What the hell is this?!

[LimaXray]

Ok, so I rejetted my carbs, and I've been wondering, what is up with the GS500F?  There are some extra vacuum lines on my bike that aren't mentioned in the Haynes manual or anywhere on this board from what I can find.  My first thought was someone got confused about the difference between NJ and CA, and I was sold a California model.  But upon further examiantion, the 'extra parts' I seem to have aren't part of the regular EVAP system found on CA GS500s, not to mention the tank was vented right to the atmosphere thus defeating the point of any kind of EVAP system.   

Now for some pictures:

First is a shot from the top.  Any idea what the circled parts are?  I don't know if the white things on the top of the carbs are normal or not, but they are part of this vonvoluted vacuum system so I figured I'd ask anyway.  My only guess for that black canister is some kind of charcoal canister.  Don't think that is correct because it only connects to a single vacuum line and seems to be otherwise sealed, so I don't see how'd that work.  Also, if you look in the lower left hand corner you will see a nice collection of vacuum hoses, T's, and check valves all connecting this stuff together.



Next is a shot from the side.  I know it probably would have been better to take the carbs out to take these pics, but I was being lazy.  Anyway, that circled thing looks to be an electronic solenoid valve and has 2 vacuum lines connected into it.  IIRC (I should have made notes and diagrams but again, lazy) the one hose goes directly to the intake vacuum, shared with the petcock vacuum line while the other makes its way up to that black canister.  Any ideas what it's for?  That other black thing in the upper right hand corner that that wire plugs into is a throttle position sensor.  The fact that this bike has a throttle position sensor, some sort of electronic solenoid valve, and only a single VR sensor (pulse generator) on the crank tells me this bike uses fairly modern electronics.  Hmm, I think I may go take apart the ECM in a little bit and bust out some of the computer engineering skillz to see how this thing ticks...
 


Does anyone else with an F have these, or am I just a freak?  What about with the 01+?  Any ideas what this system does?

[ops_south]

My F has them.  I've been researching it for a while and have found no information on the devices yet.


Good luck!

[scratch]

First is a shot from the top.  Any idea what the circled parts are?  I don't know if the white things on the top of the carbs are normal or not, but they are part of this convoluted vacuum system so I figured I'd ask anyway.  My only guess for that black canister is some kind of charcoal canister.  Don't think that is correct because it only connects to a single vacuum line and seems to be otherwise sealed, so I don't see how'd that work.  Also, if you look in the lower left hand corner you will see a nice collection of vacuum hoses, T's, and check valves all connecting this stuff together.

You are correct, the black can is not a charcoal canister.  The white things made onto the carb tops look like they have something to do with the slides and engine vacuum, because they are mounted right over where the vacuum pick-ups would be (so I'm also wondering how would I do a carb synch?  But, I guess I'd disconnect the middle tube).  They have the shape of what would contain a diaphragm, and there is a brass tube, with rubber tube (for seperating carbs) connecting the two on the slide side of the diaphragms.

Next is a shot from the side.  I know it probably would have been better to take the carbs out to take these pics, but I was being lazy.  Anyway, that circled thing looks to be an electronic solenoid valve and has 2 vacuum lines connected into it.  IIRC (I should have made notes and diagrams but again, lazy) the one hose goes directly to the intake vacuum, shared with the petcock vacuum line while the other makes its way up to that black canister.  Any ideas what it's for?

The one hose that goes to intake vacuum that is shared with the petcock vacuum line may be a way of making sure that the diaphragm stays open to prevent fuel starvation.
Until I can get my hands on one of these, for a whole day, then I could figure it out.  Or, someone buy the factory manual for the '04+

What about with the 01+?  Any ideas what this system does?

The '01-'03 does not have any of that.  It must be an attempt to alleviate the fuel starvation problem.  Has anyone with an '04+ experienced fuel starvation?

[Alphamazing]

I've got everything you're talkin' about. I don't know what it does, but it's there!

I have only experienced fuel starvation once (maybe...) when I was running it constantly above 90mph to 100mph for quite a while (got to follow behind a cop down I-35)

[CirclesCenter]

Looks like some sort of exotic emissions garbage to me!, Take it off plug up the holes and see if it runs, if it does then it's emissions garbage.

[starwalt]

Those belong to your PAIR (Air Supply) System.

What's a PAIR System?  CLICK HERE for the automobile version of the theory/details.

The Suzuki manual mentions them on page 20-32 of the manual that covers through K5 models.

From the drawings, it looks to be plumbed into the exhaust system also...as it should be from the above link information.

No detailed information on operation or function is given in the Suz manual. Just drawings of the routings of the hoses.

[Turd Ferguson]

I'm not sure where it would plumb into the exhaust system unless it goes through the head and dumps air into the exhaust ports just before the exhaust pipe.  I'll have to nose around with this stuff next time I have the tank off...this kinda unknown stuff gets me all excited...

-Turd.

[LimaXray]

Sooo... I was just about to start a new thread about what these extra vacuum system parts are for, but figured I'd search first and this topic comes up.  Damn, my memory is so bad I don't remember posting this, nor did I remember anything that I wrote about - I had to figure it all out again today in giddy excitement.

I couldn't find any more info than what is in this thread.  Feel free to let me know if my searching skills suck.

Anyway, after reading this thread, I finally got around to removing all the extraneous equipment - only took me just shy of 5 years.   Take a look in that thread, about half way down paalak posted a picture of the vacuum diagram of a California GS500F.  I'm guessing California requires these stickers so you don't mess up the routing, because my '05 NJ model has no such sticker. 

Now the California model is different than mine.  My bike most certainly does not have a PAIR system; its vacuum system lacks the PAIR C valve and 3rd 3-way connector from the diagram.  I also don't have any of the EVAP components (the canister, surge hose, etc).

So what is it and what is it supposed to do?

On to the removal.  I disconnected the hoses from the tops of the carbs and plugged the barbs.  I left the petcock connected to the intake using the 3-way connector with the third hose disconnected and the barb plugged.  I had to use the 3-way connector here because the petcock hose has a larger diameter than the intake barb and the connector acts as a reducer.  I'll probably rig up something better at some point.  Here's a picture to give you an idea:



After I got it all together, it fired right up and seemed to run fine.  I only had a chance to take it for a short ride up and down the side of a mountain, so haven't been able to really test it yet.  My current impression is that it runs and rides fine.  The plugs look good and throttle response is quick.  I almost think throttle response is better than before, but it could be my imagination.  I'll need to take it for a longer ride to get a better feel of any changes.

My guess is this bike has an actual ECM that can adjust the AFR by modulating the solenoid valve.  I wasn't able to take the tops of the carbs off with them on the bike - like the float bowl screws, these screws need a solid work bench and an impact driver to remove (and, never having cleaned my carbs, these screws are untouched from their factory state).  My thought is a vacuum on the top carb hose barbs causes the jet needle to close (or maybe open?) leaning the mixture out (or maybe richening it?).  The vacuum damper probably acts as a filter to smooth out sudden vacuum changes caused by abrupt throttle changes - maybe the throttle response is better and the damper added a slight delay.  Maybe I'm just crazy.

When I get a chance, I'm going to put everything back and actuate the solenoid myself and see what happens.  I'm guessing when it's open, the bike will run like dung.  I can then check the plugs to see if it runs richer or leaner.

Any insight?  I really know very little about carburetors other than the basic concepts - I'm an EFI man myself - so any thoughts are appreciated.             

[Allen]

If it aint broke, dont fix it.

[twinrat]

the white things you have circled are the vacum lines that go to top of carb which has a diaphram to lift the slide and needle .these are needed because you dont have a throttle cable going down through  top of carb to lift the slide and needle.

[twinrat]

the little black tank is a vacume tank,it is there tohold a small amount of vacume  to help lift your slides when you accelerate .even thoe these are CV carbs they obviously run out of vacume higher in the revs to hold the slide up.i am thinking of fitting a larger one as i get a flat spot when im nailing it hard in third gear ,it does not do it in any other gear.it seems like an ignition cut between 5500 and 6800 rpm then it haul rrrrrs

[LimaXray]

If it aint broke, dont fix it.

That, sir, is a defeatist attitude 

the white things you have circled are the vacum lines that go to top of carb which has a diaphram to lift the slide and needle .these are needed because you dont have a throttle cable going down through  top of carb to lift the slide and needle.

the little black tank is a vacume tank,it is there tohold a small amount of vacume  to help lift your slides when you accelerate .even thoe these are CV carbs they obviously run out of vacume higher in the revs to hold the slide up.i am thinking of fitting a larger one as i get a flat spot when im nailing it hard in third gear ,it does not do it in any other gear.it seems like an ignition cut between 5500 and 6800 rpm then it haul rrrrrs

I don't think this is correct.  The diaphragms in a CV carb are actuated by the venturi vacuum, not the intake vacuum.  These are effectively inverted from each other - the intake vacuum is high when the throttle is closed and little air can reach the cylinders, while the venturi vacuum is high when the throttle is open and plenty of air is moving through the venturi's restriction.  Think about it - if the intake vacuum were used, the slides would be full open at closed throttle, and closed at WOT - that obviously wouldn't work.  Furthermore, the venturi vacuum is routed internally to the carb so there is no need for external vacuum lines.

All of the other CV carbs I've seen before don't have such a complex top cover - it's usually just a simple plastic cover.  See here.  On the '04+, the cover is cast aluminum with visible chases and what appears to be a small diaphragm valve bolted to the side of it.

It looks to me the 'white valves' do something with atmosphere air pressure, altering how the slides behave to a given venturi vacuum.  See the gold colored pipe going between the tops of the carbs?  That goes to atmosphere through a small air filter.  My guess is they let air into the top of the slide valve diaphragms, causing the slides to drop and closing the needle jets. 

I now think the actual purpose for the vacuum damper and check valve is to make a vacuum constantly available to operate the 'white valves', even under WOT conditions when the intake air pressure is near atmosphere.

Seeing as the other major changes to the '04+ are the addition of a 'proper' crank position sensor and a throttle position sensor, I think this is used for tuning the fuel mixture.  RPM and throttle position (a proxy for load) are all you need for an alpha-N fueling calculation using a 2D fuel map.  So you could start off with slightly oversized mains, and lean it out to the sweet spot across the entire power range.

If this is true, those of us with upgraded intakes or exhausts on the newer models may benefit from altering the fuel map (difficult, the ECM is potted in epoxy) or removing this system all together.  After I do a bit more riding with it off to see how it compares, I'll probably put everything back and bust out the oscilloscope to delve a little deeper into how the thing works. 

[Yuri.]

If it aint broke, dont fix it.

If it aint broke, fix it until it is

[starwalt]

The ECM question is a good one regarding the GS but as of 2009, the Suzuki literature still claims it to be more of a 'dumb' CDI type of control system.

The new carbs have a TPS (throttle position sensor) so why Suzuki doesn't just integrate an EFI solution really depends on how they view the product...err GS500F that is.

The different markets, supply line parts, philosophy of the product, and often customer demand drives that kind of decision.

I have often thought about a data collection system for the GS.
Maybe as a grad school project?  Nah... that would take the fun out of it..

[ben2go]