First post! 78 GS750 - Some questions about carbs and the airbox.

[providedrailroad]

Hello! I purchased a 78 GS750 recently (last weekend) and the people I purchased it from had it running, but said it 'started cold' and they would normally start it and then let it run for 5-10 minutes before taking it out.

When I purchased it, it was running fine but they had already started it. I tested it around, it did fine on the highway, came back, purchased it, drove 2 hours home in 34 degree weather.

I've had some problems getting it to start at all at home though. I can hear the starter, it's turning over, sometimes I can hear it almost start and then die instantaneously. The other issue is, the kick start does not seem to build compression always.

I'm not sure if it's too rich or too lean - I've tried starting it with the choke on, half on, not on at all, with varying degrees of success. Most recently, I opened the airbox (both sides) and on one it seems like the rubber gasket was tightly sealed, but with one as soon as it was even half off the rubber fell off, and while mostly intact had a tear at the bottom.

I'm just not sure at this point - are the issues I'm having most likely with the carburetor, or with the airbox and filter? It seems like from what I've read the airboxes are not the most reliable part of these motorcycles, but then again, maybe the carb is just junked up? What should I look for in the airbox other than the seals?

Here is the seal that fell out:


I don't want to have to continually mess with the airbox down the road... Do you think pod filters is a good option, in a lot of ways I was planning on doing it any ways. I've never worked on a carb before, but I'm confident that as long as I'm careful I can clean it out and make adjustments (if they are needed).

What I really want to know here I guess, is just where is the best place to start as far as diagnosing and fixing this issue?

Where is a good place to get parts? and are there any stickied threads or recommended threads for information about similar issues?

Sorry for the super long post. I'm really excited about this bike and hope to hang around the forum a bunch and meet some interesting people!

-Wes

https://www.providedrailroad.com

[allojohn]

Wes, the bad news is if you want this machine to be reliable and fun you have a ton of reading to do then a ton of maintenance. The good news is you'll learn everything there is to know about your bike, it will be reliable and you will have lots of fun. It's your choice and you are in the right place to get all the help you'll need along the way. You need to start with the Bass cliff site and he'll be here shortly to tell you all about it. Good luck!

PS where the heck are you?

[providedrailroad]

Prairie du Chien, Wisconsin. Yes - I bought this for the most part to be a project, I want to know everything about my bike, the best way to learn is by fixing it I guess ha ha.

[TheCafeKid]

Don't go to pods until you have it running reliably in stock form. You need a good known baseline from which to make adjustments in jetting and moving the needle clip in the carbs. Without knowing where to start from you're just shooting in the dark and it will become a long,painful, frustrating process that may never have a good outcome.

To start with, you need to strip and clean the carbs, and install new orings in them. Yes it seems to be running, but probably not as well as it should, and with no prior experience with the bike, you may not even know it. There's a procedure in rebuilding/cleaning the carbs that must be adhered to to ensure they get done properly. BassCliff, who should post here any time now with your official welcome, will include a list of links that will lead you to tutorials that will give detailed instructions on doing a lot of the required maintenance on a 34 year old bike that has often been neglected for most of it's life. You'll need some supplies to do this, a can of Berrymans Carb and Parts cleaner (affectionately known as "dip") this isn't a spray can job, it's a gallon can that the bodies, jets, emulsion tubes and float bowls need to be soaked in for 24 hours each. This stuff will remove the years worth of deposits and gunk that collect in the tiny tiny passages of your carbs, and is an essential step in the process. Carb spray will not do it! You'll also need new orings from www.cycleorings.com. They're fairly cheap, come in labeled packages to inform you of what goes to what, and best of all they're supplied by one of our own.

Aside from cleaning your carbs, you'll need to ditch those now useless rubber gaskets on the end of your airbox and replace them with some simple sticky tape weather stripping. Works a treat and is cheap. You'll need to seal the air filter cage with the same stuff as well.

A valve adjustment would be the next really good step in the process. It's not hard, while at first it may seem a little daunting, once you get in there and understand how everything is put together and works, you'll be amazed how simple these engines really are to work on.

Oh, and behind the "boots" that your carbs go into on the motor side, there are, guess what, more orings! These are probably the most often neglected piece of consumable parts on a GS next to maybe those old nasty rubber brake lines that are supposed to be replaced every two years but never never are. These orings seal the intake boot to the engine head, and over years get flattened, crack and crumble to dust allowing your engine to suck air around the boot, leaning out the fuel mixture and creating a hot, sometimes very very hot, combustion in the cylinder which is bad news, especially if you've not adjusted those valve clearances. This can burn the valves and ruin them. Which as you can imagine is a lot more costly than some orings and some valve shims.
The good news is you can pick up those orings at the very same place you get your orings for the carbs...neat huh?

Anyway, you have some work ahead of you, but not only will you learn a great deal about maintaining your bike yourself, you'll save yourself a wad of money and know its getting done correctly vs taking it to a shop. And with the vast knowledge of the forum here, you should have her running tip top by spring

[providedrailroad]

" You'll need to seal the air filter cage with the same stuff as well. " The cage is a lot wider than the stripping that is around the edges - how do you seal this using the weather stripping? should I just put it across that opening, and let the stripping overlap?

I found BikeCliff's site - the air intake system repair section is very in detail and looks like something I can do without a lot of problems!!!

Now if only I could say I'm as comfortable about cleaning the carbs. Can I get that gallon of carb cleaner at O Reilly's? I live in a very small town and that is about all we have.

[providedrailroad]

You think I should go ahead and order the Carb O Ring kit when I get the O Rings for the intake, or should those not need to be replaced yet?

Where should I order the carb and intake boots from, does the same guy have them?

[Big T]

BassCliff has a list of online vendors

Reading thru his site will get you thru the rest of winter, then you'll be ready to hit those SW WI roads in the Driftless Area

Also, there'll be a couple of rallies right in your back yard, like Fennimore

[Redneck]

I would order the orings now. Let me give you a little advice about cleaning the carbs. Follow the guide on Basscliff's site, but also make sure that when you take apart your Carbs you keep them in the proper order. You will find out that if you don't you will have to unassemble and reassemble more than you want. You can read through my thread here and learn from my mistake before you start.

http://www.thegsresources.com/_forum/showthread.php?t=188428

Its short but guys posted some good information and pictures to go with them. Besides only one Carb body and parts will fit in the can at one time. I picked up my can of carb dip at NAPA. I used the NAPA brand.

O-rings for the air intakes may be able to get from MR.Cycle, but he did not carry the ones for my 550 not sure if yours are a different size or not.
You might want to get familiar with the parts fiche you can find on many of the parts sites. Such as cyclepartsnation.com:

http://www.cyclepartsnation.com/pages/OemParts?aribrand=SUZ#/Suzuki/GS750N_(1978)/AIR_CLEANER/02780009/5602780015

They use suzuki stock part numbers which some times can be used to gleen a lot of information from. Hope this helps.

Paul

[koolaid_kid]

" You'll need to seal the air filter cage with the same stuff as well. " The cage is a lot wider than the stripping that is around the edges - how do you seal this using the weather stripping? should I just put it across that opening, and let the stripping overlap?

You just need a good seal, width is not important. I used some double-sided foam tape from the local h/w store.

I found BikeCliff's site - the air intake system repair section is very in detail and looks like something I can do without a lot of problems!!!

Take your time, no shortcuts, follow it exactly, and you will be fine. Try shortcuts and you will suffer.

Now if only I could say I'm as comfortable about cleaning the carbs. Can I get that gallon of carb cleaner at O Reilly's? I live in a very small town and that is about all we have.

My AutoZone carries it, not sure why O'Reilly's would not carry it.

[providedrailroad]

GS specific rallies in Fennimore? What type of rally? Sorry, I'm only 21, this is my third bike, haven't been doing this super long.

Is it completely necessary I replace the actual Air Intake Boots and Airbox Boots, or just the O-Rings? The ones that connect between the carb and the engine is like $150, and since I'm going to go to pods after I get the airbox initially working I'm leery about buying the ones for the airbox since it will come off almost directly afterwards, you get me?

Thanks - I'll order the carb o rings when i get the other ones! You guys are great, I appreciate it.

-Wes

[cowboyup3371]

Most times, replacing the orings is all you'll need but replace the boots if they are torn or super hard. It will reduce the possibility of air leaks.

[providedrailroad]

I would order the orings now. Let me give you a little advice about cleaning the carbs. Follow the guide on Basscliff's site, but also make sure that when you take apart your Carbs you keep them in the proper order. You will find out that if you don't you will have to unassemble and reassemble more than you want. You can read through my thread here and learn from my mistake before you start.

http://www.thegsresources.com/_forum/showthread.php?t=188428

Its short but guys posted some good information and pictures to go with them. Besides only one Carb body and parts will fit in the can at one time. I picked up my can of carb dip at NAPA. I used the NAPA brand.

O-rings for the air intakes may be able to get from MR.Cycle, but he did not carry the ones for my 550 not sure if yours are a different size or not.
You might want to get familiar with the parts fiche you can find on many of the parts sites. Such as cyclepartsnation.com:

http://www.cyclepartsnation.com/pages/OemParts?aribrand=SUZ#/Suzuki/GS750N_(1978)/AIR_CLEANER/02780009/5602780015

They use suzuki stock part numbers which some times can be used to gleen a lot of information from. Hope this helps.

Paul

Thanks - when I take them apart I'll make sure to keep each carb labeled #1, #2, #3, and #4, unless someone already mixed them around which is entirely possible ha ha ha.

[allojohn]

unless someone already mixed them around which is entirely possible ha ha ha.

That's the correct attitude Wes, this bike is 30+ years and you must assume it's been messed with.

[Octain]

To add to the already great advise. While you waiting for your oring kit to come in I would remove the carbs and squirt each fastener(screws) with some PB Blaster about every 4 or 5 hours, for a day or so. Then when ya get the bowls off hit all the jets and anything else with threads with another dose or 2 of PB again for another day or so. May be a bit over kill but it's better to be safe than sorry.
Be real sure to use good fitting tools, very important. If ya booger up a jet or 3 you'll find that your life just got a little less fun.

I like to clean em one at a time. Disassemble the first one and put it in the dip. The next day remove the clean carb from the dip and spray all the little holes and such with carb cleaner and compressed air. (If you don't have a compressor the cans of compressed air that one might use to spray your keyboard works a treat. Can be had at the same Wallyworld where you'll get the berrymans carb dip). Wash it with hot soapy water and reassemble it. Take number 2 apart and do it all over again. If you get stumped while putting the first one together you can always use the next one as reference. By the time you get to number 4 you'll have it down pat!
I like to hit all the parts with some WD40, or the like while I'm putting em back together.


If the intake boots have never been removed you might be in for a little work. THe Phillips head screws that hold the intakes in place can be a real bear to remove. You'll need an impact driver and possibly an extension. Both can be had from most any parts house.
Patience is key. If ya get flustered take a break and read some on GSR.

[Big T]

GS specific rallies in Fennimore? What type of rally? Sorry, I'm only 21, this is my third bike, haven't been doing this super long.

Is it completely necessary I replace the actual Air Intake Boots and Airbox Boots, or just the O-Rings? The ones that connect between the carb and the engine is like $150, and since I'm going to go to pods after I get the airbox initially working I'm leery about buying the ones for the airbox since it will come off almost directly afterwards, you get me?

Thanks - I'll order the carb o rings when i get the other ones! You guys are great, I appreciate it.

-Wes

Just watch the GS Meetingplace for the rally. They show up, ride all over the place, eat, drink and tell lies. You know, guy stuff

If your boots are still soft, they should be Okay. Get the O rings that go against the head and some Allen head bolts to replace the ones holding the boots to the head