79 GS1000 problems

[Guest]

Please help,
I have a 79 GS1000 that is having a problem. The last time I rode it, it developed a sever miss. I got it home, and wanted to find which cylinder wasn't firing. The #3 cylinder exhaust header was cool compared to the other 3 cylinders. The ignition was a point set up, I thought the points looked worn, this gave me a reason to buy a Dynatek ignition and new plugs. I installed the ignition and the engine started very easily, except the #3 cylinder exhaust is still not equal to the other 3 temperatures. (Yes it is getting spark).
How do I go about testing the carburetors or fuel system to make sure all the carbs are functioning properly?
Thanks,
Ken

[Big T]

#1 -you check to confirm that the vacuum port on #3 is connected, or capped off
#2- check your plugs -what do they look like?

[ShadowFocus603]

Cylinder not firing sounds like a need for a carb cleaning at the bare minimum as well as a valve clearance check.

[Brendan W]

Swap 2 & 3 HT leads after cleaning the #3 plug. If the problem stays with #3 the ignition is out of it.
The most forgotten and overlooked reason for points misfire is a failing capacitor.

[tkent02]

Swap 2 & 3 HT leads after cleaning the #3 plug. If the problem stays with #3 the ignition is out of it.

Very true, and good advice for troubleshooting. If the problem stays in #3 I'd also swap spark plugs, they can look fine and not work, they can even spark outside the engine and not spark inside it....

The most forgotten and overlooked reason for points misfire is a failing capacitor.

He no longer has points or capacitors.


One more thing to check, the #3 carb is the one with the vacuum port to the petcock. Anytime the carb with the vacuum port is the one with the problem I'd suspect it. Petcock diaphragm could be leaking fuel into the carburetor's venturi, could be so much fuel it can't ignite properly. This vacuum line could also be cracked or too old to seal, leaking enough air into the carburetor that it's too lean to ignite properly. Both very likely and very easy to check and to fix.

[Brendan W]

[QUOTE=tkent02;2285688]
He no longer has points or capacitors./QUOTE]

I got that. Just putting it in for someone driving by in the future. A failing capacitor some would expect to affect both outputs of the coil. I've seen quite a few that have spark absent or intermittent on one side only. Stands to reason. What are the chances a coil is electrically symmetric in the first place.

[Kat4568]

I have an update on my bike. Because of your great advice,I changed the vacuum line and now the engine is firing on all 4 cylinders.
Now for the next issue, the engine idles at 1200 rpm. I want to pull the carbs and clean them and change all the rubber pieces and replace the petcock. Is there a kit that will contain all the o-rings, and gaskets available for the carbs? Is there a site sponsor or a preferred place to buy these parts?
Thanks for all your help,
Ken

[chuck hahn]

carb rebuild tutorial on right hand side menus.

http://members.dslextreme.com/users/bikecliff/

Orings here..get the intake orings on page 3 as well. Measure the ID of your grooves and order accordingly.

http://cycleorings.com/