distibutor rotor falilure

[pisten-bully]

Before rolling the Chief out for the summer I replaced igintion parts as usual; points, rotor, cap, condensor. I couldn't get the Chief to fire up, however, and proceeded to check all the usual suspects. When I lifted the distributor cap I found my brand new rotor was split in half.



So I put the old rotor back in and it fired right up.



Yesterday I was getting some misfires, I have ridden about 1500 miles this spring using that old rotor so I swapped out the old rotor for another new one. This new one broke immediately, just like the one earlier this spring. So I cleaned up the old rotor and re-installed it and had a nice ride of about 60 miles.

Can't figure this out, I suppose it could be: 1) bad batch of rotors from the vendor? 2) new distributor cap is a bad match for the new rotors so maybe the rotor hits the side of the terminal in the cap?, 3) distributor shaft has too much play, even though I can't wiggle it by hand?

Here's the new cap:



Anyone else breaking rotors?

[ChiefTwoKicks]

I have recently replaced my points,cap and rotor in two of my chiefs too. I have found one cap where one distributor cap that have the brass pins NOT centered in the cap properly. What I have experienced is severe scoring on one pin and on the opposite pin, the rotor looks as if it is about .015 away from the edge of the machined surface. I have tried to cut an inferior cap in half to see what occurs when the rotor turns, but I am unable to get results that are conclusive. My machinist friend also has seen faulty caps as well. He called Greer about it, so Todd has knowledge as to what we found. Todd said he would look into it. I have not spoken to Gary Stark or Mike Tomas. I wonder if other vendors are experiencing this same issue.
I have 4 chiefs. My friend has a pair of 741's and a sport scout.
We first discovered the bad cap issue about 6 months ago. Bert and I have been building three engines for about the same time frame. I have changed the caps in 2 of my bikes, Bert has changed only one of his. But when we found two of these bad caps, we started to wonder what's going on. I also wonder if other vendors are experiencing this problem as well.
Likely a bad batch of repop caps, and there may be a few out there.
In my case, I took a few thousands off the end of the rotor blade. works fine now. My friend replaced the cap. Both of us are using the hammer style (rounded edges) rotors.
Check and measure the pins and the machined surface on the pins. The machined surface should be exactly in the center of the pin. The distance between the inside edge of the cap and the outside edge of the pin should be equal on both sides of the cap. Since the rotor is NOT suppose to touch the pin, its difficult to determine what you're trying to achieve. Is it the cap or the rotor ?? or both ? I believe a bad batch of caps. I certainly could be totally wrong.
But, to answer your question directly... I haven't seen any broken rotors. Only found two inferior distributor caps

Roger

[pisten-bully]

That’s good info Roger, thanks! I’m going to do some measuring of caps to see what’s up. I’m not sure where I got the older rotor that works, it’s different than the new ones that split. But the new cap and rotor are both from Greer and I’ve never had a problem like this before with their stuff.

[Skirted]

Don't ya hate when you try to be proactive with preventive maintenance and it backfires! I'd give Greer a call Harry. If its a manufacturing tolerance issue, you won't be the only one having the problem. Agree one or the other must be out of spec. I wonder if caps from Starklite and Greer are from the same manufacturer.

[pisten-bully]

Don't ya hate when you try to be proactive with preventive maintenance and it backfires!

I know, right?

I tired to measure this new cap to compare to an old cap and gave up, my calipers don't have long enough jaws to reach into the cap and measure the distance between contact posts. And I can't accurately find the center point of the cap, either. Ditto with the rotors. So I'll reach out to Todd at some point and see what he says. They readily gave me a credit for the first broken rotor, so that's good!

Meanwhile the old rotor works fine!