1980 20 hp merc. wont start unless it is at half throttle

[JWT]

Hey folks! I could really use some help here. I have a 1980 20 hp merc tiller handle. compression is at 120 on both cylinders i have rebuild the carbs and the fuel pump but it will not run unless you hold it at half to full throttle as long as you are holding the throttle it will run all day but as soon as let off of it to go to idle it cuts off. it also has spark on both cylinders. this one has me puzzled ! any suggestions?

[pyro]

Timing set right?

[mn808gade]

running on 1 cyl?? excess fuel on water/driveway?? fuelpump leaking? hold primerbulb with arrow up -does bulb get hard? running and holding throttle disconnect one plug wire at a time.-th

[JWT]

running on 1 cyl?? excess fuel on water/driveway?? fuelpump leaking? hold primerbulb with arrow up -does bulb get hard? running and holding throttle disconnect one plug wire at a time.-th
Yes the primer bulb does pump hard and stays hard . I did notice slit of fuel in the barrel . I am running it in a test tank. Next chance I get I will run it and pull one plug at a time and let you know my results . Thank you

[mn808gade]

should have a flywheel key(maybe sheared).pull plugs-roll flywheel clockwise(from top) by hand with something in top cylinder to determine when piston is at top dead center (all the way back).then look at TDC (0*) mark on flywheel and the timing mark on recoil housing. if the two align then key is OK.-th

[JWT]

should have a flywheel key(maybe sheared).pull plugs-roll flywheel clockwise(from top) by hand with something in top cylinder to determine when piston is at top dead center (all the way back).then look at TDC (0*) mark on flywheel and the timing mark on recoil housing. if the two align then key is OK.-th
Ok folks, the idle adjustment screw on the carberator is stuck . I can't budge it at all ! Any suggestions on how to get it freed up?!?!?

[perfmarine1]

Hey folks! I could really use some help here. I have a 1980 20 hp merc tiller handle. compression is at 120 on both cylinders i have rebuild the carbs and the fuel pump but it will not run unless you hold it at half to full throttle as long as you are holding the throttle it will run all day but as soon as let off of it to go to idle it cuts off. it also has spark on both cylinders. this one has me puzzled ! any suggestions?

How do you rebuild the carb without taking out the idle mixture screw?:eek: lefty loosy, bigger screwdriver! Looks like you answered your own post.

[JWT]

That's the only thing I couldn't get out. I soaked it in krol oil for a week thinking it would come free but it's not moveing at all

[mn808gade]

serial number-used carb, Tims Outboards 218-682-2331 Hackensack mn...-th

[JWT]

Thanks a lot ! I'll call and see if they have one!