Running on 3 cylinders

[jsandidge]

I am bringing an 82 GS850GLZ back to life. I bought it cheap, but it has been sitting since 99. I did a full carb clean (yes, I completely disassembled and dipped them) replaced all the o-rings (thanks Robert) and installed new boots and o-rings. Did a bench synch of the carbs, and mixture screws turned out 2-1/2 turns. The bike is completely stock with original airbox and good filter. The exhaust is also stock.

New battery and new plugs, she fired right up! A little tinkering with the idle knob and got a steady idle at 1100 rpm's. Throttle response is good. The problem is #1 exhaust header stays cold. I swapped the coils (actually just moved the 1 & 2 wires to 3 & 4, and vice versa) since they would all reach. #1 is still cold. Compression is pretty close across all 4 cylinders, though #1 is a little higher than the rest.

Does anyone know what could be the problem? Maybe a stuck valve? Please help!

[chef1366]

If the valve was stuck your compression would show it.
Take out the pilot jet on #1 and reclean it.

[ozman]

I am bringing an 82 GS850GLZ back to life. I bought it cheap, but it has been sitting since 99. I did a full carb clean (yes, I completely disassembled and dipped them) replaced all the o-rings (thanks Robert) and installed new boots and o-rings. Did a bench synch of the carbs, and mixture screws turned out 2-1/2 turns. The bike is completely stock with original airbox and good filter. The exhaust is also stock.

New battery and new plugs, she fired right up! A little tinkering with the idle knob and got a steady idle at 1100 rpm's. Throttle response is good. The problem is #1 exhaust header stays cold. I swapped the coils (actually just moved the 1 & 2 wires to 3 & 4, and vice versa) since they would all reach. #1 is still cold. Compression is pretty close across all 4 cylinders, though #1 is a little higher than the rest.

Does anyone know what could be the problem? Maybe a stuck valve? Please help!

the infernal combustion engine requires 3 things to make it go
compression... you seem to have eliminated this by your checking
spark.....you seem to have eliminated this as well by swapping coils although there is the rare chance of a dud sparkplug
fuel..... the only remaining issue that must be the cause of your problem, is the plug wet ? if not your not getting fuel as chef said try clean that carbs pilot jet
at higher revs the cylinder should start to fire up when it gets fuel from the main jet have you tried that ?


ozman

[jsandidge]

Thanks guys

Thanks Chef and Oz. You guys must be right. #1 does heat up when I run up the throttle. I'll clean that pilot jet again. Next up is valve adjustment and vacuum synch.

[chef1366]

If that is not the problem the vacuum sync is way off.

[jsandidge]

Firing on all 4!

Success! After parts delays (dealer gave me the wrong valve cover gasket), I'm running on all 4. I re-cleaned #1 carb and adjusted valves. Won't get to wrench tomorrow, but Sunday will see the vacuum synch. She runs pretty good already, can't wait to hear it after the synch!