Designer & bike rider in British Columbia, Canada

KZ650 Intermediate Carb kit

Half day in the garage putting new carb kits in the 1978 KZ650. Half of that time was spent scraping the gaskets off the carb bowls and tops.

Carb kits are K&L, ordered from Z1Enterprises, Carburetor Kit – KZ650 – 1977-1979 – Intermediate, $21.92US each, times four, had them shipped to my mailbox in Blaine, WA, with some other parts for the KZ (posts coming up on valve shim and various gasket replacements).

This carb kit comes with four main jet sizes: 90, 97.5, 102, and 102.5. I think it was a 102 stamped on them…kit description on Z1 says it should be a 105, though.

Previous owner had…105 in there? I had put the old ones back in a few months ago (that he provided) and while the stamping was worn, I think they were 102…and didn’t notice a difference. So now I’m putting the 97.5 in to see if I can get better gas mileage without too much power loss (going back to this whole thing about not having to up-jet so much for after market exhaust (the bike has a Kerker 4–1)).

Old air screw middle.

The kit seems to have two air pilot screw lengths, one about 2mm longer than the stock I pulled out—I matched with the shorter kit one (the spring length matched, too).

After making sure all the new gaskets match up to the carbs, carefully started scraping the old gaskets off. Curious if they were sealed to the tops previously (at factory?) or that just happens after 40 years. Why would it only stick the top and not the bottom if not some sort of adhesive? I opted not to seal these new ones, though…seems good enough with screw tension? Plus I’ll be taking these on and off, often, plus like, don’t want ANYTHING inside the carbs except gas and air. After the fifth scraping ordeal I started getting more aggressive / faster with the blade, sometimes shaving off a bit of aluminum—not much, but best to be more careful. Wire brushed the surfaces, too.

New pilot jets in. Couldn’t quite make out the original size stamping (15?) and the new ones said…15? 16? The holes looked smaller, so I’m a bit apprehensive, as my main problem has been my idle circuit (I think, i.e. starting from a stop to about 1/4 throttle).

New needle valves and seats (old on left). Straight forward, though the washer/gasket appears to be rubberized / paper on the old and just steel on the new. The new needles and seats were packaged together inside the carb kit packaging, so I’m gonna assume best to keep that needle and seat together (don’t mix and match needles and seats, even when new (maybe they’re manufactured together to seat perfectly?)).

Half the reason I bought a carb kit was because a couple rubber o-rings on my main jet tube (is that what it’s called?) were cracked. Old at top, new at bottom. Interestingly the intermediate carb kit doesn’t include a new main jet tube thingy. Put new o-rings on the float bowl drain screw (no new screws provided, though) and on the choke plungers.





3 Responses to “KZ650 Intermediate Carb kit”

  1. […] overhauled the carbs on my four cylinder ’78 Kawi half a dozen times, what a joy to only have two to tear down and rebuild. And I don’t even […]

    1. Kevin Martiniuk Avatar
      Kevin Martiniuk

      Have same carbs how did you make out in the end

      1. Jeff Werner Avatar
        Jeff Werner

        Still riding the KZ650 regularly since I rebuilt the carbs in 2017. It probably took me another year to learn about points and timing and other aspects of air / fuel / spark, but the bike has been running great since.

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