High idle in first gear? Gs450L

[Hihowyaderrin]

While in first gear, my bike brings itself to 4k rpm and seems to hang there. I just replaced the intake boots and outlet hoses and taking a quick ride up the street that it wants to hang there. Noticed it when downshifting from 2nd to 1st, I was definitely slow enough for the gear change but it read 4k on the tach. There must be something I’m missing here. Help

Purchased dead in the water
my beloved 1985 Gs450l

Maintenance history:
carburetors cleaned and rebuilt
bench synced the carbs with a needle
floats set at bike shop (arrived a dripping mess from p.o.)
new diaphragms
new intake boots and air box hoses
airbox filter cleaned and misted with oil
(sealed to the best of my ability with a gasket made of peel and stick roofing rubber)

I spend every free moment trying to research and learn about these Suzukis cos they’re just cool asf in my opinion. wrenching is my favorite past time I’m months deep in my project at this point, that said I’m ready to ride it too

 

[Hihowyaderrin]

Air screw also set 2.5-2 3/4 turns out. Idles @ 1k not under load

 

[Rob S.]

So if you shift to neutral it idles lower?

 

[Cipher]

Air screw also set 2.5-2 3/4 turns out. Idles @ 1k not under load

Throttle cable smooth and snapping back?
1000 is a low idle speed.
where'd you get the spec for air screw?

 

[Rob S.]

Something I'm missing also. Say you're sitting on the bike on the side stand. You're in neutral and it has a proper idle (say 1k). You pull the clutch lever in. Any change in idle? (Shouldn't be). You shift down to first. Any change? What if you shift up to second instead?

In any case, a hanging idle is usually indicative of an intake leak. And since you just changed the intake boots...draw your own conclusions.

Welcome to the site. (Spraying starting fluid around the boots might help locate the leak.)

 

[Hihowyaderrin]

Throttle cable smooth and snapping back?
1000 is a low idle speed.
where'd you get the spec for air screw?

throttle cable seems smooth and snapping back
what is the recommended idle speed?
I got the spec from a manual posted on FB for carb cleaning

 

[Hihowyaderrin]

Something I'm missing also. Say you're sitting on the bike on the side stand. You're in neutral and it has a proper idle (say 1k). You pull the clutch lever in. Any change in idle? (Shouldn't be). You shift down to first. Any change? What if you shift up to second instead?

In any case, a hanging idle is usually indicative of an intake leak. And since you just changed the intake boots...draw your own conclusions.

I torqued the boots down firmly but tried not to over tighten in dear of stripping the cylinder threads

 

[Cipher]

throttle cable seems smooth and snapping back
what is the recommended idle speed?
I got the spec from a manual posted on FB for carb cleaning

1100-1200
https://gsarchive.bwringer.com/
Clymer manual here

 

[Hihowyaderrin]

Now it just seems to be happening out of nowhere, even in idle. Could the fuel line being pinched cause it? It has to be simple

 

[tom203]

You disturbed the old tired o-rings under the boots….get some new ones

 

[Hihowyaderrin]

You disturbed the old tired o-rings under the boots….get some new ones

They’re brand new O rings and boots. Surface cleaned with a rotary tool and installed snug as a bug

 

[Nessism]

Did you vacuum sync the carbs? A poor man's sync can be performed by increasing idle to about 2000 rpm or so, and then pulling off a spark plug. When doing this on both sides, the one-cylinder idle speed to be the same.

Before doing that, get some brake clean or carb cleaner, and spray down the carbs, intake boots, everything on the intake to see if the idle speed increases. This is not a definitive test, but it will show if you have gross air leaks.

And needless to say, adjust the valves if you haven't already. In fact, don't even start the bike if you haven't adjusted them.

Lastly, the new diaphragms raise a red flag.

 

[Chew19]

I had the same problem actually turned out my valves needed lapping, run a compression test if you can, if its low, there ya go.

 

[rosy76]

I had the same problem actually turned out my valves needed lapping, run a compression test if you can, if its low, there ya go.

Laping the valve can definitely help in improving sealing and compression. A compression test is a great way to confirm whether it is the problem. If compression is low, this valve is related to sealing or other engine components. Hope it helps!nulls brawl
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[cenat]

Could be a vacuum leak or carb sync issue check intake boots and throttle cable. Had the same on my GS, and it was a cracked boot. Nulls Brawl