Carb trouble

[pablohoney]

Hi there,
Here's what is going on, my 1979 xs650 starts right up and idles fine, but it does three bad things,
1: If I give it any choke at anytime it dies instantly, if I keep it revved with choke on, the plugs foul like mad.
2: If I let it just idle for a minute or two, then give it a little gas it dies. If I rev it periodically it is fine. It has stock exhaust and air filters, and pamco electronic ignition.
3:It also has a slight pinging, when I let off the throttle, none at idle. I am sure that the ignition isn't advanced.

Any ideas? Thanks

 

[TeeCat]

You should only be using your choke from a cold start, and close it as soon as the carbs will respond to throttle.

As to your second question, it sounds as if the carbs are not responding optimally to throttle from idle (off idle); the pilot jets may be partially occluded or a little too small.

Number three... is it pinging, or popping? Pinging normally occurs under load.

TC

 

[pablohoney]

Good to know about the choke,
could a rich mixture cause it? I checked the plugs and they were definitely rich.

Pinging.

 

[pablohoney]

I took the bike up to the top of my hill and rolled it down with it in gear,and the ignition off and I could still hear the pinging. Excessive valve lash?

 

[5twins]

Loose cam chain maybe. Also check your float levels. The fuel levels may be high in your bowls which would cause the bike to run rich. That would also explain not needing the choke for cold starts.

 

[pablohoney]

OK, thanks 5twins, I'll check both!

 

[pablohoney]

Well, I adjusted the float and the mixture is good, the cam was also good, but I think the sound is the valves, sounds like the exhaust valves is where it is coming from, also gets much louder after the engine is warm. When its cold I'll check it.

 

[5twins]

Yes, the valves can make more noise once the oil gets hot and thins out a bit. That's why I went back to 20W-50 oil after trying that 15W-40 diesel stuff. The top end made more noise with the 40W.

 

[TeeCat]

And make sure you set your valves when the motor is stone cold, too! It should not have been run for at least a few hours. Procedure can be found in Tech here if you don't have them.

 

[pablohoney]

I adjusted the valves, almost all of them were too tight. Lots less pinging now, still a little bit every now and again. Is a little bit normal?