72 johnson misfiring

[jtim]

I removed the carbs as Joe Reeves instructed. Found that both low speed screws are scored/grooved. Also removed leaf blocks for inspection and found 4 leaves on each block not totally closed. Slipped a .004 or .005 feeler gauge under each distorted leaf with no effect on the leaf. Used a light in a dark room and found light could be easily seen around the leaves. I am assuming I've found the rough idle demon.

 

[OBJ]

Re: 72 johnson misfiring

Tim.....if you were experiencing blow back from the carbs, yes, the reeds would be at fault. The grooves in the needles can be "repaired" by chucking the needle up in a drill and using a fine file, remove the groove. Blunt the needle end afterwards. Keep the angle on the needle as close as possible to the original. The needles are old and finding a replacement may prove difficult.

 

[jtim]

Re: 72 johnson misfiring

What I am experiencing is very rough idle with jerking and severe sputter. If I adjust the idle mixture to run smooth it will run about 10 seconds and shut down needing to be choked to start again. the motor runs great at full speed almost all the time but on occasion it will only run at half power. If I set the low speed mixture to rich it will run but it runs extremely rough.

 

[OBJ]

Re: 72 johnson misfiring

Tim....tell us about the carb rebuild. Did you use a kit....OEM with a new float or generic? Did you flow carb cleaner through all the passages and follow up with compressed air?<br /><br />It would seem that you are have fuel flow prolems through the carb.

 

[jtim]

Re: 72 johnson misfiring

I simply cleaned the carbs the first time. That is I took them down and soaked them in cleaner and blew them out. I did not remove the core plugs the first time which seems now to have been a mistake. This time I have the carbs completely disassembled and am completely rebuilding them with new kits. I assume you do not see sufficient evidence to warrant reed block changes even with the gaps in the reeds? I plan to replace them since I have it down and they are distorted but if some other problem seems more possible I want to do that too. I noticed also that there is some epoxy looking substance on and just under the front charge coil as if it has been hot at some time. I have not removed the flywheel yet but I have checked the coils and they have strong fire. Does these type coils change values when hot? that would explain some of the problem.