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Old 04-15-2014, 06:21 PM   #1
arcangel OP
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Joined: Feb 2006
Location: JeffCo, Colorado
Oddometer: 64
81 CB750c ignition issues (ignissues)

Just picked up an 81 CB750 custom. 17K miles, in the PO's family since 86, PO looks to have been pretty meticulous--ignition switch replaced, new master cylinder, new chain/sprox, SS brake lines, etc.

Just got my temp tags today, and wanted to take her for some fresh gas and a short spin. Got to the gas station, filled her up, tried to start...nada. Turned over fine, but wouldn't fire. A car mechanic pulled up, and futzed with her, not really doing anything, but she suddenly started.

Noticed the blinkers aren't flashing nearly as fast as they should be also.

Are any of these symptoms pointing to a common CB750 issue?

TIA
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Old 04-16-2014, 12:33 AM   #2
Gham
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First thing I would check is the plugs,it;s easy and doesn't cost anything.Look at the color and make sure you have fire to each one.I don't think this is the problem though.Sounds more like fuel delivery.The 750/900 bikes are notoriously cold blooded.Just riding for a mile or so and then trying to start with no choke can be futile.
As for the blinkers,this is my experience:slow blinkers at idle will occur when the battery is low.If you take the rpm up to about 2k they should speed back up if the alternator is working properly.If not check alt.output.It doesn't SOUND like anything major just need to check things off the list to diagnose.
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Old 04-16-2014, 01:01 AM   #3
Gham
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One more thing,if memory serves me (and it usually doesn't) these bikes had some sort of funky-ass fuel valve to help keep them from leaking.It may be something like that involved here at start up,or it may just be cold as hell where you live and some fairly thin air.(Colorado right?)
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Old 04-16-2014, 01:03 PM   #4
boredom
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Slow blinkers and an already replaced ignition switch points to a bad ground. Steel wool all the ground connections to the frame to get corrosion off of the terminals and bolts, then slather them in dielectric grease.
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