1985 GS550ES Idles Low, Keep Adjusting Idle

[Guest]

Ok so I have a 1985 GS550ES. I have adjusted valves, checked compression 150psi across the board, cleaned carbs (ultrasonic, carb clean and compressed air). I have drilled out the fuel screw caps and made sure all passages are clear. set to 2.75 turns out. Charging system working fine 13.5-14v.

I figured I have a air leak, so tonight I replaced carb boots and o-rings new OEM. I re-cleaned the carbs to be sure and double checked my fuel screw adjustment. Boots where dry cracked and separating from aluminum housing.

My question is what is the stock idle screw adjustment for these bikes? manual says preset. I never counted turns, since I thought it would be in the manual. I figured 2-3 turns.

The bike is still acting lean so I may turn the screw out another 1/4-1/2.

Ideas?

[Steve]

The idle screw is the one that is between the carbs and below them a bit. It adjusts the idle speed. There is NO WAY that it can be "preset".

The PILOT screws (also called "idle mixture screws") are the ones that are preset and sealed from the factory.

While I have rebuilt a couple sets of carbs like yours, I have never had the pleasure of installing them on the bike and tuning them, so I don't know what the settings would be. On other carbs, I usually start with the pilot screws out 3 turns from lightly seated. It will likely be a bit too rich, but the bike will run a lot better when slightly too rich than it will when it is slightly too lean. After the bike warms up enough to run without the "choke", you can slowly turn the pilot screws in until the engine speed slows down a bit, then back the pilot screw out about 1/4 turn. After you have done all four, do them again, just to verify engine speed slows dow a bit when you turn the screw in 1/4 turn, then turn it out 1/8 turn. Adjust the idle speed screw for an engine speed of about 1100 RPM, you should be done.

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