My gs is not firing on all cylinders

[Guest]

1978 gs from victoria bc

[gsrick]

Does it still have a points system? Which plugs are not firing? You have two coils, one fires 1-4 and the other 2-3. If there is only one cylinder not firing, then it's more than likely not a coil or the points. If either sets have stopped then thats what I would look at. Check to see if all the plugs are firing by pulling them to see if they have a good spark. It they all fire, the it may be a fuel issue with your carbs or you may even have some tight valves and your loosing compression.

[OldVet66]

Welcome to the forum. I'll answer your second post on the subject here since you added additional information. Multiple posts on the same subject can be confusing. "Purchased a new gs from Rob in Victoria BC bike ran great from Port Angeles WA to Albany OR now the bike has developed intermittent power loss not firing on all cylinders any thoughts?" As gsrick stated, it can be multiple reasons. Now we know it runs but developed problems on the trip home. It could have fowled a plug causing an intermittent miss that caused a cylinder to go cold. Check the heat on the pipes by holding your hand close to the bend where the pipes comes out of the head. Please be careful, a hot pipe can take the skin off your fingers but holding it close you should notice the difference in a hot pipe or a cold one pretty easily. Change that plug. If it fires right up then you have a starting point. You have many years of maintenance to catch up on so this is just the beginning of you becoming your own GS mechanic. You will find all the information you need right here. Above in Forum Actions, you can edit the signature line and add your bike model and year so everyone will know which bike you are talking about at a glance.

[Roger]

So problem is intermittent Runs great then maybe after 5 miles or 15 miles I stop firing on all cylinders. I have a dyna ingnition. Have not pulled the tank to check out coils I have pulled the plugs they look good but I really have to check on the plugs right after the bike stops firing on all four.

[OldVet66]

Does this bike have an external fuel filter and generic fuel line? I had a problem with my bike that sounds similar when I first got it. There is not much room under there to rout fuel line especially with a filter that you shouldn't need anyway. It would run fine until the fuel line collapsed. After a while it would run fine until the next time. It could be fuel or spark. The petcock has a great screen that sticks up into the fuel tank. If it is in good shape that is all that is necessary. Check your voltage at the coils for a voltage drop. The coil feed from the kill switch can be problematic but doesn't usually cause intermittent operation. One of the cures for that voltage drop is to run direct voltage to the coils and Dyna-S from the battery with a relay operated by the kill switch. It requires cutting the kill switch feed in the harness under the tank before it splits to both coils and then adding appropriate wiring to and from the relay. At any rate getting the tank off to check those voltages and inspect the fuel system is a necessary first start to finding the problem. The Dyna-s also runs the bike better with the Dyna green coils. I use the grey 8mm Dyna suppression wires. That would eliminate any possible coil, wire or cap problems.

[azr]

I've talked with Roger on the phone about possible issues. It's a real shame as the bike was running great. Gave him some good direction, shouldn't be a too difficult to sort out. Likely a failing dyna component.