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1974 Johnson 25hp problems

S

scruffy63

Regular Contributor
I have a 1974 Johnson 25hp that starts and runs but it runs rough. Carburetor has been cleaned with new kit. float is 1/16th above gasket like specs. Top spark plug (New) has very black carbon on it and lower plug is normal. New coils installed on head. Any help would be appreciated.
 
compression is 110 on both cyls. I don't have an open air tester but check spark with clip attached to plug with clip and grounded to block. both have good spark. I did replace points. I have a new power coil but did not install it.
 
Stick a Phillips screw driver in the spark plug lead, hold it 3/8" away from the block and see if the spark will jump that gap.
 
I set the float 1/16 above the gasket like my specs said for these big 4 screw carbs but I can take it off and do level like the 5 screw ones. Points are set .20 but will re set at .22, and check spark this morning. Only part I hate is carb since I have to take electric starter loose and lay t over to get the right carb nut.
 
Right have it in sync and I adjust carb by lightly seating the needle then backing out 1 1/2 turns then with engine running I turn it in just a little at a time and wait a few seconds until get highest rpm then I back it out about a 1/4 turn rich. I am getting close now.
 
In the barrel in N, but I have also tried it in gear. I am going to get started on it again this morning. Will advise what its doing.
 
It is somewhat the nature of that motor to run rich on the top cylinder. See that hose going to the top bypass cover? That is dumping extra fuel from the crankcase drains into the top cylinder for burning. Yeah, right. It doesn't really burn. They ran much better back when they dumped the drains overboard. But it was kind of messy.
 
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