motorbike ignition fault

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Re: motorbike ignition fault

Postby Robski » Mon Oct 01, 2012 2:47 pm

TBH I think this has more than one issue and I agree the dwell does not look right. Two long, two short - hows that fit with cylinder comps? Amp clamp?


Agreed, iirc compression's been checked ?

In theory, Yes.
But your second question disproves the first. For example if I grounded a plug lead would you expect to measure no induced voltage in the primary.


Not sure I understand the underlined part ? but interesting, so i had to go experiment ...........

DIS waste spark_secondary grounded #3.gif

DIS waste spark_plug lead to ground.psdata
(1.51 MiB) Downloaded 191 times

The plug lead was grounded (direct short) via a fly lead to the battery clamp, no change in the primary EMF kick but no secondary kick at all, but the spark line still mirrors..... would be interesting to see the effect through a high resistance resistor ??

DIS waste spark_primary_secondary.gif

Same primary/secondary not grounded.
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Re: motorbike ignition fault

Postby Avdr » Mon Oct 01, 2012 6:16 pm

Found a picture of the pick up wheel on ebay. Shape does seem to tally with the imperfect square wave of pickup.

Image

When vieiwng file: ign. pickup + pri amps
Cleary each coil is being charged once per crankshaft revolution, but then why is there the 160mA current flowing inbetween each ignition event, and timed perfectly with the pick -up?

also was battery getting low? On the pick-up file rpm is 383rpm, but on the ignition file its down to 297rpm?
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Re: motorbike ignition fault

Postby tiggerbiker » Mon Oct 01, 2012 6:53 pm

the ignition files were captured on saturday i think - the battery was getting low towards the end of my fiddling so i took it of and charged it over night.
the pickup trace was done with a freshly charged battery on sunday, hence the better RPM's.

i am now informed that the bike had its camshafts replaced with ones from a gsxr1100 - there is one particular model of gsxr that this modification will make the bandit breathe better, im now wondering if the camshafts are not from that model and that is causing the bike to not run (its great how these little bits of info are given in passing after much scratching of heads :( )

i wonder if the plugs were so wet from attempted starts with off camshaft timing that they caused the duff spark traces?

i will now endevour to replace the original camshafts and see what happens

i used to be pleased that my wife was handy with spanners and could rebuild an engine - i just wish she would talk about these bloody things she reads on the bandit owners forums!!
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Re: motorbike ignition fault

Postby Robski » Mon Oct 01, 2012 8:03 pm

i used to be pleased that my wife was handy with spanners and could rebuild an engine - i just wish she would talk about these bloody things she reads on the bandit owners forums!!


I give in ...............
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Re: motorbike ignition fault

Postby Avdr » Mon Oct 01, 2012 9:45 pm

from the way your post was written I thought it did run during your ownership and had been getting progressively worse.
Anywho...

How different can the camshafts be? and surely who ever swapped the camshafts would've swapped them back, afterall a working bike will fetch more than a non runner?
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Re: motorbike ignition fault

Postby tiggerbiker » Tue Oct 02, 2012 5:57 am

Hi, it's my wife's bike which shes had from new in 1998 and it was running great untill the carbs got gummed up with bad fuel, i then stripped & cleaned the carbs & found the camchain tensioner stuck - my wife bought a manual chain tensioner -and now I'm told - a set of gsxr1100 cams which she fitted without my knowledge.
When it was started, it ran on 2 pots - just.
The usual problem with these bikes is ignition coils failing (due to where they are located on the frame) when new coils were fitted, the problem persisted and the bike was pushed to the back of the garage until I bought my picoscope and I figured I'd use it to look at the ignition system.
Now the bike tries to start on only cylinder 2
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Re: motorbike ignition fault

Postby Avdr » Tue Oct 02, 2012 6:59 am

HMM, would be good if you could get your hands on a pressure transducer and check that your max compression is occuring when it should in relation to ignition timing.
Or take it all apart...
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Re: motorbike ignition fault

Postby antthecat » Tue Oct 02, 2012 7:50 am

Could it still be possible to check ignition timing via starter current and secondary pick up. If the cams are out though I can't imagine that we will see a difference.
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Re: motorbike ignition fault

Postby Avdr » Tue Oct 02, 2012 5:12 pm

antthecat wrote:Could it still be possible to check ignition timing via starter current and secondary pick up. If the cams are out though I can't imagine that we will see a difference.


Should still see an offset between peak current and ignition if the cams are out though - I would've thought. That said it would probably have bent a valve by now.
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Re: motorbike ignition fault

Postby tiggerbiker » Tue Oct 02, 2012 5:48 pm

No chance of a bent valve - even the worst case gsxr cams won't be valve bendingly out
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