top carb running lean

[Autotech]

Hey guys its been a while since my last post put I got another head scratcher this time. I have a 1973 3cyl johnson 65hp. that I rebuilt 2 years ago that had been running great up until the end of last season. Seens to be running lean on top cyl. Good compression and spark on all cyl.I have cleaned and rebulit carbs and installed mew fuel lines and bulb. Question is, this model fuel inlet is in the center carb and then distributes to top and bottem carbs. If top carb is running lean what else is there to check or replace? Fuel does get to the top carb with pumping bulb but seem to quit when running above half throttle. <br />thanks for any help.<br />Bobby

 

[Dhadley]

Re: top carb running lean

Are you sure fuel isnt getting there? If there was no fuel, there's no oil. I would think that it would start to show signs of sticking if theres no oil to that piston.<br /><br />Is it not running on the top cylinder after a certian rpm?

 

[Autotech]

Re: top carb running lean

I guess, I'm not sure. Here's what I did after running and cleaning carbs again. I put It on the water hose and cranked it up and ran at idle. Pulled the top plug wire off no change in RPM. applied power it did the same thing. It is getting plenty of fire at the plugs both Times. Put new plugs in just to be sure. Tried the same thing still no change. Put my hand over the venturi of top carb to choke each carb one at of time still no change. I did have fuel there when i choked it. Sooo I'm Really don't know what else to check? Maybe reed valves? I did not put them in when I overhauled. Any help or thoughs would be greatly appreciated.<br />Thanks Bobby

 

[Dhadley]

Re: top carb running lean

Lets try something before we condem the reeds. Switch the top and bottom carb. See if the problem follows the carb or stays on #1. That way we can know which direction to go.