Logo
FULL SITE MENU

1988 25hp Johnson Tiller / Manual Start - model #J25RCCA - Rough Idle

B

Boatman3

New member
I have the above engine which has sat and recently started with all new rec fuel, clean carb / bowl and no leaks in fuel line. Can't obtain a smooth idle without it wanting to die out. Checked compression - cylinders are within a 10% variance of each other with the bottom cylinder the highest at 120PSI. When I pull the top plug wire, there is little variation in engine speed at high idle, however when I pull the bottom plug wire the motor dies. Both cylinders have spark, and above idle the engine smooths out and runs evenly. What am I missing? Is this motor designed at idle to only operate on one cylinder to save fuel? Help is appreciated on where to look or work next!
 
No such thing as a 2 cylinder Johnson that is designed to run on 1 cylinder.-----Something is wrong with top cylinder.-----Check reed valves.-----Check fuel pump diaphragm.-------Does spark jump a gap of 3/8" on top cylinder?----Swap sparkplugs ?
 
racerone said:
No such thing as a 2 cylinder Johnson that is designed to run on 1 cylinder.-----Something is wrong with top cylinder.-----Check reed valves.-----Check fuel pump diaphragm.-------Does spark jump a gap of 3/8" on top cylinder?----Swap sparkplugs ?
Click to expand...
Thanks for the reply Racerone - Swapped plugs and installed new ones with gap set to .040 per the owner's manual with no change and yes the spark does jump at least 3/8" as well. I did order a fuel pump repair kit, so that was my next option once it arrives. Beyond that, I'm not sure what I would be looking at with the reed valves as I've never gone that deep on a 2 stroke. In my mind, I had eliminated that as an issue considering it runs well at higher RPM above idle speed.
 
Back
Top