{"id":15650,"date":"2023-12-29T14:51:42","date_gmt":"2023-12-29T05:51:42","guid":{"rendered":"https:\/\/www.decoboco.info\/en\/?p=15650"},"modified":"2026-09-24T13:46:06","modified_gmt":"2026-09-24T04:46:06","slug":"air-cooled-4-cylinder-hidden-gem-zephyr550-what-is-it-really","status":"publish","type":"post","link":"https:\/\/www.decoboco.info\/en\/20231229\/decoboco-cars\/zephyr550zr550\/air-cooled-4-cylinder-hidden-gem-zephyr550-what-is-it-really","title":{"rendered":"Air-cooled 4-cylinder hidden gem? ZEPHYR550, what is it really?"},"content":{"rendered":"
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April 2023
“I bought it on impulse”

Having a place to keep it is scary…

When buying something, more than cost-benefit analysis
“The one that got away is always bigger”
Choosing things without regret
is important

I live my days gambling
CMS parts list<\/a><\/strong><\/p>\n\n\n\n\n\n\n\n

KAWASAKI ZR550B9 ZEPHYR 1998 FG<\/strong>
Even the final model is from ’98

Although the build quality is good
that’sa 25-year-old vehicle<\/strong>it is.
Definitely a classic bike

Seemed sweet but wasn’t?
Even though the condition was good, there were
some subtle issues.<\/p>\n\n\n

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\u2462Ignition improvement<\/strong><\/a>
ZEPHYR400\/550 Zephyr 550\/400<\/strong><\/a>
“NGK plug cap\/silicon plug cord replacement works better than expected”<\/strong><\/a><\/figcaption><\/figure>\n<\/div>\n\n\n

The ignition coil cord
clicking
isn’t misfiring exactly
but it doesn’t spark crisply

This subtle cord replacement makes a noticeable difference
it had deteriorated for better or worse.<\/p>\n\n\n

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\u2461Pilot screw dramatically changes Zephyr 550 starting Pilot screw adjustment<\/a><\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n

Since it’s an export model for emission-controlled regions
“it’s incredibly lean”<\/strong>
it’s extreme.

When the carb is restricted
it runs poorly until warmed up<\/strong>
the idle is almost out of sync
the feeling is terrible
“Opening the PS makes a dramatic difference”<\/strong>
since it’s adjustable
I’d definitely like you to experiment with it.

<\/p>\n\n\n\n

50PS\/10000rpm\/179kg<\/h2>\n\n\n\n

Even people riding bigger bikes probably

hmm!
“This thing really goes, doesn’t it?”<\/strong>

would think

it runs quite vibrantly…
honestly, it’s quite fun.
ZEPHYR550<\/strong>
dry weight 179kg
50PS\/10000rpm
4.1kg-m\/6000rpm

RVF400<\/strong>
dry weight 165kg
53ps(39kw)\/12500rpm
3.7kg\u00b7m(36.3N\u00b7m)\/10000rpm

That’s how high-spec the ZEPHYR550 is
(*\u00b4\u03c9\uff40*)

The foot placement is so good
flat
“Rossi dismount”<\/strong>
is possible.

I likearound 10,000 rpm redline<\/strong>it’s easier
same as bigger bikes

continuously revving feels tedious in city riding
<\/p>\n\n\n\n

Opened it up
and tried it!<\/h2>\n\n\n\n

Oh, it’s slow…
No top end “missing teeth”

The tach goes up but the speed doesn’t increase
seriously, shock

If I was just riding around the area
it would’ve been fine
I have to order that old-school thing<\/p>\n\n\n

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High-speed response (‘\u0414’)<\/a><\/strong>
“Install DYNOJET ST-1”! Zephyr 550 ZEPHYR550<\/a><\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n

Still available from America
the top end becomes a different beast.
*The original was just too bad

Thanks to this, I can ride endlessly on the bay shore
and tour with liter bikes
that kind of dramatic change

can’t start without it
that kind of dream item<\/p>\n\n\n\n

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Finally found it! Preload adjuster compatible with Zephyr 400\/550 is HYPER PRO for W650 series<\/a><\/strong><\/figcaption><\/figure>\n\n\n\n


<\/p>\n\n\n\n

The fork is
squishy<\/h2>\n\n\n\n

Common with mid-displacement and below
squishy fork

initial adjuster is naturally necessary
when you check the rate…
it’s that low? kind of feeling

I haven’t written it on the blog
SS Itou’s 0.8kg\/mm<\/a>
I’ve installed (*\u00b4\u03c9\uff40*)

it’s quite firm.
You need to balance the fork oil too, but it’s really good.
Or rather, it becomes normal.<\/p>\n\n\n

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A bit puzzling? Zephyr 550<\/strong>
“mysterious misfiring” is<\/strong>
sidestand switch malfunction<\/strong><\/a><\/figcaption><\/figure>\n<\/div>\n\n\n

Whoosh~
engine stops<\/h2>\n\n\n\n

It’s a really subtle symptom
when you engage the clutch it goes “whoosh~” and stops
same thing even if you rev and engage

it’s misfiring…
jiggling the sidestand sometimes fixes it
it’s a really subtle symptom
but this kind of thing happens when bikes get old<\/p>\n\n\n

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A bit of “high throttle” works on mid-displacement Zephyr 550 Daytona FLAT throttle sleeve 29470<\/a><\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n


<\/p>\n\n\n\n

Various things catch my attention<\/h2>\n\n\n\n

Since it’s only 550, mostly wide open
number of shifts \u00d7 full throttle
= tedious<\/strong>
First, I shortened the final drive
I haven’t written it on the blog
but I dropped the front one gear.
it works quite well, even on the bay shore

with a bit of high throttle, the throttle opening issue is also resolved
hehe( *\u00b4\u8278\uff40)
it’s becoming my own<\/p>\n\n\n\n

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ZEPHYR550\/400 Zephyr 550\/400
Caliper overhaul. Aluminum piston conversion (halfway)<\/a><\/strong><\/figcaption><\/figure>\n\n\n\n

Fluid is seeping<\/h2>\n\n\n\n

Even after overhaul, fluid is seeping
*right side only
even with new seals, it still seeps

the conclusion I reached
“there’s a void”<\/strong>

replaced the caliper and it improved
there was a void to begin with and it deteriorated over time
opened up with wet blasting
this is my first time seeing this
old bikes can have this kind of thing
I remember
receiving the baptism of a classic bike.<\/p>\n\n\n

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“Zephyr x + Zephyr 750” = Zephyr 550 (modified) Yoshimura DUPLEX drag cyclone completed<\/a><\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n

Once it runs pretty well
I start wanting to customize it a bit

I had already collected parts beforehand
so I combined them to create my own version
not for performance
“looks and sound<\/strong>“
perfect fit! (*\u00b4\u03c9\uff40*)<\/p>\n\n\n

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“ZEPHYR550” AP RACING CP2195\/Sunstar neo-classic disc\/Speed Shop Itou caliper support installation<\/a><\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n

I’m the type to source parts right away

you never know when something will be discontinued
it’s important to install when you want to
“time is finite”<\/strong>

by the way
I have no complaints about the stock brakes
“looks and the satisfaction of doing it”<\/strong>
that’s all (*\u00b4\u03c9\uff40*)
bikes have an afterimage you see later
“lingering feeling”<\/strong>is also important
<\/p>\n\n\n\n

Oh… really?<\/h2>\n\n\n\n