Tomos A3 Carb Cleaning (Dellorto)

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How to Clean the Dellorto 12.14B SHA Carburetor on a Tomos A3 Bullet

What you will need:

  • Can of Carb, Brake, or Parts cleaner ($5.00 at local auto or hardware store)
  • Assortment of Metric Wrenches (10mm and 13mm used on this particular bike)
  • Flat Head Screw Driver (small)
  • Tin or Container to clean parts in

*Note* You will be doing 95% of the work on the right hand side of the bike (side with the petcock) so set up shop accordingly.

Getting started

This is a Dirty Dellorto SHA 14.12B Carburetor. It came off of a 1989 Tomos Bullet A3.

First, turn off fuel flow to carb.
This can be done by switching the petcock to the closed position (illustrated below)

IMG 3783.JPG

Unplug the spark plug boot from the spark plug.

IMG 3784.JPG

Remove the fuel line from the petcock and the carb.
Be sure to drain any excess gas into a separate container. *Note the position and flow of the fuel filter*

IMG 3785.JPG

Remove the 2 screws holding the carb to the cylinder.

IMG 3789.JPG

Unscrew the air filter clamp from the carb.

IMG 3790.JPG

Remove the 2 screws that hold the engine to the frame
Be sure NOT to strip the bolts when removing them. You will have to hold up the engine to relieve pressure on the bolts while removing them.
Lower the engine a few inches. It should stay in place without bracing it.

IMG 3791.JPG

You are now ready to take the carb off the frame.

Removing the carb

Rotate the carb towards you as shown below.

IMG 3794.JPG

Remove the cap that went inside the air filter.

IMG 3796.JPG

Remove the throttle / choke assembly from the top of the carb.
Rotate the top of carb towards you. You will see two screws, unscrew them both. Be careful! A spring will pop up after releasing these two screws.

IMG 3798.JPG

Carefully slide the throttle / choke assembly out of the carb at let it hang from the cable for now.

IMG 3800.JPG

The carb should now be free from the moped frame.

Removing the carb components for cleaning

The black "bowl" under the carb is the float bowl. There are 2 screws that secure it to the carb. Unscrew them.

IMG 3802.JPG

The gold screw in the middle of the float is called a jet. Unscrew it to remove it. *Do not lose this piece*

IMG 3803.JPG

Remove the idle screw as shown below. Do not lose the spring.

IMG 3804.JPG

Next, remove the nozzle that accepts gas from the fuel line -- this is the banjo. Note its position for re-installing it.

IMG 3805.JPG

After removing the nozzle, you will see a disc shaped filter. Remove it very gently where the notch is at the top.

IMG 3807.JPG

All removable parts of the carb are now removed, except the float. You can remove the float by pushing on the swivel pin on one side. It will slide right off. Then you can remove the float and the float needle underneath, to more thoroughly clean the fuel supply pathway.

Cleaning the carb and its components

This is very simple. Take your can of carb or brake and parts cleaner and DOUSE everything with it. You will be surprised how easily every bit of gunk and grime washes away with this stuff.

Make sure EVERY crevice, hole, screw, etc gets cleaned. Clean the float bowl, jet, fuel filter, nozzle, etc. After spraying down the jet, blow through the jet. Put the jet right in your lips and blow as hard as you can to clear it up. Don't forget to spray down the throttle/choke assembly hanging from the frame.

IMG 3809.JPG

IMG 3810.JPG

Re-assembly and re-attaching the carb

Simply reverse the steps in the wiki to reassemble and re-attach the carb to the frame. It is imperative that you put the throttle/choke assembly together correctly if you want the moped to function. Be careful not to damage the gasket as I tore it one corner while cleaning this moped. I didn't notice a huge difference, but don't do it. Also, there is only one way to put the carb back INTO the air filter on this bike. The rubber part that attaches to the carb goes OVER the fitting on the air filter attached to the frame.

If you squeeze and shove the rubber part attached to the carb INTO the rubber housing on the frame, you will get a devastating air leak (as I have discovered), and it will take you days to figure out why you mopeds tire will spin for a second and then die with full throttle. Yes, it can happen... it did to me...