2004 GS500F full carb cleaning help!

[jeffroGS]

Hi all, new to the community! Picked up this bike as a project for only $500.
Story goes is that it sat for 8 years.

I have never worked on an engine thats had a carburetor.

I have changed the oil
I have cleaned the rust out of the gas tank
I have cleaned the jets in the carb
I have installed new fuel lines w/ inline filters
I have found that the clutch safety switch is faulty so have bypassed it for now

After cleaning everything, putting it all back together, and turning it over, NO fuel is making it into the carbs. There IS fuel in the line from the frame mounted petcock to the bottom of the carb.

The jets were incredibly gunked up and took a bunch of work to clean them out, so i figured that would be it and i would ride off into the sunset, however that wasnt the case.

Is there something else I need to clean? I am sure there is. I have searched around and have not been able to find a guide on a full clean.

Any help is appreciated!

[chris900f]

If you set the petcock to Prime and let the bike sit a minute, you can see if fuel is getting into the float bowls

by opening the drain screw (attach a fuel drain line to the spigot first). If no fuel flows the next easiest thing to

check is the carb breather hose...if air can't get out; fuel can't get in. If the hose checks out, then the float needle

valves may be stuck closed or the floats may be stuck in the lifted (closed) position; but try the easy stuff first.

[jeffroGS]

Thank you for the suggestion. I will try this tonight and report back.

Is the breather hose the one that connects to the center of the air box? I can feel air being pushed out of this hose when turning it over if so

[mr72]

no. the breather hose is connected to the "T" that the fuel line is not connected to. I can't recall which one at the moment, but it should be obvious.

The hole in the airbox should be connected to the crankcase breather, which is on the cam cover. There should be a rubber hose. You feel air pulsing in this because as the engine turns the air that is displaced by the movement of the piston has to go somewhere, and they put it into the airbox rather than venting it to atmosphere because it tends to contain hydrocarbons ether evaporated from the oil or actual liquid oil, which then gets drawn through the air filter and into the engine to be burned along with the fuel.

Now, chris900f explained the possible causes of your issues, but suffice to say on a 2004 with stock 17.5 pilot jets, it's highly unlikely that you got them clean enough. You should replace them instead, with size 20. And there are two things you likely didn't clean which are critical to startup and idle: the pilot air inlet, which is a little bitty hole in the edge of the carb venturi, and the fuel passage beneath the pilot jet. You have to clean these with some kind of wire. I use old guitar strings to run through and make sure they are clear of gunk, and then put eye protection on and spray some carb cleaner in there and then use compressed air to force air through. Also, you didn't mention whether you replaced the float needles and seats, but you should if you haven't. This is literally how fuel gets into the float bowl.

And the other thing you're going to run into guaranteed is hardened or cracked o-rings, three in particular for each carb. One is the intake boot o-ring, which you get to by removing the intake boots. No purpose in removing the carbs to clean them on an 18 year old motorcycle without changing this part. Second will be the float needle o-ring, which you will have replaced if you replaced the float needle seat as you should. And the third is the hard one, it's the pilot needle o-ring, you get to it by removing the pilot "adjustment screw", which you will discover is not really a screw at all, and with it a little spring and a tiny washer. When you remove all of this, if you are lucky the o-ring comes out with it, but most likely you'll have to fashion some kind of pick like tool to pull the hard, cracked, flat o-rings out of there and then replace them.

Of course, all of this is standard issue with a carb rebuild. You did that, right?

You got a $500 motorcycle. Now spend $60 on carb rebuild kits and the intake boot o-rings and do the job right. See my signature for a link to walk you through it.

[Bluesmudge]

This is a really good carb tutorial for the 4 cylinder Suzuki GS bikes:
https://gsarchive.bwringer.com/mtsac/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf
Its from BikeCliff's website that is associated with GSresources. Most of the stuff on those websites isn't geared towards the 2 cylinder GS bikes like ours but in general the quality is better than what you will find on the GStwins wiki (no offense to this site, but we have never had the same commitment to perfection as the 80's GS aficionados).

Most of the methodology is the same but takes 1/2 the time with only 2 carbs. There will be a few more vacuum hoses and parts on your bike since the later GS's had more emissions equipment. If you properly block it off you can actually remove all of this stuff to simplify things, none of it improves performance.

If the bike doesn't run with a few easy fixes, its best just to go all the way and set everything to stock as mr72 is suggesting. That PDF will sort of walk you through it, at least the principle of the cleaning.  All new o-rings and gasket, all new jets, float valve and seat. Check that your diaphrams look good and have no pinholes from previous owners spraying carb cleaner into the carbs without disassembly. Take everything apart and soak the metal bits (and only the metal bits) in a carb cleaner bath from 24 hours. I recommend genuine mikuni parts, especially for the float needle. I have had bad luck with K&L stuff. You should be able to get it all from jetsrus.com, partzilla, or your local Suzuki dealer.

[wagnerosss]

Hey guys!

Recently I bought a carburetor kit (Tourmax CAB-S17) for my GS '07. Anyone can explain me which round seal is for what? I only found that one fits onto the main jet.

Here's an example link: https://www.mvh-shop.de/Motorcycle-Carburetor-Repair-Kit-Tourmax-CAB-S17

Maybe someone used it before or at least can easily point me out which seal I need to change.