2098 original miles, and was parked in 1981. It is box stock - no owner mods.

The bike has spoked wheels and a single disk on the front. The seat is flat - no step. The fork caps have air inlets, one on each side - no line connecting the two sides.

I've been calling this a '78 GS750C. Am I missing the target?

The PO lost the title and is in the process of getting a new one issued throught the DMV.

rickt

 

[jonr]

rickt,

You're right. You have the C model. I have the EC model (both 78). E's came with the mags, dual disks and stepped seat. I'll edit my post.

J

 

[rphillips]

Are you sure it's a "77" model? If you put your "77" model tank & tail section on a "78" or "79" 750"E" it would be just what you have here, air forks, dual disc brakes, mag wheels, & a stepped seat. By the way, yours isn't an original GS 750 seat, the 750 E seat had a step, but not as high of step as yours, and the cover isn't the right design. Your engine has steel sleeves that can be replaced or bored to a slightly larger size.

 

[dardoonk]

It is titled as a 77 & the vin matches, so I am sure I got the model year correct. I am sure the seat has been replaced because it is in significantly better condition than the rest of the bike. I suppose the mags are a plus. The spokes on my Triumph make for enough cleaning.

I do not have any connector to balance the air in the forks. Where would this be located at? Since only the right fork has an air nipple can I just install one in the left? The left fork has the Suzuki factory warning sticker on it, so I'm sure it is also an air fork.

When rebuilding the forks, are the internals similar to standard type forks? In other words, does the air required, or will they work ok without?

BTW: just to make things interesting, I learned today that the petcock does not cut off the fuel flow when turned off. I am out of town for three days and my wife called to let me know the bike had stunk up the entire house due to a fuel leak. I know she loves me since I got her to go out and give me her "expert" advice on what was wrong.

 

[rphillips]

I didn't remember the "77's had an off position on the petcock. I thought it would have pri, res, & on, it should be left in the "on" position.

 

[jonr]

Are you sure it's a "77" model? If you put your "77" model tank & tail section on a "78" or "79" 750"E" it would be just what you have here, air forks, dual disc brakes, mag wheels, & a stepped seat. By the way, yours isn't an original GS 750 seat, the 750 E seat had a step, but not as high of step as yours, and the cover isn't the right design. Your engine has steel sleeves that can be replaced or bored to a slightly larger size.

To reiterate rphillips, the E models always had dual disk brakes in the front. However, this one only has one disk and I have never come across one that had air forks either in person or on a parts fiche. Now, the 78-79 GS1000's had air forks, so it could be a swap since the calipers were the same for the 750.

Assuming your petcock is in the "ON" position, it is leaking either because the diaphragm or the oring that seats the diaphragm is shot. It's common for it to go out at 20-30 years old! If it's on PRI, it's dumping gas into the carbs 24-7. If it's leaking in the ON position, the get a K&L rebuild kit off of ebay or get a new petcock. Some on this forum will swear that rebuilding is not worth it because the kits are inferior. One of my rebuilds (78 GS750) needed some modifications while my other rebuild (GS1100G) was done in not time flat with no mods. The difference is $25 for a kit, and $50 for a new petcock. You decide...


-J