Hanging idle fixed, now bogging at speeds...

[FredSled]

Hi all! Been lurking for a little while. Proud new owner of 2004 GS500F, bought it for $1500 with only 1200 miles on it off the original owner. The thing is near mint, but obviously sat (in a garage thank goodness) for most of it's life.

When I first got it a few weeks ago, the idle would fluctuate wildly. After cleaning the carbs and messing with the idle and mixture screws I was able to get it to idle within spec with minimal fluctuation, but the idle would hang and hover before settling down.

Fast forward: I discovered two air leaks (spray test). The O-Rings on the manifold apparently failed.  Since I was too impatient to order and wait for new O-Rings, I picked up some high-temp gasket sealer. While I had the carbs off I cleaned them again and did a bench sync (planned on doing a dynamic sync too, but more about that at some other time).

Ok so I got everything back together, spent about an hour dialing-in the idle/mix and... no more hanging idle! She WAS purring like a kitten the rest of that day. BUT! the next day there were two new issues that were not there before..

1. A dead spot at low rpms. I have to rev it up a little starting off in first or else it feels like it's going to stall. This makes for slower and unsafe starts.

2. The bike is slightly "bogging down", more noticeable at higher speeds.  I'd say you "feel" it more than hear the engine bogging. You're chugging along at 60 mph and you just feel this fairly faint pushing/pulling sensation underneath you, the engine-breaking then engaging again, minor yet consistent hiccups, it makes for a very annoying ride.

Fuel starved? I checked the tank petcock to make sure it was turned on all the way. Checked the fuel lines for kinks etc. Checked the tank vent hose. Since the bike was not displaying this bogging-down before sealing the manifolds, and since I cleaned the carbs twice already, I don't think it's the carbs themselves causing this. Any suggestions? Mixture too rich?

Thanks for this great site!

[codajastal]

You're chugging along at 60 mph and you just feel this fairly faint pushing/pulling sensation underneath you, the engine-breaking then engaging again, minor yet consistent hiccups, it makes for a very annoying ride.

Hi and welcome
I had this exact problem and as soon as I replaced the chain the problem went away. Weird isnt it.
The chain may have a tight spot, as you said the bike was sitting for a while so the chain may have stiffened up around the sprockets? Maybe if you havent already you could clean it well and re-grease it and see if that works. If not try a new chain?

[vinny]

Slight surging at 60mph eh, What gear are you in? If its not fully warmed up my GS doesnt like 60 in 6th, but after 5miles its fine, could be that, or any of these:

-CHAIN - Tight spots, misaligned, worn, or wrongly adjusted chains can cause surging. It should have about 1" of vertical play in the middle of the chain when you are on the bike.
-FUEL - How much is in the tank?.. You could be about to hit reserve.
-LEAN - Check your plugs, a lean condition does (In my experience) cause dead spots in low revs >2k, and around 5-7k. Which can be caused by:
-AIR LEAK - Check again. - You never know.
-TANK CAP - Sometimes the vents in these get blocked. No air going in means no fuel going to carbs = bogging and dying. Only a 15min job to clean them.


Also, what do you mean by "Rev it up a little before starting off" - Thats normal, i usually give it 2-3k to start in town, more if i wanna move off quicker.

[FredSled]

Slight surging at 60mph eh, What gear are you in? If its not fully warmed up my GS doesnt like 60 in 6th, but after 5miles its fine, could be that, or any of these:



-CHAIN - Tight spots, misaligned, worn, or wrongly adjusted chains can cause surging. It should have about 1" of vertical play in the middle of the chain when you are on the bike.
-FUEL - How much is in the tank?.. You could be about to hit reserve.
-LEAN - Check your plugs, a lean condition does (In my experience) cause dead spots in low revs >2k, and around 5-7k. Which can be caused by:
-AIR LEAK - Check again. - You never know.
-TANK CAP - Sometimes the vents in these get blocked. No air going in means no fuel going to carbs = bogging and dying. Only a 15min job to clean them.


Also, what do you mean by "Rev it up a little before starting off" - Thats normal, i usually give it 2-3k to start in town, more if i wanna move off quicker.

Hi and thanks..

It's a slight "surging/engine-breaking" dance, very subtle but constant. I notice it in any gear above third, but seems to be more constant at highway speeds. I had the bike out all day last Monday and a couple hours yesterday and it still does it when the bike is both cold and warm.


-Not the chain,  no tight spots, cleaned and lubed last week, about an 1" of play.
-Fuel, 3/4 tank.
-New plugs look good
-no more air leaks (that I can find)
-Tank Cap, rode with the cap open to test venting, no change, still bogs down.

What I mean by rev-up before starting, is I have to give it more throttle than one normally would as I release the clutch lever because the bike has a dead spot and wants to stall.

Thanks again.

[SS Adrenaline]

I kno wthe bike doesnt have much millage but you might just want to check the valve clearance.  My buddies bike did the same thing and we checked and adjusted the valves.  it made a world of difference and the surging stopped.  Its just a thought.  Also Check your plugs for color.

[FredSled]

I kno wthe bike doesnt have much millage but you might just want to check the valve clearance.  My buddies bike did the same thing and we checked and adjusted the valves.  it made a world of difference and the surging stopped.  Its just a thought.  Also Check your plugs for color.

Thanks,

I just spoke with a mechanic at North American Warhorse, it's a HUGE motorcycle dealer here in town. I think it's the biggest on the East Coast. Anyway, he told me it wouldn't be the valves, that either the carbs are starved for fuel and to check for kinks or squashed fuel lines and clogs (I already did this), or most likely the mixture it's a little too lean and to adjust the screws richer by 1/4 turns (or less) at a time. Adjust, then go for a ride, adjust,  then go for a ride, etc, until it doesn't bog down anymore. Then adjust the screw back 1/8 turn. I'll give it a try tomorrow.

Any other suggestions from anyone, please post..

[bombjack]

Hi,

I've had similar issues twice.
The bike felt like someone grabbed the throttle every now and then, and closed it for just a second . It turned out to be a loose connection in the right sparkplug cap. All I had to do was turn the sparkplugcap clockwise a couple of times , and the problem was gone. Took me forever to find this problem.

One year later I had the same symptoms. I checked ignition system again and again, because I suspected the cause would be the same. This time it was a tight exhaust valve.

The only difference in symptoms between the two faults was, that the valve problem got worse when engine was cold. The loose connection problem got worse with rpm (more vibrations = more misfires )

Hope that helps...

[Precisi0n]

My guess is fuel starvation.  Try running the bike with the petcock on the prime position which allows the fuel to be gravity fed from the tank.  Also, you might want to make sure that the tank petcock is fully open (straight up and down).

[FredSled]

My guess is fuel starvation.  Try running the bike with the petcock on the prime position which allows the fuel to be gravity fed from the tank.  Also, you might want to make sure that the tank petcock is fully open (straight up and down).

Thanks, as noted in my first post, I did indeed check to make sure the tank petcock was fully opened. Setting it to prime is a good idea, didn't think of that. Will report back tomorrow, thanks.

[Precisi0n]

My guess is fuel starvation.  Try running the bike with the petcock on the prime position which allows the fuel to be gravity fed from the tank.  Also, you might want to make sure that the tank petcock is fully open (straight up and down).

Thanks, as noted in my first post, I did indeed check to make sure the tank petcock was fully opened. Setting it to prime is a good idea, didn't think of that. Will report back tomorrow, thanks.

Sorry, doing a bit of speed reading on my lunch break.  Hope you get it sorted out! 

[FredSled]

Well,

This morning after letting the bike warm up for 10 minutes, I hopped on to go fill the tank... about 2 miles up the road it bogged down so bad it wouldn't move, had to pull off the road. Took me 5 minutes to get it started and I had to feather the throttle to keep it running and  to get it moving. Got it on the road again and after another episode (same as first) I eventually got it to the gas station. Filled the tank and just wanted to get it home, but as soon as I pulled out of the gas station it started running better (better, as in, how it's been running, not better as in perfect). I switched the petcock from on to prime, no difference in how it ran. I stopped at friends (we don't see each other much) car lot about 25 miles away, he's a huge bike nut and has forgotten more about motorcycles than I'll ever know. He has everything from dirt bikes to a Ducati race bike to a brand new BMW GS1200. He took one rider around the lot on my bike and said, it's a fuel issue, either the carbs have to be cleaned again and/or the tank needs to be drained to see if there is any sludge at the bottom. He also told me the gasket sealant I used to seal the intake manifold will fail sooner rather than later.


Before I get the tools out I'm going to order the O-Rings for the manifold and then fix that properly an go to town again on the carbs and tank. Will report back next week.

[hawaiianGS]

Same thing happened to me. Took forever to figure it out, as the tank was the last thing I thought of.  Turns out the the petcock was clocked with gunk.  No screen to keep it clear. I guess the PO thought it was unnecessary. Anyway, check from the tank down. Who knows, may be something simple.

[FredSled]

Same thing happened to me. Took forever to figure it out, as the tank was the last thing I thought of.  Turns out the the petcock was clocked with gunk.  No screen to keep it clear. I guess the PO thought it was unnecessary. Anyway, check from the tank down. Who knows, may be something simple.

Well, I cleaned the carbs for the third time. Cleaned the tank and both tank and frame pet cocks. Though the gas I drained from the tank did have a little dirt in it, the inside of tank itself along with the petcock/screen were like brand new, no gunk, no discoloration, no nothing. So, I put everything back together and got a fresh tank of gas and she started right up.... and ran exactly the same as it's been running, which is to say... about a 6.5 out of 10. THEN, I turned each mixture screw in 1/4 turn and I think it's running a little better, was only able to ride it three miles, but it seemed not to hesitate quite as much when starting out in first, the dead spot is still there, but I think it's better than it was. I'm going to take it for a long ride later, see how it's running and try to tweak the mixture a little more to dial it in. I'm 90% convinced the whole problem is just dialing in the mixture. Will update.

Thanks everyone.

[FredSled]

Ok,


Well... messed with the mixture screw and idle more and pretty much nothing's changed. There is still a hesitation/delay at low RPM's when pulling away in first, you have to take care to release the clutch lever slowly to compensate so the bike doesn't stall. It's not a huge deal, and the bike is very ride-able, but it's just not where it should be. Still mini-bogging at higher speeds as well. I coined the phrase mini-bogging, because that's what it feels like.

Any more suggestions?

[burnchassis]

Mine is doing the exact same thing.
-CS

[bombjack]

Did you check the valves?