Pulse issue

[markn]

Hello everyone -

For the first time ever, I have a problem with my GS700ES that is getting the best of me.

When I'm going down the road at a steady speed between apprioximately 2,000 and 3,000 RPM, the bike pulses.......like it has a fuel delivery issue.

I checked all the typical things - carbs, fuel, plugs, etc....and everything is OK.

The bike starts great and idles perfectly. It accelerates like new. The only time I have an issue is steady-state driving between 2 & 3 thousand RPM.

An old GS pal told me the back ignition plate is bad, or the springs have worn. The bike only has 12,000 miles on it. He also mentioned a Dyna replacement. I'm clueless here.

Can anyone here point me in the right direction?

markn

[tkent02]

Downshift.

[tom203]

I thought I was the only one "going down the road at a steady speed between.... 2k to 3k " ! If it accelerates off idle and thru this range nicely, I don't see the ignition being the problem. Not much throttle plate openning, so maybe those little holes in slow speed circuit are slightly clogged.

[markn]

I drainied the carbs last week, and the 6-month old fuel looked quite clean.

The bike was only stored 5 months - I used the new Stabil that is specifically designed for the 10% ethanol / gasoline combo we have in Wisconsin.

Would a heavy duty carb cleaner, or Sea Foam, clean out those tiny slow-spead circuit holes over time?...........I heard that even the best "pour-in" carb cleaner can't clean them.

Is there some type of gas additive out there that can help me?.......can it do damage if used in high concentration, or if it's used too often?

mark

[tom203]

So is this the first gas after winter's rest? If so, just keep running more gas thru it and make it work harder. Seafoam won't hurt- maybe a couple ounces per tankful , but I doubt it will do much for this minor problem. If this gets worst, you know what you must do, but think positive thoughts.

[markn]

I added a small bottle of Lucas fuel injector cleaner last night before short ride. No change yet

Just curious - when you say "make it work harder" are you referring to more throttle opening in a higher gear, or higher RMP in a lower gear?

markn

So is this the first gas after winter's rest? If so, just keep running more gas thru it and make it work harder. Seafoam won't hurt- maybe a couple ounces per tankful , but I doubt it will do much for this minor problem. If this gets worst, you know what you must do, but think positive thoughts.

[koolaid_kid]

Downshift.

Yup. You are lugging the engine, which is not a good thing. The 700s were designed to rev, and you are just above idle.

[markn]

Tom203 suggested that I run it hard - my question to him was if he meant that I should run it in a lower gear with higher RPMs, or a higher gear with less throttle opening, and lower RPMs.

What are you suggesting?

markn

Yup. You are lugging the engine, which is not a good thing. The 700s were designed to rev, and you are just above idle.

[cableguy]

Probably he meant give I plenty of throttle from a low rpm up to redline, as opposed to lugging it or part throttle at high Rpms. The idea is to try to use all of the circuits in the carbs so the Lucas can work its magic.

[tom203]

Probably he meant give I plenty of throttle from a low rpm up to redline, as opposed to lugging it or part throttle at high Rpms. The idea is to try to use all of the circuits in the carbs so the Lucas can work its magic.

Yeah, make the carb work thru its entire range.As koolaid_kid said, 2k rpm is just above idle; some bikes are more sensitive than others at this low throttle opening. My 650 could care less.

[Steve]

Tom203 suggested that I run it hard - my question to him was if he meant that I should run it in a lower gear with higher RPMs, or a higher gear with less throttle opening, and lower RPMs.

What are you suggesting?

markn

Did you see the very first response to your original question?

Downshift.

Sounds like a rather definitive answer, to me.

.

[robertbarr]

I've had several bikes develop this 'problem' and the only consistent factor is the recent installation of a Plexifairing III.

My '82 GS850, my '85 Nighthawk and my '81 GS1000 all run / ran perfectly without the fairiing. As soon as I install that fairing, I'll get a flat spot around 3k r.p.m. on windy or even breezy days.

It depends almost entirely on the direction of the wind. Direct headwind = slight flat spot. 15? angle into the headwind? Annoying flat spot, and occasionally I'd swear I lose a cylinder or two now and then. Once I'm heading around 30? into the wind, the flat spot disappears. Crosswinds never cause a problem.

On the Nighthawk, it's occasionally necessary to drop down a gear. If I didn't know about this phenomenon, I would be concerned and looking for a 'repair'. Perhaps some modification of the intake snorkel would help, but an easier solution is to just twist the throttle a little more and ignore it.

None of those bikes exhibit this without the fairing.

Oddly enough, my '79 GS850 -- almost identical to my current GS1000 -- never had a problem with the same Plexifairing (or any other situation).

[markn]

Yeah, make the carb work thru its entire range.As koolaid_kid said, 2k rpm is just above idle; some bikes are more sensitive than others at this low throttle opening. My 650 could care less.

The pulsation issue has finally gone-away.

2 tanks of non-ethanol gas and Sea Foam did the trick. I made it a point to run the carbs through the entire range in an effort to get the cleaner flowing through the obstructed jets.

Thanks for the advice !

markn