Date: Sat, 20 Mar 1999 09:51:34 -0800
From: Eric Murray 
Subject: Re: Compression releases vs extra plug

On Sat, Mar 20, 1999 at 09:19:14AM -0800, Vintage Jerry wrote:
> One of my Cota 123s has a compression release in the head, but no cable or lever.  I
> would like to hook it up and use it, even though nobody else these days seem to use
> compression releases,  I used them with good success back in the 60s and 70s and
> thought they were great.  Anyway I notice that most of my Cotas have two spark plug
> holes and everybody says its for an extra plug.  This particular Cota has a comp rel
> in the extra hole.  I have never understood the idea of having an extra spark plug
> mounted, as I would think that by the time you need it, it would be fouled much worse
> than the one that has actually been firing and cleaning itself.  What is your
> experience with extra plugs and/or compression releases?

I've got a compression release on my 76 Cota 348.  On this bike, using
the comp release on a slick downhill just results in a locked rear wheel.
If I feather the release so it's just barely popping, then it
doesnt' lock the wheel but it doesn't give a whole lot of braking either.
It's easier to use the rear brake instead.  (yea, I'm mostly using
the front on downhills, but using the rear seems to help keep the bike
straight).

The release is useful for stopping the bike when the kill switch doesn't work,
for kicking it through to get gas into the bottom end for cold starting
and to clear out the engine when it's flooded.   Mostly the best part is
that it makes that cool vintage sound (well, vintage to guys my age anyhow).

I think that the deal with the extra plug is that you put a hotter plug
in the secondary position, so it won't be (as) fouled as the main plug
when you need it.

-- 
Eric Murray          N*Able Technologies                    www.nabletech.com
(email:  ericm  at the sites lne.com or nabletech.com)     PGP keyid:E03F65E5

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My vote is put another plug, and another coil and
run dual ignition.  You will have to retard the timing
slightly because of the 2 flame fronts.  Much better
low end torque, and almost never a backfire on a big
lugging session.  The unknown is if you have enough
energy on magneto to drive both coils.  On my Honda
I have just enough if I close the gap a little.

PS We have two Cota 123s, and they really didn't have
enough compression to begin with to really warrent
a release.

Jim

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> single lead from the mag, but maybe?  If I just hook up both coils in
parallel, and I

Yes that should work.

> have a strong enough mag, will that work?  It would be awesome to have a
switch so I

If the energy is low, you can close the gap on the mag coil
on the magnet.

> could test each one individually like small aircraft have.

I've been keeping my eyes open for a double ended coil.  That is
a single coil with two posts and no ground.  That way you can
daisy change 2 plugs on one coil.  The arc jump normal for the
first plug, center -> edge, then it travels across the head and
jumps from edge -> center and back to the coil.  Some of the 
performance cars are doing this.  Kind of like an airplane.
One company I read about went to the extreme, and put 5 arc
sources.

Jim