1979 GS750 starting woes... a Newbie's tale...

[StevieD]

Strong battery, good carbs, apparently gas is not the problem, but no start. It will turn over without a problem, but I'm not able to get it to start.

Won't even cough.

I know this is very little information to start, but I have very little experience. I have a rudimentary understanding of things mechanical, but I'm feeling a bit overwhelmed.

Here's what I know:

- The bike sat for about a year and a half, in an insulated garage. When I got it home, it started difficutly but it started. I noticed that only two pipes got warm at first (Cyl 1 & 2... 3 & 4 were ice cold) and the RPM wouldn't go above 4000 with the throttle wide open. There was gas in the right two cylinders, but no spark. I should say not consistent spark, because if I let it run and kept it running, I would be able to get more than 4000 RPM and #3 & 4 warmed up... once.

- A friend took the bike, checked the very basics: plugs, points, quick exam of the carbs (Which I know I'll catch flak here for, but he swears the carbs are ok.) Again, the issue appeared to be no spark. He switched coils and looked at the timing mechanism, but didn't adjust it since we had no service manual. At the end of that process, the bike WAS firing on all four and was running quite well. I took the bike home and it ran just fine for 3 days. Then I worked for two (13 hour shifts... gah.) and came home to hop on the bike before it got dark and nothing I could do would get it to kick.

- Brand new battery, tests at 12 v fully charged.

- I don't have a compression gauge, but my friend tested the compression and said it was good. I don't have actual numbers, but I expect I can get them or duplicate the test if needs be.

- I have basic tool set now (thanks to all for the answers to my "What's in your Garage thread.). I also bought a multimeter, but am trying to find out exactly how and where I need to check. Again, I understand basics, but am very new at this. (How hard is that to admit for a man? That's like asking for directions AFTER admitting your lost! :P)

So I am sure there are a hundred follow up questions I need to be asking, and I will do what I can to answer them from knowledge or get the answers if you all can help me troubleshoot this.

Thanks!

[ryonker]

The first thing most of us will tell you is;

Take off the carbs and get them surgically clean! Replace all the o-rings. Replace the o-rings on the intake manifold.

Adjust your valves. There are GREAT tutorials on Basscliffs website for all of this.

What is the condition of your airbox?

It sounds like your issue could be the points. I have a basically the same bike. New points well adjust made a huge difference!

The key here is to take your time and go through all the basic maintanence. Then you will have a base line to work from.

Good Luck!

Rick

[mighty13d]

well did you pull the plugs after trying to get it to fire? If you turn it over for a little bit, screw out the plugs and see if they are wet or not. Wet=gas but no spark. Dry=no gas.

You can see if you're getting spark by unscrewing the plugs but leaving them plugged into the boots and against the side of the motor. turn it over and check to see if they spark or not. (do this in the shade if possible to help seeing spark and to NOT hold the plug while turning the engine over. If you do, let us know so I can get a little chuckle)

Those are the most basic things you can do that literally only take a couple min with the least effort and least bit of know-how.

[StevieD]

Thanks to both of you for your quick responses!

The first thing most of us will tell you is;

Take off the carbs and get them surgically clean! Replace all the o-rings. Replace the o-rings on the intake manifold.

Adjust your valves. There are GREAT tutorials on Basscliffs website for all of this.

What is the condition of your airbox?

It sounds like your issue could be the points. I have a basically the same bike. New points well adjust made a huge difference!

The key here is to take your time and go through all the basic maintanence. Then you will have a base line to work from.

Good Luck!

Rick

Feeling a bit like the prodigal son... I know... I know. I will clean the carbs. Scout's honor. The airbox doesn't seem to be in too bad of shape. Slightly oily, but the filter looks mostly clean. Anyone have anything for me to compare to? Most filters I'm used to seeing are not the 'wet' type.

I thought points may be the issue to. They don't appear to be too pitted or otherwise scarred, but changing them was on my 'this could be the main issue' list.

well did you pull the plugs after trying to get it to fire? If you turn it over for a little bit, screw out the plugs and see if they are wet or not. Wet=gas but no spark. Dry=no gas.

You can see if you're getting spark by unscrewing the plugs but leaving them plugged into the boots and against the side of the motor. turn it over and check to see if they spark or not. (do this in the shade if possible to help seeing spark and to NOT hold the plug while turning the engine over. If you do, let us know so I can get a little chuckle)

If it will get my bike to run, I'll hang on to the plugs and send pictures! But I do know better'n that normally. Like Venkman says in Ghostbusters... "Important safety tip, I'll keep that in mind!"

Those are the most basic things you can do that literally only take a couple min with the least effort and least bit of know-how.

I pulled, cleaned and ensured the proper gap on the plugs. They had a fair amount of carbon build, but with the experience I DO have with cars, they didn't seem too bad. They cleaned up easy. Replaced them, turned it over, and pulled to check for gas. Definately wet, definately gas, and no sign of oil. Checked for spark on all four with no spark present at all.

[mighty13d]

there ya go! that really helps narrow it down now. Getting it at least running is key. then it may not run perfectly without a proper carb rebuild but at least it will run. then adjusting valves are going to happen, and so on and so on! lol Just get it running now and then worry about getting it running perfectly after!

You're going to have to get some readings on the electrical system now. someone will be around soon to give you what you need to be checking for and where.

[BassCliff]

Greetings and Salutations!!

Hi Mr. StevieD,

I don't recall giving you a proper welcome. So let me do that right now. Pay particular attention to the "Top 10 Common Issues". Let me roll out the welcome mat...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[StevieD]

You're going to have to get some readings on the electrical system now. someone will be around soon to give you what you need to be checking for and where.

Anyone around who can help with this? What and where should I start checking?

[BassCliff]

Hi,

Have you had a chance to download a manual for my site? There are troubleshooting procedures in there. Check the voltage at the coils. For checking the charging system, go through the Stator Papers. Keep us informed.

Thank you for your induglence,

BassCliff

[greg78gs750]

The first thing most of us will tell you is;

Take off the carbs and get them surgically clean! Replace all the o-rings. Replace the o-rings on the intake manifold.

Adjust your valves. There are GREAT tutorials on Basscliffs website for all of this.

What is the condition of your airbox?

It sounds like your issue could be the points. I have a basically the same bike. New points well adjust made a huge difference!

The key here is to take your time and go through all the basic maintanence. Then you will have a base line to work from.

Good Luck!

Rick

i agree with this one. follow the carb cleanup series per cliff's site, and get those valves in spec. it should be done anyway, and will eliminate 2 common problems....and it is really pretty easy, too. and it may just fix everything.....if it still is a no go, then, you can dive into the pandora's box of an electrical system....

greg

[Steve]

Not starting when cold is a classic symptom of mis-adjusted valves. Basic information is in any of the service manuals, BassCliff has a nice tutorial on 8-valve adjustment and I can offer you one more tool for your arsenal. Send me an E-MAIL with a request for my spreadsheet. I have developed an Excel spreadsheet that will help you a bit with your valve adjustment. It does the math to help you figure out what shims you need, and will also help keep track of what shims you have in there from one adjustment to the next. Just click on my name for info on my E-MAIL address.

With properly adjusted valves and clean carbuetors, you almost won't have to push the button to start the bike.
All you will have to do is think about starting it and it will be running.

.

[StevieD]

I appreciate all the advice given thus far.

I am looking forward to diving in and getting my bike running. I think I'll actually enjoy getting into it and getting my hands dirty.

The only question I have, and please understand I pretend not to know more than any of you who have owned a GS for any amount of time, but I'm curious as to why many suggest that I clean carbs, adjust valves, et al before I am able to get a spark from even one of the plugs? I am not trying to second guess but rather trying to understand. Yeah, I'm a rookie, yeah I get told I ask too many questions a lot too.

Thanks again, folks.

[etravis2]

The carbs are the usual problem for this bike. Don't overlook any electrical connections though. Make sure all connections are solid and not corrodied. Make sure to set the carbs by the link. You can then diagnose by electrical after that. Remember, even a small spark can ignite a fuel mixture that is correct.

[TheCafeKid]

well did you pull the plugs after trying to get it to fire? If you turn it over for a little bit, screw out the plugs and see if they are wet or not. Wet=gas but no spark. Dry=no gas.

You can see if you're getting spark by unscrewing the plugs but leaving them plugged into the boots and against the side of the motor. turn it over and check to see if they spark or not. (do this in the shade if possible to help seeing spark and to NOT hold the plug while turning the engine over. If you do, let us know so I can get a little chuckle)

Those are the most basic things you can do that literally only take a couple min with the least effort and least bit of know-how.

Actually, its not QUITE that simple. Wet with gas doenst necessarily mean there is no spark. It could also mean the cylinder is suffocating on gas, as in you're way too rich, or you dont have your air screws open enough. Ignition point of the air/fuel ratio is a relatively small window. And, to the original poster: while the plugs may look passable for a car, do not underestimate how delicate the balance of a smaller air cooled fairly low compression 8valve GS motor is. Hell, ANY carbureted bike for that matter. In a car, your vaccuum pull is going to be MUCH higher than on that bike, and as such, the motor will tollerate a greater imbalance of the air/fuel mix. Motorcycles are not so forgiving. You say you have cleaned them properly, so I will go with that. if you're not getting spark, then you have problems elsewhere. The voltage at the coils should be checked, and do yourself a favor, and ditch the old points and condensor ignition and go with a Dyna S. For bout 120 bucks, its set it once and never fool with it again. Points are a PITA that have way too many potential enemies. Yeah, the GSs had a fairly modern P&C set up, but they're still crap. The one bonus here is that SINCE you have a P&C set up, you DONT have an ignitor, one of those little peices on some of the more modern GSs that can make you pull your hair out and empty your wallet when they take a crap after 30 years. At any rate, check the coil connections, assure that they are clean, check the voltage at the battery, and check the voltage at the coils. SHould be AT LEAST 11.5V at the coils or you're having an issue.

[TheCafeKid]

I appreciate all the advice given thus far.

I am looking forward to diving in and getting my bike running. I think I'll actually enjoy getting into it and getting my hands dirty.

The only question I have, and please understand I pretend not to know more than any of you who have owned a GS for any amount of time, but I'm curious as to why many suggest that I clean carbs, adjust valves, et al before I am able to get a spark from even one of the plugs? I am not trying to second guess but rather trying to understand. Yeah, I'm a rookie, yeah I get told I ask too many questions a lot too.

Thanks again, folks.

Because all of these things go hand in hand. If youre valves are out of adjustment, they arent closing as soon, or as tightly as they should. If they're WAY out, they NEVER close. This effects vaccum. Vaccum is what the engine creates in order to pull fuel thru the carbs. If you arent getting the vaccum you need, you arent getting the fuel you need. If youre not getting the fuel you need, the bike is not going to run right. You can fiddle with the carbs untill your eye are red, but unless the valves are in spec, you're chasing your tail. Now, once the motor is running, it needs to idle and run respectably in order to generate the required voltage to charge the battery, which feeds the coils, which fires the plugs, which ignites the gas in the house that Jack built. There are FOUR key things required to run a motor: Fuel, Fire, Air and Vaccum. When things are right, they all live in a happy harmony. When one has a greater influence than the others, things can get ugly real fast. Think of it as the The Partridge Family vs say...oh I dunno, The Manson Family...heh. To much Fire and Air, and not enough Fuel, the burn is super hot, the heat cannot be disipated fast enough in an air cooled motor, and important parts, such as valves, piston heads, and rings start to suffer. To much Fuel and not enough Air, and the burn is cold, the Fire isnt hot enough to burn all the fuel and unburnt fuel builds up in the form of carbon on your piston heads and valves. WAY to much fuel and the excess ends up in your crank case, washing vital oil from more essential and expensive parts, creating a headache even Excedrin wont cure. Vaccum, while most would consider a secondary part of the process, to me, is just as important as the other three, because if you dont have good vaccum, you're not drawing fuel properly. Now, even if your air/fuel ratio is SPOT on, if you're having ignition problems, you may not be getting ENOUGH fire to ignite the mix properly....anyway, ive praddled on long enough, but you can see that, especially in a motorcycle motor, that the combination of the components and their delicate balance is a fine line to tread. But, once you get it right, with simple regular maintainence, its not difficult to keep up, and you'll have a fine running machine that SHOULDNT give you problems for many many years. These mills are pretty durable, and while EVENTUALLY, you'll have to replace big money parts, its not uncommon for a well maintained GS to rattle off 100,000 miles with out batting a headlight. Why, Ive got one with 140K miles on it sitting at my house. I didnt put them all on there, but i took it from its previous, caring owner, without a second thought.

[ryonker]

Golden Words

Wow, TCK!

Well said. I have always know what you said is true, but you articulated it very well in the last two posts! Especially that actually reasoning behind why EVERYONE should jump in and get those valves done.

StevieD, get Steves excellant excel sheet on valves and go for it. Doing the valves is easy and kind of fun.

Just remember, remove and replace only one valve shim at a time. Once I didn't do this !

Rick