TOPIC:

Rebuilt carburetors on 1975 z1900. Only runs with full choke. What's wrong?

I suspect that the pilot circuits are not yet perfectly clean.

Wear eye protection while spraying carb clearer because the spray always backfires. ALWAYS .

Pay extra careful attention toward cleaning the orifice into bottom of the car bore (number 6 on the following diagram).



Good Fortune!

The carbs at hand may have the pilot mixture screw instead of the "pilot air screw "as shown in the earlier diagram.



Both style carbs have an orifice into the carb bore.

Good Fortune!

What do you mean when you say you rebuilt them? What did you change? Are these the original carbs? What serial number is the engine?

The bike has been off the road since '84. Installed carb kits in all 4 carbs, however once I got into it I realized there are part variances and just because the gaskets fit doesn't necessarily mean the jets etc., are right so it's possible I installed the wrong parts. I believe the carbs are original. As for the engine serial number, I will need to look .

The reason I asked for the engine S/N is because they switched carbs mid year for 1974. Up to S/N 35,000 had the Z1 style carbs with different jetting than the rest of Z1A bikes, which used the same carbs as the Z1B.

I think I made a mistake. I thought the bike was a '74 but I see now that it's a 75. Stock carbs would be VM28SS. Pilots would be 17.5 and mains would be 112.5. Air screws should be out 1 and 1/4 turns from lightly seated. Needles should be 5J9 with the clip in second position from the top. Jet needles are O8.

What parts are currently installed?

hardrockminer wrote: I think I made a mistake. I thought the bike was a '74 but I see now that it's a 75. Stock carbs would be VM28SS. Pilots would be 17.5 and mains would be 112.5. Air screws should be out 1 and 1/4 turns from lightly seated. Needles should be 5J9 with the clip in second position from the top. Jet needles are O8.

What parts are currently installed?

Wow! The joy of forums. There you have it. What more could you ask for!!

The engine s/n is:Z1E059149.
BTW should the engine S/N be the same as the title ID #? Mine are different.

www.zedder.com/Info/75%20Z1-B%20900.htm

Good Fortune!

Danny Millhorn wrote: The engine s/n is:Z1E059149.
BTW should the engine S/N be the same as the title ID #? Mine are different.

Title should have the frame VIN, starting with Z1F- if it's really a Z1 frame.

Good Ridin'
slmjim & Z1BEBE

That S/N is definitely a '75. If your intake and exhaust are stock then the parts I described are correct for the carbs.

Did you rebuild them? If so, what did you do?

When I rebuild them I take everything apart and wash parts in an ultrasonic bath. Then blow compressed air through all the holes, particularly the three small orifices on the intake side to ensure they are clear. I use all new jets and needles and throw out the old ones. Use new gaskets for the bowls and tops. I like the Keyster kits sold by Z1 Enterprises.