GS500F mysterious vacuum leak

[Krazer12]

Please help me out.  I'm completely stumped on this.  I've been fighting with a vacuum leak since I bought the damn thing, and I'm VERY frustrated.  I rebuilt the carbs and replaced every o ring, replaced the carb boots with decent used ones, replaced the carb boot o rings, plugged up all auxiliary vacuum hoses/ports (EGR, even fuel pump line as I'm feeding it fuel manually), and even took off those white caps to make damn sure they're sealing with some o rings (in case those little diaphragm were leaking, and it's only temporary).  Holy hell, am I ever stumped.      And if I spray carb clean on the cylinder side (in the area of the boot) of the right side one, it still dips in RPM.  Maybe the old carb boots were still sealing and I replaced them unnecessarily?      If anyone has ideas, PLEASE help me.  I just wanna ride my first bike!!! 

Thank you in advance!

[Armandorf]

Clearly, you dont replaced every source of vaccum leak...no wonder
we should make a list and tick every line...

try grease on the boots

[Krazer12]

Clearly, you dont replaced every source of vaccum leak...no wonder
we should make a list adn tick every line...

try grease on the boots

Do you mean, like, grease the inside only?  Or slather some on the outside, too, around the border?

[DarkCyDE]

put it on the outside only

[Armandorf]

if it is on the cylinder it could be head gasket, you should  test compression or put oil and look for bubbling maybe.

my failing head gasket bubbles oil out when really warm

[Krazer12]

if it is on the cylinder it could be head gasket, you shoul testcompression or put oil and look for bubbling maybe.

my failing head gasket bubbles oil out when really warm

When I spray the cylinder itself, nothing.  But wgen I spray the cylinder side of the carb, it dips.

[Krazer12]

put it on the outside only

I'm going to do this shortly

[moe_tunes]

If you spray carb cleaner on a vacuum leak the revs should increase not decrease.
What is happening to make you think there is a vacuum leak ?

[Krazer12]

If you spray carb cleaner on a vacuum leak the revs should increase not decrease.
What is happening to make you think there is a vacuum leak ?

It's revving pretty high on idle, generally only wants to run with choke.  So I'm spraying it while choked.

I don't know if it makes a difference, but I'm using Canadian carb clean, which was changed recently from the original stuff that the rest of the world can get.

Maybe after all of this, it just turns out I'm dense.  If I am, I'm ok with that as long as I get to ride... lol.

[moe_tunes]

If the carb cleaner isn't flammable it would be like spraying water at the leak which does drop the revs. If it is flammable then the revs should rise.
If it only runs on the choke that could be a sign of an air leak. It will run at about 4000rpm on full choke normally. What happens if you back the choke off as the engine warms ?

[Krazer12]

If the carb cleaner isn't flammable it would be like spraying water at the leak which does drop the revs. If it is flammable then the revs should rise.
If it only runs on the choke that could be a sign of an air leak. It will run at about 4000rpm on full choke normally. What happens if you back the choke off as the engine warms ?

It will run like crap choked until I blip the throttle, then rise to 4000rpm, then rise to 5000 or 5500.  Back it off a hair, RPM rises a bit, back it off more, starts to die.  But I can blip the throttle, and it'll hang at 3-4k before falling back to dying.

[Armandorf]

how are the needle/diaphragms?

[Krazer12]

how are the needle/diaphragms?

The look good.  I cleaned the needles, and the diaphragm looks in good condition.  I changed the throttle shaft seals with o rings and greased up all my seals.  Now, it runs... different.  Choke doesn't make RPM climb anymore, but dies without.  Carbs are a pain, but at least it seems there's no vacuum leak?

[Armandorf]

Carbs are a pain, yes, but you just need to run it to clean itself a bit. The number one enemy of carb is sitting. Try to use it and see how it develops, you will also learn where and how it fails.
Check plugs to see if you aren't dangerously lean.

[Krazer12]

Carbs are a pain, yes, but you just need to run it to clean itself a bit. The number one enemy of carb is sitting. Try to use it and see how it develops, you will also learn where and how it fails.
Check plugs to see if you aren't dangerously lean.

I shall.  Carbs are clean, but probably everything else needs to clean out, eh?  Was it a good call replacing those seals with o rings?

As a side note, I'm taking the bike to my dad's.  He's built and fixed many, many bikes in his day.  Hopefully we can set everything right.

[DarkCyDE]

Agreed. Many carb issues sort themselves with seat time.

[Krazer12]

Agreed. Many carb issues sort themselves with seat time.

Kinda just "breaking in" the rebuild kit?

[Armandorf]

beware of breaking the needle clips hanger, they have an oring that stiffens up and force them between the tabs,is pressure fit,.if the tab breaks you have a hanging needle and runs unpredictably, binary-like

[herennow]

First get her good and hot and then tune the carbs, and the idle speed. Then start to troubleshoot. By hot I mean a 20 minute ride minimum.