Is this caused by incorrect adjustment of the pilot screw?

[Remco]

Hi all,

I have read a lot about high idle, and the possible reasons for this (vacuum leak), however this seems different.

If I start my GS450L it needs the choke to start (It starts immediately btw) and after 30 seconds to a minute I can close the choke, and it will idle perfectly (ca. 1100 RPM).

After driving for 15 minutes the engine will idle at around 2000 RPM. And when I adjust the idle knob down the idle speed will drop again. However when the engine is cold again, I won't keep running because the idle knob has been turned down. If the problem would be a vacuum leak, then I would not be able to adjust the idle speed with the idle speed knob right?

The other thing what's happening, when the engine is on temperature it will stutter on half throttle, and is gone when I go full throttle. Sometimes I hear bangs coming from the exhaust.

I have fully rebuilt the carbs, and all O-Rings have been replaced. The carbs need to be synced anyway.

Do these problems sound like something which could be caused by incorrect adjustment of the pilot screw? And if so, is adjusting the pilot screw easy, or should it need to be synced first?

Many thanks in advance!

[hampshirehog]

Could be....she might be running a tad lean.

But I would do a synch first or you might end up chasing your tail.

[apopleptic]

Hey and welcome to the forum.
So how is the Dam these days? Been a few years since I have been to visit. Such a beautiful city.

Sounds to me like it could be a number of things causing that. Possibly a small air leak somewhere on the airbox side. or even in the fuel line if it is loose.

Here is the website of one of the members here (BassCliff) who will probably be along shortly to welcome you to the forums. It contains a ton of useful information.

http://members.dslextreme.com/users/bikecliff/

[Nessism]

Did you replace the intake boot O-rings? If not, time to do so. If you did and the idle is still hanging, try opening the idle mixture screws some and see if the problem goes away. You also should vacuum sync the carbs and make sure the valve adjustment is up to snuff. Short cuts are long cuts.

[BassCliff]

Hi,

All active carburetor adjustments (vacuum synchronization, idle adjustment, mixture screw adjustments) should be done when the bike is fully warmed up to operating temperature. After you have ridden the bike for 20 minutes or so, then adjust the main idle knob for best idle, usually 1050 rpm (+/- 100 rpm). Do the same for the idle mixture screws. Once you have gone for a little spin, park in your garage, let the bike idle, and adjust the idle mixture screws using the "highest idle method" as explained on my little website. You can either start with the screws out a little too far and adjust "in" listening for the idle to go down, then back out 1/8th turn. Or start with the screws a little lean (too far "in") and adjust "out" listening for the idle to get faster. Stop when the idle does not go up any more and adjust back 1/8th turn or so.

Usage of the choke may be necessary until the bike is almost fully warmed up. I let my bike warm up on the choke at about 2000-2500 rpm for about a minute. Then I'll push the choke in until the idle is 1500-2000 rpm and take off. I usually turn off the choke after a few blocks. But if I stop at a light the idle may be a little low until the engine gets up to operating temperature.


Thank you for your indulgence,

BassCliff

[jacora]

In addition to the valuable hints already provided, check your pilot jets, use a steel hair from a steel brush to clean it.