RPM-Limiting rotor wasn't limiting

[mskala]

So, a bit of a scary thing started happening. I use my car for autocross so I rely
on my rev-limiting rotor a lot more than most (2.2L E engine). Sometimes you
need to just leave it in second at the limit for a short time.

Well, it dawned on me that I never seemed to hit it last event, and then a quick
check showed that it wasn't stopping at 7100. (I'm sure my valves springs can
handle a bit more, but in general am saving crank etc at this limit).

Basic check: use an ohmmeter, clip one lead to a good ground; pull dist cap and
gently touch (don't poke with sharp lead) the rotor's grounding tab (the one that
the spring-contact will eventually touch). If that is not basically a short, then
guess what, it ain't gonna limit your engine.

Reason: rust on the grounding piece; everything in the rotor is brass or something
similar, but this piece is steel, and obviously not painted or protected. Rust on the
contact area and/or the piece that touches the shaft is not good. The 2 rotors I
have are no more than a few years old, too.



This piece is removable; the white plastic clip comes out and it's otherwise a friction
fit at the other end. In a pinch, I simply scraped the rust and put it back. However,
for the long term, I'm trying to plate them (simple Eastwood tin-zinc electroplate
kit).

Here they are after plating:


Here is what the rotors look like with piece re-installed.


Hopefully this keeps the rust at bay.

Check this yourself and maybe save an engine!

[Porboynz]

20kV usually does not stop when presented with a little rust, unless you want it to jump the gap in which case it won't. Nicely caught.

[dicklague]

this is why I love the "soft" rev limiter in a modern CDI. In addition to better spark that is.

You can easily set it where you want it, and it works every time.

It also is a lot more gentle and you don't just stop the spark.

I have mine set for 6500 in my car and just starts by missing a bit.