{"id":42832,"date":"2019-09-15T20:18:32","date_gmt":"2019-09-15T11:18:32","guid":{"rendered":"https:\/\/www.decoboco.info\/en\/?p=42832"},"modified":"2026-09-24T13:45:14","modified_gmt":"2026-09-24T04:45:14","slug":"zephyr-750-carburettor-maintenance-oh-inspection","status":"publish","type":"post","link":"https:\/\/www.decoboco.info\/en\/20190915\/everyday-events\/zephyr-750-carburettor-maintenance-oh-inspection","title":{"rendered":"Zephyr 750 Carburettor Maintenance + OH Inspection"},"content":{"rendered":"\n
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The worst corrosion I’ve ever seen. Let’s see how far we can push it with our current skills.
This is a revival after two years of outdoor storage. <\/figcaption><\/figure>\n\n\n\n\n\n\n\n
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We don’t usually get non-running bikes at our shop, so I was a bit puzzled by the condition.
I just stared at it thinking, wow, it’s rusted this badly. <\/figcaption><\/figure>\n\n\n\n
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When it gets this bad, I think we need to disassemble the four-carb setup.
Even if the engine starts running, fuel will eventually leak from around the fuel passages\u2014it’s just a matter of time.

It’s important to discuss the budget and scope of work carefully so we don’t end up doing things twice. <\/figcaption><\/figure>\n\n\n\n
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I got so focused on filming video (I thought the cuts looked good, but it turned out to be too much work, so I scrapped it) that I ended up with fewer photos.
Recently I’ve modified our polishing method and now we can do both dry and wet polishing\u2014it’s super fast and gives great results.
Our equipment at Decoboco is state-of-the-art, which means we’re always improving\u2014today is better than yesterday. <\/figcaption><\/figure>\n\n\n\n
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A common issue with OEM parts: sometimes they only come as an ASSY and the O-ring isn’t available separately.

In those cases, it helps to look for the same part used on related models (in this case, bikes using Keihin CVK carburetors).
The ones I targeted were
the GPZ900R
and the Inazuma 1200.
I ordered O-rings from both and checked the dimensions (wire diameter, inner and outer diameter), and it turned out both would work. For your reference. <\/figcaption><\/figure>\n\n\n\n
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Time passes and the CVK is now sparkling clean. But then one more problem shows up.
The actual fuel level is abnormally high compared to the float level.
The fuel level keeps slowly rising and won’t stop.
That’s the issue. By the way, we didn’t replace the float valve this time either.

Since each one is expensive, if we can judge whether it’s still usable, reusing it is better.
We could replace it if we’re worried, but I think reusing is the way to go.

The fuel level was so unstable that even when I tried moving the float level up and down, nothing changed. This wasn’t right.
The CVK’s float valve seat is press-fit and there’s no separate part available. Removing it felt like I’d get stuck again.

I thought maybe the contact surface of the seat was dirty, so I applied a tiny bit of compound to a cotton swab and lapped it.

Then\u2014click!\u2014the actual fuel level matched up, and I thought, oh! The dirt was preventing good contact.
Even if we’d replaced the float valve in this state, it wouldn’t have helped.

It’s interesting how age and wear create unintended circuits. Every time, I don’t want to learn but I end up learning something.


My philosophy is that these kinds of cases are always different, so instead of looking for “the answer” or “the cause,” I enjoy asking “what would make this unintended symptom happen this way?” and eventually you either figure it out or you don’t.
Most things can’t really be said with certainty\u2014that’s what I think.
Check out the video page below.
https:\/\/www.decoboco.info\/category\/everyday_events\/video<\/a> <\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":2,"featured_media":42823,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"pochipp_cv_data":"","swell_btn_cv_data":"","footnotes":""},"categories":[1924],"tags":[209,115,82],"class_list":["post-42832","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-everyday-events","tag-genuine-carb-maintenance","tag-z-aircooled","tag-zephyr-750"],"_links":{"self":[{"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/posts\/42832","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/comments?post=42832"}],"version-history":[{"count":0,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/posts\/42832\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/media\/42823"}],"wp:attachment":[{"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/media?parent=42832"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/categories?post=42832"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/tags?post=42832"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}