[Spridgets] Midget Won't Idle Down Solved

[Bert Shirey]

Hi, Guys and Gals: A while ago I posted a “mystery” problem with the 1965 MK
II Midget that I recently passed on to my friend Jim. The car had a chronic
issue in that it was idling at about 1500 RPM and no amount of tinkering
would bring the idle down to the correct 900-1000 RPM. This condition also
was causing difficulty engaging 1st gear from stop, I suppose because the
synchros thought the car was moving. I will tell you what the problem turned
out to be.

        I had the Midget 57 years to the day from new and maintained it
myself since it came off warranty. Some say it is one of the nicest
unrestored survivors around. Anyway, about nine years ago at about 55K
miles, my wife, Sandy, and I (Sandy was my co-mechanic from the get-go and
knew as much about fixing Spridgets as I pretend to.) did a major
maintenance on the car. We did rod bearings, valve adjustment, ignition,
fuel pump, hydraulic flush, tranny and diff, and more,  just about
everything on the 50K  to-do list. One lesson: Don’t try  to do so much at
once that you don’t know where you screwed up. While we were at it, we
installed a new set of HS2 carbs that I got on sale from Victoria. Nothing
wrong with the originals, but the new ones looked real shiny. Another
lesson: If it ain’t broke, don’t fix it.

         Believe me, you don’t own British cars for over half a century
without learning how to set up SU carbs.

         When I was 18 I thought I knew it all, but, in fact knew nothing.
Nudging 80, I realized maybe I knew something, so I was making progress. If
I live to 100 could be I will have learned a lot, finally, but by then I
will be too old to be dangerous. I don’t know whether living to a ripe old
age is God’s reward for a life well lived or God’s punishment for not living
life well enough. Go figure. 

        Back to the mystery,  not long after that big maintenance project,
Sandy got sick. The only thing that girl ever did to hurt in 50 years was to
die. She got me on that one.  So, I knew the idle was wrong but didn’t drive
the Midget much nor feel like messing with it without my best buddy. Imagine
Tom Hanks in that movie. “Hey, Wilson, help me figure out what’s with my
Midget.”  Like that. Later, after I got myself together, my back went out,
so I had another alibi for neglecting the Midget. Finally, I realized time
had come to let my cars go. First  I passed our Bugeye that we had 31 years
to my friend Steve, then after screening the suitors of the Midget, I
watched her, mysterious fast idle and all, go off to Jim. Jim promised not
to drive the Midget in the rain and vowed to solve the idle problem.

        Getting to the point of all this, here’s what Jim found: First of
all the front tappet side cover gasket was leaking and the attached
crankcase vent canister had developed perforations. This resulted not only
in an oil leak, but also in, we believe, a vacuum leak that would interfere
wit mixture adjustment. But that was not the actual cause of failure to idle
down. The actual cause (And this my be helpful to you sometime.) was the
mixture adjustment hardware on the new carbs. The adjustment nut is ½ the
thickness of the original, and the threads are finer. To adjust the mixture,
we normally turn the nut up till the jet is even with the bridge of the carb
body, then down 12 flats. The carbs being otherwise in good order, that gets
the mixture pretty close, usually within a couple flats, more or less.
Trouble was, because of the different nut on the new carbs, 12 flats would
not do it. It took 22 flats. The over lean mixture resulting from improper
adjustment and the supposed vacuum leak skewed the idle. Jim says the Midget
is running beautifully now. 

         Why didn’t I think of that ? Cheers, Bert Shirey.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/spridgets/attachments/20230106/e9b82ce8/attachment.htm>