We recently posted a video to the Power Republic YouTube Channel showing you how to service your Dellorto VHSB 34 carburettor for a Rotax Max 125 go-kart engine. Here we will break down the steps in a little more detail for you, as well as providing images and links to purchase the parts.
Ok, so let's get into it. Please remember leave any comments or questions below.
The tools you'll need for this job are:
4mm Allen Key
1/4" Drive Ratchet Handle
Flat Blade Screwdrivers - Various sizes
12mm Ring Spanner
CAUTION: Always remember to wear safety glasses when using solvents, particularly if you will also be using compressed air.
Step 1: Remove the 3 cap screws with a 4mm allen key.
Step 2: Remove the jets with a flat blade screwdriver.
Step 3: Remove fuel sieve with the 12mm ring spanner.
Step 4: Using a flat blade screwdriver, remove the air bleed screw.
Step 5: Measure your float height with a set of digital verniers. Make a note of the measurement, so that when you replace the needle and seat, you can adjust to the same measurement.
Step 6: Use the side-cutters to remove the pin and float lever, then, using the 9mm socket remove the old seat and needle (remembering to remove the old seat gasket at the same time).
Step 7: Using your solvent/carburettor cleaner, clean all the jets and orifices and dry with compressed air.
TIP: Use your pointy-nose pliers to hold the parts whilst cleaning to avoid skin contact with solvents.
Your carburettor is now ready to reassemble with a new needle and seat.
Step 1: Firstly install the new gasket and seat, followed by the needle.
Step 2: Install the pin and float lever and check the float lever for correct height, using your verniers.
TIP: There are 3 settings for the float that we have found to work well, 23.0mm is the leanest (for wet races), 23.5mm is medium and a good all-round setting and 24.0mm is the richest and used when the engine is leaning out/hesitating off slow corners.
Step 3: Install air bleed screw all the way to its home position, then return it to 2 complete turns anti-clockwise.
Step 4: Replace the fuel sieve.
Step 5: Re-install the jets, starting with the smallest pilot jet.
Step 6: Replace the float bowl gasket, install the floats so that you can read the weight of them when you are looking at the carburettor and install the float bowl. Tighten the 3 M5 cap screws and you are all set.
Step 7: Clean the bench, put away the tools and enjoy the rest of your day :)