Idling really high.

[Los D]

I'm really confused.
First it should be stated that the bike was just rewired and the carbs recently cleaned.

('74 TX650)
The bike fired up really easily, and sounded great. Initially it idles really well, but when given throttle, it stays high. This is in no way related to the actual throttle mechanism, problem occurs even when disconnected.

Even more strange, it idles perfect when I give it choke, which seems to be completely backwards to me. Normally, the bike would die when given choke, as if it was being flooded.

Not really sure where to start with this issue as I am still relatively new to this bike. Please help.

 

[BigJimmyW13]

Any chance you have an intake leak? Leave the barb plugs off?

 

[retiredgentleman]

High idle that won't come down (hovering):

-air leakage at carb manifolds or throttle seals

-ATU (advance unit) sticking

-air/fuel mixture not correct ( need to adjust pilot screw, using "dead cylinder method")

-carbs not sychronized ( use a manometer to sync......look in "Tech"......Homemade tools.)

 

[BigJimmyW13]

Spray some starter fluid onto the boots while running and see if it revs then you have a leak in your intake somewhere.

 

[Los D]

No barb plugs on this particular year, maybe leaking elsewhere.
Pilot screw adjustment did not help, tried that first.

I'll start with those other possibilities though. Thanks!

 

[littlebill31]

Your pilot jet can cause this as well. Your pilot circuit is idle to about 1/4 throttle. Too small a pilot jet will cause the slow return. Did you adjust the cam chain, valves, and check timing prior to carbs? Most of the time I found it was either a leak, pilot jet, or synch.

 

[Los D]

Cam chain, valves and timing have all been previously adjusted.

 

[retiredgentleman]

No barb plugs on this particular year, maybe leaking elsewhere.
Pilot screw adjustment did not help, tried that first.

I'll start with those other possibilities though. Thanks!

For the pilot screw adjustment, did you do it with only one cylinder running at about 300 to 400 rpm?

 

[Los D]

Sounds like my pilot screw adjustment was not done correctly. Also, no tach on this bike.

 

[retiredgentleman]

With no tach, just keep lowering the one cylinder rpm (using the idle speed screw) until it is just about to stop running. Adjust the pilot screw for the smoothest, highest rpm. Use a fan to cool the engine.

On the side with the spark plug removed, make sure the spark plug body is grounded to the engine.