motorbike ignition fault

tiggerbiker · Post by **tiggerbiker** » Sat Sep 29, 2012 11:25 am

hi peeps,
one of my wifes bikes (1998 suzuki bandit gsf1200) has had a bad running issue for a while now which has now got to the point of not even starting or running now.
i have only had my picoscope for 2 days and am really in at the deep-end!
previously we compression tested, valve clearences checked, new plugs, carbs stripped & cleaned - and new coils fitted (old ones from this bike fitted to another bike which ran perfectly - swapped back and same issues)
here is a trace i ran on the coils this morning - i can see that there is a problem, i just dont know how to read the traces - please could someone point out to me whats causing what?
(btw - the coils are wasted spark types, one coil for pots 1+4 & one coil for pots 2&3)

Robski · Post by **Robski** » Sat Sep 29, 2012 3:00 pm

tb

I'm no bike guru but you can't really diagnose an ignition problem by just the primary & secondary.

Can you take another capture using the amps clamp too so we can see the coil current ramp with primary & if you have another channel the secondary too ?

Put some more time on the screen to see more than one event & sample at an interval of 1µs.

Grab a CKP/CMP capture too while you're at it.

tiggerbiker · Post by **tiggerbiker** » Sat Sep 29, 2012 3:37 pm

thanks for that - ill redo the tests tomorrow
i could only afford the 2 channel kit so ill just have primary current & voltage on one screen

*warning - daft question alert* whats a CKP/CMP capture?

antthecat · Post by **antthecat** » Sat Sep 29, 2012 5:05 pm

May pay to scope the crank signal, I've got a 600 and could scope that as I believe they use the same pick up.

Robski · Post by **Robski** » Sat Sep 29, 2012 5:48 pm

Grab a CKP/CMP capture too while you're at it.

May pay to scope the crank signal

antthecat · Post by **antthecat** » Sat Sep 29, 2012 6:31 pm

Sorry Rob, I skim read the post.

My bad

Avdr · Post by **Avdr** » Sat Sep 29, 2012 7:02 pm

Setting aside the pico files for a moment. You have pretty much covered all potential problems, excepting ignition control unit, and back pressure problems in the exhaust.

Are you actually getting a spark at the plugs? Take it you've changed plugs too?

Doubt you bike will have a camshaft position sensor - given it has got carbs not FI.

Any backfiring?

tiggerbiker · Post by **tiggerbiker** » Sat Sep 29, 2012 7:08 pm

i am getting a weak spark - it only seems to be firing on one pot (no. 2), its the only downpipe that gets warm - the others are stone cold - which is very odd as i would of expected 2 pots to be trying to fire at least
its has new plugs and theres no backfiring

Robski · Post by **Robski** » Sat Sep 29, 2012 8:16 pm

Do you have a schematic of the system ? post it up let's have a look.

I missed you saying you had cleaned the carbs so ignore the CMP & grab coil current/primary/secondary/CKP, I don't suppose you have an adjustable spark tester ?

Fat Freddy · Post by **Fat Freddy** » Sun Sep 30, 2012 10:55 am

To me, it kind of looks like it's tracking to ground.

What colour are your plugs?

FF

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