76 Johnson 115

[rcollicott]

Still dealing with a miss at part throttle. Runs great wide open. Checked ignition with timing light and so on. Had a carb problem while back, Would die at idle ran rough. Ended up replacing carbs. Rebuilt the new carbs and now Doesn't die.
Could the miss at part throttle still be a carb problem? Still idles little rough but fished with it all day trolling and never died. Coming off full throttle doesn't miss right away but will come back. Where do I go next?

 

[jbjennings]

Re: 76 Johnson 115

The changeover from low speed to high speed jets at low throttle is where you seem to be having your problem. It sounds like it might be a synchronization problem with timing and fuel delivery. However, usually a dead miss is caused by igntition problems. Make sure you're running the right spark plugs, and look at them to check for steam cleaning or fouling.
See if you can find a procedure in your manual for synchronizing the carbs. I'd check that first.
JBJ

 

[rcollicott]

Re: 76 Johnson 115

The changeover from low speed to high speed jets at low throttle is where you seem to be having your problem. It sounds like it might be a synchronization problem with timing and fuel delivery. However, usually a dead miss is caused by igntition problems. Make sure you're running the right spark plugs, and look at them to check for steam cleaning or fouling.
See if you can find a procedure in your manual for synchronizing the carbs. I'd check that first.
JBJ

Thanks for the info!

 

[emdsapmgr]

Re: 76 Johnson 115

When idling, the carb butterflys are closed. Fuel is drawn through special dedicated fuel passages. These passages are small. If these passages get restricted (dried fuel) the engine won't idle well. Called a lean sneeze. Occasional miss or cough. Once you crack the throttle even a little, other jets take over and the engine may run great, incl up to WOT. If this miss sound familiar, you need to pull the carbs apart and clean the idle passages with some carb cleaner-to dissolve the dried fuel.

 

[rcollicott]

Re: 76 Johnson 115

When idling, the carb butterflys are closed. Fuel is drawn through special dedicated fuel passages. These passages are small. If these passages get restricted (dried fuel) the engine won't idle well. Called a lean sneeze. Occasional miss or cough. Once you crack the throttle even a little, other jets take over and the engine may run great, incl up to WOT. If this miss sound familiar, you need to pull the carbs apart and clean the idle passages with some carb cleaner-to dissolve the dried fuel.

Thank you for the info! I had just recently rebuilt carbs for a dieing problem at idle. Idles good now.