1970 9.8 spark weakens as throttle is retarded

[Oldcraneguy]

My old 9.8 with CDI stator will only run above half throttle and once in a while at dead idle, When spinning it over with a drill and the plugs out I get a nice hot blue snap, but as I retard the throttle the spark turns orange and gets faint, quitting completely just below half throttle. when I get it completely closed I get a occasional weak spark, I think one of the low speed coils on the stator is shot but I dont know any way to test them short of cutting them out...It has new points and insulators so I dont think thats my problem. The thing is I hate to spend $220 on a $300 motor if thats not the problem anyone have any other thoughts....OCG

 

[Texasmark]

Don't know what you mean by "low speed coils" in the Stator. The stator has 1 set of trigger coils used at all speeds and if it has elect start has a set of alternator coils to charge your battery. One thing your engine does is increases the timing when increasing speed. You could have something binding as you approach the low speed setting, or you could have other issues that only show up with low spark advance settings. I wouldn't suspect a CDI as problems there would probably occur at the higher rpms, unless you had a cold temp thermal problem in a CDI which I had happen on my last 90 hp engine.

So look for the smoking gun. When was the last time you put in carb. kits? What about your linkage to the carbs and spark advance, all intact, no slop, butterflies open with spark advance, anything feel like it's binding? If all that looks good then pop the flywheel and check out the stators and magnets in the flywheel for any sign of damage.

That's a start.

Mark

 

[quicktach]

Check to see that wires going under the flywheel aren't binding or dragging.