I read up a bit on carbs today and took the air filter cover off my EA81 to play around and see what was inside. Searching on here for more info didn't turn up too much about the stock Hitachi carb other than it being complicated. So, looking down the top of the carb, there are two barrels. Only the bottom one has a choke, and the top one's throttle body only opens just barely at WOT. I tried propping the choke open and starting the car to see what would happen, and there was a spray of fuel out the throttle body and a lot of noise I let the throttle body close, and for the first time ever, my EA81 went into fast idle mode After letting the car warm up fully, the choke opened by itself. I played around with the throttle, and the fuel going into the bottom barrel was readily visible, but the top barrel would still only slightly crack open at WOT, with no noticable fuel going in.

 

Questions:

 

1) Why does my top throttle body (the one with no choke) only barely open at WOT? How much is it supposed to open? It seems like I'm losing a lot of potential performance here if I'm only using half the air intake.

 

2) What could be stopping my car from going into fast idle mode? Why did it go into fast idle after starting the car with the choke manually propped open?

well for number 1... it could be your secondary sticking... we had to replace the carb on the 86 GL.. afterwards it worked perfect.... (hehe i think its so funny that it has 1) hey what did the noise sound like.. you mean like screeching or engine noises or just sucking wind???

Fast idle on the Hitachi is very tricky to get right. It's all about adjusting the choke settings, and cleaning the linkage. Basically you have to tear it down.

 

Secondary is vacuum operated from inside the carb casting. It will only open under load usually. WOT will not open it unless conditions dictate (in gear, up a hill in third for example).

 

GD