hitachi carburator

I've done this modification to my carburator with great results in acceleration and highway speed's. This modification may impact emissions results so if you need to pass emission tests in the future you might want to get a spare carburator from the Junk Yard to perform this operation on. NOTE: This modification will only work on the EA81 series Hitachi's. Although the same modifcation is possible for the EA82 Hitachi's, I have not performed it, or do I have images available for the modification.

Just alittle background about this modification and the reason why I did this. The Hitachi carburator has 2 barrels, but only the primary barrel will open under acceleration. It is not until the gas peddle is fully depressed and a certain amount of vacuum is created in the intake manifold that the 2nd barrel will open up. This modification will bypass the vacuum actuator on the hitachi and force the 2nd barrel to open when the 1st barrel reaches 1/3 throttle.

Lets Get started shall we? Here are some diagrams of the part of the carburator we will need to play with. You will not have to dissasemble the carburator at all, so almost anyone should be able to do this mod.

Here in this figure we see the diaphragm that will need to be removed. It is held on by 3 screws (#2 in the diagram) and is also held on by the snap ring at the end of the diaphragm arm. You will want to plug the hole in the carburator that the diaphragm connects to.

After you have the diaphragm removed, play around with the carburator alittle and notice how there is a lever for the primary and the secondary barrel.

Here is a closeup of the moving parts that we will play with. #3 in the diagram is the actual throttle lever that connects to the throttle cable. #4 is the secondary lever that we need to make move. I've put red arrow's on the contact point where we need to atatch the primary and secondary plates. I have heard of people welding it together right there, but I dont have a welder, nore do I like that idea all too much.
I took a piece of coat hanger and cut off a piece about 4" long and bent it to the desired shape.