'81 GS650G not starting anymore??

[cowboyup3371]

Cycleorings.com will have your carb orings as well and you really need to do the valve adjustment at the same time in order to ensure you get them synced correctly. Get yourself a set of metric feeler gauges and go look at Basscliff's site again as it contains a good set of directions to do it.

As far as testing fuel flow, put your fuel hose on the petcock and into a container, turn the petcock to prime and make sure that fuel flows. After that, you'll need a vacuum source (your bike) to test the on and reserve. However, I'm wondering if you don't have some junk in there so if it doesn't flow on Prime I'd take it back off and make sure something's not clogging it.

[tom203]

You did say it was "running great", till the painting and playing with tank/petcock. Fiddling with petcock and kreeming tank has altered the gas flow to carbs ( restricting it). I wouldn't worry about valves, orings until you know the petcock is doing its job. After all, it was "running great".
But please, get filter and some kind of airbox cover. The cover holds the filter in position.

[ssanderson111]

New Problem! : (

So I decided to take the easiest pieces of advice first. I took the tank off and removed/cleaned the petcock. I got some rusty looking gas out of it....

Next, I installed the new airfilter and closed off the airbox.

Last, I thought to myself, "if there's rusty fuel in the petcock, maybe there's rusty fuel in the float bowls?" So I pulled the drain screws on all 4 carbs and let the gas run out(tank was off at this point). Sure enough, rusty gas! No big chunks...just powder mixed in with the gas, or it looked that way anyhow.

Soooooo, I put the screws back in, put the tank back on, put some gas in it...........low and behold.............started right up. No problems idling. Let it idle for a few minutes and rode it about a half mile. Ran fine. Gave it 20 minutes to sit. Went back out around the same half mile. Still ran fine! So I decided to take it up the road. I decided to pick the most uphill route incase something went wrong. Unfortunately, I choose correctly. I started out slow....but it seemed to be back to normal, plus some! It felt quicker/more responsive than ever. I got it up to about 70 and it felt great. Then I decided(probably a dumb decision) to hot rod it a little and see how it felt. I got up to around 75-80 in third and then it felt like the throttle went limp and the RPM's shot up to 10500-11000! I pulled in the clutch lever and hit the kill switch asap and pulled over. With the bike off, I twisted the throttle and it felt kind of loose. I tried to start the bike and it wouldn't start. The starter would turn the engine, but it woudln't come close to starting. I pushed the bike up a hill and pop started it on the way back down. Started right up, no throttle, RPM's shot through the roof again. Stopped/turned the bike off. Hit the start button, started right up, RPM's through the roof. Pushed the bike a mile back home, which wasn't as downhill as I was hoping. Is the throttle stuck? What happened?

[BassCliff]

Hi,

My first guess would be that one of more of your carbs have a butterfly valve and/or slide stuck open. Check the cable and linkage. You'll find a lot of information, with pictures, on my website. Have a look.


Thank you for your indulgence,

BassCliff

[tom203]

"What happened?"

Gee, maybe you are a bit impatient. 70 mph in third, etc. I didn't think a 650 would pull 10k rpm- I like learning new stuff!
As Basscliff said, check cable for hangup. Pull gastank and check that no carb throttle plate is sticking or cable is frozen . Fix this ASAP as you do not want it to happen again EVER. While you're at it, clean tank and petcock again, since it's unlikely you got all the crap out.
Definitely head to Basscliff's site for mandatory maintenance tips for folks who like to push the limits.

[cowboyup3371]

And CLEAN THE CARBS. If there was some rust in it before you have no idea what's still in there.

[Steve]

My son had the throttle stick about half-way open on his brother's bike. The problem was the clutch cable got stuck in the throttle linkage. Your clutch cable should go down between the intake tubes on 1&2, but should have a guide to keep it away from the throttle linkage. You can see the guide here, at the bottom of the picture.



If you don't have that guide, you can make a simple one using a coat hanger and mount it to the intake boot bolt.

Anything to keep the cable away from the throttle.

By the way, even though it seems to be running OK right now, it will do MUCH better if you take the time to strip and dip the carbs, then replace all the o-rings in them. The o-rings are available rather inexpensively from a forum at cycleorings.com.

A valve adjustment should also be performed, it can be done while waiting the few days for your o-rings to get there. See the end of my sig for info on the valve adjust.


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[81GS750]

The answers to your problems have been laid out on a silver platter. Go to BassCliff's site and read the tutorials. There is a great one on valve adjustment and carb cleaning. If those cables are old, buy new ones, they are cheap. When I was a "poor student" not too many years ago, I tore right into the carbs and valves on my 86 GS550E. I had 4 angry roommates for awhile, but they got over it. Gather the tools and parts to do the jobs now, once you've done that, start with the valves. If you need shims, post here, I'm sure someone will be glad to help, while waiting for shims to arrive tear down the carbs. Since it should take you at least 4 days to do the carbs the shims should be in and it can all go back together at once. It's really easy to do the work and doesn't require a lot of hours to do it, mostly waiting for carbs in the dip, or you can take it to a shop and pay triple the cost of a DIY job.

[ssanderson111]

O-rings are on their way. Picked up some feeler gauges yesterday. Plan to tear the carbs apart and adjust the valves in a week or two when I have time. Do I need anything else to tune the carbs after I get them all put back together? I've read over the article on how to clean the carbs, but I don't recall it containing any info on how to tune them?

Guys, I REALLY appreciate all the help. There is no way I could do any of this stuff without you. Thank you so much for your time and willingness to help me out. If I have more problems or can't figure something out I'll post again.

[ssanderson111]

Looks like basscliff's site contains everything I'll need. Thanks again!

[Steve]

Do I need anything else to tune the carbs after I get them all put back together? I've read over the article on how to clean the carbs, but I don't recall it containing any info on how to tune them?

As far as "tuning" them, there's not too much to do. Are you running stock airbox and exhaust? If so, then stock jets in the carbs will work just fine. Start with the idle mixture adjustment screw about three full turns out from lightly seated. When the bike is warmed up, sync the carbs (you will need a "special" tool for that). Once the carbs are synched, adjust each of the mixture screws for highest idle speed (adjust the master idle speed screw as necessary).

The "special" tool you will need to sync the carbs is something you will need to use every so often as part of your tune-ups, so plan on getting one. You are looking for a multi-cylinder manometer. Generally accepted as the best, and not much more money than the rest, is the Morgan Carbtune. As of today, the exchange rate (it comes from England) shows it at $91.29. Some dealers will charge you close to that much to sync the carbs, even though it usually takes less than 15 minutes, start to finish.

By the way, if you get into reading ALL the info on BassCliff's site, keep in mind that ALL of the different service manuals say that you should adjust your valves before you sync your carbs. Adjusting the valves is not that hard. The hardest part is figuring out what shim you need to use. I have developed an Excel spreadsheet that will help you figure that out. See my sig for ordering details.

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[BassCliff]

Hi,

After you've dipped your carbs you will want to "bench sync" them. This procedure will tune them enough to get your bike running. Fine tune the idle using the "highest idle" method or the Colortune. Then a vacuum sync will really dial them in. You'll need a special tool for that procedure. The Carbtune is a favorite but a set of vacuum gauges will work too. I have a Carbtune with the Carbtool and you are close enough that we might be able to get together, schedule allowing.

EDIT: It looks like Mr. Steve hit the <Enter> key a couple minutes before I did.

Thank you for your indulgence,

BassCliff