Flooding Carbs? 80 GS450

[Westy62]

WOW....I've been reading this forum for weeks about petcocks and fuel issues figuring I had it figured out, but I guess not!

My 80 GS450 has a new petcock and rebuilt carbs, but will only start and run for about 3 minutes before gas starts to fill up the airbox and leak out the drain.

One of the float bowls had a small leak so I soldered it and it's fine. The bowl level is set at 22.4 mm, and the petcock IS working correctly.

I'm totally confused on this, and will take the carbs off again. Could anyone shed some light on this issue? I've owned the bike 2 weeks and this problem has been slowly getting worse as I try to fix it!

I know cars all too well, but a newbie on bikes! The plugs were tan when I first looked at them when the problem started, but now appear black.

Thanks!

[Westy62]

P.S. The only thing that's different is the position of the fuel outlet on the petcock....the previous owner had it pointing down with an inline fuel filter and lines going under the airbox and up to the carbs to the fuel "T", now I have the fuel outlet pointing in (back toward center of bike), and a shorter fuel line going right down to the "T".

I don't have a Clymer manual yet, so I can't see how this is supposed to be routed....Any difference?

TY

[bgmart450]

I doubt the direction of the outlet matters. Most likely they are designed for space in mind per model.

How are the floats? I had both carbs on mine get small leaks at different times. After you pull them off next time give the floats a shake, if they rattle they are likely leaking. When they were the gas was pouring out of the vent tubes.

[Westy62]

One float (of the 4 brass floats) was a leaker.....I soldered it up and it seemed fine, it was full of gas, thought I found the problem! I'm going to tear them off again tonight. I'll also replace the plugs, oil/filter because they're soiled from the gas.

Maybe I checked the float level wrong? Upside down carbs, measure from the bowl gasket surface up to the bottom of the float?

[spyug]

Apart from floats that don't, if you have the height set correctly ( which you seem to) the issue is likely with the petcock and or the float valve.

I am very familiar with this from my XS650 and it is a very common issue with bikes that use vacuum assisted petcocks. You may think the pcock is good by pulling off the gas line to the carb and watching for drips but those little buggers are just lulling you into a false sense of security. You need a long term test. Get a couple of feet of clear hose and stick one end on the pcock and the other in a jelly jar. Leave overnight. Check in the morning. Warning: Only do this in a place where there is plenty of ventilation and be really careful about flame or spark ( I.e water heaters, light switches etc, remember gas vapour makes a great bomb...just ask the Air force) If no joy juice in the jar your pcock is likely good but for real peace of mind repeat the test a few times. If it is good the culprit is likely the float valve.

Often a tiny spec of crud will end up where the pointy end of the valve is supposed to seat and or the valve itself is worn from years of service. The easiest solution is to buy the carb kit and drop in the new valve set.

These old bikes are great when they run but carbs are always an issue.Doesn't matter if its Suzuki, Honda or Yammie.

Hope this helps and let us know what you find.
Spyug,

PS I've just cleaned and rebuilt my carbs on the 83 750 for the 3rd time in a row over 2 days. Finally got the bike to run \\/ and now gas is ****ing out of one carb into the airbox doh:shock: . So I'll be checking float height and changing those damn valves too.
You are not alone.

[Nessism]

PS I've just cleaned and rebuilt my carbs on the 83 750 for the 3rd time in a row over 2 days. Finally got the bike to run \\/ and now gas is ****ing out of one carb into the airbox doh:shock: . So I'll be checking float height and changing those damn valves too.
You are not alone.

Remember the Aamco Transmission commercial where guy brags about having fixed one particular cars transmission 42 times?

[Westy62]

So.....Nobb question here, is the float level measured at when the float closes the fuel valve, or do you push the float down until it runs out of travel?

I may have adjusted mine wrong....I'm showing 26mm where they close the fuel off (I'm blowing into the fuel line), and 23mm when I push it down all the way.

This is from the base of the gasket surface (with the gasket off) to the bottom of the float.

TY

[ta473]

floats

i did the same thing and had the same problem on a gs 1100./ the float just needs to close off the fuel when you set the level.Do not push it down.adjust your 22.5 from just closing off the fuel.

[Westy62]

Ahhh, yes. I read my Clymer manual for a little 2 stroke Yamaha dirt bike I have (I didn't even think things might be similar). In the Mikuni carb section it says to let the floats weight rest on the fuel valve spring (don't push down) while inverted, man.....mine is 26mm on one and 27mm on the other. Not sure why this would flood, because it seems to be the opposite like lean, but I'm going to make some adjustments and do the petkock test also!

Maybe I should stand on my head and do this while looking into a mirror (and pat my head at the same time), maybe I can figure it out then.

Burnin' the candle tonight!

[Westy62]

WOW, drained the oil and it came out like gas! The filter smells like gas also, this thing flooded more than I thought! I hope I don't have a bigger mess in the bottom end of this motor now....:?

Well, not going to run it tonight without a new filter and oil change!:shock:

Thanks for your help tonight.....Wes

[Nessism]

The float height is set where the tap on the float just contacts the spring loaded point on the needle.

This diagram is from a '81 550 so I'm not sure if it's the same as a 450. Inspection method is the same though.

[Westy62]

Woo Hooo! Getting the right float height (or setting it correctly this time), and soldering the leaky float did the trick! The bike runs great, but I have a slight lean condition from what I've read here. My air intake is not sealed correctly causing an occasional backfire (about 6 in a 1/2 hour ride), and the bike runs flat at about 7-8k (pulled a small wheelie shifting into 2nd though!):shock: This was the first time getting on it since I've owned it.

This bike really runs out for an 80 GS450E, and the bike was stored for 21 years! It currently has 7,900 miles......now I can put my new tires and tubes on!

Between the petcock and the float issue, it's been over a week of head pounding.....\\/ No more gas leaking all over and filling up the crankcase!

Thanks for the help!:-D

[bgmart450]

Nice! I know the feeling of pulling off the carbs a few times, then replacing the petcock, etc etc only to have to change the gassy oil AGAIN....