Delayed idle issues

[Guest]

Hi everybody,

I own a 82 GS550LZ that has a idle issue. It starts fine...a little choke but after a couple minutes I don't have to use the choke....It will idle fine then after a 45 min...maybe 1 hour ride the bike doesn't want to idle...I'm not sure where to start looking. Have any of you heard of this issue before? It has spark.........

[tom203]

Hi everybody,

I own a 82 GS550LZ that has a idle issue. It starts fine...a little choke but after a couple minutes I don't have to use the choke....It will idle fine then after a 45 min...maybe 1 hour ride the bike doesn't want to idle...I'm not sure where to start looking. Have any of you heard of this issue before? It has spark.........

Do you have any idea when carbs were cleaned last? Probably, your slow speed circuit is partially restricted and once warmed up can't deliver enough fuel mixture. BUT did you set your idle stop correctly ?- should be set after bike is nice and warmed up, so there's no influence from "choke" circuit.

[Steve]

... after a 45 min...maybe 1 hour ride the bike doesn't want to idle...

By "doesn't want to idle", do you mean that it will die or that it hangs at a higher RPM?

There are different solutions to these two options.

.

[Big T]

A dying idle when hot generally indicates tight valves

A rising idle means air leaks

[BassCliff]

Hi,

Valves need to be adjusted. Carbs need to be properly clean. All carb adjustments (vacuum sync, individual idle mixture screw adjustments, main idle knob adjustment) need to be done while the engine is up to full operating temperature. Make sure there are no leaks in the air intake system.


Thank you for your indulgence,

BassCliff

[mash35231]

Had the carbs cleaned at a shop in Xenia. The carbs haven't been sync'd. Steve, it wants to die and stop running. Tight valves never entered my mind....that's a great place to start.

[Steve]

If you are mentioning Xenia, it sounds like you are dangerously close to me.

When do you want to have some help with this?

.

[tom203]

A dying idle when hot generally indicates tight valves

Wouldn't they be even tighter cold ? He did say bike "starts fine"

[tkent02]

The valve stems get longer when they are hot. When the stems are too long, the valves can't close all the way. This makes them get hotter, and longer. Vicious circle. First it starts to not idle when hot. Next step is the valves burning up. Adjust them.

[mash35231]

Hi Steve, Yea I live close to Xenia. I started dismantling the bike a couple days ago. D-Mac inspired me to improve the looks. It will be low budget compared to his but we all make due with what we got. I will be putting it back together after I get the frame and tins painted. I'll be in contact with you when I get ready to run again. I would never have thought of tight valves.

[Steve]

The valve stems get longer when they are hot. When the stems are too long, the valves can't close all the way. This makes them get hotter, and longer. Vicious circle. First it starts to not idle when hot. Next step is the valves burning up. Adjust them.

But doesn't the aluminum that holds them (the head) expand more than the steel valve stem?

I have often wondered about the actual valve clearance when the engine is at full operating temperature, but not quite badly enough to burn myself checking it.

.

[tom203]

But doesn't the aluminum that holds them (the head) expand more than the steel valve stem?

I have often wondered about the actual valve clearance when the engine is at full operating temperature, but not quite badly enough to burn myself checking it.

.

This has always been my thought in this lobe-over bucket system - I figure hot running clearances are more like .005 inch-just to ensure some time on seat.

[Steve]

Whatever it is, I am reasonably certain that back in the development days, somebody took the time to check all that stuff to find the best clearance/seat time specifications.

Then, when the engine cooled down, they meaured what was there and said "you need this much clearance".

.

[Big T]

A dying idle when hot generally indicates tight valves

A rising idle means air leaks

I speak directly from experience

A few years back, my 78 started dying at stop signs/lights

Pulled the carbs, fiddled with the settings, etc, etc. Finally, decided I needed that baseline we refer to so often

3 tight valves later, my idle returned, nice and steady

[mash35231]

If valve clearance needs adjusted, where are you guys getting the new shims from? The dealer or some other supplier?