Running Rich. Not sure why

1982 Seca 650

Running rich. I had to change to reserve at 100 miles. My last Seca 650 sometimes got to as high as 155 miles before changing over to reserve. Everything is stock. Jetting, stock airbox, valves in spec, float levels correct. Carbs are synched. Air filter is clean. Compression is excellent. When I turn the bike on it goes straight to idle almost like it's a fuel injected bike. When I put the choke on nothing really changes. When I make quick stops the rpm's dip for a second and then come back up. I've checked for air leaks with starter fluid and looks like it's good to go. I've also tried applying pressure to the tops of the choke plungers to see if they're not going all the way down and no change. I've heard that the air jets can get mismatched but that isn't the case here. I also don't hear any popping of unused fuel nor any black smoke. I've gone through about 4 tanks of gas. I've also included pics of the 1 and 2 cylinders. Any advice would be great. Thanks

 

How old are the float needles and seats?
Your petcock shuts gas off when parked but when riding uses too much? Just a thought

 

Are you using the stock paper air filter? Not a foam or oiled type?

 

Can the wrong spark plugs cause this situation?I’m using Champion spark plugs. According to a cross reference chart by NGK I’m using the correct ones.

Also, I noticed when opening the tops to the carbs there is residual fuel on the air jets just below the diaphragms. Could this indicate something?

 

Have you checked your fuel levels in the carbs?

 

yes further back that is discussed
@MrSeca I think if you’re riding the bike then the spark plugs will be ok for idling.
Fuel issue, too rich will be difficult to get a smooth idle

 

Yes

 

Hmm, maybe check cam timing...

 

Kind of seems like the obvious culprit might be the idle mixture set a little rich (???)

Is this bike new to you? If miles per tank until reserve is throwing you off, perhaps the height of the pick up straw is different (taller)??

Maybe the tank capacity is somewhat smaller - like somebody filled a dent with a giant blob of filler instead of properly doing the metalwork - not that I've ever seen that before - cough cough

 

You had issues before with emulsion tubes and gas mileage. Wasn't that your 900? Anyway, if high mileage or non OEM parts perhaps the emulsion tubes or needles are contributing to poor mileage.