Gas in airbox

[Colorado85gs550]

there was some information that this bike of ours being a "buzzy" little motor causes the fuel to froth up at sustained high rpm........I think that given the right outside air conditions/altitude, etc you could be experiencing some of this.....just a thought!

[Colorado85gs550]

DATE: September 27, 1998
QUESTION: Performance info needed - 1983 GS550
I have a 83/84 GS 550 es that I am racing in AMA/CCS sportsman competition here in Fla. Do you know of any place that I can get tech tips for engine updates, help on those miserable dualthroat carbs, cam degreeing numbers, performance parts availability, etc.? I can find listings for headers, jetkits, and such, but I would like to know what was done to these bikes (the 550tscc)back when they were new. Do you know if Yoshimura, or Yoshima, ever fiddled with them? Any help that you can give me would be GREATLY appreciated!
I have the chassis working pretty well at present, with Katana forks, brakes, and wheels, and GSXR shock/w modified linkage. I would like a little more guts in the engine though. At present the carbs are set up with 118 mains, 37.5 pilots @2-3/4 turns out,and sc15 needles. I'm running a yoshi header, a k&n filter, and undercut trans. I have the ignition advanced 4deg.On the top end it's good for about 125mph as geared. But I would like more grunt in the mid-range. I realize this is all pretty confusing, but if you have any insights, I would sure be interested in hearing them.
RIDER: David Starling
REPLY: Zack Schultz
I have an 84 GS550 myself. I'll start with your last comment first. These things were supposedly good for 125 new. I saw this myself (indicated) several times. And I'm glad someone is campaigning one. Tuning the carbs. Think of them as siamesed singles and the problems minimize. Everything is separate except the float bowls. Hence, the bowls are undersized. Make sure that there is enough fuel flowing to feed the motor.
Kevin Cameron once wrote that some buzzy engines (and this qualifies0 have trouble with fuel frothing at sustained high R's (like Daytona). Foam doesn't lend itself to accurate jetting. Adding weight to the carb dampens it's vibration and frothing is eliminated. I think he said something about a pound of welding rod wrapped around the float bowl. I did speak to someone a few years back in the Galveston area that was racing one of these. I don't keep up on the class rules, but he was using 600 Hurricane pistons (63 mm) in the engine. These are the same size that Wiseco was using in their big bore kits, so there's metal to go that far over (+3mm). Good luck and pass along results.

[don]

It will do this even if I just take it out around the block. 40mph or so.

[Colorado85gs550]

I definately think something didn't get put back on properly inside atleast one of the carbs........have you removed the air box and run it static to see if you can see fuel sputtering out of the carbs in a mist or if it is simply running out of one?

I think your next step would be removing the airbox and running it at rpm in a static state to see what you can see coming out of the carbs and where......

[Dave8338]

If the petcock (once back together) still flows fuel down the vacuum line...I'de suggest a complete new one. I put a rebuild kit in mine and after futzing with it for several hours, I used it to test my throwing arm!

If need be...buy a new one and save yourself a TON of PITA.

[don]

Good idea Colorodo. I see you have one of these. (Giant pic of a perty blue one as your signature.) I'd love to try that. I have 2 concerns though. One being it's gonna run crappy and WAY lean, and B, how the @#!% does that sugar coated airbox come out of the frame?

[Colorado85gs550]

the airbox is a piece!!!.....first thing I did was remove my tank, seat, side covers, battery, and battery box. There are a couple of bolts on the top of the box that bolts it to the frame, remove them. remove the boots between the box and the carbs....I removed them by prying them gently out from between with a crowbar after spraying them down good with WD40.

Once the boots are out, you can wiggle that thing out from the side........it takes a little persuasion!

Paul

[Colorado85gs550]

you can put it back in after you figure out the problem......

[don]

Out the left or right side? I take all that crap off every time I take the carbs off anyway. I spend 15 minuits cursing at the lack of room to get them out or spend the 10 minuits taking all that stuff out of the way and 15 seconds getting the carbs out. The 45 second gain is way better than ulsurs from getting all ****ed off. From fully assembled, (side covers and all), disassembled, then reassembled, I can do it in about 15 minuits.

PS
In your post about the gear ratios.
The bigger the big sprocket, the higher the rpm. The smaller the small sprocket the higher the rpm. Higher rpm = lower top speed but snappier till red line.

[Colorado85gs550]

I just went down to a 13 tooth on the front and back up to a 48t on the rear....just ordered them

if you can get the carbs out in that time.....you can get the box out in the same amount of time

just make sure after you unbolt the box you slide it forward towards the carbs and then out the side....either/or is just as hard

[DimitriT]

I had the carbs overflowing into the airbox on my 550 until I checked the flloat
level and adjusted them according to the manual. The problem would only happen
when I was riding up a steep hill. Just a thought.

[don]

Good thaught Dimitrit. Double checked that and other things. All seems to be in order. Thanks for the suggestion.

[don]

Valve springs

As mentioned in an earlier post in this thread, we're going to put new intake valve springs and gaskets in it and give it a whirl. One problem, can't find valve springs anywhere. My bud works at a Suzuki dealership and he can't find any. Would anyone know where we can at least look?

Thanks.

[don]

OK fellas. Been working on this deal for a while now. Did a valve job at a suzuki dealer, adjusted the valves, checked the valves, checked the valves, and checked the valves, put a different set of carbs on it, put the original set of carbs back on it, put the other set of carbs on it again, checked and adjusted the float hight, checked the float hight, and checked the float hight, checked the actual fuel level, checked the fuel level, and checked the fuel level, put new suzuki needle and seats in, new jets all around. Looked in the airbox with a mirror and a mini mag light. #2 is the culperit of the gas leaking out of the airbox. (remember these are those siamese carbs, two carbs in one.)

With either set of carbs on the bike, the 1&2 carb is the one that causes the overflow but only the #2 port. When I looked in the airbox at the carbs I could see the gas purculating up from between the slide needle and the main jet body, where you would expect it to come from when you're on the needles. But this was at an idle. The factory spec for the float hight is .077-.085 and the fuel level is .240-.280. I have set the floats to .930 with a fuel level of .310 and everywhere in between, it still happens. I have removed the vaccum fuel valve and the carbs don't overflow while the engine is not running.

Please help......WTF????????????

[MacGyver]

Hi Don,

Having recently taken apart a 1983 GS550E with issues, I can understand your frustration. I believe there is a reason those twin carbs were used for just a couple of years, they caused more problems than the money they saved.
My exploits - http://www.thegsresources.com/_forum...d.php?t=141950

My thoughts:

Go to BassCliff's site and get the service manual if you haven't already. Check out page 4-7. The fuel is splashing up from your Needle jet according to your description. Pull the carb apart (again... likely) and check the seat of the Needle jet along with the washer and Main jet seating. Something stuck in the Main air jet could cause a higher than desired vacuum around the Jet needle and to much pure gas being drawn up. I would swap all the parts from one side of the carb (except for the Main jet - they need to stay with their respective cylinders) to the other and see if the problem follows the parts.

Also, just because you can, check your starter plungers and make sure they fall into place effortlessly - that was the main source of my issues. I did have a fuel in the air box issue for a while, but I attribute that to very dirty needle valve screens and the need for a proper cleaning, that issue is gone now.

For what it is worth, when I cleaned my carbs, all my parts were mixed up. The only parts that could have gone back into the same carb except by random chance was the 50/50 on the main jets. Swapping around some parts may reveal some tolerances that are out of whack.

Good luck! I have one minor issue with my GS550E, but I think that may be an idle mixture/pilot screw adjustment, I think I am running to lean. One of those fancy Colortune plugs would be great right about now.