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1974 6hp Johnson - mid range sputter

F

FishyBC

Contributing Member
I have a 1974 powerhead I replaced and it runs OK at higher throttle and at idle but in the mid range it sputters and runs rough.
I did soak and clean the carb including the high speed jet, replaced the coils, set the points, put in fresh plugs, plug wires and ends.
There is good spark from both cylinders.
What is the sign that they need new condensers and points ?
 
Did you adjust engine sync between throttle opening a spark advance?
http://www.ebay.com/itm/JOHNSON-EVI...ash=item25d3b9d64c:g:mDYAAOSwcLxYI8El&vxp=mtr
There are two marks on the throttle cam under the flywheel put the follower roller for the throttle center of the two marks and then loosen the two bolts that hold the cam to the plate so the cam is just touching the roller. The carb butterfly should be fully closed and tighten the bolts. Then check that the throttle butterfly just begins to open as the roller passes center of the two marks. You can get it exact with a paperclip and a straight wire just clip it to the throttle shaft on the carb and watch when the wire just begins to move the roller should be center of the two marks on the cam.
 
Thanks. I did set this and it looks to be right on. To replace the ignition wires I did have to remove the entire magneto plate which I had never done before but I did mark it so it went on lined up. I would think with the 2 screws holding it on, that would insure it could only go 2 ways (the right way and backwards).
When I test run it I put inline spark testers on both cylinders and there is a good strong spark out of both at all throttle ranges.
I will pull the carb apart again and clean it but it has been off once already. Not sure what else to try.
Only the mid range is an issue. It idles down perfectly and it runs flat out no problem.
 
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