Arrow TR1 Carburetor Synchronization Tool ...

For a twin engine running smooth, it is necessary to adjust the carburetors to
get the same power from both cylinders. The synchronization of carburetors is
appropriate after adjusting the valves, cleaning the carburetors or similar activities.

Basically, the negative pressures at the carburetor joints are measured and attuned to
each other. Of course, the values by themselves are not very interesting (TR1.: 180 mmHg),
but the difference between both values has to be very small.

In a hose connecting both carburetor joints, the air moves to that cylinder, that "sucks"
more than the other one. With some oil filled in the hose, that movement is visible and
can be used to synchronize the carburetors.


4 m transparent plastic hose (PVC), inner diameter 5 mm
2 hose joints (e.g. accessories for garden fountains)
2 x 20 cm gasoline hose, inner diameter 5 mm
1 wooden board, ca. 60 x 30 cm
7 cable clips (suitable for the hose)
engine oil
insulating tape


gasoline hose
(to extend connection between fuel tank and carburetors)
long screw driver (30 cm)
block of wood (to lift fuel tank)

Fix the middle of the transparent hose on the board in an U-shape, using the cable
clips and lead the both halfs of the hose to the upper side. Fill in some engine oil until
the oil levels reach the upper side of the board. Stick together 50 cm of the both
sides of the transparent hose with some insulating tape and lead it upwards.

With the hose joints, fasten the gasoline hoses at the both ends of the transparent tube to
prevent it from getting soft and leak on the hot negative pressure junctions.

Check this picture how it should look like.


warm up the engine and turn it off
apply the longer gasoline hoses between the tank and the carburetors
lift the tank at the rear side to reach the adjusting screw between
the carburetors, base it on the block of wood
pull off the negative pressure hoses (to the fuel cocks) from the
carburetor joints and put on the the ends of the synchronization hose,
use hose clips if necessary
switch the fuel cocks to "PRI"
start the engine and watch the oil levels in the transparent hose
!!Attention!!: At a high difference in pressure, the oil rises !!
quickly and could be sucked into the engine !!
set the engine idle speed to 2000 rpm (by turning the throttle stop screw)
adjust the synchronization screw between the carburetors until the
oil levels in the transparent hose reach the same height (the levels
are pumping about 2-4 cm with the motor speed)

When it's well adjusted, my TR1. engine starts at a fingertip, without turning the
throttle grip, works very smooth and doesn't spit or bang when closing the throttle,
even at high motor speed.

Good luck !

On further questions: send e-mail to Lutz.

I'm just thinking about an electric measurement and presentation of the
difference of pressure ... has anybody an idea about cheap measurement
of negative pressure ?