1981 GS650 GL won't fire

[Skaat]

Hello, All. OK, so I’m stuck. Possibly in over my head. Where to start… I am a complete newbie to all of this: Bikes, Engines, all of it. I have some mechanical aptitude, but never really got into fixing anything with a motor. So I decided last summer that I wanted a bike (call it a mid-life crisis if you like), but it had to be done on the cheap. I looked at it (and still do) as a great opportunity to learn about motors, electrical systems and the like.

So, with the help of my cousin (who IS knowledgeable in the area of bikes and mechanics) I found a CHEAP bike on craigslist and drove about 50 miles to buy it. It’s a 1981 GS650 GL. I bought it knowing that it wasn’t running, but optimistic that I could get it running with the help of my more experienced cousin.

So the P.O. told me that it ran the summer before (that would be summer of 2008), but that it didn’t run now & he couldn’t figure out why. In the process of trying to “figure out why” the P.O. had done some crazy electrical splicing (speaker wire!) and had apparently inadvertently wired some things (most notably the starter relay) incorrectly. So we started there. Got a new(er) relay, hooked it up the right way, bought/installed a new(er) wiring harness and got her to turn over, but not fire. Good compression. Good spark. Just no VROOM. I should note that the P.O. had also gotten “tired of the airbox getting in his way” and just got rid of it all together. So the next step we took was to do a quick and dirty carb cleaning. The carbs didn’t look all that bad, just a little varnish in the bowls. So after I “spit shined” the carbs and got all the airbox components and filter installed, we tried again. After MUCH encouragement she fired up on her own – twice… and then nothing. Winter set in and I decided to do a thorough carb cleaning this time, following the steps on this site. I tore them down completely, dipped them individually (for several hours each) replaced all the O-Rings, set the float heights to the right specs, and replaced the intake valve O-Rings.

When spring rolled around, I got out and eagerly put everything back together and… you’ve probably already guessed by now – no VROOM. So I’m stuck. I’ve searched through this wonderful forum here on this site but so far, haven’t found the holy grail. So I guess what I’m asking is, what direction should I look in next? Any (dumbed down) suggestions would be greatly appreciated.

[waterman]

Welcome to the forum, we are glad to have new members.

As for your 650, it sounds like you are close to success. I would start with the basics, do you have a freshly charged battery? Often the bike will crank but not start, especially if it hasn't ran recently.

Next, are you getting wet sparkplugs after trying to start? Simply pull 1 or 4 and take a look, damp means you are getting fuel. Dry means you need to let carb bowls fill with gas by using the Prime position on fuel petcock. The accepted method of starting these engines is to engage "choke" level fully, in your case pull out about inch and then crank with no throttle. It should fire and rev up to 3 or 4000 rpms. Cranking the throttle while starting will defeat the choke circuit and not aid starting.

Finally, you may have other problems that are preventing it from running. If the valve clearances haven't been adjusted, it will be difficult to start.

[BassCliff]

Greetings and Salutations!!

Hi Mr. Skaat,

Here are some tips...

Diagnosing Slow Cranking
Ignitor/Signal Generator/Coil Test
Testing The Ignition System

But the best procedure is to start at the beginning and go through all the systems, making sure each one is in good working order. You will find a couple of maintenance lists in your "mega-welcome", which begins now:

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

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

[teddux]

The carbs didn’t look all that bad, just a little varnish in the bowls.

Your answer within.
BassCliff will guide you further.

[Big T]

After you determine whether gas is getting to your spark plugs, check the spark by laying the removed plug on the head and cranking over the engine

You have compression, so you need gas and spark

Two other things in your troubleshooting

1. This bike needs an airbox to run decently. It's not clear whether you obtained one, or have pods, or what?

2. Did you adjust the valves?

3. Did you use a rebuild kit when you dipped the carbs? (okay, I lied) Those parts are often inferior to the OEM

[Skaat]

Thanks for suggestions everyone. Big T: already checked spark & it's good. purchased and installed airbox. Have NOT adjusted valves. - thinking this could be where the problem is.

[Jeepeater]

If you are confident the bike ran before it was stored, the valves are probably not keeping it from starting. You can confirm this with a compression test, although it won't be a true and valid test since the bike will be cold. Just remember to conduct compression testing at Wide Open Throttle (WOT).

Sometimes just seeing a spark is not enough. It has to be a strong spark as well. It is a good idea to check for good voltage at the coils. Using a volt meter, check the voltage at the primary sides of the coils (skinny wires) with the key ON and the ignition kill switch in the RUN position. Should be within 1 volt of battery voltage. If not, you have to clean the connections or modify the ignition with the popular coil relay modification (instructions are available at BassCliff's website).

Try dumping a teaspoon of gasoline into the spark plug holes before trying to start it (work quickly). If it makes an attempt to start, then you have carburetor issues. Buy the orings from http://www.cycleorings.com/ and follow the detailed write up on BassCliff's website to completely rebuild the carburetors. My 1981 GS650 sat for 12 years and that was the only way I was able to get it to run right.

Good luck and welcome to the forum!

[Skaat]

Again, thanks to everyone for the helpful suggestions. as soon as i get a few moments to myself, i'm going give them a try. one question that's been buggin' me, though... i seem to have only found incomplete or conflicting info on this... when re-assembling the carbs after a re-build, what are the proper settings for both the AIR SCREW and the AIR JET? Again, I'm working with an '81 GS650 GL.

[teddux]

Again, thanks to everyone for the helpful suggestions. as soon as i get a few moments to myself, i'm going give them a try. one question that's been buggin' me, though... i seem to have only found incomplete or conflicting info on this... when re-assembling the carbs after a re-build, what are the proper settings for both the AIR SCREW and the AIR JET? Again, I'm working with an '81 GS650 GL.

Okay, so I broke my own golden rule and drilled out my "pilot screw cap".
FTW WTF FTW! Dave? LoL
Read Basscliff's website.

Your answer within.
BassCliff will guide you further.

[BassCliff]

...when re-assembling the carbs after a re-build, what are the proper settings for both the AIR SCREW and the AIR JET? Again, I'm working with an '81 GS650 GL.

Hi,

There is only one mixture screw on the CV carbs. Note that they are mis-labeled in the carb cleanup series. They may covered be by a cap. The cap can be removed.



According to THIS CHART, you should probably start with this screw about 1.5 turns out.


Thank you for your indulgence,

BassCliff

[Skaat]

Thanks, BassCliff. I think that clears it up for me.
So If I understand correctly, this screw (see below) screws in all the way (seats) and is not a "mixture screw"? Like I said, I'm a complete newbie to all this. Thanks for YOUR indulgence.



-Skaat

[mike_of_bbg]

Thanks, BassCliff. I think that clears it up for me.
So If I understand correctly, this screw (see below) screws in all the way (seats) and is not a "mixture screw"? Like I said, I'm a complete newbie to all this. Thanks for YOUR indulgence.

You are correct, sir.

[Steve]

As mentioned the air jet in the intake is fully seated.

I will respectfully disagree on the amount that the mixture screw should be turned out. The stock setting is usually around 1 to 1.25 turns out. This was intentionally very lean, to satisfy the EPA at the time. The bikes ran poorly and took forever to warm up. Simply turning the screws out some more would greatly alleviate the starting and warmup problems. After a THOROUGH carb cleaning (which I have not seen mentioned, yet), start with the mixture screws out 3 full turns. After the engine is running and fully-warmed up (take it around the block, to be sure), adjust each of the mixture screws, listening for highest idle speed. If you don't detect an increase in speed, turn it in slowly until you hear a decrease in speed, then back it out about 1/4 turn and proceed to the next carb. You may find that you will end up about 2 turns or so out, but 3 turns is a good starting point.

Since you are working on the bike and are having starting problems, one other typical problem is mis-adjusted valves. Even if your carbs are set perfectly, tight valves make it very hard to start a cold engine. There are guides on how to adjust your valves in every service manual. BassCliff has a tutorial with some excellent pictures. May not be exactly like your bike, but the concept remains the same. I also offer a spreadsheet that will help you a bit with the adjustmet process by helping you determine what shims you need and then will help you keep track of them from one time to the next. See the end of my sig for details.

.

[BassCliff]

Mr. Steve,

Thanks for being so thorough. I am sometimes less than thorough because I assume that people actually read and follow the maintenance list instructions in the "mega-welcome". Silly me.

Those are "tried and true" procedures folks. They really work. Don't take shortcuts.

Thank you for your indulgence,

BassCliff

[Skaat]

Thanks again for all your suggestions. I will be following the recommendations suggested by BassCliff and others. Will keep you posted.

FYI per my first post, carbs have been thoroughly cleaned.

[QUOTE=Skaat;1179101] Winter set in and I decided to do a thorough carb cleaning this time, following the steps on this site. I tore them down completely, dipped them individually (for several hours each) replaced all the O-Rings, set the float heights to the right specs, and replaced the intake valve O-Rings.