Cylinder not working

[mmwanderscheid]

I have a 82 gs 650 that has a cylinder not firing. I just took the carbs off and cleaned them thoroughly along with changing the air filter and spark plugs but after riding it I could tell it wasnt all there. The third exhaust tube from the left, looking at if from the front is not heating up at all while it runs. I switched plugs and same problem persisted on the same cylinder. I have spark at the plug so I dont know what is wrong. I also have gas in the bowl at the carb. Any ideas?

[tkent02]

That's #2, the one that supplies vacuum to open the petcock... If the petcock diaphragm fails, fuel runs down the vacuum line into the carburetor, making that cylinder run way too rich.
Is that what's happening here?

[hjfisk]

Have you checked compression? have you adjusted your valves?How did you clean your carbs? did you just spray them or did you tear them down and do a complete strip and dip with new O-rings ect? also you don't need to start 2 different threads on the same subject here. The people on the forum will answer your ? you just have to be patient and let them read it.

[BassCliff]

Greetings and Salutations!!

Hi Mr. mmwanderscheid,

In your "mega-welcome" you will find a couple of lists of maintenance tasks to perform on your classic GS. Taking shortcuts or skipping steps will leave you frustrated and can lead to catastrophic failures. You have a 30 year old bike that probably needs 20 years worth of maintenance. So let's get started.

Let me dump a TON of information on you and share some GS lovin'.

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Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. 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!

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Thank you for your indulgence,

BassCliff

[mmwanderscheid]

Thank you for your replies. I cleaned the carbs by taking them apart piece by piece and cleaned each part as I went. I did not do any valve adjustments. I checked the compression by holding my finger over the hole and it seemed strong. The exhaust does smell strongly of gas so a problem with the petcock flooding it out would make sense. I took off both vacuum and fuel hoses and no gas leaked from the petcock when it was open to run. Is there a way to check if the diaphragm is not working in the petcock? I appreciate the help.

[tom203]

Put 1/4 inch clear vinyl hose on petcock vacuum fitting- suck on it, gas should NOT show up in this line; the diaphragm might be torn. Mine did this last summer.

[Big T]

MM,

The petcock flooding the motor is a very common problem and causes many a PO to park the bike because it "doesn't run right". Bike sits for a few years, dried up gas causes rings to stick in #2 cylinder.

Things to start with:

1. Oil - really full? smells like gas? - change it and the filter now
2. Petcock test per above
3. Adjust your valves and the other things in the top ten
4, Buy/rent a compression tester (after you adjust the valves) and see what you have for compression. If the rings are stuck in #2, you can often free them up without tearing the motor apart

[mmwanderscheid]

I checked the petcock and fuel came out when I sucked on the hose. I will head to the local shop tomorrow to get a kit for it and hopefully that will take care of the problem. Thanks for the advice.

[tom203]

Folks here have found poor success with rebuilding petcocks- just buy new unit and this problem is eliminated. Here's where I got mine for $45-

http://www.georgefixs.com/servlet/the-148/SUZUKI-GS450%2C-GS650%2C-GS750%2C/Detail