Runs rough between 3k and 5k.

[dcb]

I just bought an all stock 1980 GS750E. This is my first GS so I am still trying to learn the basics. I put in new plugs. The bike runs fine at idle and above 5k. It is also barely runs when I first start it; it has to idle to warm up. If the rough running was low rpm or high rpm, I would think clean carbs. But since it seems more like it is not getting spark between 3k and 5k. I am thinking signal generator or coils. Any advice would be greatly appreciated.

Thanks,
David

[semerm]

airbox

Is it a stock airbox or pods on the carbs?

[dcb]

It has the stock airbox.

[tconroy]

It has the stock airbox.

Have you been through the carbs yet?

[dcb]

I hate to admitt it but I cleaned the third carb only. It would not idle and poping the third plug wire told me it was that carb. I did not clean the others since I did not have new gaskets. I plan on getting a set of gaskets and cleaning them all.

David

[dcb]

It has the stock airbox.

[Jethro]

Loose wire or cracked wires or bad coils or bad signal generator would all be apparent all the time. Coils are either bad or they aren't. Many people do not realize that the mechanical advance unit should be lubricated every 2000 miles or so. Check that it's functioning with a timing light and lubricate it. Make sure the bike is timed right as well.

If your bike is having a hard time starting, I would ensure that the starter jets are clear. Not only the jet itself, but the port that feeds the starter jet. It's in the bottom of the float bowl and is tiny, so it can get clogged very easily.

[dcb]

How do you lubricate a coil? Also is there any adjustments that may need to be made to the signal generator? I have always had points until now.

Thanks,
David

[tconroy]

I hate to admitt it but I cleaned the third carb only. It would not idle and poping the third plug wire told me it was that carb. I did not clean the others since I did not have new gaskets. I plan on getting a set of gaskets and cleaning them all.

David

The carbs are the heart of the bike .Without them cleaned and set right your diagnosis is hart to pin down.Start there and you might solve 80 % of your problems!

[mark]

How do you lubricate a coil?

Thanks,
David

Coils are not lubricated. Jethro was speaking of the mechanical advance unit that advances timing at higher engine speeds. I'm not sure if your bike has a mechanical advance or not.

[dcb]

It does have a centrifical advance on the Signal Generator shaft. I will take a look at that. I am also going to go ahead and clean the other carbs.

Thank you to everyone who replied. This is my first GS bike and my first post on this site. It is great to have this resource and I am looking forward to becoming part of the GS community.

David
GS750E

[Macmatic]

Since you're going to be doing all the carbs you should order a set of carb o-rings from cycleorings.com. His name escapes me at the moment but he's well known and respected here on the board.

O-rings seem to be the only parts you really need most of the time unless you're rejetting or have known bad parts like a torn diaphragm.

/\/\ac

P.s. If you think of it could you check the diameter or your throttle shaft and let me know what it is? Also I'd like to know if you have X-rings, o-rings or no seals in the body of each carb where the shaft passes in and out. This goes for anyone reading this at any point.

[dcb]

I will let you know as soon as I get to work on the carbs. Hopefully it will be this weekend.

Thanks,
David

[dcb]

Mac, I have torn my carbs down and I only see o-rings. I am not sure what you mean by x-ring though. I posted another thread titled 1980 GS750 Cleaning CV Carbs for some additional questions I had.

Thanks,
David
GS750E