GS450 Running way too rich. HELP!

[vivisected]

Ive been trying to remedy this problem for over a year now.
My bike is my dominant mode of transport, not just a hobby, so to have it act up like this makes things alot more difficult.
Ok so heres the bike:
1988 Stock Suzuki GS450
Regular oil changes, 75% rebuilt carb (only the diaphragms and related assembly, needles and slides, werent replaced)

The Problem:
When I got the bike it didnt run. I cleaned the carbs out really well and that got her going. As time went on, I started to notice that the RPMs would stay elevated after acceleration or throttling in Neutral. I figured i was sucking in some air somewhere so i did a refresh on the carbs and replaced about 75% of the parts leaving only the diaphragms and related parts original (they seemed fine and were very expensive to replace.) After this, the bike ran the same as it did before. More time goes on (6-8 months) and now the problem is so bad that between shifts, the bikes RPMs will actually rise to about 5k (tach broke a few months back, but i can tell its not redlining but its definently not sinking either) and when I come to a stop, I have to make sure i leave it in gear until the RPMs drop to under 2000, and then it will idle without shooting back up.
That basically sums up the problem, if the REVs go above 2kish then it shoots up to 5-6kish when not in gear (or with the clutch in)
Like I said, i thought it was excess air for a while until i found out that the "choke" on the bike is actually a fuel enricher and noticed fuel condensing in the vacuum lines. Also, I shot carb cleaner around the carbs in all different places, and no surges developed from that. My carb boots were replaced not long before I got the bike, and look in fine order.

Other symptoms include, but are not limited to:
1. Very hard to start in the cold

2. When the "choke" is on, after the engine starts to warm up, the RPMs shoot way up(this happened ever since i had the bike and what had led me to believe it was an air problem, not a fuel problem)

3. If the bike revs up right before I shut her off (coming in to a parking space or something, and not bothering to attempt to get the RPMs down since im parking anyways) she'll backfire(another reason i figure its excess fuel)

4. Seems to be eating alot more fuel. when i first got the bike, it would do between 42-50mpg. Now its getting 35-40mpg... horrible for a old jap bike as far as i know.

Its very annoying when coming to a stop light, and having to let the clutch out to make the RPMs drop enough to keep it under 2k to get it to idle revs.
That about sums up the problem, any help would be GREATLY appreciated.
Thanks

 

[Larry D]

Hard starting is a classic symptom of a needed valve adustment. When were the valves adjusted last ?

You have an air leak somewhere. Normally, it's the intake boot orings. Behind the intake boots that are bolted to the back of the head, there are orings, over time they will flatten out and leak air. You may also have air leaks other places, make sure your air filter is clean and there are no leaks in and around the airbox itself.

 

[tom203]

Hard starting is a classic symptom of a needed valve adustment. When were the valves adjusted last ?

You have an air leak somewhere. Normally, it's the intake boot orings. Behind the intake boots that are bolted to the back of the head, there are orings, over time they will flatten out and leak air. You may also have air leaks other places, make sure your air filter is clean and there are no leaks in and around the airbox itself.

Yeah this stuff. Hanging/high idle means air leaks.
You replace 75% carb parts with suzuki stuff or aftermarket items?

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. vivisected,

Yes, these are classic symptoms that are usually relieved by sealing up the air intake system (replacing intake boots and O-rings, sealing the airbox, etc) and adjusting the valves. You may also want to take a good look at cleaning the carburetors properly. There is a guide specific to the 450 carbs on my little website along with valve adjustment, air intake repair, airbox sealing, etc. Now let me share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Rebuild Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

 

[vivisected]

Yeah this stuff. Hanging/high idle means air leaks.
You replace 75% carb parts with suzuki stuff or aftermarket items?

100% suzuki stuff

I will have to look at valve adjustment, cause thats one thing i havent done yet.

Ill check the O-rings behind the intake boots just to make sure that its not leakin in air there.

however, black sooty plugs, backfiring and fuel condensing in the vacuum lines can indicate running too lean? Just want to make sure im heading in the right direction.

I just stopped by to welcome you to the forum in my own, special way.

Thanks for the welcome

 

[vivisected]

ohh yeah, one more symptom
what seems to be condensed fuel is driping out of the breather hose. Its not comin out at an alarming rate, but you can definantly take notice.

 

[BassCliff]

Hi,

Could the throttle cable be getting pinched or pulled, not allowing the engine to return to idle quickly?

Vapors in the breather tube is normal. This should be connected to your airbox so that those vapors get introduced back into the air intake to be burned. Or are you running without an airbox?

Fuel in the vacuum line is not a good thing. Faulty petcocks are common. There should only be one vacuum line between the carb and the petcock. Other hoses should be vents. Do you have an aftermarket petcock?

Where are your idle mixture screws set? How many full turns out from lightly seated?


Thank you for your indulgence,

BassCliff

 

[vivisected]

Hi,

Could the throttle cable be getting pinched or pulled, not allowing the engine to return to idle quickly?

Not likely, ive checked that pretty closeley, and it feels perfectly normal. Watched it return right back to where it should be and can feel it happen in my hand.

Vapors in the breather tube is normal. This should be connected to your airbox so that those vapors get introduced back into the air intake to be burned. Or are you running without an airbox?

Ive just had it off the box temporarily, watched it drip, then put it back on.

Fuel in the vacuum line is not a good thing. Faulty petcocks are common. There should only be one vacuum line between the carb and the petcock. Other hoses should be vents. Do you have an aftermarket petcock?

Both, the original tank one and a simple inline on/off. Let me explain.
Last year, i noticed the original petcock going south (gas pouring out of my airbox cued me in on that one) and overhauled it. Got a petcock rebuild kit and fixed her up, but just thinking about all that gas in my engine gave me the willies, so i installed a inline on/off valve just incase, and use it when i shut the bike off.

Where are your idle mixture screws set? How many full turns out from lightly seated?

Theyre all the way seated, it makes absolutly no difference what position i put them at, it idles the same... so, as you can tell... bikes not running that great right now.

 

[vivisected]

100% suzuki stuff
Ill check the O-rings behind the intake boots just to make sure that its not leakin in air there.

Actually, i replaced the o-rings last year, just forgot if i did or not.

 

[earlfor]

Two things come to mind.
1. Did you replace the "O" rings on the fuel inlet needle valves in the float bowls.
2. Are the float heights set to the correct level.

As said previously, if the valves are beyond tolerances, the bike is not going to run well no matter what else you do.

Earl

 

[vivisected]

Two things come to mind.
1. Did you replace the "O" rings on the fuel inlet needle valves in the float bowls.
2. Are the float heights set to the correct level.

As said previously, if the valves are beyond tolerances, the bike is not going to run well no matter what else you do.

Earl

Thats funny, before i posted here i thought... Float height? But i HATE having to rip those things off! i cant tell you how many times ive done it... but obviously i have to again.
Anyways, when i rebuilt them i did replace the fuel inlet needle valve o rings, and i checked the float heights, but ill obviously have to check them again.

But yeah... Im definantly going to have to check those valves. That seems obvious. Ive got some oil leaks around the breather gaskets anyways. Looks like its time to take care of them.

Thanks