High Headwinds Stutter

[danny01975]

This is a strange one. I went for an 80 mile ride yesterday and it was VERY windy out. I was cursing along at about 70 mph or so and occasionally I would get hit by a huge gust of wind, either from straight on or from about 10:00, (nearly head on). The bike would start to stutter, almost like it was running out of gas. Sometimes I can roll on the throttle and it would clear up, sometimes it would get worse. Once the wind is gone, it goes back to normal.

I've had this happen a few times but yesterday was the worst episode yet. At first I thought I was just imagining it, but I don't think so now.

Again, this only occurs when there is a strong head / side wind and I'm cursing in 4th or 5th gear.

What in the world is going on here??

Edit.. For reference, this is an 82 GS1100GK. Without the K. (all fairings and luggage removed)

Edit #2.. Does anyone know if there's supposed to be a boot on the back of the air box? I saw an image of a similar air box with a boot that routes the opening at the bottom to the top side of the air box. Mine just has an opening at the bottom.

 

[Rich82GS750TZ]

Are you running pod filters on your carbs, or the stock airbox?

 

[robertbarr]

I had the identical problem with an '82 GS850 I had. Drove me nuts. Primarily diagonal headwinds (crosswinds) would cause this-- as you noted, around 10:00 or 2:00.. I could punch the throttle and get plenty of smooth acceleration; what I couldn't get was steady power to maintain a constant speed. It was like the engine was missing or breaking up, but without any backfire. It would bog enough that I'd be concerned about getting hit from behind. I never had that problem with my earlier '79 850 with VM carbs.

Stock carbs, jets, filter and airbox.

Trying to cure this led me to the lack of availability of replacement carb O-rings at the time. Solving that problem led to the sale of about half a zillion O-ring kits. Never did solve the original problem, though.

Wish I had a suggestion for you.

 

[dgates1]

I was cursing along at about 70 mph or so

That would make me curse as well..

 

[danny01975]

Are you running pod filters on your carbs, or the stock airbox?

No pod filters. Stock airbox. Everything is stock except the jetting. Larger pilots and main jets.

 

[danny01975]

I had the identical problem with an '82 GS850 I had. Drove me nuts. Primarily diagonal headwinds (crosswinds) would cause this-- as you noted, around 10:00 or 2:00.. I could punch the throttle and get plenty of smooth acceleration; what I couldn't get was steady power to maintain a constant speed. It was like the engine was missing or breaking up, but without any backfire. It would bog enough that I'd be concerned about getting hit from behind. I never had that problem with my earlier '79 850 with VM carbs.

Stock carbs, jets, filter and airbox.

Trying to cure this led me to the lack of availability of replacement carb O-rings at the time. Solving that problem led to the sale of about half a zillion O-ring kits. Never did solve the original problem, though.

Wish I had a suggestion for you.

Thanks for the validation!! At least I know I'm not totally crazy. What you describe is exactly the same thing I'm experiencing. What I suspect is the crosswinds are forcing too much air into the airbox, making a temporary lean condition. The underside of the airbox is exposed from both 10:00 and 2:00. Or maybe the air is blowing across a vent somewhere changing the pressure in the carbs.

Edit.. I also read that a drastic change in air pressure at the air inlet can affect the vacuum controlled slides in the CV carbs causing fluttering or instability.

 

[rphillips]

Sorry if I missed it Danny, but wondering if you got a "82" 850 like robert's or something totally different? bout as strange of problem as I've heard of.

 

[danny01975]

Sorry if I missed it Danny, but wondering if you got a "82" 850 like robert's or something totally different? bout as strange of problem as I've heard of.

Actually, it's an 82 GS1100GK (de-K'd) So essentially it's a G.

The lack of fairings may play a part in this which is why I added that fact.

 

[pdqford]

Are the carb vent tubes terminated in a protective area?

 

[danny01975]

Are the carb vent tubes terminated in a protective area?

As far as 'm aware, the only tubes attached to the carb body are the vacuum line for the fuel petcock, and the fuel line. I don't think there are any vent tubes.

 

[KiwiAlfa156]

Sounds like the cross wind is disturbing creating a momentary partial vacuum at the airbox intake (generally air moving faster = lower pressure).

 

[JMHJ]

For what it's worth, I have a vague memory of something like that, on one of the GSs. Can't remember which though, and maybe not quite to that extent. Maybe the 850 ('83)??

Had some exposure to a 700E with pods and a V&H 4-1 for a while too (which someone set up very nicely); can't say it was that one though.

 

[Burque73]

My '83 850G does that too. Stock pipes, jets, intake etc.
Huh! Actually thought it was running out of gas or something as well. Thanks for bringing it up.

 

[dgates1]

As far as 'm aware, the only tubes attached to the carb body are the vacuum line for the fuel petcock, and the fuel line. I don't think there are any vent tubes.

There are two vent "Tees" higher up on the carbs between 1-2 and 3-4 that should have a length of tube on them running over the airbox and down. Might not be your problem.. but worth a shot.

Parts 75 & 76 on the parts fiche linked below.

https://www.adeptpowersports.com/oem-parts/1982-suzuki-gs1100gk-carburetor-assembly.html

 

[danny01975]

There are two vent "Tees" higher up on the carbs between 1-2 and 3-4 that should have a length of tube on them running over the airbox and down. Might not be your problem.. but worth a shot.

Parts 75 & 76 on the parts fiche linked below.

https://www.adeptpowersports.com/oem-parts/1982-suzuki-gs1100gk-carburetor-assembly.html

Duh! I'm a dummy! I totally forgot about those. They are in place and properly routed. However, they do route to the back side of the airbox. The forced air could be coming under and around the back side of the airbox. Right where those tubes sit.

 

[Rich82GS750TZ]

In most configurations, I believe the 2 vent tubes are to go up, over to the top of the airbox and terminate in still air, under and between about where the seat and fuel tank meet, where they should not be disturbed under normal conditions. But I suppose that even there, very strong winds from a certain direction could have an effect.

 

[danny01975]

In most configurations, I believe the 2 vent tubes are to go up, over to the top of the airbox and terminate in still air, under and between about where the seat and fuel tank meet, where they should not be disturbed under normal conditions. But I suppose that even there, very strong winds from a certain direction could have an effect.

That's how mine are configured. Im not sure if that's where the disturbance is occurring or from the opening at the bottom of the airbox. Do you know if the bottom of the airbox should be open, or if there's supposed to be a boot over the opening? I saw one airbox that had a boot that routed the intake closer to the top edge rather than taking air in from the bottom.

 

[Rich82GS750TZ]

Sorry, I do not know. Maybe someone else can describe or show the snorkel size/location in the stock airbox of a 82 GS1100GK

 

[dgates1]

Looks like that airbox should have a "snorkel" on the back. Don't see a separate part number for it. I had to find a decent used one for my GS850GL as the seal around the bottom hole was all blown out. Not having that could definitely affect the air turbidity. It does close that hole at the bottom and move the intake up to under the seat.

You can see the top of it peeking out from the back of the fiche here. Below parts 11-12-13.

https://www.adeptpowersports.com/oem-parts/1982-suzuki-gs1100gk-air-cleaner-assembly.html

 

[danny01975]

Looks like that airbox should have a "snorkel" on the back. Don't see a separate part number for it. I had to find a decent used one for my GS850GL as the seal around the bottom hole was all blown out. Not having that could definitely affect the air turbidity. It does close that hole at the bottom and move the intake up to under the seat.

You can see the top of it peeking out from the back of the fiche here. Below parts 11-12-13.

https://www.adeptpowersports.com/oem-parts/1982-suzuki-gs1100gk-air-cleaner-assembly.html

Ah ha! I thought I had seen an image like that before. From a different angle, for an 850 no less. And yea, you're right, I can see what appears to be the top edge of it in the fiche image.

Mine does not have that snorkel, and instead just has an open hole on the bottom. Not sure I'll ever be able to find that part, but I do have a 3d printer!