So, I'm rebuilding my Hitachi carb.  The good news is that there are actually some parts missing (which hopefully means better/proper performance once the rebuild is complete).  I'm obviously also using a complete rebuild kit for new washers, seals, etc...

I have another hitachi that came with the Zuk, and I'm robbing missing parts/springs/washers from it to make mine complete.

One thing I noticed, is that the idle adjusting needle is different in the two carbs.  How do I know which is the right/better one to use?

If you look at the attached picture, from left to right, you will see:
- The contents of the carb that I'm rebuilding (shorter pin, spring, and o-ring only).
- The contents of the carb that I'm using for spare parts (longer pin, spring, WASHER and o-ring).
- The new o-ring I'm using.

So, which pin/needle should I use?  I know the others (spring, washer and o-ring)...

So, I'm rebuilding my Hitachi carb.  The good news is that there are actually some parts missing (which hopefully means better/proper performance once the rebuild is complete).  I'm obviously also using a complete rebuild kit for new washers, seals, etc...

I have another hitachi that came with the Zuk, and I'm robbing missing parts/springs/washers from it to make mine complete.

One thing I noticed, is that the idle adjusting needle is different in the two carbs.  How do I know which is the right/better one to use?

If you look at the attached picture, from left to right, you will see:
- The contents of the carb that I'm rebuilding (shorter pin, spring, and o-ring only).
- The contents of the carb that I'm using for spare parts (longer pin, spring, WASHER and o-ring).
- The new o-ring I'm using.

So, which pin/needle should I use?  I know the others (spring, washer and o-ring)...

You'll want to keep the needle and seats (carburator) together. Don't mix and match those because there maybe / are things that are different, suble but different, like threads and more importantly pitch of the needle itself. If it doesn't match the seat, the carburetor's fuel mixture adjustment may not work.

YMMV
-Eric

Thanks so much for the response.  It was a good rebuild, and I'm cautiously optimistic about the results.

One thing I'm concerned about, is the picture below.  The red arrow, is pointing to a large gap between the Idle Up Actuator, and the Adjusting Screw on the throttle lever.  Could it be related to an improper installation of the blue area?  I can't tell exactly from the service manual.

Sorry the pic is so bad, it's from my phone (wife's got the camera).

You all are great, thanks so much for your help!

Trey

The rebuild is complete, and she's running fairly well!
Blue smoke while cold, once warm, no smoke!   

Black smoke when I REALLY hit the gas hard.

Do I need to adjust the mixture?