Distributor Cap and rotor fit issue

I recently bought a side distributor 8N. Runs great. I notice that when running the distributor cap wobbles. The bails hold it in place, but it orbits about as the rotor inside spins. With rotor in place, the cap won't seat down tight to the flange on the distributor housing. It's held up by the rotor inside. With rotor removed, the cap will snug down tight to the flange. I think I have the wrong rotor .. or maybe I'm supposed to have the dust cap. I need advice, thanks, Jeff
 
did you check to make sure that there's nothing jammed in the hole on the bottom of the rotor making it stick up too high?
 
Sometimes the new ones are junk and other times, even from a reputable source, they just don't fit. Usually they do not go down on the shaft as far as the old ones did. This is particularly true on frontmounts as the bridge on the point plate will prevent an out of spec rotor from seating low enough to keep from the cap from hitting it. Sometimes you can look under the top blade of the rotor & file away a little of the plastic. You need just the slightest gap, 1/8" or so, between the top of the rotor and the center blade. Of course the center blade on the rotor must contact the center of the cap.

Another fix (and probably easier than filing down a new rotor) is to buy the same brand cap & rotor from the same source at the same time.

Other causes are bad bushings which will cause the shaft to wobble; that should be evident by gouge marks in the cap from the tip of the rotor hitting. And brass shavings inside the cap.
75 Tips
 
The dust cap should not make a difference with the rotor fitting unless the dust cap is not sitting down far enough on the distributor. If I recall there is an indicator on the dust cap to properly locate it. You may have to push it down and twist it back and forth a bit to get it seated. From what I gather from your post you don't have the dust cap, so I suspect your suspicions are right and you don't have the correct rotor. I would not run the tractor until I determined the cause of the problem and correct it.
 
Mike, sorry, I should have been more clear. I have no dust cap. Should there be one? What I see on the web is unclear .. it looks sort of optional?? However, it looks like the dust caps fit down on the housing flange, then the distributor cap sits on the dust cap, which would raise the distributor cap a 1/6 or so and provide more room for the rotor under the cap. AM I on the right track?
 
Bruce, my first thought was that the shaft was loose, but it feels tight, I also cranked the motor over without the cap and there's no visible runout. There are no witness marks inside the cap other than the scuffing around the bottom flange diameter caused by the relative motion between the cap and housing. I like your idea of purchasing a rotor and cap from the same source. See also the reply I posted to Mike above regarding the dust cap. I don't have one and don't know if that's the problem or not.
 
The dust cap was OEM on the NAA's & a retrofit on the N's due to excessive point wear.

I use them.

My neighbor had a problem w/ his 50 sidemount last summer; the inside of the distributor was a mess. He now uses a dust cap.

I think the dust shield will raise the cap slightly, so that might help.....but it doesn't really fix the problem.
75 Tips
 
(quoted from post at 12:00:40 04/15/14) I recently bought a side distributor 8N. Runs great. I notice that when running the distributor cap wobbles. The bails hold it in place, but it orbits about as the rotor inside spins. With rotor in place, the cap won't seat down tight to the flange on the distributor housing. It's held up by the rotor inside. With rotor removed, the cap will snug down tight to the flange. I think I have the wrong rotor .. or maybe I'm supposed to have the dust cap. I need advice, thanks, Jeff
ust cap on my 8N side mount raises the distributor cap by just about 0.1 inch, which I call quite significant.
 

Dust cap on my Jube makes a difference on the fit.

Another thought. If it is not the original OEM distributor it may not have the notch hickey to mate to the cap. For instance, I worked on one today that had a bump INSIDE the distributor that mated to the dust cap. The dust cap then had the notch-mate for the distributor cap. And...you do need the clip for the shaft that the rotor fits on. Otherwise you usually have 20 degrees of "slop" in the rotor. If you don't have a clip you can order one for a few dollars (search fleabay), or in a pinch fabricate one from the springy part of an old set of points.
 

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