Hitachi Air/Fuel adjustment?

[cobcob]

My '82 brat isn't giving me the mileage I was expecting and the sooting in the tailpipe suggests to me that she's running a bit rich.

I've searched here and in the USMB but I haven't been able to find any diagram showing the location of the mixture screw for the Hitachi carb or any tuning info.

Can anyone shed some light on this? A 220 mile highway run on the weekend got me about 23mpg, my usual daily commute gets me around 26mpg (85% highway @ 60mph, 15% City @40mph and 4 or 5 stops) Is this the best I can expect from the EA81/Hitachi combo?

[archemitis]

i've heard of people pulling off 30mpg, but i think its all about the condition of the motor, and the rest of the car too.

id kill for your mileage

if i remember right the air screw is to the right of the idle adjustment, right smack in the middle of the front of the carb.

id like to know the recommended way to set it, doesnt it only effect idle to part throttle, or does it effect the whole throttle range?

[cobcob]

id like to know the recommended way to set it, doesnt it only effect idle to part throttle, or does it effect the whole throttle range?

I really don't know... just trying to get this thing tuned so it's not running as rich... hopefully there's some Hitachi guru's out there

[Frank B]

Is your carb in good shape? Are the throttle shafts worn. Is it dirty?

Remove and completely clean and rebuild the carb first. There is one mixture screw on the Hitachi, but it's for the idle mixture which has nothing to do with the rest of the circuits. It's on the very front just above the mounting gasket. There is a roll pin blocking it, so you have to remove the carb to drive out the pin to get access. As you clean and rebuild the carb, remove the roll pin and idle mixture screw and spray some carb cleaner in the hole then turn the screw all the way in being careful to not bottom it out. If you do you will damage the end, just go easy untill it stops. Turn the screw out 2 1/2 turns. Set the idle speed, let the engine warm up, then turn the idle screw in untill the engine wants to stall, counting the turns or partial turns(1/4, 1/2 etc.) Then back it out untill it wants to stall, then turn it back in untill its in the middle of the two spots. You should be good. In is lean, out is rich.

 

Then look at the ignition. Is the cap and rotor worn? Does it need new plugs and wires? Does the engine use oil?

 

I had an 86 EA81 Hatch that went from 26 to 37 MPG ( highest not average) after a good carb cleaning and rebuild.

[cobcob]

Thanks Frank B!!

I'll get onto that in a couple of weeks... sadly my weekends are booked up almost to Christmas so I guess I'll just swallow a couple more weeks of the mileage. It's really not THAT bad to be honest but when driving 300+ miles a week every little bit helps!