{"id":12982,"date":"2024-07-11T21:00:30","date_gmt":"2024-07-11T12:00:30","guid":{"rendered":"https:\/\/www.decoboco.info\/en\/?p=12982"},"modified":"2026-09-24T13:46:26","modified_gmt":"2026-09-24T04:46:26","slug":"bandit-1200-idling-mystery-illness","status":"publish","type":"post","link":"https:\/\/www.decoboco.info\/en\/20240711\/everyday-events\/bandit-1200-idling-mystery-illness","title":{"rendered":"Years of mystery ailment? Bandit 1200\u2014solving the won’t-idle disease."},"content":{"rendered":"
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They were having fun with DIY work, but then
at some pointa symptom called “won’t idle”<\/span><\/strong>started happening.

Just hearing about it is a little scary, but let’s tackle it quickly (*\u00b4\u03c9\uff40*)<\/p>\n\n\n\t\t

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\n\t\t\t\t\t\n\t\t\t\t\t\t\"\"\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t
\n\t\t\t\t
\n\t\t\t\t\t\n\t\t\t\t\t\tOil-cooled 750\/1100\/1200 common Yoshimura aluminum pulsar cover GSX-R1100 (86\u201392)\/750 (85\u201391)\/GS1200SS YOSHIMURA 280-511-A400 khaki small\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\n\t\t\t\t\t\t\t\t\t
\u30e8\u30b7\u30e0\u30e9(YOSHIMURA)<\/div>\n\t\t\t\t\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\"\"\n\t\t\t\t\t\t\t\u53e3\u30b3\u30df\u3092\u898b\u308b<\/span>\n\t\t\t\t\t\t<\/a>\n\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t<\/div>\n\t\t\t\t
\n\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\n\t\t\t\t\t\tAmazon\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t<\/div>\n\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\n\t\t\t\t\t\tRakuten\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\t\t\t\n\t\t\t\t\t\n\t\t\t\t\t\tYahoo!\t\t\t\t\t<\/span>\n\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t
\n\t\t\t\t\t\"\"\n\t\t\t\t\t\u30dd\u30c1\u30c3\u30d7<\/span>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\n\n\n\n\n\n\n
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The cause: two points. Intake manifold O-ring and MSA<\/h2>\n\n\n\n
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The result is simple to state, but it took some tedious work.
A simple troubleshooting method is“return to original”<\/span><\/strong>

but that part is pretty tricky, right?
Systematically eliminating one thing at a time<\/span><\/strong>is the effective approach. <\/p>\n\n\n\n

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\u2460 Reduce variables: “compression, plug, and cap”<\/h2>\n\n\n\n
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Symptomatically,“rough idle”<\/strong>revs up fine at the top.
It resembles a slightly bent valve.

If we confirm compression is solid on cylinders 1\u20134,we can rule out valve and piston issues<\/span><\/strong>
*We’ll skip valve timing. <\/p>\n\n\n\n

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The plugs are heavily fouled.
The spark looks solid, but to be sure, we’ll trim the wire and re-seat it. <\/p>\n\n\n\n

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The ignition harness is pretty sharp<\/h2>\n\n\n\n
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For now, we’ll return to stock.
We’ll eliminate uncertainty and keep checking. <\/p>\n\n\n\n

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We swapped the igniter with a spare.
No major change at this point. <\/p>\n\n\n\n

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We also swapped the coil and cap, and routed the signal externally<\/h2>\n\n\n\n
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We should be fine, but to be certain we’re eliminating the cause, we swapped the coil.
We also externalized the signal line to account for possible harness breaks.

We swapped the main switch too, but no change. *We have a used one on hand<\/p>\n\n\n\n

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Check carburettor synchronization<\/h2>\n\n\n\n
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Nothing too far off, so let’s move to the main suspect: the carburettor. <\/p>\n\n\n\n

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No problem with the main suspect carburettor?<\/h2>\n\n\n\n
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They’ve touched a lot of things, and finding nothing wrong with the main suspect carburettor is shocking. . . .
At this point we’re entering a bit of a puzzled mode. <\/p>\n\n\n\n

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The Mikuni BSR36 is nice like a Keihin carb, I think wistfully while checking the actual fuel level.
We’re eliminating causes one by one.

The intake manifold was new, so we cleared it by touch and sight\u2014a step into the swamp.
The big culprit was“O-ring failure and loose fastening”<\/strong>

on the intake manifold, so at this point we’re still in question-mark territory. <\/p>\n\n\n\n

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Check air gap and pickup<\/h2>\n\n\n\n
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Since we haven’t pinpointed the cause,we’re swapping the pickup. <\/span><\/strong>
*Note: Bandits with optional switches have different connectors, so watch out. <\/p>\n\n\n\n

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My stock is the old type, so I made an adapter and swapped it in.
Air gap differences really matter \u266a<\/span><\/strong>It’s one of those moments when you think wistfully about it. <\/p>\n\n\n\n

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I’m really stuck now. . . Unbelievable. Back to basics<\/h2>\n\n\n\n
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Wait a minute. . . The owner said there was a change when they sprayed parts cleaner. . .
When we removed it, it looked like this (*\u00b4\u03c9\uff40*) Goal!

By divine providence, we have an intake manifold O-ring in stock! Whee \u266a A wave of emotion washes over us. <\/p>\n\n\n\n

Pom-pom! Oh, pom-pom! Oh<\/span><\/strong><\/p>\n\n\n\n

It’s running pretty lean, I’d say. . . <\/p>\n\n\n\n

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We don’t have jets, so for now we’ll lower the needle position.
Note that the engine and cam are different too, so please be careful. <\/p>\n\n\n\n

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Clean up the boost and MSA wiring too<\/h2>\n\n\n\n
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I simplified it like this. . . . but?
When we connect it, it runs rough. . . ( ,,`\uff65\u03c9\uff65\u00b4)\uff9d\uff9d\uff9d?

We’re checking the wiring diagram on YSD’s page. <\/strong>
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