How do you rebuild the carburetors on a 1978 400 cc Honda motorcycle?

Answer 1

You'll need tools. One 7mm wrench. One small and one medium flat head screw driver. One #2 Phillips screw driver. One bottle of spray carb cleaner and One parts cleaner can (carb cleaner in a bucket). Lots of Pacience. A manual to follow and get specifications from.

Depending on the age, you'll also need an impact hammer, a small drill and maybe some super glue if your going to use a rebuilt kit.

1) Remove the Carbs off the bike.

Drain the fuel from the carbs with the drain valves (flat head on bottom of float bowls).

Take the rear fender off, the battery out and the battery box out as well. Take the air cleaner box top off then move the air cleaner box backwards. This will save so tons of hair-pulling and hardships.

Next loosen the carb boot clamps with a Phillips screwdriver and gently push down and pull up on the carbs until they pop out. Don't push down way too hard because the carb boots tend to break after 30 years of use, ha ha.

AFTER you get the carbs loose from the carb boots, remove the choke, push and pull cables. You will have to slightly twist the carbs down and wiggle them until they come out. You'll be glad you moved the air cleaner back by now :)

2) Get a clean workspace, at least 2 feet by 2 feet. I lay clean rags down and arrange them into 4 sections. Middle for the carb bodys, left for the bottom internals and right for the top internals. Top section for tools.

3) Remove the bottom of the carbs. Remove the pin for the float bowl. Remove the float bowl and float pin. Use the 7mm wrench to pop break free the needle jet holder, then the Philips to take the top off of it. Remove the rubber stopper then the primary jet with the flat head. Remove the seconday with the flat head. Remove the fuel idea mixture screw (by hand) and make sure you have the pin, spring, flat head and small round rubber gasket.

Be Careful, don't force ANYTHING. Use WD-40 if the jets don't come out. If the heads of the jets break a little, then it was not ment to be.... rather keep them in and clean the best you can then to break the heads off.

4) Remove the top of the carbs. You should have a long spring, a long needle and a solid metal vaccume "piston". Take the rubber stopper out of the piston then use a flat head to unscrew the aluminum plug and just tilt the piston to get the needle out.

On the carb body itself there is a single screw in a kidney bean looking plastic peice. Take this out to expose some small holes.

5) Soak all non-rubber items in the can of carb cleaner. Leave for 30 min., in the mean time use the carb cleaner, clean rags and anything else you have to clean the cab bodies as the best you can! Clean clean then clean some more. Clean the float bowl itself.

6) Reassymble. Set the idle screw to the manual's standards or screw it back in the same amount of turns it took to screw it out. Make sure all the little bits are replaced or at least put back the bits the same way you took them out.

You'll know if everything is ok if you can move the "piston" up with your finger and you feel a firm pressure, then it goes back down with a small 'air' sound.

Hint: Put the cables back onto the carbs before installing the carbs. Remember to reassymble the air box and rear fender/battery box.

Hope this helps!!!