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SU assistance needed

To: "'MG List'" <mgs@Autox.Team.Net>
Subject: SU assistance needed
From: George Merryweather <merryweather@venus.connectware.com>
Date: Wed, 5 Feb 1997 09:01:50 -0600
OK folks, I am hoping that some wise sage on the list has had this =
problem before.  A quick fix would be nice, but just a fix at all would =
be great!

948 MOWOG special
twin SU HS's     The young man who brought it by complained that it was =
running rough.  He was right.  Barely running at all.  Carb linkage all =
screwed up, etc.  (Dad had tried to fix it)

Straighten out the linkage, replace the adaptor bushings on each one, =
put the carbs back on and fire it up.

It run real rough.  Actually both son and dad says that it sounds better =
but it is not anything I would take out on the road.

Uncouple the linkage, and put on the trusty Unisyn.  Rear carb appears =
fine.  When placing the Unisyn on the front carb, RPM picks up about =
1500!  OK, so maybe it REAL lean?  Adjust the 'jet nut'.  The rear carb =
is at 7 flats, the front is now at 15!.  Unisyn has about the same =
effect.  Engine is still running, sort of.  Check linkage, jet seating, =
etc., while it is running, and no success.  Now the interesting =
part.....Both pistons are about 1/8" off the body at idle.  OK.  On =
acceleration, the rear slides open nicely, the front one CLOSES! Piston =
problem?  Shut it down, exchange pistons and housings front to rear, =
fire it up, problem stays to the front.

Check the spark plugs, #1 looks OK, but they get darker as you move =
back.  So it appears that its running off the rear carb.  That is =
further validated by the Unisysn problem.  Rear is running rich to carry =
all 4 cylinders, #1 is real lean.  Maybe a blockage in the jet?  the =
little tube from the bowl? etc.  But it could be running real lean if =
there was a vacuum problem.  As evidenced by the piston dropping on =
acceleration.  But why would the piston drop.  They are on the same =
manifold.

So have I given you enough info to come up with a miracle answer.  I =
hope so!  All suggestions welcome.  I fooled with this till about =
11:00pm last night, with dubious sanity at the end.  (It was probably =
dubious to begin with!)  Before I give it another shot, I thought I go =
for some advice from the group!

And it still amazes me that the guys thought it was running better than =
before.  Before must have really been bad!

Your assistance is appreciated.

I won't be insulted is you suggest something dumb, simple, or stupid.  I =
do those three real well! =20

(I must be missing something real obvious!)

George Merryweather
merryweather@connectware.com

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