Saturday, November 17, 2012

Carb Sync Tech Day

No, not trying to synchronize the carbohydrate intake in my diet, Martha feeds me just fine, thanks.

Today I hosted a Carburetor Synchronization Tech Day for my fellow Uralisti in the Denver Metro Area.  Scheduling conflicts however resulted in only two of them showing up: Darrell S on his wife's '07 Patrol and Tim L on his Patrol Sidecar Rig.

Before we got down to business, Tim and I kibitzed and "assisted" Darrell as he used my Harbor Freight tire changer to change out the tire on his spare wheel.  The weather today was in the low 60s and sunny and we all remarked that we should have been out riding instead of doing a tech day!  The tire swap went with no issues in spite of our kibitzing.

 Darrell puts a bit of air into the inner tube so it has somewhat of a 
shape before he uses the mojo lever to mount the tire.

Tire mounted and seated on the beads, its now time to insert the
ceramic beads that will balance the tire without the use of wheel weights.

Tire swap done, Tim took off on his rig to warm the engine up to operating temperatures.  He was soon back and we tried the spark plug shorting method of synchronizing his carburetors.  His carburetors were actually pretty close already and all it took was a slight turn on his right side carb idle screw and they were in sync!

A view of Tim's rig's left jug, with the shorting stick attached.

The shorting plug method involves the metal stick you place between the spark plug and the spark plug connector.  You lay your insulated screwdriver, carefully making sure you only contact the stick and the jug with the metal portion of the screwdriver, and note your tachometer reading.  If you're shorting the left jug, you're reading the performance of the right jug and vice versa.  You keep doing this back and forth till the tach readings are the same on both side and your idle tach reading is where you want it.  I like mine at 900 rpm.

Once you got the idle speed sync dialed in.  You do same procedure but while holding the throttle open as steady as possible at 2000 rpm.  You don't want any change in between the carbs, they should be rock steady.

We didn't get to do this bit with the shorting sticks as we were getting arcing from the left side spark plug for some reason.  We tried some insulating electrical tape to no avail.

So we switched to Darrell's Harmonizer which use readings of the vacuum being pulled by each carburetor.  It showed Tim's idle sync darn near perfect so it matched what the shorting plug results had been, which validated in my mind the method I'd been using.  We went to 2000 rpm's and the digital indicator on the harmonizer was steady in the middle, just like you want it.

The LED displays tachometer-like rpm readings based on the vacuum, and 
a bar with digital number readouts tell you how far off you are from 0 or dead center.

Next it was Darrell's and my turn at the synchronization operation.  We both took off, leaving Tim watching things and when we returned we hooked up the harmonizer to Darrell's Patrol  We found his idle a bit low so he adjusted for that and he did adjustments to the idle screws till the harmonizer indicated 1 off from 0....good enough!  You're apparently allowed up to +/- 25 from center and still be in sync.

Revving up to 2000 though, we found the right side carb pulling too much vaccum as the bar went too far to the right on the LED.  We tried going counterclockwise on the adjusting screw on the cable but that proved to be the wrong direction.  Reversing the turns plus one bit more got us back to center at 2000 rpms and Darrell was happy.

Next it was Valencia's turn, we found the idle at +13, still within spec mind you but about a quarter turn on the right side idle screw brought things to the center.  At the 2000 rpm check, no adjustments needed, she was rock solid in the middle.  Good to go.

It was past 4:00 at this point so tools were put away, stuff secured and goodbyes said.  A good tech day, that harmonizer device is the cat's meow!  I like the spark plug shorting method but it does require the presence of a tachometer as my ears are not "trained" to use just them to judge the sync of the carbs.  The Harmonizer removes the guess work and I think is better than a Twinmax as I've found the bouncing needle to move too much.

 Check out the big lights on Tim's rig!
I think he's smiling as he poses by his rig before departing.

A happy Darrell and his stepson Nikari who played video games
with my sons while we wrenched in the garage.  The rig above is his
wife Piper's rig.  Both rigs are green.  His and Her Rigs!

1 comment:

RichardM said...

Pretty cool. That harmonizer gadget sound pretty good. I need to rebuild my carbs this winter as my mileage took a dive about 5500 miles into my trip. The guru types tell me that it's probably the rubber diaphragms in one or both of the Bings. I've had the rebuild kit laying around for almost a year. Not that I'm procrastinating...