TOPIC:

I dropped down to a 130 no change. I have done a little bit more research and am going to try a new needle and needle jet.

I suspect you are trying to get too much out of that one carb.
Steve

Quite a few people have had success with the single mikuni mod, but I don't have the specific jetting details. Does it run better if you roll the throttle slowly, or if you crack the throttle open quickly? If slowly, then it's likely rich, as rolling it slowly keeps it leaner, (and vice versa for opening quickly).

It's not about more power, it's just about simplicity and parts availability. It can cost over $100 just to get new diaphragms for the factory carbs, if you can find them.

It is running rich, fires up and idles without issue. Cracking the throttle causes popping and kills it.

I'm not trying to gain power or anything. This whole project is simply for shits and giggles. I knew jack shit about carbs and am slowly learning more and more, which was exactly what I was wanting.

Get to the point it pops and rattles, shut it down with the throttle in that position. Check the plugs. That will tell you a lot. Pic? Black smoke?
Steve

They are black and oily. My original thought was that the main jet was the issue, but I have not even gotten to a point where the main jet would be a factor.

Stock settings were
Main Jet : 260
Pilot Jet : 35
Needle Jet : Q-2
Throttle Valve : 2.5
Jet Needle : 6DH4
Air Jet : 2.0
Needle Valve : 3.3(VM34/39)

I dropped the pilot to a 30, have main jets 130 to 160 and have the needle on the top clip.

After reading up at bit on the kz400 forum, I'm getting a new needle and needle jet.

There are, of course, all of the other factors you would check before jetting. Sorry if this is repeating, but this thread goes back some time:

Compression
Valves
Valve timing if the motor was apart
Voltage to the coils
Ignition timing
fuel flow
fuel level


Have you checked other sites for more specific jetting suggestions for this combination?

I'm getting stuck on the oily part. While I was burning oil because of valve guide seals I had to step down on my pilots and main jets to compensate. When I fixed it, I was too lean. Might be going in the wrong direction.
Steve

Oily was probably a really bad way to describe it, they are just really black.

On a side note, what would you guys say a good price for an 81 kz440 running good condition with title would be? I might have a deal on hand I can't pass up.

I din't know but you can try the 400 sites. Pics and asking price?
Steve

dom2570 wrote: Oily was probably a really bad way to describe it, they are just really black.

Is that carb normally for a two stroke?
Steve