Hi All
Riding a 05 gs with 28,000 miles on the clock

Was just on the motorway traveling at 70 +  mph and the bike began bogging down, hardly any power even with downshifts, so I pulled over and the bike cut out rather than returning to idle. The bike started again after a moment or two and i carried on for the same thing to happen... 2 months ago I did a 400 mile trip at motorway speeds without any problems so this is a mystery.

I usually ride the bike around town at least 3 times a week up to 50 ish and never have any problem with bogging or power

Does anyone know what could cause this ? running lean ? Unfortunatly the previous owner stripped some of the screw heads to get to the jets of the carburetor    The bike is completely stock engine wise so has stock jets

Any help guys would be much appreciated ... If its any help the bike has always had a minor bog at around 9 - 10,000 rpm when harshly accelerating in 1st or 2nd, but would literally last for half a second and then disapear.

Cheers

Since you have a bike with fairings it isn't as likely but... Search for 'crosswind engine stumble'
Your symptoms sound similar to that.

- Bboy

Another similar thing to search for would be "vapor lock" Caused by a clogged gas cap vent.

-Bboy

Its actually a E model so no fairings - But i will look into vapour lock ... would vapour lock only occour at high speeds though ? and is there an easy fix to it ?

Cheers

Given you have an E model, then the first suggestion is more likely than vapor lock, but I'll provide some resources for both (hard to do that from my phone earlier).

The first has to do with your carb vent hose routing.  If wind gets ahold of the end of your vent hose, it will stall cause fuel starvation symptoms and may even stall out the engine.  The best place for that vent hose is tucked between the airbox and the battery.  Read more about it in the thread linked below.

http://gstwins.com/gsboard/index.php?topic=60976.msg705248#msg705248

The second suggestion regarding vapor lock:  If your tank vent hole is clogged you will get fuel starvation symptoms all of the time; however, if it is partially clogged you may only get these symptoms during higher fuel demand situations such as 70+mph.  There is a link below showing how to fully clean your fuel tank cap and vent.  To diagnose vapor lock, pull over quickly and open the tank cap when the symptoms occur at speed.  You will hear a whoosh sound when you open the cap if it is vapor lock.

http://gstwins.com/gsboard/index.php?topic=41061.0

Keep us updated!

- Bboy

+1 on BockinBoy's suggestions.  If those don't fix the problem, you might want to consider the possibility that you have a problem with the diaphragm in your petcock.  At lower speed the fuel demand may be able to be met by fuel flow through the petcock, but at 70+ it might not -- leading to fuel starvation symptoms.

Next time you're out on the bike, try and/or take notice of the following

When the bogging starts at 70+:
1. open your gas cap and see if this helps (after pulling over, of course, or using an extra key kept in the tank cap)
2. slow to around 50 (where you don't normally show a problem) and see if the problem straightens out after a few seconds.
3. switch the petcock to the PRIME position and see if this helps.

Answers to these questions won't necessarily indicate what's wrong, but could be useful for diagnosing the problem.

Hi guys

Thanks for the advice but no luck I'm afraid

Just went out on the motorway with the gas tank open & closed and still the same result. About 30 seconds into being + 70 the bike just bogs, and it doesn't smoothen out as I slow down. This time was quite bad as it started jolting as it was bogging ... almost as if decelerating and randomly blippng the throttle for a milisecond repeatedly. The petcock didn't change anything either :/

Once the bike stops and dies, it starts again after 5 - 10 seconds of cranking, but if i don't keep the revs up above 2000 while sitting idle it will die and then it returns to normal idling maybe 20 seconds later.

I don't know if this is a recent problem thats sprouted as I haven't been on the motorway for a while - however I just installed heated grips ... maybe they are sucking the power from the bike at high speed ? ... I doubt it very much but worth a mention

So yeah any other suggestions guys ? it must be the fuel, as no electrical problems occur while the bike is bogging ... I have a helmet cam so might try and record it happening - might give you a better picture ?

Cheers

Have you checked your carb vent hose yet? If it is pinched or the wind is catching it, it could cause fuel starvation. 
You may check the fuel line from frame petcock to the carbs for any leaks or pinches as well.  On one of my shred peds I had fuel starvation problems at higher speeds, and with basically one fuel line I went nuts all over that tiny carb.  After much frustration I found that the fuel line had a tiny slit in it... It was just enough to cause a leak from the added pressure during high fuel demand at 'high' speeds... But it was so little fuel, it was dry before I could examine it at a stop.

- Bboy

The first thing I'd address is the bogging the bike has always had from 9-10k RPM. If there is a fueling issue that needs to be ironed out, it could be contributing to the highway bogging you're experiencing. Of course, check the carb vent hose (I route mine next to the battery, seems to work pretty well) as the others have said, and also I'd even recommend checking to see if the carbs are synchronized. I had a very similar problem with highway bogging, and after synchronizing the carbs, setting the idle, and adjusting the idle mixture I haven't noticed it once.

Hi guys

Being quick as i have a lecture in 20 mins - I just had a sneek peak at my carb vent hose but it seemed to be in the right place - routed over the airbox and then behind the battery without any kinks

(Also ignore the kink in the fuel line from the tank - I didn't have enough time to take the tank off so im just holding it at the side - that kink is not usually there )



... however I have noticed one thing that seems odd and from memory im pretty sure there should be a hose. At the top right of the picture theres a black cylindrical object (ive forgoten its actual name) and it appears as if there is no hose connecting to it.
Should this have a hose ? ... what even is it ?



I havn't had the carbs syncronised/ balaced in over 15,000 miles so maybe that could solve the problem.

Cheers guys  - I shall have a better look tonight if I can juggle girlfriend, uni, jitsu and library studies around the bike

Oh definately try a carb sync!  Especially if you have done a valve adjustment!  Have you ever had the valves checked?  Suzuki recommends a valve check/adjustment every 4k miles, and a carb sync is paired along with that every time.

Also, that black cylinder is your ignition coil I think (Don't flame me if I'm wrong, I said I think lol... but looks like the plug wire comes out of that and that would by default come from the coil)

- Bboy

WTH guys ... bogging @70 clicks has nothing to do with valves ... or a carb synch ... or nearly anything ...

You're likely getting no fuel cos your tank has vacuum locked itself. Clean the cap, and dont put a tank bag.
Or ..
Blocked air filter ...

I cant think of anything else.

Cool.
Buddha.

Maniaka - The thing is - carburetion is related to throttle position, not to rpm or speed. So mark your grip and switch assy and get it to where you say ... 1/2 throttle bog etc.
Cool.
Buddha.

Haha, The Buddha has spoken!

But really, we suggested this early on... and when that didn't pan out, we made it complicated... can you blame us?  Besides, these are things (carb sync/valve check) that obviously need done - probably prevent a much greater heartache in the future.

Nevertheless, blocked air filter is a good suggestion.  Though the little bit of it I can see in the pic, it doesn't look bad, but that can mean very little.

- Bboy

hey guys
In a lecture atm - Coastal engineering ... not fun
Anyway its actually a brand new air filter maybe 400 miles old ? ... a highflow air filter ... which isnt stock so maybe this is causing the bogging ? I only went with this as i was told its fine with stock jets and was cheaper than a genuine. I stil have the old filter so ill pop that on later and see if theres any differences.
cheers

also, try checking the vacuum line that goes to your frame petcock for kinks and cracks. replace it if need be.

Quote from: The Buddha on October 22, 2012, 06:52:21 AM
WTH guys ... bogging @70 clicks has nothing to do with...a carb synch

Not arguing with you, it was just a "this couldn't hurt" suggestion.

Quote from: maniaka on October 22, 2012, 07:23:50 AM
hey guys
In a lecture atm - Coastal engineering ... not fun
Anyway its actually a brand new air filter maybe 400 miles old ? ... a highflow air filter ... which isnt stock so maybe this is causing the bogging ? I only went with this as i was told its fine with stock jets and was cheaper than a genuine. I stil have the old filter so ill pop that on later and see if theres any differences.
cheers

BOOM! Thats it!  Or at least, I would put some money on it.  You can find various threads throughout the forum which note users having problems when they replace their stock filter with the HiFlow.

Edit: after checking a couple threads, it appears that the HiFlow might actually be more restrictive than stock (contrary the the name, I know!)  This would be similar to a blocked air filter ... at 3/4-WOT, there isn't enough O2 there to ignite the larger amount of gas = bogging down... able to restart shortly after the plugs recover.  Have you check your plugs at the time this occurs?  They would probably be wet or at least look dark if this is the culprit.

- Bboy

Oh Yea high flow filtro flows too hi and filtro's too little ...
Maniaka, drop a tennis ball in the open mouth of the filter ... oops, I mean filtro. My friends son's katana that worked like a dream.

Cool.
Buddha.

BOOM - problem solved - I stuck on the old air filter and the problem disapeard so it was the hiflo filter presumably not letting enough air into the engine.

however while i have the attention of you genei ... The bike still boggs at high rpm when harshly accelerating in 1st or 2nd ... Must be a similar issue with the feul ? - Tho i might look into carb syncronisation as it sounds like a good thing to do for the bike

Cheers for the help guys
Many thanks