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help needed with electrical issue


bigpants

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Hi everyone. I just got my 1100 slabby up and running after a lay off of 8 years . I had a few short fun filled journeys but it's now developed a problem. Sometimes when  I start it it pops and drops out just above about 2000k and wont run through it. But here's the weird bit (almost) every time when this happens all I have to do is change to a spare cdi and the bikes fine. Next day I get the bad running again and switch back the cdi . Any ideas ?

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sounds a bit strange , I would say possibly when your changing over the cdi you disturbing a connector or wire that's the problem .

I would personally check all multi pin plugs and put a drop of electrical grease on them . Check earth points and fit some new plugs . Also worth checking the voltage at the battery when its running with the lights on , I once had a strange running fault on my 750 slingshot and found I had nearly 17v when it was running due to a faulty reg .

I take it the carbs are all free from any muck that might have developed from being sat 8 year ?

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Sounds like connections to me or a dodgy wire.  When you do the swap you disturb the wiring, which 'fixes' it for a while before it plays up again soon after.  Probably something loose or a wire which is internally fractured but makes a connection a bit of the time.  Have a thorough check of all the connectors and wiring which will be getting disturbed.

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5 hours ago, bigpants said:

Yeah the wiring blocks were my first guess so I have gone over and over them and can't find any problems. When it's running badly I can give them all a wiggle and it's never made any difference . Carbs cleaned and new plugs and coils fitted.

have you a spare pick up , have been known to play up .

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Std coils or aftermarket? Does the misfire occur 2 or 3 days in a row whatever CDI is fitted? Maybe coil breakdown through heat is a possibility - one pair or cylinders or across all 4? 

Mind you running any engine at 2 million revs is gonna lead to issues LOL! But 2000 is fairly low for electrics to give up - maybe it is gunge in a carb - idle / pilot circuits?

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When I've swapped the cdi 's it's usually been ok for the whole day though couldn't swear it's been 100%. And coils were cheap aftermarket ones off Eblag , I know that's not a good choice but I had a non running bike and couldn't throw too much money at it. And I'm pretty sure it's all 4 cylinders breaking down , also I forgot to mention earlier -when it's bad the Rev counter stops working in a way that suggests it's lost all signal/power.

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I wonder if the coils are the wrong resistance for the slabby CDI . Probably too low on the primary resistance value which could cause the CDI to overheat. Slabby coils are I recall about 5ohms and slingy coils likely to be around 3ohms. I recently converted my slabby to run coil over plug ones and needed a resistor to be bring the coil resistance up .

 

 

Edited by Macduff
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