TOPIC:

I have a 77 kz400 with an odd petcock. It has Off/On/Pri positions at 3 6 and 9 o'clock. It has two hose connections. When the selector is On or Pri, fuel comes out of _both_ hose connections . It seems to work fine without a vacuum hose connected.

It has the look of a stock petcock, but doesn't quite match the petcock in any of the three shop manuals I've downloaded. I was wondering what the second fuel port us for. Did Kawi make a version of carbs with no fuel crossover pipe, so the petcock fed them separately? I have one capped right now.

A photo might help. Does the fuel cock have a vacuum port? Asking, because if it has ON-OFF-PRI, it seems like it would be a manual fuel valve & not a vac petcock. You can try the diagrams at Partzilla, then search the part numbers on EB.


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So you have three ports total on the petcock? 1 vacuum and 2 fuel ports.

Someone probably fitted a vacuum-petcock from another model.

The earlier Kz400's used one fuel line to each carb, so yes, it had two fuel lines. Most (but not all) 77 models had one fuel line and the carbs had a fuel rail to feed both carbs. 77 was a transition year from the piston-slide carbs (dual fuel line) to the diaphragm-slide carbs (single fuel line).

Sorry, I mis-spoke: the petcock has three positions, "STOP" (right), " "ON" (down) and "RES" (left). On the back-side, it has two ports. Both are facing down. When I set the fuel selector to either ON or RES, fuel flows out of both ports at the same time. I wasn't sure if there was something "different" about one port versus the other. Thanks, LoudHVX, it sounds like I must have the earlier petcocks, meant to feed carbs separately; but they feed the carbs with one hose. This '77 D4 bike has a '79 B2 engine, so the carbs may be newer than the petcock.

Back-right port, which I have hooked to the carbs:


back-left port, which I have capped with a vacuum cap (probably won't last 3 years without cracking):

That doesn't look like an early Z fuel tap to me. Early Z fuel taps dont have a screwed on plate with the letting on on the front. The lettering is cast into the tap body. Additionally, the outlets are horizontal, not verticle.

yes, I often see this mismatch on Kz400's. Someone gets a petcock for a pre-1977 dual feed, but installs it on a 1977 or later single feed bike.

The 1977 D4 should have diaphragm carbs with a single fuel line so you can simply cap off the extra fuel port. However, don't use a vacuum cap from a parts store. They are not designed to handle fuel and will crack and disintegrate within weeks or months. It would be much safer to use a small piece of fuel line with a smooth metal plug like the shank of a stainless steel bolt (cut the threads off).

Agreed on the vacuum cap. I figured that it would be leaking by next spring. I'll do the "bolt in hose + clamp" thing.