[Healeys] BN2 Dieseling

Alan Seigrist healey.nut at gmail.com
Mon Aug 16 00:27:01 MDT 2010


Bob -

A BN2, even with M pistons, should not be running-on at all, especially if
using premium fuel.  My stock BN1 doesn't run-on even with regular unleaded,
so something is wrong.

Given that you've gone through the timing & mixture, I'd say the last thing
to check is carbon deposits.

Pull the plugs and make sure they are clean.  If they are clean then you
need to proceed to undertake an Italian tune up.  Apparently adding a can of
Marvel Mystery Oil to your tank can help here (but I've never done that).

Ok, the Italian tune up:  Take the BN2 and run it on a highway or country
road at 4,000 + revs for a good 5 minutes.  Probably best done in either
second or third with no OD.  As you get to your five minutes, all of a
sudden let off the gas and just let the motor do the braking while you coast
to a stop, best if done going down hill.  Do this two or three times and
that should help dislodge carbon on your pistons and valves.

Alan

On Mon, Aug 16, 2010 at 9:27 AM, Bob Spidell <bspidell at comcast.net> wrote:

> Listers,
>
> I know this topic has gotten flogged many times before, but we're having a
> severe dieseling (runon) problem with our BN2/100M.  Carbs rebuilt,
> otherwise running good, but she refuses to shut down.  Have cut the idle way
> down and retarded the timing a bit, mixture is spot on according to
> Colortunes and 'lift test,' coolant temp OK.  One data point: if we pull out
> the choke when turning the ignition off she shuts down immediately.
> All suggestions, SWAGs, etc. welcome.
>
> TIA,
> bs
>
> --
> *******************************************************************
> Bob Spidell           San Jose, CA            bspidell at comcast.net
>
> *******************************************************************
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