1976 KZ400 D3 idles rough, revs high, dies. Jets?

I recently bought a 1976 KZ400 D3 for $100. It had no fuel lines and did not run. It is my first project bike.

To begin, I changed the oil and filter, cleaned the carburetors (a pair of keihin vb32), and got a new battery. The inside of the fuel tank looks disgusting, and I am looking into ways to clean it. In the meantime, I filled two plastic water bottles with gasoline and connected them to the carburetors using fuel hose.

The bike only starts when the choke is on. For ten or fifteen seconds, the engine will idle very roughly. It revs high, then dies. It also dies immediately if the choke is turned off.

What are the first steps I should take to alleviate this issue? I assume it has something to do with the jets. Furthermore, now that I know the engine runs, what kind of maintenance should I perform on it?

Thanks for the help.

To me it sounds like you didn't get the idle jets cleaned. Very common especially for someone not familiar with cleaning carbs. Those jets are tiny and clog easily and most of the time hard to clean. Not familiar with you exact carbs so I don't know if you can unscrew them or not. If you can get the jets out I like to boil them in distilled water for about 20 minutes and check them. Another boiling if not clean. You can hold them up against a bright light or background and see there is supposed to be a hole in the bottom of them. And that hole has to be absolutely clean. Plenty of carb or brakes cleaner squirted through them until you get a nice stream. Then the circuits above the jets have to be clean. I like to wrap a carb cleaner or brake cleaner straw with electrical tape until it fits snug in the hole and squirt cleaner until you see it come out near the butterfly on the engine side of the carb body throat.

Don't feel bad. I've done dozens of carbs and sometimes it take me 2 or 3 or more attempts at getting the entire carb clean.

As for the fuel tank. Search on youtube for various methods of cleaning them. Never fun and always messy.

You might consider posting those different questions in separate postings so each can be addressed in turn. Keeps confusion to a minimum.

jdvorchak wrote: Don't feel bad. I've done dozens of carbs and sometimes it take me 2 or 3 or more attempts at getting the entire carb clean.

Yep. 2 to 3 times is not uncommon. Not just the jets either as jd pointed out, You have to trace all the passages, particularly in the pilot circuit.

Thanks for the advice and encouragement. Tore down the carbs to give them a second cleaning and discovered that one of the rubber passage plugs covering the pilot jet and slow jet had torn. Replacement part is in the mail; in the meantime, I'll give everything another thorough cleaning, double- and triple-checking to make sure everything is spotless as I go.

Will report back on results. Thanks again!

One tip I can offer is that if you squirt cleaner into a passage it has to come out somewhere or it's plugged. It's hard sometimes to see where it comes out but with enough twisting and turning and looking into the carb throat you should see something come out somewhere.

Keep at it.. You'll get it running like a champ.