1983 gs450l Engine knock then idle drops?!?!?!

[Guest]

When I am sitting in neutral the engine makes a knock sound (kind of like a rough shift sound) then the idle drops about 200 to 500 rpms. I have cleaned the carbs, replaced the rectifier, changed the oil, changed the air filter, did an oil change and changed out the carb boots. I have also checked all control adjustments. This is my first bike and I am learning as I go, so please help!

[Tempted]

Sounds like a jumpy starter to me. Check for shorts.

[Mekanix]

Not sure what you mean, Could you take a video ?

[tkent02]

Too lean, backfire through the carbs, idle drops and then comes back up. It sounds kinda like that.

Try using a little more choke and see if it stops.

[MotoNew]

The idle doesn't go right back up it stays down. It might slowly come back up or be back at the next stop light then knock sound, idle drop. I will try to get a video posted today.

[tkent02]

Just try opening the choke a little to see if it stops. If it does you are just idling too lean. Easy to fix.

I have seen this on several bikes, it sounds just like you describe.

[MotoNew]

I think you were right about idling lean. Do I need to adjust the pilot screw? If so is it plugged up with a brass cap up top on the engine side of the carbs?

[tkent02]

Yes, they are tamper proof. Makes it harder to adjust. Use a dril bit to remove the plug, take the screws out. They used a drop of paint at the factory to keep them from moving. Take them out first, clean them off.

Actually you should do a complete carb cleaning, if the plugs are still there its never been done before.