Owner's manual

COLD STARTING & TUNING INSTRUCTION

(ALL SU ELIMINATOR CARBURETORS)

Turn the fuel on allowing a reasonable time for the fuel bowl to fill. NOTE: if any fuel runs from the

hollow shaft on the end of the tickler pump, shut fuel off (if this occurs the needle is stuck in the

open position and must be corrected -see setting the fuel level). Assuming no fuel is running from

the overflow, place a finger from your left hand on the piston lift pin located on the left side of the

carburetor body near the center top. Push up and hold this pin while pumping the tickler a half

dozen times.This procedure will induce fuel into the venturi by pressurizing the fuel bowl and

forcing fuel through the mainjet into the venturi. By lifting the piston you allow no obstruction to the

fuel flow. Release the lifting pin and set the choke to the on position by rotating the choke lever

clockwise until it locks into a pre-cut groove on the cam. Use of the choke is optional. In warm

weather it may not be necessary. With the choke on, press the button or kick the engine to life.

Allow a few minutes for a warm up period noting the increase of RPM as the engine warms.

It is a good idea to cut off the choke as soon as possible as it may load your engine if left on for

over a few minutes. To automatically turn off the choke simply twist the throttle grip. It will release

the cam lever.

All tuning should be done on a warm engine. Ride the motorcycle until it reaches normal operating

temperature. If the engine seems strong and pulls well throughout the RPM range it is probably

tuned very close. If there is a question we suggest running the motorcycle at a sustained speed of

55 MPH for a few miles. Pull in the clutch, turn off the key and brake to a stop. At this time a plug

reading can be obtained from either cylinder which will indicate a rich or lean condition.

All carburetors are shipped with a standard needle and spring unless ordered for a specific purpose.

The standard needle can be changed to a richer or leaner as two extra needles are sent with each

carburetor kit.

The mainjet adjustment (see diagram) on the bottom right side

of the carburetor adjusts the main jet up or down on the tapered

needle installed. All carburetors are shipped with the mainjet in

the neutral position which allows an adjustment of two full turns

either way for mixture strength.

Turning the adjustment screw clockwise or to the right will richen

the mixture. Turning the adjustment screw counter-clockwise will

lean the mixture.The adjustment on the mainjet affects the

position of the mainjet down onto a smaller taper needle which

allows more area for fuel to flow, hence a richer mixture.

The normal or standard position is preset at Rivera Primo.The way to find neutral is to remove the

dome and piston andvisually look at the position of the mainjet in relation to the mainjet holder

which is the part the mainjet moves inside.The correct position for neutral is when the mainjet is

1/16 ” below the bottom edge of the main jet holder. Then you will have 2 turns either way to correct

any mixture problem you may have. For altitude we suggest using the leanest needle supplied

with the kit. Any altitude above 3000 ft. will benefit from a leaner needle.

A motor that has ported heads may very well require a leaner needle as the efficiency of the engine

increases with such modifications. There are no set rules for tuning as no two engines will ever run

exactly the same. We will make some recommendations based on many years of experience plus

feedback from customers on tuning tips.They may vary and not apply to your particular require-

ments, so use them as as guide only.

SU Instructions 1108-0001_SU Instructions 1108-0001.qxd 10/4/12 10:13 AM Page 6