83 GS450L Idle/pilot screw

[gs450L]

So I'm working on a friends bike. 1983 GS450L. Here is what we have done so far.

Disassemlble carbs, clean and rebuild with fresh o rings. The only o rings we could change were the pilot screw and one on the brass thing that holds the float needle. I may have set the float height a little bit wrong. So its off by like 3 mm. I went off the edge of the body, not the surface of the gasket. Ill fix this shortly.

New rubber pieces between carbs and airbox, and carbs and engine. New o rings between the carb outlet and the intake manifold.

Stock airbox, cleaned out and re-oiled air filter.

Synced carbs with vaccum gauge.

New vaccum line to petcock, and just in case of bad petcock I tested it with that line capped and the petcock in pri position.

Exhuast valve shims are a little tight. I think this causes a slight backfire during running. I cannot get the damn things out to see the #s on them. I bought the tool and will keep trying to get the shim out to see the # on them. Even with tweezers and the tool i cant get it out.


I still can't get it to run correctly. It will only idle if I turn in the idle knob more than I should. Then the engine will run up to 4k rpms and idle will be unstable.

So here is my main question. How far should do you normally screw in the idle adjustment knob past completely closed? I have tried the pilot screw at everything from completely closed to 3 turns out. Just cant get it to work.

Here is what has me stumped. If I manually hold the throttle at 1500 rpms it runs fine. But if i set the knob to 1500 it will not drop back down to 1500 after it runs up to 4k or so.

What feeds air into the engine during idle?
What are some normal positions for the idle knob and pilot screw?

Thanks.

[gustovh]

Adjust your valves, you will have to resync after you do. Basic start on pilot 2 1/2 turns. Check and make sure cables are correctly installed and adjusted.
V

[gs450L]

Thanks Tom. That picture is great. I did replace the o rings between the boot and cylinder head.

How open should the carbs be during idle? Should the 2 rear holes be covered and only the pilot screw hole exposed?

I'm gonna pull the carbs apart and spray some cleaner through the holes and see if I'm clogged.

[tom203]

Believe it or not, but...... with idle circuits functioning correctly (flowing fuel and air), the throttle plates (sitting on idle stop screw) will be barely open . Before worrying about vac sync, get carbs clean and a good bench sync will get you real close. Getting the valves adjusted is a must

[gs450L]

You were correct. I found a clog between the pilot jet and the pilot screw. I guess that tiny brass pipe is clogged or something. There is no airflow to that carb at normal idle. Under close inspection, it looks like someone was jamming something in there to try get it clean or pound that brass pipe out. I just bought an empty carb body for $34 shipped. So ill know in a few days if that fixes it.