1980 GS750L sputters at steady speed around town

[Anonymous]

I bought this 1980 GS750L through eBay January 2004. I'm not sure how many miles are on it because the odometer now reads 31K but it came with another speedo/tach set that had 45K on the other odometer. Presumably one of the gauges went out and they were replaced as a set. When riding around town at a steady 25 mph or 30 mph, the engine seems to sort of sputter and surge and won't hold a nice steady RPM. It seems to do this mostly at lower RPMs, and it is kinda uncomfortable at city cruising speeds. I have had the carbs synched and the valves adjusted, but the problem persists, although the valve adjustment made it sound quite different and have a LOT more power. It seems to run nice and smooth at speeds above 35 mph or so. One thing that may be pertinent is that a previous owner modified the exhaust making it MUCH louder, unfortunately. I am willing to try/do almost anything to get it to run smoother around town. Any ideas, anyone? Thanks in advance.

[Detman101]

Hmmm....I've got the same bike.
Good to hear from another 750L rider.
Well, it sounds like your bike may be running lean and lean-surging through the streets when you're riding it.
Does it have the stock filters on it or the little pod filters on the carbs?

Dm of mD

[chuckycheese]

Lean

Hey Riverrafter, I got your email message and hope we can help you. I think it's probably a situation that resulted from the change in your air set-up. I would suggest you check your plugs....they can really "tell a story". If they're white and ashen, you could try adjusting your air screws by (backing them out). If they're black and sooty, you can adjust them inward...I think that's probably your problem because I think your plugs are fouling due to richness. Hopefully, someone will have already removed the caps that cover them. This might not do the trick since you're no longer running a stock system but it's certainly worth a try. :?

If that doesn't do it, you'll probably have to do some rejetting. A bunch of the guys here have done it and I'm sure will be willing to give you all the help and advice that you need.

Good luck, let us know what your plugs look like and.....thanks for the compliment on my bike!

[Anonymous]

Hmmm....I've got the same bike.
Good to hear from another 750L rider.
Well, it sounds like your bike may be running lean and lean-surging through the streets when you're riding it.
Does it have the stock filters on it or the little pod filters on the carbs?

Dm of mD

It has an after-market air filter, I think a K&N. I'm not sure if that's good or bad.

Hey Riverrafter, I got your email message and hope we can help you. I think it's probably a situation that resulted from the change in your air set-up. I would suggest you check your plugs....they can really "tell a story". If they're white and ashen, you could try adjusting your air screws by (backing them out). If they're black and sooty, you can adjust them inward...I think that's probably your problem because I think your plugs are fouling due to richness. Hopefully, someone will have already removed the caps that cover them. This might not do the trick since you're no longer running a stock system but it's certainly worth a try. :?
If that doesn't do it, you'll probably have to do some rejetting. A bunch of the guys here have done it and I'm sure will be willing to give you all the help and advice that you need.
Good luck, let us know what your plugs look like and.....thanks for the compliment on my bike!

Golly, how funny that you should ask me about my plugs! The day before yesterday, I bought one of those really long 12mm plug wrenches. I took out *all* the plugs (one at a time) and squinted at them as if I knew what I was doing, I tried to hold my mouth just right like a motorcycle mechanic would, and they looked pretty good to me, but in all honesty, I really have no idea whatsoever what they're supposed to look like. Heck, I don't even know how a mechanic is supposed to hold his mouth (lol). They had a very small amount of grayish ash (?) on them, but really seemed to look very much like genuine actual spark plugs. In fact, the resemblance was uncanny- I'm pretty sure that they were in fact actual spark plug devices (lol). I showed them to my roommate who had a GS1100 that he put over 100K miles on (!!) back in the olden days, and he said that they looked pretty good but that it might be running a bit lean.
Yesterday I bought a bottle of fuel-injector cleaner on the off chance that it might help clean the jets in case they're dirty. The guy that sold it to me assured me that it fit into the 'can't hurt' category.
Okay so now what do we have here? After-market air filter, modified (dang it) exhaust system, and a surging/sputtering engine when cruising around town. Okay everyone, thanks again in advance for your thoughts and your time. I appreciate your efforts on my behalf!