Igntion on only Cylinder 1

[Andrwbunker]

Ok. Its a 1982 GS850G(z). I have had so many problems now I think I bought it from someone who took all the good parts off it for like 3 bikes and put all the bad ones on the one I bought and sold it to me. Ive replaced the ignition system with a dyna S. I now have spark on all four cylinders after replacing the caps as well. I only have ignition on cylinder number one. There is compression on all cylinders(I can't hold my finger down on them without it pushing off). Already rebuild the carbs according to the book. Where should I look next. I am past my technical knowledge and am looking for further assistance.
Thank you, Brian

[Steve]

Measuring compression with a thumb over the hole is not quite enough. :shock:

Since you obviously don't have a compression gauge, you would be better off to just adjust the valves, which probably needs to be done anyway.

If you don't already have a manual, go to BikeClliff's website and download one. While there, also check out his valve adjust tutorial. For further assistance, click on my name and send me an e-mail requesting my valve adjust spreadsheet. It will help you with the math to make sure your valves are adjusted correctly and will also help keep track of what shims you have.


.

[BassCliff]

Checklist

Mr. Andrwbunker,

Well, it sounds like you have spark and your carbs are clean. Is your airbox sealed? Here is a great pictorial from Mr. Roostabunny on how to make sure there are no air leaks at the airbox or air filter:

http://picasaweb.google.com/roostabunny/GS850AirboxFixup

Well adjusted valves, as mentioned by Mr. Steve, are a must for a good running bike.

Well tuned and balanced carbs are necessary also. Let me just give you Mr. bwringer's list of things to check:
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Every GS850 has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting. It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years. It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

1. Intake O-rings (install NEW OEM or Viton only - common nitrile O-rings will quickly deteriorate from heat)
2. Intake Boots (install NEW -- these cannot be repaired)
3. Valve clearances (more important than most people think)
4. Carb/airbox boots
5. Airbox sealing
6. Air filter sealing
7. Petcock (install a NEW one)
8. On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)
9. On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.
10. Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.
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The winning combination is a sealed air intake system, well adjusted valves, clean and well adjusted carbs, good spark. It sounds like you are very close. Keep up the good work. Let us know.

Thank you for your indulgence,

BassCliff

[trippivot]

your carbs are still plugged up.

blue spark present at the "F" mark= proper timed ignition

the thumb compression test is accurate enough to tell if there is any squeeze in there.

#1 spark
#2 compression
#3 fuel mixture

carb cleaning is a complex procedure not for beginners!!! do it again