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Hanging Idle (I know, but bear with me) and different carbs

Katana1074 said:
Check your fuel tap, place a piece of temporary clear hose from the vacuum port on the fuel tap to the carbs and check if any fuel is entering the vacuum hose
Click to expand...
(y) Petcock leaking through the vacuum line seems like a prudent thing to check.
 
Katana1074 said:
Check your fuel tap, place a piece of temporary clear hose from the vacuum port on the fuel tap to the carbs and check if any fuel is entering the vacuum hose, they look like the proper carbs for the bike, there should be a 5 digit number stamped on the side of them just above the float bowls....
View attachment 1786875View attachment 1786876
Click to expand...
I think this was it.

Replaced the petcock and tested last night for just a bit and it didn't run away from me like it was. Rode twice today for an hour or so and didn't have any issues.

The startup sequence is a little weird, not sure how long bikes usually take to get warmed up, but if I put on the choke, then open the idle adjust a bit, I can get it to idle without the choke in about 5 minutes. Then once I ride it a bit, I can back the idle adjust out. I'm sure this isn't normal, but it's been working so far.

I did another vacuum leak check with the propane torch and still haven't found anything so I *think* she's running well.

Thanks again to everyone who helped me figure this out and offered multiple things to try and investigate.
 
Idle w/o choke in 5 minutes is a tad long, but letting it idle with (varying amounts of) choke for a few minutes after start up is not improper. Your choke is there for a reason - use it.
On the other hand, the idle set screw is not normally meant to be used every time you ride. Quite the opposite - on a well-running bike, set it and forget it. For a long, long time.

In fact, you seem to be using the idle set screw instead of (or together with choke). See if you can find a start up procedure that doesn't include the idle set screw.
 
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Rob S. said:
Idle w/o choke in 5 minutes is a tad long, but letting it idle with (varying amounts of) choke for a few minutes after start up is not improper. Your choke is there for a reason - use it.
On the other hand, the idle set screw is not normally meant to be used every time you ride. Quite the opposite - on a well-running bike, set it and forget it. For a long, long time.

I fact, you seem to be using the idle set screw instead of (or together with choke). See if you can find a start up procedure that doesn't include the idle set screw.
Click to expand...
Yeah I just took it out this morning and it's been giving me issues. It appears to be running too lean still. The sparkplugs are basically spotless.

It rode fine for a minute, but then a few miles down the road after going about 55 in 5th gear, it suddenly lost most of its power. After pulling over and turning it off, it wouldn't even start again unless I did the choke/idle screw nonsense again. Something is still borked regarding fuel.

IMG20260528080703(1).jpg
 
Have you checked the fuel height aka float height ??

are the correct size jets installed ?

sorry just looked at the start of the thread, make sure you have the correct float needles (not to long)

float height adjustment from 17mm to 22mm is a long way out....

and do you have the black rubber caps on the pilot jet orifices ?
 
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@LambBrainz If If it loses power and stalls, but starts again after sitting that's a sign the vent in the fuel tank cap is clogged. If that happens again, pull the cap and listen for the tank to inhale. Maybe that's part of what's happening, maybe not....
 
Katana1074 said:
Have you checked the fuel height aka float height ??

are the correct size jets installed ?

sorry just looked at the start of the thread, make sure you have the correct float needles (not to long)

float height adjustment from 17mm to 22mm is a long way out....

and do you have the black rubber caps on the pilot jet orifices ?
Click to expand...
Float height should be correct (at least according to several manuals).

I do have correct jets installed

I *think* I have the correct needles, I'd have to check

I do have caps on the orifices
 
Burque73 said:
@LambBrainz If If it loses power and stalls, but starts again after sitting that's a sign the vent in the fuel tank cap is clogged. If that happens again, pull the cap and listen for the tank to inhale. Maybe that's part of what's happening, maybe not....
Click to expand...
This might be it, I filled for gas before the ride and noticed it didn't click like normal but just assumed I did it wrong. I'll try that and see
 
I was just going to say what rphillips did. Wait until it is hot. The choke is for AT LEAST the first 5 minutes to keep it running. If the carbs are in or past the transfer slot it will never idle right.
 
is this a 450? i'm gonna assert that the carbs are just not tuned well. you probably have the idle circuit too lean. if it's anything like mine - my idle screws had to be set at 5 turns out. i'd try turning yours out some more, maybe half a turn at a time, and go test. if this is the problem, you'll notice you can set the idle set screw lower without it dying.
 
bren said:
is this a 450? i'm gonna assert that the carbs are just not tuned well. you probably have the idle circuit too lean. if it's anything like mine - my idle screws had to be set at 5 turns out. i'd try turning yours out some more, maybe half a turn at a time, and go test. if this is the problem, you'll notice you can set the idle set screw lower without it dying.
Click to expand...
Oh yeah! I'd forgotten about those lol

This is a 450

I remember reading your adventures and how you solved it by backing them out a crazy amount.

I'll give that a shot as well, thanks!
 
Alright, gas cap seems to have been then issue on the high end. I rode around today and it didn't do it to me as often as it did before. I rode the same route and it only happened once. Not sure why

Backed out the idle screws out in half-increments to about 5. That seemed to help but I think it needs more adjustment. Because even once I got it idling and backed the choke off a little, it didn't wanna idle without choke until I helped it by turning the idle adjustment screw in.
 
Still seems pretty lean. How on earth do I give this thing more gas without it getting weird on me lol
 

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Until bike is warmed up, the choke regulates the idle. When bike completely warmed up the idle adjustment screw (knob) controls the idle, with choke completely off.. When completely warm, can you turn the idle adjustment "in" enough to keep it idling with choke completely off?
 
Can we all agree on one thing? That the choke is meant to be used virtually every time the bike is cold started. Particularly on these old GSs, which were known to need a lot of choke adjusting on start up.

And on another thing? That when the GS is performing like new, there should not be ANY adjustments necessary or made on the idle adjustment screw. It's set at the factory, or by the last person to rebuild or tune your engine (or carbs).

But in our cases (50-year-old bikes), the idle adjustment screw is sometimes used as a bandaid for underlying problems.

And I think we can all agree that original poster's carbs are not functioning correctly. If your car is leaking in the rain, you can 'fix' it with duct tape, but...
 
Hope I wasn't wrong say'in if needs some choke to keep idling when warmed up, increasing the idle adjustment knob may possibly help or correct problem.
 
rphillips said:
Until bike is warmed up, the choke regulates the idle. When bike completely warmed up the idle adjustment screw (knob) controls the idle, with choke completely off.. When completely warm, can you turn the idle adjustment "in" enough to keep it idling with choke completely off?
Click to expand...
Yes.

Once it's warm and running fine, I can have the choke completely off *and* turn the adjustment screw all the back.

I realize this is not normal, but I can't figure out why it's necessary to get it started and running happy. Obviously the idle circuit isn't happy, but I can't fathom which portion. These carbs have been dipped and cleaned, I sprayed cleaner through every port to prove it. Floats aren't sticking and are within spec for the manual (and that one big spreadsheet floating around)

My only guess are the two idle screws between the carb and engine. I think I just need to keep playing with those.
 
Alright, the idle screws are backed out to 6 turns. Start up was a little better (didn't need to use the idle adjustment screw hardly at all).

However, after getting it warm and doing some easy riding I then took it out for something harder. Once I get up to 5th or 6th gear (around 60mph) it will lose power and die. The frustrating thing is that it isn't consistent. Sometimes it dies completely, other times it's fine, and one time it would oscillate between losing a bit of power and being fine before dying.

I'm still new to this, but would that suggest an air issue? Or something with the slides/needles? When it completely dies I have to turn the choke back on and (sometimes) turn the idle adjustment screw just to get it to start again. Once it runs for a few seconds, I can turn the choke off and back the idle adjustment out. This suggests to me that it still isn't getting enough fuel.
 
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