Rough idle need ideas

[klrbruce]

Hey all, I have a 1985 johnson 60hp, 2 cyl. I have rewired it, new coils, new plugs, new fuel lines, cleaned carbs 3x completely with replacement parts, new control cables, new filters, and fresh gas. It starts fine, runs great, but when it is at idle the motor is not as smooth as it should be (dances and twitches). I thought it was the idle jets but they are clean as can be, thought it was the primer solenoid that was left in the bypass mode, but nothing I can think of solves the problem. Don't think it is the carb as they only have high/low jets with no adjustments, and have sprayed exterior of carbs with cleaner while running and no vac leaks, throttle butterflys are not sloppy and synced...I'm running out of theories... Anyone have any ideas??? Thanks Bruce

 

[jhebert]

Re: Rough idle need ideas

Check the air path to the engine. If the air intake manifold has a bad gasket you could be getting too much air, causing the fuel-air mixture to be wrong.

 

[ezeke]

Re: Rough idle need ideas

With everything else checked, it's probably the capillaries leading from the idle jets to the carburetor throats. You might want to watch the throats while you force fuel through the idle orifice to see if the fuel is flowing evenly.

 

[klrbruce]

Re: Rough idle need ideas

Little confused by air intake manifold. Are you talking manifold between carb and motor, or the silencer assembly (black square plastic before carbs?
I sprayed carb clean around base of carbs, but not around the manifold the carbs bolt to. I just went out and looked at that gasket and looks like a little silicone has been used there. So will try spraying around that gasket tomorrow and see what happens..Thanks for the idea, something new to think about....

 

[klrbruce]

Re: Rough idle need ideas

When rebuilding the carbs, I pulled the aluminum plugs out to check the 4 little idle air orifices, they are super clean. Fuel flow out of them seems ok, but I will check again.

 

[klrbruce]

Re: Rough idle need ideas

Well I got to pull the intake off the motor cleaned all up and found a small score on the engine casing. It looks like someone may have replaced the intake(intake is white, engine block is black)and used an icepick to crack the seal, which probably left the defect. I cut a new gasket and resealed the problem area with rtv black. I will start her up tomorrow and see how she runs..Thanks all for your help.. Bruce